Older power tools containing nickel-cadmium (NiCad) and nickel-metal hydride (NiMH) batteries can develop memory effect. Memory effect occurs when a battery remembers how much charge was drained before being charged, so it changes its capacity to a lesser charge. This happens when a battery is constantly partly drained and charged without fully discharging first. For this reason, you want to allow NiCad and NiMH batteries to dissipate fully before recharging them to avoid developing a battery memory. Lithium-ion batteries do not have a battery memory, so recharging is recommended after each use to ensure your batteries are fully charged when you need them.