A more flexible power system for Dirona

A little over a year ago, we worked our way south from Fanning Island, Kiribati towards Nuku Hiva in the Marquesas Islands. We were on a long, fuel-constrained run where we would cover 2,600 nm without fueling. For most of the trip, we were heading up-current and into 30 kts of wind on the bow. The waves were fairly well-developed and spray filled the air day after day. The outside temperature was well over 80F, and the master stateroom was 88F, which made sleeping more difficult. With the doors open for ventilation, a thin layer of airborne salt soon covered the boat interior. But we were not crazy about closing the boat up and running the air-conditioning, because that consumes more fuel and would be a couple of weeks of generator run time at very low load.

As we neared Nuku Hiva, we concluded that we had far more fuel than we were going to use, so we might as well be comfortable and run the air conditioning. I’m not crazy about extended run times on the generator at under 20% load, but it’ll live with it, and it was so wonderful and relaxing to finish the last few days of the crossing sleeping well in air-conditioned comfort. This convinced us we needed to find a way to air-condition the boat underway without running the generator.

In the Tuamotus, we were diving daily and just loving it. It’s just amazing to look up from 140′ down and be able to clearly make out our dinghy floating above us and then look down and see 150′ down to the ocean floor and be surrounded by beautiful fish, sharks swimming by, and a sea turtle making a pass through the area. It was incredibly beautiful, but we found ourselves wondering what would happen if our generator failed. Without the generator, we can’t fill SCUBA tanks, can’t make water, and can’t use the washer, dryer or oven. The inability to make water when that far “out there” is not at all appealing. Our goal is to never have a trip ended early or be redirected by a fault and it would be very difficult to get generator parts flown into some of the obscure, uninhabited islands we visited on this trip. We needed a backup to the generator, but really have no space for another generator on Dirona.

As we continued across the South Pacific we spent the vast majority of the time on anchor. But when we did go to a marina, the shore power was rarely better than 15A. Some of those 15A connections could only reliably deliver 12A without the breaker triggering, and in some places the shore power capacity was over-taxed by the visiting boats and, consequently was sagging badly. Also, they were often 50-cycle connections and Dirona is a 60hz boat, so we couldn’t run most 240v appliances without running the generator. We really felt we needed some way to draw what the shore power had to offer, but to not trigger a breaker and not have to manage the boat to a consumption of less than 15A. Both Atlas and ASEA offer shore power frequency converters that would handle the cycle difference, but they are expensive—friends have spent as much as $50,000 on shore power conversions—and they still don’t allow running the boat well at over 25A while drawing under 15A on the shore power connection. The frequency converters didn’t look like a good solution for the entire problem.

After many nights of thinking through options on passage, and planning and drawing up different solutions during the day, we came up with a solution that appears to solve all the problems outlined above. We installed the new design when we arrived in Whangarei, New Zealand and, having used it for the last year, it really does seem to nail every requirement listed above and a few more. Summarizing what the system delivers:

Backup generator: If our generator fails, we need to be able to operate all 240V appliances including the water maker and SCUBA compressor and produce up to 8kw of power, without installing a second generator. This is super important were the main generator to fail (it never has), and is also very useful for quick 240V loads like running the oven for 10 min without bothering to start the generator.

Efficient light 240v loads: Light 240v loads, such as running a single HVAC while underway, is not an efficient use of the generator. While light loads generally aren’t ideal, our bigger concern is that running the generator 24×7 increases the maintenance frequency. Changing the oil and filter every 10 days is not where we want to be.

50hz/60hz invariant: We have a 60 Hz boat, but more often than not are plugged into 50Hz power. We needed to be able to connect to 50hz or 60hz and run all appliances without restriction and not have to start the generator.

Very low amperage shore power invariant: We want to be able run all appliances regardless of draw without any restriction, without having to run the generator, and with only a single shore power connection that might be as small as 10A at 240V or 20A at 120V. Boats are getting bigger and better equipped all the time and many marina shore power systems are not up to the draw they are asked to deliver. It’s not unusual to see shore power voltage drop down 20% below nominal line voltages. Voltage sags can damage equipment, so we needed isolation ensure that our equipment gets clean, voltage stable power even when the shore-side system is sagging under the collective load.

110v failover: If the 110v inverter fails and we’re not connected to 60hz shore power, we must start the generator to get 110v power. We wanted a backup for a 110v inverter failure without plugging in or starting the generator.

Battery protection for shore power loss: A big concern when leaving a boat unattended at a marina is the shore power could get disconnected, unplugged, the breaker may trip, or a variety of other mishaps could leave the boat unpowered and drain the house batteries. This is bad for the batteries and might result in other problems such as spoiled freezer food. We want the system to ride through a shore power fault by failing over to the generator, running it if needed to save the batteries, and return automatically to shore power if it comes back.

I’ll start with the equipment we installed and how the different components work together to solve the requirements we have itemized above.

1) Install 240V, 60Hz Inverter: This is the most important part of the design. Install a sufficiently large inverter system such that all appliances in the boat can be run off the inverter. On Dirona, we have a 4kw inverter to feed the 110V appliances, so 6kw is sufficient to support the 240V equipment we have on board. In our case, we installed 2 paralleled Victron 3kw 110V inverters to achieve 6kw of 240V power. We particularly like this inverter choice because they are simple and don’t include a charger—all they can do is invert—and are capable of delivering far more than their specification. The inverters are specified to deliver 6kw at 240V, which is roughly 25A, but they can deliver peak loads over 50A and can operate for extended periods at or even beyond their rated output without sag, over-temperature, or cutting out. They are tanks, and just keep delivering no matter what. I’m amazed to report they can start the SCUBA compressor, where the required inrush current at startup can exceed 50A. After a year of use, we just love these units. The key to making this design work is to ensure that the inverter capacity is sufficient to run the boat without restriction, using whatever combination of 240v equipment you need. So, if you chose to duplicate this design, ensure you have adequate inverter capacity. 6kw is enough for us but you can get 240V inverters in a variety of sizes up to 20kw. And if your boat is 60hz, you’ll need a 240-volt split-phase inverter–some appliances need that neutral connection.

2) Upgrade Ships Service Selector Switch: The Ships Service Selector switch as delivered on Dirona (leftmost of the three in the first picture below) allows the operator to feed the 240V breaker panel from either shore power or the generator. We replaced this switch with one supporting a 3rd input (2nd from left in the second picture below) so we can feed the 240V panel and all 240V appliances on the boat from 1) shore, 2) generator, or 3) inverter. This third position runs the entire house system off the new 240V inverter.

3) Install Battery Charger Selector Switch: As delivered, the battery chargers on Dirona draw power from the 240v panel. In other words, one of the 240V “appliances” are the two battery chargers. It would be a very bad configuration indeed to be running the 240V appliances off the inverter and have the battery chargers taking power from the inverter, using it to charge the batteries, which are then feeding the inverter. To support many of the use cases above, the chargers must be powered separately from the 240V panel. We want, for example, the 240V panel to be running off the inverter while the chargers are running off shore power. So we separated the battery chargers from the 240v panel and added a Charger Service Switch (leftmost of the four in the second picture above) to supply the chargers from either shore power or the generator.

An electrical diagram showing these first three modifications is below.

4) Upgrade Start Battery Alternator: The final component upgrade to complete the system is replacing the 85A start battery charger with a 190A @ 24V alternator and installing heavier cabling for this larger alternator. The house battery bank already has a 190A @ 24V alternator so, in this new configuration, we have two 190A @ 24V alternators on the main engine. With the two alternators in aggregate, we have 9kw of power generation on the main engine. But, you probably wonder why we would ever want a 190A charger on the start battery system. The original 85A alternator was arguably already far more than would ever be required. Well, it turns out that bigger is not really a problem in that a large alternator with a high quality smart regulator can produce whatever the start batteries need regardless of how low. So, having an extra-large alternator does no harm but is unnecessary. When this second large alternator becomes very useful is when we parallel the house and start alternators onto the house battery bank. In that configuration, we can produce over 9kw of charging for the house battery bank. In our standard configuration, with only a single house battery bank alternator, we have 4.5 kw of power available all the time. We can run air conditioning units, the water maker, and charge the batteries. If we need more power, we can parallel in the start alternator and have 9kw available. This is useful if we have a generator failure but there are times when it’s nice to be able to charge the batteries at 300A for an extra fast charge and still be able to run the water maker or air conditioning system.

To make it easy to parallel in the start alternator when needed, we mounted a switch and warning light on the dash that closes a 200A continuous duty relay to make the second alternator available to supply the load when needed by just flipping a switch.

With these four sets of new components and changes installed, we can solve all the problems we outlined above by combining these components in different ways. Repeating the requirements list above, we’ll see how each is solved.

Backup generator: The combination of the 6kw 240V inverter and the 9kw of main engine charging capability allows us to have a backup generator without giving up the space. Generators are reliable and we have never experienced a disabling fault, so it’s hard to justify giving up the space for a second generator in a small boat. If we do end up needing the backup, the hours on our main will go up marginally, but the trip will be saved. It’s nice to not give up space for a second generator and yet still have the redundancy protection that comes from one.

