Your laptop battery will deteriorate over time whether you use it or not. Although the Li-Ion industry does not publicize this fact, your battery’s clock began ticking the moment it was assembled. The elements inside your battery slowly react with each other, eventually rendering the battery unable to supply the required power to your notebook. In addition, your battery is rated to last between 300 and 800 charge/recharge cycles. It will gradually lose charge capacity rather than abruptly fail to power your notebook.
The general consensus is that notebook batteries last one to three years. While you can slow the battery’s aging and loss of capacity, you cannot stop either decline. The temperature of the battery, combined with the amount and nature of its usage contribute significantly to your battery’s lifespan. You can ease the aging process with some care and maintenance.
Lower temperatures slow down the self-discharge (loss of charge while disconnected) and aging process of the elements within your battery. Therefore it follows that higher temperatures shorten the life of your battery. Leaving your battery connected while on AC power causes the internal temperature of the battery to rise. Removing your battery and storing it in a cool, dry place will help to slow the aging process. Keeping your notebook in a hot environment is also detrimental to your battery.
Amount of Usage
The Lithium-Ion batteries used in notebooks are rated to handle between 300 and 800 charge/discharge cycles. Some of these cycles are used when you leave your battery connected to your notebook while on AC power. On AC power, the notebook will routinely “top-off” the battery when its charge reaches predetermined levels (i.e. 95%). Removing your battery and storing it in a cool, dry place will help to preserve some of these cycles.
Nature of Usage
Li-Ion batteries do not suffer from the memory-effect (requiring complete discharge before recharging to avoid loss of capacity) like older rechargeable batteries. Regular full discharge/recharge cycles result in an increased loss of capacity per cycle. A series of partial discharge cycles are better for Li-Ion batteries than a single full discharge. You should, however, calibrate your battery routinely.