Instructables

How do I revive dead lead-acid batteries?

I have one that's been dead for several months. It's 12v, 4AH. It's sealed lead-acid rechargable battery, any ideas on how to revive it? Also, how would you charge this kind of battery?

lemonie5 years ago
lrdforster2 years ago
In my experiance Lead acid batteries although simple they can be unforgiving if treated badly

Once acid is added they are no longer shelf items and must be constantly managed.

If your car, boat, bike or whatever is not going to be used for a period of time typically the winter, i would recomend removing the battery to a "battery happy place" perhaps a garage or shed and somewhere with a temperature above 5 celcius but not too warm. In addation conect it up to a battery charger with trickle charge facility and keep it switched on. plug the battery charger into a mains timer so it switches on for 1 hour a day, This will keep your battery happy for months.

If you havent done this and you go to your battery after several months of no use find its discharged, you charge it and it doesnt hold its charge DONT PANIC you may be lucky hopefully the cold hasnt killed the battery and it just needs some excersize.. YES i said excersize I have found theat wireing a 40w bulb across a 12v battery and a battery charger on a timmer can fix it, i repeat sometimes. typicaly when ive done this is bike battery so they tend to be about 10AH thats 10 Amps per hour a 40w bulb draws 3.3Amps per hour so should last 3 hours and a battery need 1.5 times its rating to charge from flat so a 10AH battery needs 15AH of charge an 8amp charger will take about 2 hours (dont forget your lamp drawing 3.3amps) so give it 3hours charge time.

you set the timmer on for 3 hours and off for 2 repeat this over the 24 hours, yes you spotted that 25 hours so take 15 mins off 4 of the off times (gives a little longer charge) let this run a cpl of days. Now you have exercised the battery you will find it works much better I wouldnt like to say its perfect but you may get another year or two out of it.
theRIAA5 years ago
something like this?
http://www.batteryspec.com/cgi-bin/cart.cgi?action=link&product=61&sub2=610003

look at "charging information"
seems like you can use a car battery charger as long as you monitor the voltage with a multimeter the whole time (only a good idea if you already have a multimeter and car battery charger, if not, buy a custom charger)
polird5 years ago
Is it like a car battery? They sell chargers for those. The only problem is if it's an old battery, it may not hold a charge.