Efficient light 240v loads: There are times when you’d like to run the oven for just 10 minutes, but it’s just not worth starting the generator for such a short period. The 240V inverter is happy to deliver the power and although the battery draw is high, it’s short enough that it doesn’t really consume that much power. It’s a nice efficient way to deliver the power for short periods without having to start the generator. Another usage model is low loads when underway. A single air conditioning unit draws less than 8A. It’s not worth having the generator on 24×7 and having to change the oil every 10 days if you only need a small amount of power. The combination of the 6kw 240V inverter and the large on-engine alternators allows even fairly large 240V loads to be run any time without needing to start the generator.

50hz/60hz invariant: The combination of #1 (install 240V inverter), #2 (upgraded Ships Service Selector switch), and #3 (new Charger Service Selector switch) allows the boat to be run entirely on the 60hz inverter, while dual redundant 100A @ 24V Mastervolt ChargeMaster 24/100s charge the batteries. The Mastervolt chargers will run happily on either 50 cycle 60 cycles, so the batteries stay fully charged even on 50 cycle power while the boat continues to operate at full capability as a 60hz system. We never need to start the generator to use the oven or laundry for example. The combination of the chargers and the inverter can run any appliance at any time.

Very low amperage shore power invariant: Extending on the 50hz/60hz invariant point above, we can run on shore power connections as low as 10A at 240V or 15A at 110V even though our peak draw is often nearing 30A at 240V. Because the shore power is charging the batteries and the inverter is powering the house, instead of needing the shore power to provide the peak power requirements of the boat, we only need the average requirements. Often when a hair drier comes on and, say the water heater is already on, the sudden additional 8A draw will cause the shore power breaker to disengage. This is because the shore power is insufficient to meet the peak requirements of the boat. But, if running using the battery charger and inverter pair, as little as 10A is enough to power the boat even though our draws are often approaching 30A. Shore power only needs to supply average power draws rather than peaks. It’s amazing what a relief it is to not have to manage loads, worry about what is running when, and not have to go out and reset the breaker multiple times each day. Suddenly shore power “just works.” And there will be times when old shore power breakers can’t deliver their rated output. I’ve often seen 16A breakers that will pop at anything over 12A. That’s fine too. We just set the charger draw to what is available on shore and forget about it, knowing we will take what we need but never more than the shore power system can provide.

Shore sag invariant: The 240V power systems in many US and Canadian marinas is actually 208V. And, when overloaded the “240” can sag down below 200V, which can damage electrical appliances. With the combination of a 240V inverter powering the house and only the battery chargers connected to shore power, the boat always sees rock solid 240V power through the inverter, while the battery chargers deal with voltage sags and other shore power problems. The Mastervolt chargers will charge on just about any voltage and frequency in the world, so it all works without exposing the boat systems to sags, spikes and other shore power related anomalies.

110v failover: Our boat has both a 240V system and 110V system. The 110V system has a 4kw inverter and, if it fails, the only way to get 110V is to plug into 100v, 60Hz shore power or start the generator. With the 240V inverter, we can still get 110V anytime without running the generator via the 240V inverter. It feeds single phase 240V to the 240V system just as the generator would and the Nordhavn standard step down transformer will just keep producing nice, clean 110V output even if the 110V inverter fails. You might ask why bother with the 110V inverter at all? It could be eliminated without giving up any advantage described here but a larger 240V inverter would be required if we gave up the 4kw of 110V inverter. If we were doing a new build today, we probably would opt for a larger 240V inverter and omit the 110V inverter entirely.

Battery protection for shore power loss: Our battery selector switch (#3 above) has 3 input options: 1) shore, 2) generator, and 3) auto. Auto is an interesting configuration. In this mode, a large 120A continuously-rated relay is used to select between shore power and the generator. If shore power is available, the battery chargers are run from the shore power system. If the shore power system fails, is unplugged, a breaker pops or any other fault causes a loss of shore power, then this relay switches the battery charger source to generator.

Since the generator is not running, you might wonder what value there is in switching to the generator. Dirona is equipped with generator auto-start so, if the batteries are discharged to 50% capacity, the generator starts, the load is brought on after 2 minute warm-up, it charges the batteries back up, the load is removed for 1 min of cool down, and then the generator shuts off again. The auto-start system is a simple extension of the Northern Lights Wavenet system. The normal use of auto-start is to take care of the batteries and ensure they get charged when needed rather than when I remember. Jennifer and I are often late getting back to the boat after shore-side exploring. Rather than allow the batteries to discharge excessively, shortening their life, the generator just turns on and gets the job done without attention. Auto-start is a personal decision where each owner needs to weigh off the risk of running a generator without attention against the risk of allowing the batteries to discharge. Our take is well-maintained equipment works well and, just as most people wouldn’t think twice of having their furnace kick on to prevent frozen pipes when they are not at home, we think auto-start is good for the boat. Even if you don’t decide to install auto-start, the Northern Lights Wavenet system is strongly recommended. We love it.

The combination of the “auto” position on the Charger Selector Switch with generator auto-start/stop means that if something goes wrong with the shore power, the generator will start a day or so later, charge the batteries up, and then shut down and wait for when needed again. If the shore power comes back, it switches back to shore power and uses it again. We will also get email notification if the shore power gets disconnected and there are on-board alarms that signal this event but it’s still good to have backup to protect the nearly $8,000 worth of batteries.

Even if we weren’t cruising in 50hz countries, or remotely, where a generator failure would be difficult to deal with, we’d still install a 240v inverter. In fact, we’ve become so dependent on the system that we’re considering getting a spare. In the past, we needed to run the generator underway or at anchor to make water, do laundry or for baking. We now only run the generator at anchor, either to charge the batteries or for extended large 240v loads. The 240v inverter and either shore power or the main engine can handle the rest. A shore power connection anywhere in the world is now effectively the same as if we were in the US, with the added advantage of isolation from low or sagging supplies. And having air conditioning while underway in hot weather is wonderful.

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65 comments on “A more flexible power system for Dirona
  1. Tad Heckaman says:

    Speaking of running on inverter all the time, this is the reason why I prefer online UPSs vs Line Interactive or standby UPSs in our customer’s server rooms. With an Online UPS, I’m getting 100% clean power, 100% of the time. And the charger, which is running 100% of the time, can take some of the nastiest input power and just ‘deal with it’. Did the voltage sag and frequency slow down due to the generator getting bogged down because an AC unit kicked on? Don’t care, it can still keep everything powered without touching the battery bank. And of course there’s no transfer switch to fail. And on the larger UPSes, the inverters/chargers and batteries are hot swappable… makes it super easy to add capacity, just throw another power module in. If a module fails, you don’t go down, you just lose some of your capacity (or you run N+1).

    What’s really got my mind churning is the fact that you can effectively adjust your charge current based on what kind of shore power you have available. This is pretty awesome. I could see expanding on that, and adjusting the charge current dynamically… start low, and step up to higher and higher levels until you see the shore power start to sag. If the input power recovers eventually, continue ramping the charge current up, all the way to the max level you define. If the voltage starts to sag, back the charge current down until it recovers. With this you can not only ‘hide’ your varying onboard power requirements from shore power, but also handle varying shore power conditions. An example would be starting the day being able to handle 15A of current, but while you were on-shore exploring, three other boats showed up and started drawing power, reducing your available current down to 5A while they get settled in. Rather than trip a breaker and have no power, you take what you can get.

    Is there any plans for switching to Lithium batteries? There are advantages and disadvantages going with them, the biggest advantage is the greater depth of discharge, 80% on LiFiPO4 vs 50% on Lead Acid, so you get more usable energy out of a single charge (plus being lighter, you can put more on-board, if the space is available). Plus it can sustain a higher output amperage for longer, and charging can be done much quicker (which means less generator run-time and allowing the generator to run at it’s most efficient power output, conserving fuel). Downside is the higher cost of course, and if not taken care of properly you can damage the battery (not unlike a lead acid battery, but less forgiving).

    • You 100% right. We’re effectively running in UPS online mode rather than line interactive. In the case of a data center, you might do this to get cleaner power. In our case the power is usually 50hz so, by definition, not appropriate for our onboard loads. But, other issues like the voltage drop from services that are under-wired or utilities that are over-subscribed are also well handled. In the data center, there is an efficiency cost of running in this mode and the same is true here. The double conversion isn’t free but, overall, I like the advantages.

      We could do what you are saying of slowly ramping up the draw until the voltage drop is more than we like. But, we have chargers that operate well down below 200V so we mostly don’t worry about those issues. Where there is concern is staying below the amperage availble from the shore service. As breakers get older their effective carrying capacity can go down. We usually adjust for 13 to 15A draw but there are times when we can’t go over 12A due to low quality or failing breakers. Being able to adjust and not constantly go out and reset a breaker is nice. We could also adjust for other factors as you bring up but, for the most part, we’re able to put up with low quality power so we elect to just take what there is.

      There have been a lot of boats put on Li-ion batteries. The downsides is the form factors are usually different, all the chargers need to be changed or adjusted for the new power regimes, and some operational characteristics are very different. But it can be done and many have done it successfully. We’re using absorbed glass matt (AGM) batteries and, as you said, they can’t be drawn down nearly as low as a Li-ion bank but unlike many Lead-Acid variants, these can be charged at very high rates. We can charge at 300A and are nowhere even close to the max charging rate for these AGMs. In fact, the minimum charging rate for our battery bank is just over 200A. They are fine with high charging rates.

      There is no question that Li-Ion will eventually take over boating applications but the change has just begun. It’s still early days and the vast majority are still on Lead-Acid chemistries. In the data center world, some of the bigger operators have moved or are moving right now to Li-Ion so the change is underway but it’s still early days there as well and most still run Lead-Acid.

