Revitalising old lead-acid batteries

MacG · Post by **MacG** » 11 Oct 2005, 10:06

Here is a bit of trivia for those of you who are a bit careful with expenses. Lead-acid batteries wear out with time and refuse to accept charge. This is probably due to sulphate accumulation, and there are de-sulphators out there to fix the problem. A cheaper way:

1) Discharge the battery completely. First using a 12V 40W light bulb for a day or two (until it stop glowing), then using a jumper cable for an hour or two. CAUTION! There is a lot of energy left in a discharged battery.

2) Recharge the battery using OPPOSITE polarity. Since the internal resistance of the battery is close to zero, you have to connect the light bulb in series with the battery and charger for the first 20-30 hours of charging.

Now you have a battery with switched polarity and you have to mark it so you dont short-circuit some other battery when you belive you connect it in parallell. Also, the connectors have to be switched on any equipment. I dont know how this work with sealed and gel batteries, I've only used it on classic open cell types.

There is a lot of CAUTION! everywhere when dealing with lead-acid, mostly due to hydrogen and explosion risks, but the sulfuric acid is not very nice either.

Bootstrapper · Post by **Bootstrapper** » 11 Oct 2005, 12:53

I have an old, sulphated motorcycle battery I'm going to try that out on. Thanks for the tip!