Cordless drill...

Best to charge it all the way if it has been used any amount of time. It will lose some charge over time. Most of the newer chargers can shut off when the battery is filled so leaving the batteries in them is not a problem. While I don't do it as a rule, I have left the battery for days at a time when I forget about it. Ed

Battery discharged but only discharged till drill slows. I have 18 yr old makita and RC packs that still work. Never leave a pack in a non peak charger, the cells cook. If you use it regularly just charge when needed.

Batteries shouls be left in a charged state because they selfdischarge. When left in the drill there is no drain, thus is equivalent to leaveing them outside. Modern charger shut off, but cheap or old ones finish off the charge in a trickle mode. On the long run a poorly controlled trickle charge may be unhealty.

I have bougth a timer and set it for the max 8 hours because I regularly forget to turn it off.

MG

Thanks all...

The only type of battery that should be stored charged is lead acid or it will sulfate. But tool companies wont tell you this because their big money is selling you a new pack .