  2. Van Anderson says:


    I’m trying to better understand what impact low shore power environments have on your battery life. So for example, if the shore power available can meet the average power draws but not the peaks, don’t the constant draw-downs and charging “count” as cycles and so reduce the life of the batteries? There’s no free lunch here, correct? How do you operate at marina’s with adequate power? Do you still use shore power to charge the batteries and run the house off the inverters, or do you give the inverters a rest? Finally, did you configure your chargers differently compared to a boat that does not have the “flexible power” system you have on Dirona. Thanks for sharing Norway with us all!!

    • We always run in the same mode where power is sent to via the chargers to house loads. It might seem like the power is flowing through the batteries but, when the shore power is adequate to meet the needs of the house loads, the batteries just sit in float and it has no impact on their longevity and there are no battery cycles. But, when running on less than we peak it, battery cycles are used. For example, we are currently we are running on a single 16A power connection and we are doing the laundry and running the heat. In this mode, we do cycle the batteries and these cycles are no different from cycles at shore power. There is no free lunch as you said. Each cycle is roughly 1/1000 of the batteries life so they all count.

      We have found we can run far more than 1,000 cycles but the battery bank capacity gets very small as the cycle count goes up. But, if the batteries are well maintained, they keep working and the generator just needs to run more frequently. With autostart, we barely notice the difference and the total run per day is roughly the same. Shorter periods discharging are matched with shorter periods of charging.

      Where we are moored right now is without any shore power anywhere near. I have very long cables so I figured “no problem” but it turns out that these 16A marine receptacles are actually only 10A services. I eventually found 16A but it was way further away.

      I’m currently working on a design that will allow us to run on as little as dual 8A services for these conditions and, where there is more power available but it’s only 16A, we’ll be able to take 32A on 2x 16A cords without doing anything unsafe like wringing or non-code compliant the two 16A connections together. Our winter spot in Amsterdam only has 16A connections so being able to get two will help.

      • Van Anderson says:

        Hi James,

        Thanks for the reply. Very helpful. While dockside with less shore power than you need for peak draws on the batteries what prevents your chargers from jumping into bulk charge even for momentary high loads on the batteries? I’ve heard that’s a problem? Maybe you have your generator auto-start on high current or you’ve made changes to the charger config, or maybe jumping to bulk charge described as a problem for others is for some other reason not a problem for you? Based on your previous posts (and above) about having the ability to use two cords to charge the batteries, we’re looking into doing the same.

        • No, we don’t start the generator when running on shore power even if we see a period of high load. It is true that high draws, if persistent, can pull the charging system back into bulk mode. If it lasts for hours and the chargning system is consistently behind, the generator will eventually start but that is an undesirable condition and we both put up a warning light and send email first.

          We program the charging system threshold from bulk to absorption and the threshold to absorption to float to occur at fairly high current levels and as short a duration as supported. Mastservolt allows 10 min, so we use that.

          • James, this subject, the one Van brought up, is of particular interest to me. I have cases where a 60 Hz vessel is operating in a 50 Hz environment for months at a time. The batteries are typically sitting at float until someone turns on a microwave or hair dryer. That triggers a bulk charge stage. When this happens repeatedly, as it will when living aboard, it seriously shortens the life of the bank. I understand you’ve tweaked your Victron chargers to essentially, mostly ignore this. Can you explain how you did that, and how you did it without affecting their ordinary charge protocol, i.e. when charging genuinely discharged batteries?

            • Hi Steve. I’m a huge fan of Victron but we are using mostly Mastervolt gear on Dirona. The 2x 100A@24V chargers are both Mastervolt as is the combined 4kw inverter/100A charger. We do have a pair of Victron inveters delivering 6kw@240V and really like them. Overall, the Victron equipment is super robust. I like there their strategy of being less parental than many (including Mastervolt). They run until they can’t rather than some arbitrary engineer-set level. I’ve seen the “6kw” inverter delivering 7.5KW for short periods. It’s a beast. I also respect Victron for their contribution to open source and opening up access to their protocols.

              Mastervolt has a good product. Where they are really strong is in chargers that can accept a wide range of voltage and frequency and deliver stable charging. The nominal 240V chargers work well from 195 to up around 250V. My only complaint is that Mastervolt isn’t great at documenting their parameters and they are parental about some choices. Where the Victron runs if it can (not yet in thermal problems), Mastervolt will derate. For example, at less than 195V, they derate whether or not the system is feeling thermal load. 195 sounds super low but, on a 208V feed with some voltage loss, it’s easy to get down to 195F. In South Africa which is a 220V nominal country, we often saw less than 197V and rarely down below 195V during high utility load times.

              Some of the Victron chargers have terrible time based charging algorithm and, as much as I like Victron, I would avoid these. For example, the Victron Centaur (https://www.victronenergy.com/chargers/centaur-charger-12v-24v) use a time driven algorithm and run for 4 hours in bulk and absorption. These fixed time schedule approaches are a disaster and need to be avoided.

              The Mastervolt chargers provide a vast number of mostly poorly documented parameters that can be changed. They essentially leave the problem mostly up to you but they leave enough flexibility to get most of what you want. This is not ideal but, in the absence of measuring and using the current going into the batteries, this is best you can get or, if there is an option in the market giving more control, I’ve not come across it.

              The Mastervolts provide a pretty good solution where they accept a wide range of input voltages, are very configurable (but poorly documented) so they work fairly well. The “real” answer is to have the chargers measure the voltage going into the batteries rather than the current leaving the charger. This would completely eliminate the problem but it would make the solution harder to install so, to my knowledge, nobody supports this configuration.

              I ran the Mastervolts 100A@24V chargers for a long time as described above and they worked well. The tactic that I employ is to avoid long periods in bulk is to make it as hard as possible (high threshold) to switch to bulk and then set the timing as short as possible in bulk. Mastervolt allows as low as 10 min so a transition into bulk is super short and hardly noticeable. In this config, it takes a long big load to switch to bulk and it’ll be back in float in 10 min so doesn’t really matter if it does switch.

              There is one more trick that isn’t really needed but it does help. In the older versions of the Mastercharge firmware there was an option called “mastershunt” that could be set to “mastershunt” — this configuration actually was the “real” solution I described above. In this configuration Mastercharge uses Mastershunt to measure the current actually flowing into the batteries rather than the current flowing into the chargers. Like all params, this one is poor documented and engineering strongly recommended that it not be used and insisted that it “wasn’t needed.” They have since dropped support for this option from newer Mastercharge firmware but I was interested and explored it somewhat. I can see why they dropped support. The option has warts and bugs — I suspect they never got it working fully and it was a service problem with too many confused customers. This mode does reads the amperage going to the batteries at the shunt but it seems to get voltage wrong which sort of breaks the feature. However, the voltage is off by a repeatable amount so you can get exactly what you want with some experimentation. It doesn’t seem to be explained by voltage loss in wiring. It’s just wrong but it’s wrong by a fixed amount so you can fairly quickly figure out what to use for float, abs, and bulk voltages if you know what you want.

              Even without this unsupported mode, the system works very well and that is what I would recommend. Operating this way, the system performs somewhat better but you have to run back-level firmware and it’s a bit of hack to get it configured correctly. I’ll send you my configs but the voltages levels will look weird. I’m targeting 26.2V float and 28.8 bulk and absorption but, because of the firmware bugs when running in Mastershunt mode, end up setting the voltage to different data points.

              I ran without the unsupported Masterbus option for a year or so, set this option after some experimenting, and having been back to look at it in years. It works fairly well. If I was doing a new install now, I would probably go with Mastervolt chargers, use the newest firmware, and set the settings to sensible values. It works very well. I might be tempted to install the old firmware and return to the setting I’m currently using but it’s not a supported option and prevents you from using newer firmware. I’m happy to share the old firmware if you end up deciding to try it. It works well with the newer firmware with far less bugs and it works slightly better with the old firmware but the configuration looks strange.

      • Tad Heckaman says:

        Your last comment on designing a solution to combine diverse power sources to get more current than what’s available from a single provider sounds awfully like ‘SD-WAN’ on the networking side… you’re designing a ‘Software Defined PowerGrid’. 🙂 Use the boat’s existing 240V AC infrastructure to be the conduit between the various sources of power.
        Some crazy ideas:
        Need to add another shore power service (keeping it isolated from existing shore power)? Connect the shore power to a variable output DC power supply, which then feeds into a grid-tied inverter that can supply as much energy into the boats ‘grid’ as it can extract from shore power. The DC power supply could monitor the shore power and adjust its output on-the-fly to allow for varying power quality.
        Have solar? Let a grid-tied inverter feed that power directly into the boat’s AC grid, skipping the wasteful double-conversion to DC and back to AC. This also reduces the demand/cycles on the battery bank/inverter.
        Need to charge the batteries and shore power isn’t supplying enough to keep up with demand? Software can fire the generator up as needed and let the generator synchronize to the onboard AC power grid, taking over the load from the battery inverters, and allowing chargers to begin recharging the battery bank.
        Boat is underway? Main engine alternator/generator comes online and supplies AC power to the grid, battery bank goes into charge/idle mode until needed.
        Generator dies? The battery bank’s grid-tied inverter immediately starts starts contributing into the boat’s power grid, preventing the voltage and frequency from sagging. Any ongoing charging would stop immediately.

