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paradis
08-07-2006, 10:48 AM
I have a dual battery setup. One to start the engine, and one for everything else. I recently replaced this second battery with a deep cycle battery. The previous one was a 'dual purpose' style and only lasted a year. Nothing else has been changed that I know of.

My problem is that in about 7 days this battery is dead!? The old battery had no problem that I know of other than the fact that it did not last long. Nothing else has been changed in the electrical system. I have one pair of very large gage wires that go up front to a fuse panel. From there the power is distributed through 4 fuses. When the boat is off and sitting in my driveway, I get 12.5V or so at the input side to this termial block. I put a meter across the 4 fuses and get 0.0 Volts......ie, there is nothing left on or draining the battery.

When I went out the other day this battery was dead. I have the old 'original' charging system and not a belt driven alternator. I turned the isolator switch on to charge it and the meter on the dash showed 12.0 V or so. Concerned, I went back and turned the switch off and the ammeter jumped up to 13.5V or so.....When a battery is deeply discharged shouldn't the ammeter be reading 13.5V or something high? The ammeter slowly climbed to @ 12.5-12.8V after running for over 2 hours.

Any idea why is this battery dying? Do deep cycles discharge and go dead quicker than dual purpose batteries?

TheTinMan
08-07-2006, 11:06 AM
do you have a dual battery switch?

Is this an O/B or I/O?

paradis
08-07-2006, 11:15 AM
It is a very simple dual battery switch of sorts. The switch adds the second battery inline to the charging system (and to backup the starting battery) if turned on. If off it is isolated and feeds only the accessories.

It is a mercruiser I/O.