How to Flash an Old Rechargeable Battery

Look at the battery and if it's corroded at all, stop here because it can't be flashed.

Ground the battery by hooking the black alligator clamp from the 12-volt battery charger to the negative end of the old nicad rechargeable battery. The negative end of a single cell battery is the flat end.

Use the red alligator clamp to "flash" the old rechargeable battery. Tap the positive, or raised, end of the single-cell nicad rechargeable battery with the red alligator clip. Sparks may spray out of the ends of the battery during this process.

Securely hold both the black and red alligator clamps to the battery for up to three seconds to complete the flashing process.

Remove the alligator clamps. Retest the battery with a battery tester to see if it has been charged.