Reverse charged trolling motor battery

[jcummins]

Somehow, couple of months ago, I hooked up the charger backwards on this battery.....and instead of shutting down, it charged it in reverse. Positive become negative and vice versa. I blame faded markings on the charging wire...not an old man's mistake. Things sort of run right, but wrong at the same time, so I did not find it immediately.

I've discharged the battery by hooking a spot light to it. It is still charged wrong, showing < 10 mv positive on the negative terminal. I hook the battery charger to it the correct way try to charger...it does for a few seconds, then the charger shuts off with a pop, and I can watch the small charge that it took, trickle back to the incorrect charge. Then the charger comes back on and the process repeats. I was hoping it could be charged back the correct way....since it took an incorrect charge I was thinking once discharge it should charge back normally.

Is the battery toast, or is there a way to correct this. From research, it appears it may be.

 

[buickanddeere]

Try a different charger but consider that battery will have a shortened life with reduced capacity .

 

[Old Guy in Tenn]

I think the battery needs to be run way down before correctly hooking up the charger. The charger voltage plus the reversed battery voltage gives a voltage difference of 23-26 volts, probably getting too much current flow for the charger.

Was the battery dead before you charged it backwards?

 

[kc5dlo]

Most chargers these days require some voltage before it will start charging. Perhaps you could trick it by providing 12 volts from another source?

 

[jcummins]

I suspect the battery was dead before being reversed charged.

The battery was drained as low as it was going to go. I've been hesitate to go off and leave the charger hooked to it with it popping like that, but today I had things to do in the barn. Left it charging correctly going off/on, and left for 40 minutes or so. When i took a look...it was then charging normal. So...got it back, but as said here, bet it will not be a strong battery now.