The batteries have had it. They are not holding a charge
The fact that they read full voltage is not relevent, as you are taking the reading with no load on the drill. As soon as you put the batteries under a load (by switching on the drill and holding) you lose whatever charge the battery managed to hold during charging, so the battery voltage drops and the drill does not function.
If you then remove the batteries you will probably read full voltage again.
THis is a problem after repeatedly charging ALL rechargeable batteries (but some are better that others)
THe WORST thing you can do is to leave them on trickle charge, or charge them again before they are FULLY discharged. (the fact that the drill does not function DOES NOT mean the batteries are FULLY discharged, its just means that the battery voltage on load is too low for the drill to function).
The best thing you can do is to leave the drill switched on (as if drilling) for several hours (even though it may not be turning), BEFORE recharging the battery.
NA
August 2009