Craftsman cordless tools use rechargeable batteries for their power source. Most Craftsman tools come with 19.2-volt NiCad batteries. According to Isidor Buchmann at Cadex Electronics Inc., NiCad batteries fail because the crystals within the NiCad cell combine over time and become larger and less conductive. The primary cause of this is overcharging the battery. Rapid chargers should recharge in about 60 minutes and standard chargers take two to four hours. Surging the NiCd cell with a higher-voltage source causes the larger crystals to shatter back down into smaller crystals.
Turn on the digital multi-meter (DMM) and set it to measure the rated voltage of the battery.
Place the positive (red) lead on the positive battery pole. Place the negative (black) lead on the negative battery pole. Read the meter and record the value.
If you get a negative reading that is significantly more than a few volts (for example, a reading of -10 volts on a 12-volt battery), the positive lead is on the negative battery pole. If a negative value of one or two volts is displayed, the battery polarity has reversed, but the DMM leads are oriented correctly to the battery poles.
Connect six 6-volt lantern batteries in a series to create a 36-volt power source. For the purpose of this example, a standard 19.2-volt Craftsman battery will be pulsed by a 36-volt source for six seconds.
Cut the copper wire into five 4-inch lengths and two 7-inch lengths. Strip 1 inch of insulation off each end of the 4-inch sections.
Strip one inch of insulation off one end of the longer wires and remove only enough insulation off the other end to see the copper wiring.
Take one 4-inch section and wrap one stripped section around the positive pole of the first battery and the other end around the negative pole of the second battery. Use a 4-inch wire and repeat the process, connecting the positive pole of the second battery to the negative pole of the third battery. Continue until all but the positive terminal of the first battery and negative terminal of the last battery are connected in the series. Do not connect the last pair of terminals. The last two terminals are the positive and negative terminals of the 36-volt source.
Wrap the stripped end of one 7-inch wire around the positive terminal of your first battery and wrap the stripped end of the second 7-inch wire around the negative terminal of your last battery.
Connect the negative terminal of the battery series to the negative battery terminal of your Craftsman battery.
Tap the positive terminal of the battery series to the positive battery terminal two to three times per second for six seconds.
Allow the battery to cool 15 minutes.
Place the power tool battery in its charger for 15 minutes and then remove the battery from the charger.
Measure the voltage with the DMM.
Let the battery sit for one hour and then measure the voltage again. If the two voltages are the same (within 0.3 volts), the battery is fixed. Charge it fully following the manufacturer's instructions.
If the second voltage is significantly lower, the battery has not been repaired. Repeat Step 3. You can pulse the battery up to 25 times during the life of the battery.