willys_wonka
Member
Hi all, I have a 40' trojan with twin 6-71 DD, and there are 3 different battery setups. First two are the stock system: 8D batteries, one for each engine but the port one is also used as a house battery running water pumps, interior lighting etc. The 3rd bank is 450AH of golf cart 6v batteries, powering a 2kw inverter running a fridge, microwave, and various electrical outlets in the boat. The PO set up this last system to only charge when the boat is plugged in at the dock, no onboard charging capacity. I found that inadequate as I spend a lot of time on the hook, so I installed 600w of solar panels which keeps everything fresh except on the wet months of the year. But since we are motoring from anchorage to anchorage it seemed crazy to not be charging this last bank when the engines are running, so I disconnected the starboard engine alternator from the start battery and connected it to charge this bank.
These engines light up immediately so I wasn't too concerned about the starboard battery going flat, but of course I can only start the engine so many times before that battery will be toast. Often I have to use an emergency solenoid to also use that battery to start the port engine, as the port battery gets pulled down as we sit at anchor. Long story short, I want to be able to charge the starboard battery as well as the port battery and house bank, all three batteries with different needs, with two alternators.
Recently a battery isolator came into my hands and I set it up so that the port engine alternator will charge the starboard battery, but we won't draw from it when we're using the port battery at anchor.
But here's my concern: the port battery is constantly being drawn way down. The starboard battery gets drawn down only for a few seconds at startup. My fear is that while the alternator is pumping out all that juice for the port battery, the starboard battery is going to get boiled alive. Is this a valid concern with these batteries? What's my (inexpensive) alternative?
These engines light up immediately so I wasn't too concerned about the starboard battery going flat, but of course I can only start the engine so many times before that battery will be toast. Often I have to use an emergency solenoid to also use that battery to start the port engine, as the port battery gets pulled down as we sit at anchor. Long story short, I want to be able to charge the starboard battery as well as the port battery and house bank, all three batteries with different needs, with two alternators.
Recently a battery isolator came into my hands and I set it up so that the port engine alternator will charge the starboard battery, but we won't draw from it when we're using the port battery at anchor.
But here's my concern: the port battery is constantly being drawn way down. The starboard battery gets drawn down only for a few seconds at startup. My fear is that while the alternator is pumping out all that juice for the port battery, the starboard battery is going to get boiled alive. Is this a valid concern with these batteries? What's my (inexpensive) alternative?