For your battery powered tools, check the battery. If the battery is marked Ni-Cd (as shown in the picture), this means it is a nickel cadmium (NiCad) battery. This is older technology to the more modern lithium iron batteries.
NiCads are known to build up a memory if they are repeatedly charged without running flat. The problem with power tools is that you tend to recharge when the battery isn't delivering enough power, which is usually at the same level of charge every time.
This will cause a memory point, which will eventually prevent the battery from being charged properly and you'll end up throwing it away, which costly to replace.
Every few months, simply run the battery flat, by running the power tool until it is dead. Use insulation tape to hold down the trigger of the tool until it works no more. Once dead, you charge it up again. This little tip will prolong battery life and save money.