Two More House Batteries for Dirona

When we’re cruising farther from home, we typically move the boat each day. The engines are run enough to charge the house batteries fully, and power is never a problem. But when out on the weekends, we often work and don’t move the boat as much, if at all.  Usually we have several computers running and, in the winter, the lights and furnace are on much of the time, so we consume considerable power. In a recent Pacific Yachting article, Portable Power, we wrote about using a portable generator to recharge at anchor. And in a recent PassageMaker article, In Pursuit of a Perfect Charging System, we described how to configure and tune the main engine charging system to get the most from it.  However, there are times when we simply need more house battery capacity than is available, and fixing that was last weekend’s project.


For start batteries, our boat came with one 8D for each engine.  These seem like overkill for engine start banks, but Cummins uses engine intake air heaters to improve starting and reduce exhaust smoke when cold.  The air heaters draw over 110A when operating, which is more than the alternators produce, so large start batteries are a requirement in this configuration.


For a house battery bank, we use golf cart batteries and argue that they are the best value available.  Golf cart batteries are sold in enormous quantity for commercial applications and consequently, they are inexpensive. At 66 lbs each, they are much easier to manage than the 8Ds, which are just over 140 lbs each. The only downside to golf cart batteries is that they need to be topped off every couple of months depending upon your usage patterns and charging rates. If you don’t mind adding water, it’s hard to find better value than the golf carts batteries.


The challenge we face with Dirona is that we have already placed house batteries in all the easy places. We have four golf cart batteries between the engines and four more on the starboard side between the engine and the hot water heater.  All are easy to see, easy to service and don’t block access to other equipment. The challenge was to figure out how to add two more golf cart batteries to our house bank without resorting to hand-fabricated battery boxes or operating without boxes.  Since golf cart batteries are six volts each, they are typically added in pairs connected in series to yield a 12-volt pair or quads to get 24 volts depending upon your house voltage level.  As a consequence, most battery boxes house pairs of golf cart batteries and there simply is nowhere left in Dirona for another pair of golf cart batteries side-by-side where they would still available for service and excessively long cabling isn’t required.


I did find a wonderful location from a servicing perspective behind the starboard engine. The steps running from the salon to the aft stateroom are directly above this location and, in a Bayliner 4087, these steps are removable as a unit offering access to the starboard transmission and potentially for easy servicing of these batteries. However, two golf cart batteries will not fit side-by-side in this location.  There is room for two batteries end-to-end, but a ½” hull stiffening member crosses through the middle.  Allied Battery produces a twin golf cart battery box where the batteries fit end-to-end,, which is worth keeping in mind for future projects. But we really needed individual boxes and they couldn’t be much bigger than a golf cart battery.  We found the perfect unit: Single golf cart battery box.  These Noco HM306 boxes fit perfectly and, as an added bonus, the price (and service) from J.C. Whitney was excellent at only $8.99. We almost overlooked this box because the exterior dimension was listed at 10 1/8”. This however is the width at the widest point, the lid. The width at the base is less than 8 inches.


The final solution is neat and tidy and adds 25% more capacity to our existing house battery bank. We now have 1,125 Ah of house battery bank capacity. It’s great waking up in the morning with more than a 60% charge instead of less than 50%.


James Hamilton


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