Art Deco wrote:

I have a 18V cordless drill (without instructions) and the charging
base has both green and red LEDs.

They'll mean "power is applied" and "battery is connected"
Unless it's a real charger, then you certainly _won't_ have a "charging
complete" light.

Cheap chargers kill batteries. Your best option is to either replace it
(which is certainly worth it if they're quality cells in there) or at
very least to run it through a timeswitch and never run it for more
than the recommended 5 hours. Personally I have an old half-hour
"boost" timer that I use for this and charge the battery in a number of
short blasts. This gives it a chance to cool down between bursts.

But those cheap chargers are just crude battery killers. Avoid them if
you possibly can.