How to Resurrect a Drill Battery

Take precautions when bringing your old cordless drill batteries back to life.
Take precautions when bringing your old cordless drill batteries back to life. (Image: battery image by Alison Bowden from

It's possible to revive both nickel cadmium (Nicad) and nickel metal hydride (Ni MH) cordless drill batteries. These batteries wear down and eventually die over their normal life cycle. The cordless drill battery resurrection process is simple and quick, but can be hazardous if you overcharge or mishandle the rechargeable batteries.

Things You'll Need

  • Needle-nose pliers
  • Small container
  • Voltmeter
  • 12-volt power source
  • Black 14-gauge wire
  • Red 14-gauge wire
  • Small red and black alligator clamps
  • Scissors
  • Electrical tape

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Mark the positive and negative leads on the battery case, using the voltmeter to determine which is positive and which is negative.

Unscrew the cordless drill battery case to reveal the rechargeable batteries within the case. Carefully remove the top of the cordless drill battery case. Keep the screws and the spring in a container so you can find them during reassembly.

Lift the battery cells from the battery casing. If the batteries are shrink-wrapped together, cut enough of the plastic away with scissors to reveal the top and bottoms of the battery cells.

Locate the point at which the wires from the battery pack terminal run down through the silver cardboard insulator. Mark this opening before you remove the battery terminal for easier reassembly.

Needle-nose pliers will remove the terminal piece.
Needle-nose pliers will remove the terminal piece. (Image: pliers image by Jakub Cejpek from

Loosen and lift off the terminal piece, using needle-nose pliers. The metal band underneath the terminal piece must be insulated with electrical tape before you proceed.

Remove the silver cardboard insulation piece and place this piece aside. Remove the shrink wrap from the top and bottom of the battery cells, so the battery leads are exposed.

Test the batteries within the pack to determine which cells need reconditioning. Use the battery tester and mark all batteries that are not at full charge capacity.

Find the positive, or raised end, on the first battery to be reconditioned. Place the black alligator clamp from the 12-volt power source on the negative end of the battery cell, while holding the red alligator clamp to the positive end for no longer than two seconds.

Release both clamps. Using the battery tester, test the battery cell to see if it has been fully recharged. If not, repeat the zapping process.

Repeat the zapping process with all batteries until they have all been reconditioned and then reassemble the battery pack.

(Image: battery tester on white image by JoLin from

Tips & Warnings

  • Put on safety goggles, insulated gloves and long-sleeve shirts before beginning the reconditioning process.
  • Don't get your wires crossed or an explosion may occur.


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