While you can leave the battery plugged in constantly, this is not a good idea if you want the battery to last longer. There are two primary reasons to avoid this, which include the following:
The battery will self-discharge at a natural rate. This means that they gradually lose power, even when not in use. Keeping them plugged in increases the rate of self-discharge.
When you leave the batteries plugged in, the risk of tool failure and accident increases.
It is always preferable to unplug the batteries and safely store them. If necessary, charge the battery correctly before storing it.
If the battery is in good condition and does not require charging, you may store it in a sealed container or case until you need to keep it again.
If you’re pressed for time, store the drill and recharge it before using it again.
Sure, nickel-based batteries will lose close to 40% of their charge in the first two days of storage, so it is a good idea to charge the battery before using it on a project.