If the battery is full, it is full and it stays full and the charger does not try to charge it anymore. Especially in laptops, where the charging circuitry is m

If the battery is full, it is full and it stays full and the charger does not try to charge it anymore. Especially in laptops, where the charging circuitry is more advanced. It may top up once a month. What I know, it is better to keep Lithium batteries full than keep them empty. If the voltage drops much below 2 volts, it is dead and stays dead. 40/80%-rule comes from satellites, where they continually charge and discharge batteries every day. With this regime Li-on lasts forever indeed.