Trolling Motor Batteries Problem

[loadmaster]

Hear is my problem. Used the heck out of my motor yesterday got home and plugged in charger I charge one battery at a time. My charger shows 0-100% charge with voltage that battery is at and charger output. First battery showed 9% charged and volts 12.5. Left charger on all night and this AM it showed 100% Started charging second battery and it showed an 80% charge with 12.5 volts. I am sure one of these are bad but which one. Seems like all the juice is coming from one battery but this is a 24 volt motor. not sure how this works. Put a battery tester on both batteries and both showed good. Have not changed any wiring and all connectors look clean and free of corrosion, Any ideas

[BobT]

Voltage test alone is not a reliable test for batteries. Even a poor battery may show 12v when tested with a tester. Do you have a specific gravity tester? This may be useful in finding bad cells. A load test is also a good test for determining battery health but it must done properly. It's best to load test a battery after fully charging then leaving it set for a while off the charger and then test with a load tester. I don't recall how long you should wait after fully charging but I want to say maybe overnight or a few hours at least. The reason is that a battery may not be holding its charge and letting it set will show this.

Another thought about load test is that I'm not entirely sure how this may apply to deep cycle batteries since they are designed for a different purpose and function.

I know I'm not giving you very much useful information so someone with more experience may be able to offer better response.

[marine_man]

I agree with Bob... I'd get them load tested to understand which one is the bad one...

marine_man

[ssaamm]

Had a similar issue. The in line fuse was blown. The LED light was green. One battery was charged. The other wasn't. I wonder how long this was the case. I replaced the fuse. One battery is %100, the other is about %75. Might be as good as I can get it. Good luck.

[Whoaru99]

Have you checked the water level in the batteries?

Some are truly sealed, but many you can still remove the caps to check.

[CaptainMusky]

I agree with Bob... I'd get them load tested to understand which one is the bad one...

marine_man

Not saying this is a bad idea, but every time I have had a battery load tested it literally destroyed the battery. Example, I brought my truck in to Batteries plus to have my battery tested. I was NOT having any issues, just knew it was old. They put a load on it and you guessed it, said it was bad. I said I will hold off (meaning I was going to get one somewhere else) I go back to work and the battery was completely dead when I came back out at the end of the day. Wouldn't start. I never even had any trouble prior to this.

[aanderud]

Not saying this is a bad idea, but every time I have had a battery load tested it literally destroyed the battery. Example, I brought my truck in to Batteries plus to have my battery tested. I was NOT having any issues, just knew it was old. They put a load on it and you guessed it, said it was bad. I said I will hold off (meaning I was going to get one somewhere else) I go back to work and the battery was completely dead when I came back out at the end of the day. Wouldn't start. I never even had any trouble prior to this.

My wife's car had this same thing, but they said the battery was good. It was about 6 years old, so it wasn't new by any means. She had it load tested and they said it was good to go. Two hours later I had to go jump start her at the daycare parking lot when she dropped off the kids before work. Did a quick car swap so she could go to work, and then put in a new battery for her (bought it at a different shop than the one that 'tested' hers).