1 check the SG (specific gravity) of all cells after fully charging the batteries when they have rested for 24 hours.
2 note the SG of any cells that are lower than the others and mark them. Leave the caps off.
3 place a thermometer on the negative battery post.
4 make sure the plates are covered by electrolyte.
5 apply voltage until there is one bubble per second.
6 make sure temperature does not exceed 115 F, if it does cease charging until the jars cool down.
7 monitor the voltage, you may have to "hit" them with up to 16 volts (for 12 volt).
8 monitor the SG of the "best" cell, and the worst cell.
9 do a capacity test using a load of 5 amps per 100 amp-hours of capacity.
10 recharge
11 go to #1 and repeat the above until all cells have reached the SG you decide is the target.
Notes:
Wear eye protection.
Wear pure woolen clothing.
Have water available to rinse your skin or any where else the battery acid may contaminate.
The charging device must be capable of producing amperage at the c/20 rate (higher is better and may take less time).
If the electrolyte changes color it may be time to abandon the attempt and replace them.
What we are attempting is to get "hardened" sulphate off the Negative Plate.
Positive plates do shale off and there is no way to recover the material.
The detritus from the plates often drops to the bottom of the cell and when enough accumulates the plates may short out.
It is possible for "dendrites" to form which may pierce the plate separator membranes. If that happens the cell shorts out.
Remember that welding used to be done with batteries. Treat the energy stored in them with great respect. A Group 29 jar, fully charged, represents 1300 watt-hours of energy.
Folks if I have missed a step--please chime in.