  3. Chris Barber says:

    Hi James, I’m trying to formulate a summary in my head of your basic power architecture and coming up short on the charger side. So you’ve got the Victrons providing the 240V, and the MV MassCombi 4K doing the 120V. That’s an inverter/charger; does it do the whole charger duty, or is there another charger? You briefly mention an MV Master Charge but I don’t see any further discussion on that.

    • Yes, you are correct. We have two Mass 24/100 units for 200A at 24V of charging when not using the inverter or 300A at 24V when the inverter is in use as well. 300A is wonderful to have. I would slightly prefer to have stand alone units (3x 100A chargers) rather than combined inverter/chargers. However, the combined units are much better value than buying one of each since they share so many components. The downside of combined units is they have a few extra failure modes the most serious of which is the high current automatic transfer switch that switches between inverting and direct power with charging mode.

  4. Mark McGillivray says:

    Hello James,
    Mastervolt MasterAdjust software has 2 parameters that I do not understand: under the “Configuration” Tab, the “Absorption” section lists “Return Amps %” and “Return Amps sec”. Can you advise their significance?
    Thank you

    • I read the manual and, like you, I found it hard to parse. I eventually sent a note to Mastervolt and, after many interactions determined, that I probably wasn’t going to talk to the engineering team and the service team didn’t really know either.

      I’m using an older firmware version and, on my version of firmware and Masteradjust, there is no “Return to Amps %” and “return to amps seconds” under the absorption title. I’ll send you the configuration I’m using but under bulk I have bulk return voltage and I believe this is the voltage level that causes a transition from float back to bulk. There is min and max absorption time (with obvious meaning) under bulk there is “bulk return time” which I believe to be the minimum time before the system is allowed to transition from float back to bulk.

      I’ll directly send you my configs but, be aware, I’m using an old version of the firmware that allows the system to sense current at the shunt rather than the at the chargers. This has the advantage of them seeing the current going to the batteries rather than the current leaving the chargers. You can recognize this level of firmware by looking for the Mastershunt option. You can see it’s set on mine to “mastershut” which says monitor the shunt rather than measure current at the chargers. The downside of this config is that’s it’s off by a fixed, linear offset so is actually pretty broken unless you investigate it deeply. Mastervolt has removed this support and doesn’t recommend that it be used probably due to these issues. I’ve tested it over the voltage range and set the absorption, bulk, and float values to get the deliver the right values but these values would not be appropriate use directly.

      Mastervolt has one of the most configurable charging systems available that is able to accept both 50 and 60hz over a wide voltage range but it is still a long way from the level of control I wish we had. We have some Victron gear on the boat and, the more I use there equipment, the more I like it. They even open source some of their work but I’ve not gone through the charger specs to see if they are better than what Mastervolt is doing in multi-frequency and wide voltage range.

  5. Stuart Martin says:

    Hi James and Jennifer

    Thank you for all of your efforts to help other Nordhavn owners and dreamers through your incredible website, blog, dreamers list, etc.

    I am particularly interested in your comments about the possibility of your Dirona electrical power system being feasible on a 50Hz boat.

    One boat on our very short list is an N55 with 50Hz system. It does not have an Atlas/ASEA system. Key features otherwise are :

    Upgraded Northern Lights 20 Kw 50 Hz generator
    175 amp alternator on main -house batteries
    75 amp alternator on main-start batteries
    Ten (10) 24VDC 8D 255 Ah Lifeline AGM house batteries
    Five additional batteries in typical setup for engine/generator/wing engine starting and communications
    2x Victron Phoenix Multiplus 24/3000/70 Charger / Inverters rated at 3 Kw each
    Additional Victron Centaur 24V 100A battery charger for 60Hz in USA, etc.

    Any comments regarding feasibility, costs, etc would be greatly appreciated

    Thank you

    Stuart and Liz

    • Yes, absolutely, you can setup a either a 50hz or a 60hz boat to run everywhere and, arguably, a 50hz boat might be the simpler solution. As you know, there are two broad approaches to a world power boat. The most common on larger boats is to use a frequency converter which are big, power intensive, but simple (on the outside) black box solutions. An alternative is the one we use on Dirona: //mvdirona.com/2014/08/a-more-flexible-power-system-for-dirona/. Here we have all the incomming power going to a large bank of chargers and then run the entire boat on inverters. This requires both more charger and more inverter capacity than is commonly used on small boats but the overall solution is less expensive and more flexibile than a frequency converter. Also, when a component fails, you lose a bit of capacity rather than having the entire frequency converter going off line.

      On the charger/inverter approach, the frequency of the boat dictates the small appliances you buy. If you have a 60hz boat, then all appliances come from the US. If 50hz, then they have to come from elsewhere. 60hz isn’t a bad choice since the US appliance market has a healthy ecosystem with lots of competition and it’s easy to get equipment shipped from the US. But there are also advantages to 50hz. Simpler on board wiring requiring only 240V rather than both 240V for large appliances and 120V for small. Most of the world is 50hz but, from peripherally watching the boat sales market, it seems like 60hz boats sell slightly easier and perhaps a bit faster. In the end, these latter issues are fairly small and I would more or less ignore them and just factor in the cost of making the boat world power capable and not having to worry about where you happen to be.

      To make this system work effectively you need at 200A to 300A at 24V of chargers (200A works fine and consumes most of a 32A connection) and sufficient inverter capacity to run all appliances on the boat.

      • Stuart Martin says:

        Thank you very much James.

        The boat in question has the TWO Victron Phoenix Multiplus 24/3000/70 Charger / Inverters rated at 3 Kw each

        On the inverter side,these actually produce only 2400Watts, not 3000. As 2400 W @ 24v gives 100 amps, the two units will yield 200 amps. Is this enough to handle A/C, oven, washer/dryer loads adequately if those loads were turned on individually?

        On the charger side, these units produce only 70 Amps each for a total of 140A.

        Therefore, do those Multiplus 24/3000/70 Charger / Inverters units fit the bill or would a third unit be required to fulfill the requirements?

        Can the “Additional Victron Centaur 24V 100A battery charger for 60Hz in USA” be utilized to fill the charging component gap ? As far as I can tell, these produce only 60A @24v (100A @12v)

        All the best


    • What you need is 200A to 300A of charging at 24V and, to be world capable, this equipment needs to be able to run on 50hz or 60hz and preferably has a very wide range of input voltages acceptable. The Victron Multiplus input specs are:

      Input voltage range 187-265 v AC Input frequency 45-55Hz Power Factor: 1

      Not what you want. These are 50 cycle only units. The Victron Centaur looks great. This is it’s input range:

      Voltage 90 – 265 Frequency: 45 – 65

      The Centaur looks impressively good but the Multiplus 24/3000/70 need to be replaced for what you are trying to accomplish. When choosing chargers, you need to chose chargers that are known to be highly adjustable so you can set charge profiles without restrictions and can avoid overcharging due to frequent shifting between discharge and charge in some operating modes. I use Mastervolt 24/100 which have these input specs:

      230 V (180-265 V), 50/60 Hz

      What they don’t tell you is the derate the charge below 197V so it’s not really as wide a range as advertised. It’s still been pretty good in all of our uses around the world but it underlines that the specs are often somewhere between wrong and optimistic. You need to chose a product that is in use in the way you want to use it successfully in another application.

      As much as I like the Victron Centaur input specs, as a smart charger with lots of configuration, it doesn’t look like a good choice. This is the charging spec:

      “The Centaur charges at bulk rate until the output has reduced to 70% of the rated Amps, at which a 4 hour timer begins. After the timed period the charger switches to float rate.An internal temperature sensor is used to compensate the charge voltage with – 2 mV/ºC (– 1 mV/ºF) per cell. A DIP switch is available to select the optimum charge/float voltages for Flooded Lead-acid, Gel or AGM batteries.”

      This doesn’t look adaquate for your usage and I’m pretty sure I recall Victron Centaur’s removed by owners unhappy with the charging profile control. They just keep jumping to bulk and restarting 4 hours.

      It doesn’t look like any of your chargers meet your future needs but, compared to the price of the boat, installing new chargers isn’t a big deal. On the inverters, I recommend ensuring you have enough capacity to be able to run any appliance on the boat. Our Victron Pheonix 120V/60hz 3000 KW inverters are paired to deliver 6kW at 240V and they are absolute tanks. They are capable of driving short duration loads over 7kW and can even handle the inrush current of the SCUBA compressor. They are absolute tanks but they invert only and do not have charging capability as well. There is some upside in separating chargers and inverters so they can fail independently and it also avoids the Automatic Transfer Switch in charger/inverters that often fails. However, the upside of combining is the two functions can use the same components and combined is far less expensive. I went for simple and reliable.

      • Stuart Martin says:

        Hi James

        Your advice is so much appreciated.

        I have travelled over to perform a personal inspection and hopefully make an offer on that 50Hz N55 within the next few days. Would the need to replace all of the chargers/inverters suggest that I should defer making an offer? ie would the cost of converting it to a Dirona type power solution eliminate any pricing advantages of a 50Hz boat purchase that you had mentioned on the “Dreamers” site and that I have now found first hand. Please feel free to email me privately at smartin@mcmaster.ca if you would prefer not to discuss pricing issues on this site .

        Many Thanks


        • When thinking through the purchase price and comparing with other boats on the market, I would just factor in the cost of the charging system (and other) equipment required to get the boat the way you want it. If we were buying a new boat today, we would want to install a 50hz/60hz capable charging system whether the boat was 50hz or 60hz so it wouldn’t make a tremendous difference to us whether the boat was 50hz or 60hz.

