Remove the battery when it's fully charged and plugged in. If you have a constant power supply use it. no use to overcharge the battery. Don't leave the battery out of use for too long though. Drain it and recharge it every 2-3 weeks if you haven't used it at all. Overcharging laptop battery will decrease its lifespan, on the other hand, recharging the battery also decreases its lifespan. If the laptop runs on continuous power adapter supply with the battery plugged in and being overcharged (battery always full 100%), will this decrease the lifespan of the battery as much as if the laptop ran on battery supply. Disconnect the battery from the laptop and store it in cool (room temperature) place.