josephsc

How the heck did I do this?

I had a completely dead lead-acid battery I was trying to revive. I figure if I just slap it on a trickle charger over the weekend it would be fine. I'm not sure what happened, but now the battery's polarity is reversed! I triple checked it with a multi-meter.

I must have plugged in the trickle charger backwards -- but I didn't think it was even possible to reverse the polarity of a battery. Has anyone ever heard of doing something this stupid?

V2Rocket

does it run?

Bri Bro

It can be done, but most of the time the remaining charge on the battery will cause enough sparks to warn you. I bet it took out some electronic components if you turned on the ignition.

josephsc

Fortunately, I was checking the battery charge with a multimeter before plugging it in -- I thought about skipping that step, though....

eniac

Funny thing, this JUST happened to me on a battery from a Ford over the weekend. The car came in with a fully dead battery. I took the battery out and plugged it into my variable cycle pulse charger and left it over night. In the morning the needle on the charger read that the battery was fully charged so I stuck it in the car. BIG SPARKS and a blown out ignition module were the results. It took me a bit to figure out what was going on but I finally noticed the little minus sign on my voltmeter before the 12.76v when i was checking for a short. Yeah it was -12.76.

Apparently this happens when a battery reaches the end of it's lifecycle. The cells inside colapse and some combine which can make the polarity reverse. I have heard of this before but this weekend was the first time I have ever seen it personally.

I understand how it can reverse, I don't understand how the charger could have charged the battery after the polarity reversed. If I hook my charger up to a charged battery backwards it blows a breaker. Shouldn't it have tripped the breaker while charging since it would have been effectively hooked backwards now? Somehow it managed to charge the battery as if it wasn't reversed.

Any battery that does this needs to be repalaced ASAP as it could explode.

marky522

I had a 993 come in not to long ago that the owner had done this, ended up melting the positive lead to the alternator!!!

Mark

eniac

Did he simply connect a good battery backwards or did his battery reverse it's polarity on it's own also?

marky522

Battery was dead, and somone who had NO buisness under the hood of a car charged it for him, connected the leads incorrectly and charged it backwards...

Mark

eniac

LOL certainly someone that can't tell a + from a - would have no business under a hood.

The battery I had over the weekend I did connect correctly to the charger yet it charged and still reversed polarity. I'm still stumped how it could have charged the battery.

joes

When a battery is completely dead you can charge it the other way and it will come up to full charge and work---- just re-lable the posts and throw it in there.
Which is totally different than hooking up a battery positive to negitive ground on your car which will destroy things..

Jay W

I have heard of some of the cells reversing polarity. I had a dead battery I was trying to bring back but the one reversed cell made it impossible to charge. I even tried several times to drain it completely with a 12V light bulb attached, but after 2 tries it would not swap back. I just paid $60 for a new one after that.

bearone

what is a "variable cycle pulse charger"?

krystar

instead of applying a constant voltage, pulse chargers....well send pulses of high voltage to the battery to charge it. timing of pulse amplitude, duration, reptitions are all controlled by a microcontroller.

eniac

Correct

bearone

who has them, have a link?

so what makes this way of charging better or more efficient?