  6. Ryan Taylor says:

    Hi James!
    Absolutely wonderful article (as is the entire contents of your blog).
    As a diesel mechanic and automotive electrician by trade, your technical articles are amazingly stimulating reading.

    Just a couple of questions if you have the time;

    When at anchor for extended periods (beyond the capacity of the house battery bank), and you run the generator to charge the house bank, do you transfer the house AC load to the generator as well? Or keep everything on the inverter? Does the battery charger sufficiently load the generator with the house load still on the inverter?
    I guess that raises my second question.
    I understand you have quite a few computers and a NAS and other assorted electronic gear on board; do you use a supplementary UPS to power these for periods such as above; switching between the inverter or generator as the AC service supply, and for general power conditioning, or is the AC system on board clean and stable enough to not need supplementary UPS/conditioning?

    Unfortunately I found your blog and learned of your travels too late and missed your time here on the East Coast of Australia. If you ever find yourself and Jennifer over here again I’d love to shake your hand and buy you a beer. Would be the least I could do in thanks for the amazing entertainment and interest that your blog provides.
    Hope all is well.

    Ryan Taylor

    • Thanks Ryan. We’ll always accept the offer of a beer and would enjoy the discussion.

      We essentially run the boat like a small apartment and no longer make any effort to conserve power so the generator runs around 1/4 of the time when the batteries are in good shape and now they that they are getting close to end of life, the generator is running even more. The way we are set up, the generator comes on when the battery discharge level gets down near 50% and runs until it’s back to about 85% when automatically shuts down. With this system, we mostly don’t care how frequently it cycles. The system sends daily email showing the gen cycles over the last week and summarizing the generator time and battery time per day.

      We have a lot of charging capacity on board and can fully load the generator on charging alone so the generator load levels average fairly high.

      You asked about the inverters. The 120V inverter stays on all the time and 120V power is always available and it always at least 20% loaded which is ridiculously high but we have satellite gear, computers, entertainment systems, the fridge, etc. all running. When the generator turns on the inverter switches the load without interruption from inverter to generator. Generally I’m not a fan of automatic transfer switches as they are frequent failure points in inverter designs and also in larger data center designs as well. A slightly better approach is to leave it inverting all the time but this gives up some minor efficiency and we prefer to have the charging capacity of the inverter available. However, we have 200A@24 without using the inverter to charge so we technically don’t need that capacity.

      The Nav computer and monitors and navigational critical equipment are all UPS protected. We should a bright red indicator light and send email when the UPS is discharging. We should a yellow indicator light when the UPS is charging but not yet fully charged. The NAS, entertainment, and satellite systems don’t have UPS protection and will go down if the 120V is interrupted. All these devices do have power conditioning. I don’t know it is necessary but we had an internal circuit breaker pop on the entertainment system in the early days so we went to conditioned power and it’s not been an issue since. In the early days, 120V interruptions were frequent do to inadvertently overloading the system with, say, the hair dryer and the microwave at the same time. We did two things to avoid: 1) I put large active cooling fans in the top of the inverter and turn these on when the load goes over 50% — these allow the system to reliably produce it’s full rated output, and 2) we have a load shedding systems that dumps the least important loads during momentary peaks. At this point, 120V interruptions are rare — we’ll go many months between instances.

  7. Alex Benson says:

    Hi James: While you are researching Blue Sea and other relays to parallel the alternators, I’m curious whether an Automatic Charging Relay might be the ultimate choice. See https://www.bluesea.com/products/7623/ML-ACR_Automatic_Charging_Relay_with_Manual_Control_-_24V_DC_500A . This relay has logic to parallel the alternators only when there is a charging voltage. It also has a remote panel override switch with status light.

    This means the on engine alternators would always be sharing the charging load when underway. It also means that when on shore or generator power, the AC powered chargers would cause the relay to close, charging the engine battery bank as well.

    I like this solution and am curious if you can see a downside.
    Thanks again. Alex


    • Alex suggested just using the Blue Sea Systems ACR. This is what we did on our last boat and it worked perfectly well so, yes, good suggestion. Years back we did a Passage Maker artaicle on the overall power design of our last boat — I think it’s posted on mvdirona.com.

      So, why didn’t I jump on this solution. Two reasons? First, I want the switching under programatic control and I want it to be able to deliver power from the start alternator to the house bank and also to be able to deliver charge to the start bank when needed due to long periods without the main engine running. The ACR will work fine but I prefer to control the system with my own software. Teh second reason is it’s a simple problem. This one is kind of naive on my behalf but we really aren’t doing anything difficult. We have a max continuous load of 177A and a max peak load of 190A. Not hard at all. So I bought two Prestolite 200A relays which are cheap and marked the problem down as “solved”. The first one failed in 30 days and the second one didn’t last quite as long. OK, got it. The 200A spec was optimistic as they so often are. So I put on a Trombetta Bear rated at 225A and it went 13 months which isn’t a disaster but isn’t close to waht I want. I took apart the relay and rebuilt it and it’s worked fine since and runs a constant 104F (40C) under high load.

      Because I’m well under peak load for commodity relays, I’m convinced this is a pretty solvable problem but I haven’t succeeded yet. I really like the Blue Sea Systems and Kissling relays recommended because they are bistable. This means they use power to open or close but are mechnically connected in the close and open position rather than held in by the coil. I like this design considerably and will try onne of them.

      • Chasm says:

        Let’s take a step back.
        Is there an underlying problem? If so a bigger hammer is not really a solution. 😉

        Parallel alternators. What about the battery banks, are they also connected by the relay? Equalizing the batteries that way would add a significant amount of current.
        That seems kind of obvious and was probably recognized & solved (say with diodes) during modification but sometimes it’s better to ask the stupid question anyway.

        Another option is to put a clamp ampere meter in peak reading mode on the cable to get an idea about the real world currents during switching.

        • Your rigth to think through and perhaps remeasure the actual loads when you have a part that is operating well within specs and yet has failed. Equalization sounds like a big current producer but actually is very low. Equalization is done on fully changed batteries and, as a consequence, the altual current flow is fairly low even at the high equalization charge. Underway, which is the only time this relay is on, the highest current that can cross the relay is about 200A and the most continuous is 177A. The limiting factor is the 190A alterator. When it is at room temperature it actually get produce nearly 200A for a very brief time which warms it up which drops it down to the specified 190A. As it continuous to warm under load, it’ll settle down to max continuous output in this application which is 177A. It can’t prodcue more and we are isstrumented and know it does not.

          There is one condition where far more than 190A can be available and that is when on shore power or on generator. In that mode, there is 300A available. However, the relay is currently only connected when the engine is running and, under these circumstances, the generator is never run and, of course, it’s never plugged into shore power with the engine running. In this usage pattern, we are not able to exceeed 177A continuous. However, it might be worth me changing the control logic to not allow the relay to close when on shore poower as a way to prevent that unlikely but possible configuration.

          I’m talking to the manufacturer, Trombetta, at this point to determine if it’s just a manufacturing or component failure or if the relay is not able to support this application. What it looks like has happened is the synthetic slider that supports the contactor plate moving up and down on the central shaft has broken up (likely at least partly due to heat). At that point the contacts are not firmly closed so massive heat is produced and the contacts welded together. This irreparably damages the contacts but, since I don’t have a spare on board, I cleaned them and built small shims to replace the failed part. It’s been back in service for a couple of weeks now and, even in it’s current hobbled state, it seems to be operating perfectly. At load it runs 104F to 110F.

      • paul greenhalgh says:

        Hi James…a bit of a micro question. I know you are using Balmar MC614 regs ( I use & like them too) but to combine the outputs of your alternators, are you also using Balmar’s CenterFielder?

        • No, both alternators have their own individual regulator and we don’t use a center fielder. This is one of those issues where people work very hard to solve an apparent problem that really isn’t there. When running two alternators or two charging sources of any type, people notice that one is charging and the other one hardly is or is off. They feel like the charging sources are fighting each other and so want to “fix” the problem.

          Let’s look at what is going on and then talk through why it’s not a problem. Batteries go through three broad charging phases (Balmar devides it up into 12 phases but there really are three overall phases. The first phase is bulk charging where the regulators give a target voltage and the alternators produce as much currrent as they can — they run at max output (it’s just about impossible with AGMs to have so much charging capacity that you exceed the batter acceptance rate). During this phase, you get max alternator output current from both alternators until the target voltage is hit.

          The next phase is acceptance. During this phase the voltage leven is held constant and the amperage the batteries can accept slowly goes down until it gets down to aroumd 1 or 2% of overall capacity at which point they are charged and the system switches over to fload mode.

          It’s during this acceptance phase that the concern arrises with many owners using two alternators. During this phase the batteries will accept (that’s the reason for the name) a certain amount of current. Initially it’ll be max charging system output but this value falls continuously until the battery is charged.

          If you have two 100A alternators and the batteries are accepting 80A, then most owners want to see each alternator producing 40A. but, they might see 1 producing 80A and the other 0A. It does seem like a problem but, if you think about it, the batteries are charging as fast as they would with a single 200A alternator so there is no problem there. The only problem is one is doing the work and the otherone isn’t.

          “Who cares?” is the short answer but it is worth looking deeper. With one alternator doing all the work, it’s spending much more time at 100% output so will get hotter and wear more. It’s harder on the bearings, etc. to have it pegged. There is some value in having something close to ballanced so one isn’t always maxed out but the value is pretty minimal and remotely close is good enough.

