Battery Voltage
 

For about 6 months now, I've struggled with battery issues which ultimately ended up being a bad charger that was over charging my 12V GC lead acid batteries.

I have replaced 3 of the 4 batteries but used the bad charger on them (before I knew it was bad) once which caused them to boil and lose most of the water.

Since then I got a replacement charger and refilled the batteries and everything seems to be good except for the voltage capacity.

I have a voltage meter on the house bank and now the max voltage I've seen with the key off is 12.8V. Last year it was usually around 13.8-14V.

I have verified that the charger is charging at 14.4V. Should I replace the 3 house batteries?

I haven't ran the stereo with the boat off for very long so I really don't know how well the batteries will do but I don't think it will be near as good as it was last year.

The batteries resting voltage should be 12.6-12.8V. You should only see 14V+ immediately after taking off the charger. Charge the batteries fully and see what they measure the next day. If 12.6-12.8v they are probably fine. If you have a portable digital multimeter throw play around with it.

That 14.4 volts you see on the batteries shortly after a charge is whats called a surface charge. Once taken off with a little load or over time, the at-rest or static charge for a wet cell should be right around 12.8. I think the 13.8-14 volts you saw last year was result of the faulty charger over charging.

Thanks Brett and Mike! I'm hoping the batteries didn't get too damaged the one time I charged them with the bad charger. It took a little over a gallon of distilled water to refill all 3.

I guess we'll see during the season.

TJ,
It's going to be equally important to know what the minimum resting battery charge (after any type of external charge has had time to dissipate) after a long stay at rest and after the batteries have been depleted.
Yes, you could have been over-charging with a charger that has too large of a capacity or a blunt garage charger and do damage. However, you could also be doing similar damage by depleting the batteries well below 12.0 volts with any repetition.

David
Earmark Marine