I have had this drill for quite awhile. I believe the twi original batteries expired long ago. I recently googled replacement batteries and found that they are available, my question is, I still have one of the original batteries, I have put it in the charger and the green light stays on as if it is charged, however it is not. Is there a way to make sure without buying another battery, that it truly is the battery being bad, and not the charger. If I new the charger was still good I wouldn't hesitate purchasing a couple of batteries, this was a great drill when I first purchased it. Thanks.