Do you want to extend your laptop battery life – don’t use it! No seriously, what I mean is if your laptop is connected to the mains, then you should remove the battery to extend its life.
Why? Well when you battery is inserted in your laptop it is constantly charging. Batteries are only capable of a finite number of charges, so reducing the number of charges will extend its life. Also, by removing it from the mains it will allow the laptop battery to discharge properly when you actually use it, which will allow it work nearer its capacity.
Are you certain that this is true for all laptops? My HP 530 seems to ignore the battery (ie. charging current is 0 mA) when the level is over a certain limit (95% perhaps). So I hope maybe my battery won’t get eroded by constant charging.
Others say the source of damage to the cells while using from mains is the excess heat coming from the computer, which tends to use more power when there’s plenty of it available.