0framistan 8 years ago ReplyUpvotei have successfully restored many nickel cadmium chargable batteries using this method. I have a power supply that puts out several hundred volts... I use it to charge up a large hi-voltage capacitor. Then quickly apply the charged capacitor to the nickel cadmium batterypack. This is best done using a pre-wired jig and a toggle switch. Alligator clips to attach the terminals to proper wires. then flip the toggle switch to ZAP the batteries. Then charge the batterypack normally. This ZAPPING is done to batterypack by itself while it is NOT attached to the drill or device it powers (of course). Nickel cadmium batteries develop a kind of internal "short" that the ZAPPING clears away. Doing this to the batterypack may give you a couple more years usage out of it... or sometimes not. This charging of a capacitor to high voltage is DANGEROUS of course... so do this at your own risk and dont blame me if you get killed doing this... Another method is pulling the pack apart. Check each cell inside the pack for voltage. Usually only one or 2 cells go bad and have very low voltage on them. Just replace the one or 2 lowvoltage cells and re-assemble the pack. FIXED!!!