Most common is an old battery or damaged battery.
BUT your charge light isn't lighting. Here's some troubleshooting:
1. Check the charge cord (i.e. wall wart). At the two contact pins, voltage should be between 13 and 22 volts.
2. Check the voltage coming from the charger, should be between 13 and 22 volts. During this test, the LED should NOT light up. If the voltage isn't w/in perameters, the base should be replaced.
3. If the above checks out, see what color the switch is in the light. If it's a clear or tinted, replace it. The newest switches are black plastic and were redesigned.
4. Put in a new battery stick and see if your charger works.
What's bugging me about yuour issue is the LED not lighting on the base, that's why I listed 1. and 2. before battery stick replacement.
--dan