Put on all safety gear. Remove the screws from the top cap of the battery pack and set them aside. Lift off the cap carefully, as most battery packs are spring-loaded. Set the cap and spring aside.
Wrap the protruding metal band terminal with electrical tape, taking care not to complete the circuit between it and any other metal. Turn the battery pack upside-down into your hand and pry out the bundled batteries carefully. Remove the plastic shield from the top and bottom of the bundle, taking note of their original positions. Peel back any tape covering the top and bottom of the individual battery cells.
Lay the bundle on its side so that both ends of each cell are accessible. Turn on the multimeter and set it to "2V," as each cell should be 1.2 volts. Touch the red test lead to the positive terminal of a cell (the positive side has the protruding button) and the black lead to the corresponding negative terminal (the negative side is flat). Mark the negative terminal with an "X" if the readout is below 1.1 volts. Repeat for each cell.
Connect the red alligator clip to the positive terminal of the car battery and the black to the negative, taking care not to touch them together or to anything conductive. Touch and hold the black clip to the negative terminal of one of the "X" marked cells. Touch and hold the red clip to the positive terminal of the same battery for no longer than two seconds. Repeat this procedure for each "X" marked cell.
Check each cell again with the multimeter, marking any sub 1.1-volt cell with a star. Repeat the restoration procedure above until each cell is repaired. Reinstall the plastic shields and pack the bundle back into the housing. Remove the tape from the terminal band. Screw the cap back onto the battery pack and charge it overnight.