          I put 4,100 hours on the previous boat with two alternators never worrying about it. And we have put on 7,800 on this one again, just not worried about it. I tune the two regulators such that they are “close enough” such that both alternators using contribute something. Right nwo, I have one running at 158A and the other running at 64A. It’s fine. Earlier tonight we had two air conditioners and the oven on and they were both running flat out — these alternators can do that for hours at a time so I don’t worry much about ballance.

          The immportant things to think about: 1) the two alternators won’t be ballanced in productionn during the acceptance phase and it really doesn’t matter, 2) they are charging your battery bank as fast as a single alternator of the same agregate capacity of your two alternators, and 3) there is some (small) value in setting the two regulators close but don’t sweat it once they both doing something during acceptance. And remember that this is very easy to do with Balmar Maxcharge systems and other fully tunable regulators.

          • Larry Williams says:

            Hi James,

            Forgive me for jumping in late on this post, but while reading your reply to Paul regarding the Balmar MC614 alternator regulators a question comes to mind: Is there an output, sensor, jumper location, or anything internal on the Balmar MC614 Regulator where one could determine when the regulator is in bulk charging, acceptance, or Fload mode? If so, perhaps a simple circuit of some sort could be created so that when the house bank regulator goes into bulk charge mode a relay could be closed to automatically put the start battery alternator on line with the house battery alternator to charge the house battery bank. And and then later when the battery bank regulator goes into Fload mode the circuit would open the relay placing the start battery alternator back onto the start battery bank. You could still have the manual switch, if desired, but also a little green light next to the switch to indicate relay status, and perhaps a red light and alarm if the relay is supposed to be closed, but isn’t. If nothing is apparent under the regulator cover, perhaps a call the Balmer people would advise whether this is even feasible, or not. This way, the relay would only operate when the main engine is running, and only when additional charge capacity is needed for the house battery bank, but automatically and seamlessly.

            Your thoughts and tweaks?

            As an X-MMC(N), USN dreamer, I find your web site to be absolutely awesome, very inspiring and extremely educational – my favorite. Thanks for putting in the time and hard work to make it possible, for sharing your incredible knowledge base with us and especially for answering our questions. James, you and Jennifer are to be applauded!

            • An interesting approach Larry and, surprisingly, I do something very similar to what you suggested. Here’s how the system works. There is a 500A DC contactor in parallel with the manual start bank parallel switch. Either the manual rotary switch or the contactor can parallel the start battery bank.

              This large DC contactor is controlled from software Jennifer and I have written that runs on the navigation computer. This software system has access to all the data on the NMEA2000 bus and, in facts, stores absolutely everything in a relational database every 5 second. It’s not related to the current discussion but it’s great to have historical data going back years.

              Because the software system knows the current house and start back charging rates, it knows whether each is in float or not. It also knows if we are plugged into shore power, whether the main engine is running, etc. The software system closes the relay when the main engine is running and the main alternator is producing. This way we have the benefit of both alternators whenever the main engine is running. We have taken to running 2 or 3 air conditioners all the time, so we need the power of both most of the time.

              We also close the relay where there is a power source whether generator or shore power and the system is in float mode. The logic here is that the start batteries are basically never used so almost never draw down much but they still need a float charge periodically. This idea came from replacing our start batteries after 6 years. 6 years is actually very good but, the more I thought about it, the more I suspect that the start batteries are not getting proper charge. Telephone switching station backup batteries last close to 20 years. Batteries that don’t get used but are never over-charged, excessively discharged, or even cycled much should last 10+ years. Conclusion, the start batteries are not well enough managed on Dirona.

              So we put on voltage monitoring and now alarm on high than acceptable voltage and ensure they are float charged whenever needed. I believe this should make a huge difference in their longevity but it’ll take a decade to prove it.

              We actually can’t tell if the system is in float or not directly but a good and very reliable proxy for “being in float mode” is voltage between 26V and 27V. Higher voltage is bulk or absorption. Lower voltage is not charging or the charger is not keeping up.

              I suspect that this automatic battery management system should increase the life of the two start battery banks on Dirona.

  8. Chasm says:

    There is also the option to use a different relay, say from Kissling. See http://www.kissling.us/en/products/relays-contactors.html
    OTOH their prices are roughly in the Blue Sea range, so going with something that is known and replaceable in the marine market seems to be more sensible.

    • Another excellent find. As soon as I get in a more economic satelite coverage area, I’ll check them out. But, from just scanning the intro page, they look excellent. Bistable relays of up to 1,000A. Thanks for pointing me to Kissling Chasm.

      • Chasm says:

        Lets add even more relay choices.

        High amperage relays beyond 200A are not that common. Search method also plays a role, I mostly used octopart.com and did not find Trombetta parts. Gigavac has a handy competitor cross reference, easy to find more companies that way.

        Kissling, the 1000A bi-stable relay is a bit pricey at $2k, the 300A version is more affordable at $200.

        E-T-A offers the PR60 (normal) and PR80 (bi-stable) power relays, both come in a 300A version. They look like the Kissling relays to me so a price comparison might be be interesting.

        Kilovac / TE Connectivity offer several high amperage DC relays. The EV200 and LEV200 lines are 500A both rated, prices start at $90-100 depending on configuration. Available from several distributors, estimated 10k+ make&break cycles at 28VDC 500A.
        They also have a bi-stable variant, the EV200P, $330 with a 12V coil.

        Gigavac (founded by the ex Kilovac management team after the TE buyout) unsurprisingly also has a large line of high amp DC relays including latching variants. They seem more modern are but are harder to price.
        GV200 as direct replacement to Kilovac LEV200, ~$120
        GX14 350A 24V coil, $130 – according to one datasheet 100k+ make&break switching cycles in 75°C ambient
        MX14 400A 24V coil, $150 – mil-spec rating
        GX16 600A 24V coil, $240
        MX16 600A 24V coil, $270 – mil-spec rating
        GXL14 and MXL14 are the latching versions, I was not able to find prices.
        (!) Beware test and rating constraints like 400 KCmil cable (approximately 7/0 or 200mm^2).
        Going with the MX versions might be interesting for the better vibration rating, the price difference seems to be minimal compared to other brands. OTOH the GX series is already intended for boat, vehicle and rail use.

        From the truck / heavy machinery world comes the Cole Hersee / Littelfuse 24824-01, a 225A continuous duty relay for ~$100. Hm… aka Trombetta Bear.

        Albright (albrightinternational.com) seems aimed at the industrial / TelCo market but has some interesting stuff including latching versions.
        Say the SU280-1179MP 350A latching 12V coil, sold as winch isolator in the offroad market for £48 a pop.
        A quick look shows that there is more in the DIY electric car market. Mostly older style and surplus, low prices though.
        The Albright SW180 200A is sold as part of the SmartGauge.co.uk battery systems. (Bought by Merlin power systems, also sold by Balmar.)

        I’d be tempted to simply use a Kilovac LEV200 series relay, ~$100 in single quantities from various distributors, estimated 10k+ make&break cycles at 28VDC 500A. Pretty much a direct replacement for the Trombetta, what could go wrong? 😉
        Or maybe Gigavac for something a bit more shiny.

        Since this post is already way to long, one more thing:
        Going bi-stable needs a bit of additional attention. Most relays seem to use separate set and reset coils (Which come in a high and low side switched versions). Others use current reversal. Some might be impulse relays.

        Given the price differences staying with normal relay might be more effective.

        • Nice job Chasm. I’m lucky to get the benefit of your research. I’m in conversations with the Trombeta service team and they are getting a review of my tear down pictures from the engineering team. Let’s see what Trombetta concludes. The interesting thing (at least for me) is after my primitive rebuild of the welded up relays, it’s been operating in production for two weeks without issue and it measures only 104F to 110F under load.

          I agree that the Kilovac LEV200 and EV200 look pretty interesting. Both rated at 500A. The bistable version prices out at just over $300 and the coil held version with built in economizer is only $100. Incredibly inexpensive. Thanks for the research.

          • A follow up to my post yesterday. Trombeta went through my pictures and concluded that the relay failure was caused by shock breaking up the plastic slider insulates the contact plate from the central slide shaft. Their conclusion was no manufacturing defect — just a failure caused by the shock and vibration conditions the relays is operating under. Their recommendation was a somewhat amusing “buy more and get spares.” I suppose that approach might be good for the Trombeta business but, baseed upon your research, the Kilovac LEV200 looks like better value and I think I’ll give it a try. My goal is to use parts that can last 5 to 10 years rather than “buy spares” although we certainly have plenty of the latter.

            My inexpert post mortem having torn down the Trombetta Bear is the plastic slide insulator Trombeta is using for the contact plate is not sufficiently durable. I would think the vibration it would see in a boat is likely less than in manufacturing and RV applications. Certainly it didn’t last nearly as well as I was hoping it would. I suspect they have a design problem with that plastic part and I’m planning to find a relay that can hold the load and last 4 to 5 times as long. Given all the suggestions you folks have found, I’m pretty confident we’ll find a relay easily able to hold this load in these operating conditions. Thanks for the help in rounding up alternatives.

            • Tod Sanger says:

              Hey James,

              You are living my dream, congrats! I am hoping in the next 3-4 years to acquire a Nordhavn and set out with my wife on our own adventure. In the meantime I’m trying to digest and research as much as I can to prepare for that day. I can’t tell you how your website has helped me in every aspect. I find your idea of running the ac while underway without using the generator a very attractive option. If you don’t mind me asking what was the approx. cost for the setup on Dirona. Thanks!

