When your coast LED lens flashlight is no longer on, it's time to replace the battery.Depending on the model of the Lenser flashlight you have, you need one or four AA or AAA batteries.The battery can power the flashlight for up to 64 hours before it needs to be replaced.Unlike traditional flashlights, LED flashlights feature LED bulbs that provide brighter light and last longer.Twist the upper half of the coast LED lens flashlight until it is separated from the handle.Tilt the handle and remove the battery or battery from the housing unit.Insert the new battery into the handle with the negative pole (-) One side of the battery is down.By screwing the flashlight back to the handle, reconnect the upper half of the flashlight.