what happens when you charge a battery backwards?

mxz550fan asked:


last night i did a stupid thing, i went to charge our minncota trolling motor and put the clamps on the wrong sides. Left it on a whole night. what does this do to the battery. Is it fried,
when i checked it, it still had 3/4 charged on it?
Help please

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7 Responses to “what happens when you charge a battery backwards?”

  1. johnny q says:

    all you did was reverse the polarity, so it wouldn’t charge. i would suggest use up the whole battery power until its dead then charge it completely. by draining the battery completely it allows it to do a complete and good charge.

  2. justme23005 says:

    if it was completely dead, it will simply charge it backwards… it will actually work if you hook it up to the trolling motor backwards… positive on bat. to the neg. on trolling motor.
    hook it up to something, i’d suggest an old car headlight, & run the battery COMPLETELY dead. let it sit over night, then charge it the right way.. & it should be fine… then, lets go fishing.. :D

  3. Questioner says:

    Does not charge

  4. stewpid says:

    modern chargers protect against such. it probably didn’t charge and nothing is damaged. put a simple tester on it to make sure + is still +.

  5. rocky b says:

    If the battery was completely dead you would just reverse the polarity. Don’t try using your trolling motor until you have got your battery discharged and charged properly,if don’t do this you could fry the circuit board in the trolling motor.

  6. vtx.1800retro says:

    a charger won’t usually charge a 100% dead battery. but back to your main question,your charger probably has internal protection for exactly what you did, you’re ok. just hook it back up normally and let it fully charge.

  7. jojo234 says:

    hahahaha It will make your trolling motor run backwards hahaha

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