Need a battery guru

[billyruffn]

I arrived back on the boat yesterday. It has been on-the-hard in Trinidad since June. First thing I always do is check the batteries and there was good news and bad news. Good news was that the house bank was fully charged. Bad news was the other bank indicated 1.36V. A quick check of the chargers indicated the problem wasn’t there. I eventually traced the problem to the battery bank’s cirucuit breaker. My guess is one of the workers on the boat tripped it by accident and the guy who was in charge of periodic charging didn’t notice the state of charge in the second bank. He had the volt meter set for the bank that was fully charged and probably looked no further than that as a sign of successful charging.

I don’t know how long it’s been down, but it’s probably been several months.

Questions for the battery gurus:

1. Are these 1 year old, wet cell, 16” high, big mother Trojan 6V deep cycle batteries toast? (It will break my heart and my wallet).
2. I’ve been charging them for several hours with a 50 amp charger and the voltage is up to 13.3V and seems to be rising slowly. If they don’t come up to 14.4 (as they normally do when fully charged), will equalization help?
3. Assuming I have to replace them, does the fact that the two banks will not be the same age create a problem? (When the two banks are charging on shore power, each bank is on it’s own charger. When they’re charging on the engine alternator, they are connected together).

[BubbleheadMd]

It's difficult to say, without knowing how long they've actually been dead. Don't "hammer-charge" them though, put them on a 2-6 amp trickle charge for a few days and see if they come up to charge, and then load them and measure the voltage.

If the voltage under load collapses, they're toast. If they maintain 11 or 12 while you crank (ok, it really depends on how big a load you place on them) then they'll be ok.

[hellosailor]

The trickle may help, the equalization may help--but keep a close eye on the temperature.

After 30 days of self-discharge, some of the sulphites that have precipitated out of the electrolyte fall to the bottom irreversibly. No amount of cooking will make them soluble or reverse them again. How much capacity you may gain back, depends on how long the batteries sat discharged. Presumably at least as long as the last date that bozo was aboard.

Of course there's always a chance that the yard will do the right thing if you tell them that one of their workers tripped your breaker, shut down your charger, and now owes you some batteries.

Don't assume "full voltage" means you have full capacity, you'd have to load test them to see what harm really has been done.