Desulfator...

Find a C-Tec battery maintainer. The one I have has "revived" many batteries that has set for a while and gotten weak. If I understand the principal, they charge for a period of time, then switch to a light "load", then switch back to a charge. This process desulphates the plates. Some of my batteries will be on the maintainer for a week or more before I get a green (charged) light on the unit.
-Donny

 

I've had not that much luck. They do seem very useful for maintaining a good battery or repairing a slightly weakened one if it hasn't run dry, but if it's really damaged it's time to move on.
I've tried a few fancy chargers, desulfators, and even the extreme measure of drain acid, etch plates with baking soda, rinse, add new acid to try to revive some vintage batteries. All with *very* little to show for it.

My top ways to ruin a lead acid are:
* Run it dry and leave it that way
* Run it low and leave it that way
* Run it down half way and leave it that way
* Run it down low and charge it back up within an hour

 

My most exciting way was to explode the hydrogen in the cells with a welding spark....

 

Had a AGM battery in the TJ. Severely dead. Other chargers would couldn't tell they were hooked up.
The Genius 7200 did the maintenance and got it back going right.
Amazon.com: NOCO Genius G7200 12V/24V 7.2 Amp Battery Charger and Maintainer: Automotive

This will do 24V also and has saved me replacing batteries.




Dave