This rechargeable lithium-ion battery is a spare/replacement battery for select Nightstick Tactical flashlights including the TAC-400, TAC-500, and TAC-550 models. Not for use in Nightstick Xtreme Lumens series of tactical flashlights. Just like all Lithium-ion batteries, this unit has no recharge memory effect meaning it can be charged a little or a lot with no impact on the life of the battery.