On Board Charger Question

I have a question about my onboard charger. Last fall I put my batteries in the basement for the winter and hooked them up to my charger. It’s a ProSport8 2 bank charger. Normally I just plug it in overnite and unplug it the next day. Then I’ll usually plug it in every month or two just overnite. When I went back to it the next day it was still charging full bore (overcharging). So I unplugged it and could here the water in the batteries bowling. I let them cool down and checked the water level in them a day later. Well the level in my starting battery was below the plates, the deep cycle was low but still above the plates. I had not checked the levels before charging (I know, I know). I’ve since added water to both and the deep cycle will hold a charge, but the starting battery is shot. So my question is do you guys think that the charger will be alright to use still and it was just the batteries being low? Or did the automatic part of the charger fail and wreck my batteries. I just bought a 24 volt minn kota and would like to use this charger but am afraid to try it if it is no good. Sorry for the long story but I am a bit puzzled on this one and would appreciate any help I can get.

I think the best way to answer those questions would be to put a voltmeter on the batteries to see what they read. A good 12 volt battery will read up to 13.7 volts when fully charged. While the charger is on and in a charge mode, the voltmeter will read around 14 volts. I have a trickle charger on my batteries in the garage all winter, I’m going to look tonight and see what it says when the trickle is running.

On your starting battery, if you don’t have a charge of 12 volts, I wouldn’t want to be out on a big lake with that battery. You may want to go out and get a new one for the year.

Since you are getting a new battery, it’s the perfect time to test your charger, plug it into the new battery and keep an eye on it for an hour. I should actually just go to automatic mode in less than 5 mins, if not the automatic mode is definately not working. (keeping in mind new batteries are usually 99% charged)

As for checking your other batteries, going to have to use a voltmeter on them to check the state of charge at full, but you will have to get the specs for your batteries to see what the Open Circuit Voltage is when fully charged.

Here are a few pages to read up on:

All about batteries #1
All about batteries #2

If you do need a new onboard, I would definatly say that you should get any 3 stage charger.