Source: http://www.batteryuniversity.com and http://uber.la/archives/1232

* A typical lithium-ion battery provides approximately 300-500 discharge / charge cycles.

* Avoid frequent full discharges because this puts additional strain on the battery. Several partial discharges with frequent recharges are better for lithium-ion than one deep one. Recharging a partially charged lithium-ion does not cause harm because there is no memory. Short battery life in a laptop is mainly caused by heat rather than charge / discharge patterns.

* Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as “digital memory”. Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery’s state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate.

* The worst environmental condition for a lithium-ion battery is keeping a fully charged battery at elevated temperatures, which is the case with running laptop batteries. If used on main power, the battery inside a laptop will only last for 12-18 months. The pack does not die suddenly but begins with reduced run-times.

* Avoid keeping the battery at full charge and high temperature. This is the case when placing a spare battery in a hot car. Running a laptop computer on the mains has a similar temperature problem. While the battery is kept fully charged, the inside temperature during operation rises to 45°C (113°F).

* Removing the battery from the laptop when running on fixed power protects the battery from heat. With the concern of the battery overheating and causing fire, it is advised to eject the battery of affected laptops and to run the machines on a power cord. It should be noted that on a power outage, unsaved work will be lost.

* If removed from the laptop, store the battery in a cool place at about a 40% state-of-charge. Some reserve charge is needed to keep the battery and its protection circuit operational during prolonged storage.

* Should the laptop be disconnected from the main when not in use? Under normal circumstances, it should not matter with lithium-ion. Once the battery is fully charged, no further charge is applied. However, there is always the concern of malfunction of the AC adapter, the laptop or the battery.

* Avoid purchasing spare lithium-ion batteries for later use. Observe manufacturing dates. Do not buy old stock, even if sold at clearance prices.

* If you have a spare lithium-ion battery, use one to the fullest and keep the other cool by placing it in the refrigerator. Do not freeze the battery. For best results, store the battery at 40% state-of-charge.