Originally Posted by markpj23
After our 2nd extended time away from the dock since purchase I feel safe in saying that our house bank is toast. There are 6 - 8d batteries less than 4 years old. Hard to believe they have such a short life but I have no clue as to how they have been treated. The right components seem to all be here: Balmar alternator controls, Xantrex inverter/chargers, BlueSeas ACRs and all seems to be functioning.
Assuming 200ah for each 8d, I should have 1200ah @50% discharge = 600ah or pretty close if I've got the math right. My Victron battery monitor showed a whopping 168ah consumed when the inverters shut down for low battery voltage (11.6 volts if I remember correctly).
My load averages 48 amps (measured by the Victron). We run a big residential refrigerator, plus a dorm sized fridge, plus some engine room blowers on 120v. Add to that my 12v loads for nav gear, etc and we are the definition of why trawlers love to travel from one dockside power connection to the next
I could go the cheaper and quick route and just swap out the 8d AGMs. I want to be able to get through the night w/o the generator and new AGMs would probably allow that. Not much reserve though.
You mean average load is 48A per hour, yes?
If so, that low voltage shut-down after 168Ah consumption was at about the 3½-hour mark?
If so, and if I understand what you're describing, yes I'd guess batteries are toast -- or maybe one battery, or one cell in one battery (or something like that) is hosed and drawing down the rest of the bank. But maybe a load test would pinpoint some of that better.
Lifeline 8D AGMs (for example) are rated at 255Ah -- so 1530Ah for a bank of 6x. I've read it's not great to parallel more than 4x 12V batteries.
A 6x bank of their 6V L16s, 400Ah each, would give you 1200Ah total. (Or 8x for 1600?) Maybe worth a look?
(Other less expensive brands exist, of course.)
Either route, or some other route, oughta be able to get you through the night without needing to start the genset... even without many reserve issues, I'd think.