Salvaging sealed lead acid batteries

[AndyL]

Have a couple 12v 4.5ah SLA batteries in a kids toy - that I kinda want to revive at least temporarily (gotta test this minibike)

I remember being told there's a few ways to do stupid things to lead acids to wake em up a bit, at risk of explosion and venting... But I usually just said - I'll just go buy a new one...

I'm going to swap them out to probably a pair of 14.4v drill batteries once it's tested.

Currently when I disconnect them (soldered in series for 24v) - one never really charges beyond 8-9v, the other on the smart charger shows reversed polarity - dumb charger connected correctly - it sits at about 1amp but doesn't warm up or charge to a positive voltage.

Any ideas?

[nobb]

Pop the sealed plastic cap and underneath there is a rubber cap for each cell. From there you can stick an electrode in to do a voltage test on each cell. Alot of times, one or two cells short out which is why the whole battery can't charge beyond a certain voltage. Attempting to charge the battery with shorted cells means the remaining cells are being overcharged.

You could try dumping out the acid, fill the cells with distilled water, charge that, shake the battery + dump the water (to get rid of the sediment that might be causing a short), filter the old acid through a mesh, then dump that back in again. But usually with shorted cells it's a lost cause because there's something physically wrong with the plates.