Laptop Battery Care

Most laptop batteries these days are made from lithium ion technology. This guide is specifically written for that particular battery type. Should yours be NiMH, some of these hints are not directly applicable. Consult your battery or laptop manufacturer for details.

A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.

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.

Aging of lithium-ion is an issue that is often ignored. Lithium-based batteries have a lifetime of 2-3 years. The clock starts ticking as soon as the battery comes off the manufacturing line. The speed by which lithium-ion ages is governed by temperature and state-of-charge. High charge levels and elevated temperatures hasten permanent capacity loss.

Some lithium-ion batteries fail due to excessive low discharge. If discharged below 2.5 volts per cell, the internal safety circuit opens and the battery appears dead. A charge with the original charger is no longer possible. To prevent failure, never store the battery fully discharged. Apply some charge before storage, and then charge fully before use.

If possible, 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. The most harmful combination is full charge at 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 but some battery and laptop manufacturers caution against it. They say that dust and moisture accumulating inside the battery casing could damage the laptop.

The total run-time of the battery is dependent upon the design and use of the notebook computer. The use of the screen, the hard drive and other peripherals results in an additional drain upon the battery, effectively reducing its run-time. To ensure maximum performance of the battery, optimize your computer’s power management features. Refer to your computer manual for further instructions.

*Decrease screen brightness as low as possible.

*Remove any PCMCIA cards not in use.

*If the battery will not be in use for a month or longer, it is recommended that it be removed from the computer and stored in a cool, dry place. When storing for long periods of time, keep the battery at 40% to 50% full charge. If you store a battery when it’s fully discharged, it could fall into a deep discharge state, which renders it incapable of holding any charge. Conversely, if you store it fully charged for an extended period of time, the battery may experience some loss of battery capacity, meaning it will have a shorter life. Aging will take its toll much faster at high temperatures. Ideally store it in a fridge (sealed in a zip-lock bag to prevent moisture accumulation). However, it should not be subjected to freezing temperatures. A charged battery will eventually lose its charge if unused. It may therefore be necessary to recharge the battery after a storage period.

*Charge often. Don't try to fully discharge the battery packs frequently. This only adds strain. Several partial discharges (regular use) with frequent recharges are better for lithium-ion than one total discharge. Recharging a partially charged lithium-ion battery pack does not cause any harm because it has no "memory".

*Battery manufacturers recommend fully charging and discharging the battery at least once per month.

*Avoid heat, a hot car, for example.