Battery reverse polarity?

Downunder Bob

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Hi guys, I recently set up a LED lamp above my lathe, it required 12v. I had a spare 12v gel cell battery looking for a purpose, so I hooked it up. Nice bright light with it's own on/off switch. I added a small plug pack charger, 1 amp, and capable of floating when fully charged. I also intend to run a few more low power items off this setup.

After a couple of hours running I switched it off and retired for the night. The next day I went to switch it on and the light didn't work, put multimeter on battery = 12.5v ? assuming the new light fitting was faulty I took it down and pulled it apart, Another similar battery was on the workbench so I touched the light wires to it and presto it worked. Went back to the original battery, wouldn't work? checked battery again 12.5v? take a second look at meter -12.5v switched the meter leads around and got+12.5v. hooked up the led light wrong way around, yes it worked. ????

The two batteries are identical 12v gel cells about 2 years old, now one of them suddenly decides to switch polarity, overnight with every thing turned off.

Any clues gentlemen, and ladies? Can I get the polarity to switch back, or can it be used like this.????
 
OK, that is a new one. Is it possible that you had the charger connected backwards? I really don't understand how a battery can switch polarity. Hopefully someone here can explain how this is possible.:confused:

This is just a guess, but I would think that the battery is done.
 
Yes, you can put a reverse surface charge on a lead/acid battery with the charger reversed. Just drain it down and charge it the correct way around.
 
Take the battery outside and connect the charger. Plug the charger into a long extension cord and plug that in far away. Maybe a shield between you and the battery or a bucket over the battery to contain the flying parts and acid should something bad happen.
 
Wow, learned something new today. I used to work in automotive too, never did I see a car battery reverse polarity. I would have never thought that was even possible!
 
Wow, learned something new today. I used to work in automotive too, never did I see a car battery reverse polarity. I would have never thought that was even possible!
I blew up a car battery by reversing the jumper cables when I was young. I was very lucky, I turned my head away from the car when it blew. 40 years later, my ears still hurt thinking about it and all of the acid that got on me, too. I assure you, that was the first time and the last time I did that too!
 
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