              • The dual alternator solution is not that expensive but there is more to it than that. What you need is a high output 240V inverter that is capable of driving all your on board equipment. For us we use a pair of Victron Pheonix 3,000kw at 120V inverters setup to produced 6,000kw of 240. The inverter is expensive — I don’t have exact number handly and it was purchased in New Zealand but I would expect around $6,000 for the pair. They need to be installed which is a fair amount of work. They need a high amperage MBT and proper fuses, heavy 24v wiring on the DC side. The AC sides needs a new wire run to the breaker panel where I added a new position to the ships selector switch so that you can power the boat via 1) shore, 2) gen, or 3) inverter rather than just the first two options. This is where most of the work and cost is.

                Then, for power underway, we already have a dual alternator setup and this is fairly commmon where one powers the start battery and the other the house. Cascade Engine delivered the new John Deere main engine wiht a Balmar 190A@24V alternator on the house and 85A@24v on the start system. We replaced the start alternator with the spare 190A@24V alternator bringing up the overall power available to 9KW.

                The second alternator can be made available by closing the start battery parallel switch. We do this all the time and don’t want it left paralleled when the system is not charging so we have a 225A@24V contatactor that closes this circuit. We close the circuit when on shore power and not discharging to keep the start batteries charged. And, of course, we close the circuit when the start alternator is charging to make it’s power available to the house system.

                The Balmar 190A@24V alternators are over $2,000 each which is a bit on the high side. However, they are essentially Leece Neville large frame altnerators with some tweaks. Leece Neville are heavily used on over the highway busses and are both widely available and very econommic. These alternators are tanks and can be abused incredibly and they will just run through it.

  9. Alex Benson says:

    James: Wondering if you have replaced the relay installed to parallel the start alternator with the main bank? Last I recall you had repaired the “biggest, smokin’est 24v relay on the market” by Trombetta Bear, but were hoping to replace with a new unit. Although a bit more costly, this BlueSea product would seem to handle the load, and the manual override may also be useful. See https://www.bluesea.com/products/7702/ML-RBS_Remote_Battery_Switch_with_Manual_Control_-_24V_DC_500A Your thoughts? Thanks…. Alex

    • Alex, you are my hero. That switch might indeed be a better choice. IT’s rated at 300A when switching under load and is rated at 500A continuous. Given that I only need 195A, that’s excellent. All switch gear installed in the ER or Laz needs to be derated since operating temperaturs are higher than most gear is spec to but this gear is rated at 50C which is also higher than usual. I deffinitely need to learn more about this unit.

      The Trombetta Bear gave a year of great results but failed a few weeks ago. I don’t have a spare so decided to take it apart. I drilled out the rivets and took it apart and found that a synthetic insulator had failed which allows the contact plate to get loose which drove up resistence due to poor conenction, which lead to high heat, which welded the contacts on. I fabricated replacement parts and put it back together and it’s operating super well for the last few weeks and doesn’t seem to get over 104F. I also put a small muffin fan on it to help with the longevity.

      I’m well within the design point of the Trombetta Bear so it may be that I just had a rare fault and a replacement unit will last far longer. It’s really hard to tell. My usual solution is to go with large safety margins over rating with switch gear since they operate in nasty conditions and faults are a hassle to deal with. I’ll send pictures of the fault in to Trombetta and get there assesment and I’ll research the Blue Sea systems switch you pointed out. Thanks for drawing my attention to that one.

  10. Mark McGillivray says:

    Hi James,
    N5002 is in dire need of a power revamp and your article and experience is a great help. Would you mind advising what 190 amp alternators you chose and why?

    • Sounds like you have a good project underway. Technology especially inverter tech has come a long way over the last decade so it’s good you are carefully researching what is possible. On alternators, Cascade Engine Center the Deere distributor that supplied the main engine for Dirona to Nordhavn, supplied the engine with a Balmar 190A@24V house alternator and a Balmar 85A@24V start battery. Both are regulated by seperate Balmar 624 external regulators. I’ve since upgraded the start alternator to be identical to the house 190A@24V. The Balmar alternators appear to be Leese Neville alternator frames with Balmar parts or they might just be OEM built Leese Neville alternators. These are very durable alternators that we run mercilessly at full output for 100s of hours in a row. I generally don’t recommend running alternators over 225F continously but we don’t take our own advice on these two units and, 1000s of hours later, they just keep going without a fault.

      Leese Neville are common in the bus and truck industry. Particularily buses where large loads need to run without a seperate generator in many applications. The Leese Nevilles are generally less expensive than Balmar and many aspects if not all aspects of the alterantor is the same. I’m super happy with Balmar and think you would be happy with them or any other Leese Neville derivitive.

      Best of luck on your power upgrades.

  11. Alex Goodwin says:

    A late and (possibly) dumb question, James:

    What happens when your mean power draw exceeds what’s available from shore for an extended period?

    Shore power supplies what’s available and your batteries draw down from the net deficit, with genny kicking on as needed?

    Or has that been rare enough to not worry too much about?

    • If average power draw exceeds shore power capability for short periods of time, the batteries provide the bridge and the system can peak to 25A while plugged into 15A. If the average draw is higher than shore for extended periods of time, the batteries will discharge. If the water heater is warm, then it get load shedded first. If the batteries continue to discharge, the system will shed HVAC and the hot water heater. If they continue to decline, alarms sound and email is sent. The generator will take over from shore power failure but not from falling behind correctly functioning shore power.

      • Alex Benson says:

        Hi James: How does the “system” shed the HVAC and water heater? Is this controlled via the Maretron software? I suppose if you were leaving the boat for an extended period and the shore power was minimal, you could disconnect and let the generator recharge as needed. After cruising BC with its various crazy AC power sources, and having to shed water heater or charger so the toaster or microwave could operate for short periods, Dirona’s flexible power system is the way to go!

        • Alex, the HVAC and water heater are shed by custom software that monitors system load and sends off/on requests to a Maretron DCR100 that turns contactors off/on controlling the HVAC and water heater circuit. The 50A HVAC system is switched by a 63A conactor and the 15A water heater is switched by a 20A contactor.

          You were asking about unreliable shore power. The way the system is set up, as long as there is shore power, we use it. However, if someone inadvertently disconnects the boat, a shore breaker pops, or there is some other utility outage, then the system will start start the generator when needed and then shut it off again once charged. If the shore power doesn’t return, the generator will run as needed. As soon as the shore power is restored, it takes over.

          I also get email when there is a shore power interruption and there are on-boat alarms and lights warning of a fault.

          You are right that auto-load shed makes the overall system much easier to manage. You hardly notice the HVAC or water heater going off for a minute or two during a peak but, without load shedding, you would heading out to reset the shore power pedestal breaker.

  12. JP says:

    The Victron inverters ( atleat the multi plus) can also automatically the generator.
    Plus it has the power assist mode, where t will only accept a much shot power as needed and uses the batteries for the rest of the energy
    plus with their new CCGX display/control unit, it will even emil you if the batteries are getting low

    • Thanks for the note JP. The Victron inverters we are using are simple and dumb units that produced 6kw at 240V but don’t charge or do anything else. I actually slightly prefer seperate chargers and inverters but there are many advantages to combind units. Combined inverter/chargers are less expensive than seperate components and take less space. We do use a combined 110V Inverter and charger from Mastervolt and the Mastervolt system has the scame capabilities as the Victron system you pointed to. It’s pretty common to include auto-start signalling and power sharing in modern combind inverter/chargers.

      Power sharing won’t work when running a 60Hz boat on a 50Hz dock connection or vice versa so, as a consequence, we don’t use it. But, what we have implemented a similar capability on Dirona. For example, we are currently plugged in Surfers Paradise Australia plugged into a 50hz 16A connection. The boat is running on 60Hz and consuming at peak over 25A even though we are running set to draw no more than 15A from the shore connection.

  13. Peter, your approach sounds like a nice design. I particularily like your choice of going 48V. I’ve also heard good things about Magnum inverters. It’s still too early to know for sure but the Victron’s we’re using look pretty good so far. I like them because they are simple, just deliver the load and never shut off and can deliver prodigous peak power (right up there with our 12KW generator). But the only real test is time.

    I can see upsides to your use of the battery equalizers. My only concern is that each can only deliver 100A and you are giving up 9% efficiency at peak and likely up to double that at some off-peak loads.

    You were asking if we can run off phase-to-phase wiring (2 phases from a 3 phase configuration). Yes, that fortunately works fine and is actually a common configuration in some places in North America. In this config the voltage delivered is 208V which can, under high load pull down to below 200V but it works fine. Our shore power cable has only 3 conductors: Phase 1, Phase 2, and ground. If you can get us a good ground and something approximating 240V across phase 1 nd phase 2, it’ll run fine whether phase to neutral or phase to phase. The boat can tell the difference and it’ll work.

  14. James,
    Thanks for the great blog. I set up my boat quite similar to yours except I opted for a 48V main bank with a Magnum 240V split phase inverter. As you say, no need for a single phase inverter when you go this route.

