Did it on a car battery when it went bad and I could not pay the money for a new one. I still had to use the car.
The battery must be totally disharged, a lamp until the light went out and then jumper cable shorting it out for a whole day did it. Then it was charged backwards, first using the lamp as a current limiter or the charger circuit breaker would trip. Once the battery had gotten so much charge through the lamp that the charger could do without it the lamp was removed. The charger was at work for a day and the battery came ot of the process with reversed polarity. The battery poles are made with different diameter to make it difficult to connect them in reverse. Wrapping some soft copper around one of them and it could be connected.
The probably 7 years old battery that was practically dead got another 4 years of service reversed and then the car was sold with the reversed battery, still as perky as the day it was reversed. I wrote "LUCAS, made in england"on the battery with a marker pen, to honour the lord of the darkness, and marked out actual polarity. People often don't believe me when I tell them, the MOT inspectors just shook their heads, stared at it, looking tired, but never ever uttered a single word about the reversion.
Do it at your own risk and enjoyment. Regards.
