If your RYOBI Ni Cad Battery will not take a charge than this little trick may work for you. This is to be done on Ni Cad Batteries only. Trying this on other types of batteries can result in possible injury or damage. This is not a permanent fix but will get a old battery going a for a bit.

Try this at your own risk. Do not try this on any other batteries other than Ni Cad. I'm not sure that this is completely safe or that this not harmful to your equipment. Use caution.