Battery life in laptops slowly deteriorates over time, because of the
way laptop batteries store and use power. No matter if you buy your
laptop online, off-line and no matter what sales person tells you
otherwise. Even if you left the battery out of your laptop, you might
still notice a difference in usage times over a period of years. But
following a few simple tips can save your battery life.

Quote :

Note: This also
works for phone batteries as well.

1. Charge the battery early and often.

Lithium-ion (Li-Ion) batteries will lose charge from age, but
recharging it early and often makes sure that the charge is kept
throughout the cells.


2. Don't Frequently Discharge and Recharge the battery.

This is called a “Deep Cycle” and should be only be done every 30 – 40
charges to re-calibrate the battery meters in the electronic device.


3. Take out the Battery when using the laptop plugged in for an extended period of time.

Batteries are more affected by heat than any other factor. The heat
produced by a laptop is designed to keep it away from the battery, but
if you don't need the battery in, it's better to take it out and store
it somewhere away form the heat produced by the laptop. Preferably in
the fridge or freezer*


4. *The battery should never be frozen.

Although the freezing point of Li-ion batteries is around -40
degrees C, (way below what most conventional freezers), when storing
the battery just make sure it'll never reach those sort of extreme
temperatures.


5. Never deplete the battery to below their minimum voltage (2.4 – 3.0V per cell)

With these few tips, you should be able to keep your laptop, no matter
what brand, continually performing well. Battery life also depends on
what operating system, programs and strain your putting on your
computer.