Battery loses charge

[svzephyr44]

OK - new line of inquiry on my previous post.

I am losing battery voltage rapidly when the boat is sitting at the dock with the shore power turned off and no load on the DC electrical system. I have a house bank and a starter battery. With the two banks electrically isolated and the starter battery switch disconnected from the engine I get a volage drop on the starter battery from 12.8 to 12.4 volts in about 12 hours. The only thing connected to this battery would be the DC side of the shore power charger. The starter battery has a dedicated shore power charger.

The house battery bank drops from 12.8 to 12.2 volts during the same time frame with about a 1 to 2 amp load. Note that the house bank is 2 400 amp hour batteries in parallel - it should not even see the load. The batteries are attached to a Freedom 25 charger/inverter with the inverter side turned off (no AC load)

I did find one 0/2 gauge battery charger wire capped off and in the bilge area of the boat. I thought that it might be the source of the load but is is now out of the way and I am seeing the same thing.

I have toyed with the idea that the alternator diode might be burned out or shorted but I don''t know how to test for that. Also, with the engine electical switch in "OFF" I would expect the alternator to be isolated from the circuit. I also don''t have a good ammeter that I can put directly in series at the battery terminal to see what the load looks like coming off the battery but if I have to purchase one to fix this I guess I will have to do that. The panel ammeter is showing a load of 1 to 2 amps

Any and all thoughts, ideas, etc. would be most appreciated.

[wwilson]

svzephyr44

This suggestion is a long shot given the drop of both the house and starting banks, nonetheless, is there a dead cell possible in any of the batts? One battery with a dead cell will drain the bank pretty rapidly. A specific gravity test of all the cells may be worth while.

Best of luck to you,
Wayne