Note: I take no responsibility for any damage or injury by using this method , you do so at your own risk.
Step 1: Reviving a Ni-Cad Battery
First check that it will not charge , if your charger has a discharge function , try that first , if it still wont charge try the following procedure , you will need a variable power supply or at least a power source that can deliver 3 volts at 1 amp , my variable PSU can deliver 24 volts at 3 amp.
Connect your battery to the PSU and set it to 3 volts , then leave it for +- 2 hours , if your PSU is only 1 amp you might have to leave it longer. The battery will get hot , so be careful when handling it.
Step 2: Reviving a Ni-Cad Battery
After +- 2 hours turn your PSU down to +- 1.3 volt for a couple of hours until the battery has cooled down.
Then put it in your charger and it should start charging.
See the video clip on YouTube here: http://youtu.be/jd10T1GOj2g