Originally Posted by W3GAC
..... Maybe our long life two bank experience was due to having plenty/ over capacity on either bank so that our typical use never taxed either bank that may be been working alone. .......
Your two bank system obviously works well for you, with a capacity of 400+ AH in each bank. Clearly, as a knowledgeable boat owner who pays attention to such things your system works fine for you.
I happen to have a two-bank system, too, but I ALWAYS keep them combined into one large 700AH bank. Why? Because:
1. I get more actual AH from the system, since I'm drawing only half as much average amperage (about 6A or 150AH in 24hrs) from the single
bank as I would from each bank alone;
2. It's cheaper to recharge them via mechanical means....I can put twice as many AH back in the same amount of run time for my generator
or main engine
3. I don't have to worry about which bank I'm on today; no need to switch....ever;
4. If any battery
in the system goes bad, it's a piece of cake to remove a battery
cable or two and isolate or remove the offending battery; and
5. If a shorted battery should pull down the bunch...and I don't notice (which is unlikely, since I have a large digital battery voltmeter which is visible from anywhere in the cabin)....then I always can run the engine/alternator or the generator
to recharge after removing the shorted battery, since these share a common independent start battery.
How has this worked for me? Well, I'm kind of a battery nut, having done quite a bit of research
in my shop and on my boat and in collaboration with other marine
electricians and battery companies and installers. I can only say that it's worked very well: I, too, get 7-8 years from my golf-cart flooded batteries, before they drop below 80% of measured capacity and I replace them.
Whether or not a two-bank system (operated as such) or a single
bank system is more advantageous depends on a host of factors, including:
1. size of the bank vs. daily AH budget
2. onboard charging
capability and means;
3. chemistry of batteries (flooded, gel, AGM
, TPPL, etc.);
4. type of cruising service
5. interest, knowledge and practices of owners.
For most small boat owners who want a reliable and trouble-free electrical
setup, I believe that the recommended single bank house battery system with a separate start battery automatically charged via a voltage follower device (EchoCharge or DuoCharge) or battery combiner is the way to go. Hands down.