Originally Posted by babymog

First, be sure it is full. Use distilled water to bring it up to the bottom of the fill tubes, most batteries do have removeable caps although they're a bit more difficult than the old days.

Leave the caps off for charging.

Then charge at 13.4vdc at a high-amperage if necessary, until it is drawing only an amp or two.

Now you can charge at a 14.3vdc equalization rate for an hour to 12hours. Best to do this in a cool environment, and monitor battery temperature. If it gets too warm it will warp the plates and ruin the battery.

This can recondition a battery that has become weak from partial / incomplete charging, and remove much of the sulfate from the plates. Results will vary, some batteries bounce back better than others.

You should be aware of and take all necessary precautions around the battery, the sulfuric acid will boil during equalization and hydrogen (explosive) is produced during charging and discharging.