    For battery balancing (in series) I use 3 x Vanner 65-100 equalizers which keep all batteries at identical voltages. I would recommend this setup even for a 24V bank so that the two batteries stay in sync. If needed you can also pull 12V out of the bank without losing sync on the 24V. In my case I use the house bank for all 12V loads (gen start, nav system etc) without needing separate 12V batteries. See http://www.vanner.com/manuals/65-80.pdf

    My only concern occurs when some marinas provide two phase power by using 2 legs of a 3 phase source. In this case a balancing transformer is needed. I see you have one, but my boat did not and was quite a learning experience to set up both a balancing and isolating transformer in the same device. Most split leg transformers can be set up to do this job and it might be worth checking you can still operate this way the next time you are at a marina with "240V" power.

    Best luck in your travels and thanks again for the blog.


    PS. I note the USCG at Depoe Bay are ‘experts’ at bar crossing http://youtu.be/zs4uQ_HBfXc
    When caught in breaking sea they use reverse to depower the wave and reduce the chance of a broach. If you are ever chased by a breaking wave again, I would recommend full reverse power (not full forward!) as the boat will not gather speed down the wave which is the kinetic precursor to a broach.

  15. Hi JC, it’s funny you should ask. In the picture at the top of this blog posting the domes are "white" but one of them looks pretty gray partly due to light but mostly due to long running with a side wind at light load. So, when we arrived in New Zealand, we painted them grey. I think they look better now and I don’t have to clean them as frequently. We find that grey disappears into the sky and makes the domes less obvious/intrusive. We actually think the boat looks better in with gray domes and there is no question that it is easier to maintain. Pictures after landing in New Zealand are all grey — I’ll be interested if you agree that it’s somewhere between aesthetically neutral and positive.

  16. JC says:

    This question is off this topic but I just noticed, are your satellite domes grey? or is that soot from the engine exhaust covering them? That appears to not be a pleasant place for washing. Maybe it is just the clouds shadows. You have a supreme website and I’m "stealing" your ideas 🙂 Thanks!

  17. A split phase inverter like we are using, does produce 110V phase to neutral so we could drive the 110V system directly from the 240V inverter. The challenge is most Nordhavns only have 1 phase of 110V rather than the the two seperate circuits used in most North American homes. So, it would be hard to get anywhere close to phase ballance running the 110 circuit unmodified off of the 240V inverter.

    The easiest solution is probably what we currently have where both the 110 and 240 circuits have their own inverter.

    The 8A loss at 12V does seem credible and is high but tolerable. I thought you meant at 8A at 240 which is close to unexplainable. I think actually could live with the loss of roughly 100A on the backup circuit side.

    I like your level of redundancy. We have a spare 110V inverter, probably should have a spare 240V, but we don’t think we can find the space for a backup generator. Were we to do the boat again in the same size, we probably would stay single generator. If we did a 60, I’m not sure. We might easily go with a backup generator. We have never had a generator disable but it certainly can happen. I guess it depends how satisfied we end up using the main as a backup 9kw generator. Since the expected need is quite unusual, we might actually use the main again as the backup generator on a new build.

  18. Bob Ebaugh says:


    It’s not quite that bad! The circuit is 12VDC into the Quattro, 240/60 cycle out of the Quattro fed into the transformer, with the output of the transformer open and not connected to the ships systems. The 8A was at 12VDC, the input to the Victron Quattro. An ACME isolation transformer spec is 90W loss at no load, so add in a small loss for the inverter and that’s exceptionally close to the spec. This was not the brand of transformer in the boat, but it was similar. Maybe there are some that are more efficient? That 8A is not a killer, but significant. On this boat, it was probably 20% of his overall usage and on my boat would be closer to 33%.

    Your boat doesn’t have that problem until you go into the 110V failover mode described in the blog post. But on a clean sheet install for a US 240/120V vessel, I would consider an inverter that can natively do this and skip the transformer, or perhaps use 2 inverters, just as you have.

    Personally I am a big believer in redundancy, we have 2 generators and 2 inverter/chargers wired so we can charge with both off the gens, but inverting, only one or the other can be selected for use since they are different brands. But the engine room on our boat lends itself to room for that, unusual for a 44 footer. We have to lose both gensets or both inverters to have a power crisis where power would come off the main engine alternators, or a 24×7 genset depending.

    Best Bob

  19. Great question. Transformers absolutley do have a loss and that is one of the reasons why we chose to have both 4kw of 110V inverter and 6kw of 240v inverter. This configuarion gives us both the 110v and 240v power we need while avoiding using a step-down transformer and enabling us to use small individual inverters and still meeting the overall load requirements of the boat.

    The rule of thumb I use is an auto-transformer generally will cost around 10% loss. This loss is generally proportional to the power draw and there is also some power consumpiton at idle. However, loosing 8A at 240V is nearly 2kw. Something is deffinitely wrong in the case you describing. If you have the circuit diagram and the componnets used, I would be happy to look at it. There is no need to suffer 2kw loss in stepping down to 110V and fairly highly efficient transformers are pretty inexpensive.

  20. Thanks for the comment Raimund. You asked what is the 24 hour power consumption aboard Dirona and what capacity the battery bank is. We have 1020Ahr of battery bank. The draw varies all over the place with night draw down in the 20A range and draw during the day ranging from 35 to a couple of hundred amps depending upon what is running. The run the batteries down to 50% and then back up to about 85% on each charge cycle and usualy run two cycles a day. Under unusual circumstances more and just about never less. The boat is our house and we consume a fair amount of power.

    You argued that paralleling batteries leads to substantially reduced lifetimes. I generally agree that paralleling will reduce the lifetime of the bank to worst performing string of batteries and this will decrease average lifetime slightly. But that’s the reality of large battery banks — at some size, it’s hard to find single cells that have sufficient capacity at a commodity price point. As you know, since lead acid batteries are roughly 2V per cell, 24v strings are formed by putting 12 cells in series. In the case of our boat, it was desiged using Lifeline AGMs in the 8D form factor so 24V requires two batteries in parllel. If you can live with 255Ahr of capacity, then you can avoid paralleling strings. In our case, we wanted to have longer periods between generators runs so we 4 parallel strings of 2 8Ds each. It might be possible to source 1000Ahr 2v cells but re-engineering the battery storage and hold downs was unappealing, so we went parallel. There is some shortening of average battery life in this configuration but we don’t expect the difference to be all that large. Just about all boats end up with parallel strings in order to stay on a high-volume battery form factor which lowers costs while still getting the desired capacity.

  21. Thanks Peter. I know you have a vey high standard in systems design so it’s great you like the approach we outlined here. Thanks for the feedback.

  22. Bob Ebaugh says:

    Hi James,

    That’s a great system. We use the same concept of a universal battery charger and inverters to power our 120V 60 cycle boat at European power marinas. One day we will add enough inverter power to kick one of the AC units for sleeping, but it works for everything else.

    But a question, I recently installed a Quattro 240V inverter charger in someone else’s boat, and fed the AC output into the isolation transformer for the exact same reason…to power 120V requirements. It worked fine, but there was a parasitic load of about 8 amps on the batteries because of the transformer primary, even with absolutely no ship draw on the transformer. At anchor, for everyday use that’s not trivial. I’ve wondered if that was this particular isolation transformer or would apply to all. Can you comment on what you see?


    Bob Ebaugh
    MV Mar Azul

  23. Raimund Müller says:

    Hello James,

    You made a perfect Job.

    Many years ago I run a solar energy Company in South America.
    We faced similar problems: Grid connection with
    voltage drops to 180V, generator and solarpanels for back up.
    So I made a similar system as Yours.

    My question: In order to recieve an extended battery life time,
    I calculated a battery volume of 10 times of the daily
    energy consumption. In my house I needed 100Ah/24V per day,
    so the batteryblock was 1000AH/24 V. I used 1000Ah/2V batteries
    in line. If you connect batteries in parallel you will have
    uncontrolable currents, depending on the internal resisctance
    of the single battery. This will drop the lifetime dramaticly.
    What is your daily energy consumption on Dirona and what is your
    battery capacity?

    Best regards


  24. Hayden says:

    Hi James,

    Absolutely the best information I’ve ever read about operating a 60Hz boat in a 50Hz environment without going to the expense of installing a dedicated frequency converter. Sufficient battery capacity with the 2 X Victron inverters providing 6kw, along with a multi-voltage/frequency charger is a great idea.

    Your blog has been a wonderful resource.

    Phuket/Krabi Thailand

  25. You are absolutely right Frank. All the same components used much the same way. I suspect knowing how UPSs are built probably influenced my thinking on the boat electrical project.

  26. Frank Ch. Eigler says:

    Fun design. It reminds me of midrange double-conversion UPSs for humble computers.

  27. Good question Steve. Both alternators have their own smart regulators. We use Balmar MC-612s and really like them. These regulators are both durable and incredibly configurable. We ran them for 4100 hours on the last boat and over 4400 hours on this one and never seen a fault.

  28. Good hearing from you Jacques and thanks for the feedback.


  29. Steve Heath says:

    Hi James

    I enjoyed your dissertation on the modifications to Dirona’s electrical system. Being a boat owner myself, I’m always interested in the technology of boat systems and how to make things work better. Great idea to install a large start alternator and be able to select parallel it with the house alternator to accommodate high power demands like air conditioning. But when your start alternator is paralleled with the house alternator which voltage regulator takes control? Are they both 3 stage?


    Steve Heath
    Gig Harbor

  30. Jacques Vuye says:

    Well, here’s a masterpiece in a boat electrical systems engineering!
    I like the whole idea of redundancy and fail-safe without giving up space.
    This one is also definitely an additional piece added to the specs of my future boat!

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