It is not possible to overcharge a laptop battery. Leaving your computer plugged in after it is fully charged will not overcharge or damage the battery. However, it may not be the best idea to keep the battery on the charger consistently if you want to maximize battery life.
Lenovo Tech Talks. Can I leave my laptop plugged in all the time?
Most modern laptops use lithium-ion batteries, as do many smaller consumer devices such as watches and flashlights. These batteries can be recharged hundreds of times without affecting battery life.
Lithium-ion batteries have an internal circuit that stops the charging process when the battery is fully charged. The circuit is necessary because without this circuit, the Li-ion battery can overheat and possibly burn during charging.
Older laptops use nickel-cadmium and nickel-metal hydride batteries. These batteries require more maintenance than lithium-ion batteries.
