Here’s how to fix a battery on a Craftsman drill that shows it has a defective battery when trying to charge it.
There are four terminals on the battery, as shown below. Double check your battery pack to make sure the polarities are the same as the one in the picture below.
1.) Use a Power supply brick that’s approx 19 V – The one I initially used was from an old scanner, (rated at 19V @700ma, and actually puts out 22.2 V). I also successfully used my 3 – 28V Power supply that I use for electronics (will do about 1.5 amps, and has overload shutdown if too much current flows). I set it on 28Volts.
2.) Hook the Negative lead to #1
3.) Now touch the Positive lead to #2, 8 times, very briefly, ie: 1 second per touch.
*** (see note below)
4.) Leaving the Negative lead on #1, now touch the Positive lead to #3, 8 times, very briefly.
5.) Move the Negative lead to #4, then do the 8-touches with the Positive to #2.
6.) Then touch the Positive on #3 8 times.
You are done! Try charging the battery now, and you’ll see that it’s now taking a charge! If it isn’t, repeat the above process another couple of times until it does.
PS: This will likely work for other ‘dead’ NiCad battery packs. The only things that will change are the Power supply that you will need, and finding the polarities of the battery pack pins. Your power supply brick should at least be close to the same voltage as your battery. (You’ll need a voltmeter to check the battery pin polarities). *** This only works on NiCad Batteries, not Lithium ones!
I’m not responsible for problems or damage you may run into as a result of trying this. You are totally on your own! Should work for you, though, if you follow the instructions.