Join Date: Jul 2010
Thanked 9 Times in 9 Posts
Rep Power: 6
Re: Battery Charging Assistance
That all sounds good to me. I think the easiest way to sum things up is to say that the batteries should only be on All or Both when they are charging. Any other time combining dissimilar batteries means that one battery will end up charging the other. This just wears them both down over time. It's probably ok to start from all/both only if you're trying to save time or avoid forgetting to switch to all/both after the engine is running. But it's probably ideal to avoid combining batteries until after the engine is running.
That said, dealing with the switching is a big pain. A great upgrade is a battery combining relay, or an echo charger (I just installed a relay). Lots have been written about them here. Both serve to effectively combine the batteries automatically when the alternator is running. This means that if you can start off the house bank (you nearly always can) then you can avoid switching at all. Just switch to house motor, sail, motor - no switching. The starter battery is just there in-case you leave the lights on and kill the house.