6 volt battery polarity reversal

John

I have done it back when I was younger and not paying much attention to what I was doing or not really knowing what I was doing.

Zane

I don't know anything about lead-acid battery theory, but I can tell you from practical experience that a dead lead-acid battery CAN be charged so the actual polarity is opposite the post markings.

I have seen this a number of times.

The first time was when I was young, in the late 60's. My Uncle had a 1964 Ford car with a GENERATOR, with a solid state radio.

The radio quit working, and after a year or so he got a wrecking yard radio, which didn't work in the car, either, but had worked at the wrecking yard. About that time, I was beginning to work with electronics, and one way or the other, I figured out that the battery was charged backwards, and was frying the radios. We left the lights on untill the battery was dead, and recharged it with the correct polarity, polarized the generator, and installed another radio, and all was well.

The car was kept in a dark carshed, and for one reason or another, the battery had been run down, and he apparently mis-connected the battery charger, starting the radio problems!

Another incident was a John Deere combine. The owner had taken the battery off for the winter, and stored it inside. The next summer, he charged it up, and carried it out to the Quonset, and was connecting the cables, and had a big spark. He called me, thinking he had a short in the wiring.

It turned out he had charged THAT battery backwards, and the reversed polarity was causing the spark at the battery cable connection of the alternator-equipped machine. We hooked a spare headlight to the battery and drained it, recharged it correctly, and all was well. He was lucky in that he had just momentarily touched the battery cable to the post, and noticed the spark. He did not even "kill" his alternator.

I have seen a couple of more "reverse-charged" incidents since then, so I can tell you that, theory aside, this can and does happen.

He may as well run down his battery, and charge it correctly, and then have it load tested. The ones I have dealt with were non the worse for the experience! If the battery is any good, it will charge correctly just fine.

Hard sulfate cannot be converted back to lead dioxide by any form of charge cycle....proper polarity or level.....period. Once formed it is there to stay and can only be removed through remanufacturing processes. Eventually hard sulfation will shed from the plate usually taking active material with it leaving less material available for the electrochemical process that creates the electricity ultimately reducing the ampacity of the cell.

Once hard sulfation occurs less and less lead sulfate is converted back to active material through recharging. This causes the lead dioxide material to produce an abnormal paste which further loosens the remaining good active material in the plate further reducing the cells ampacity.

Finally, physical buckling of the plates occurs which breaks any remaining good plate material out of its grid. Bottom line is....ok...yes, I suppose a battery can discharge to the point of reversing its potential.....but it will never, ever be the same again.

Soundguy

BTW... I'd also disconnect the battery from the charging system prior to charging it....

HTH
Steve

John

Again, in my case, I always remove the battery from the tractor and vent the fill holes, that way if the battery overcharges and boils over, I've not got acid running all over my tractor...

HTH
Steve

Soundguy