Guidelines for Prolonging Li-ion Battery Life
Written by Administrator   

Storing a Li-ion battery at the correct temperature and charge makes all the difference in maintaining its storage capacity.

 

It is significantly beneficial to avoid storing a lithium-ion battery at full charge. A Li-ion battery stored at 40% charge will last many times longer than one stored at 100% charge, particularly at higher temperatures.

 

If a Li-ion battery is stored with too low a charge, there is a risk of allowing the charge to drop below the battery's low-voltage threshold, resulting in an unrecoverable dead battery. Once the charge has dropped to this level, recharging it can be dangerous. Some batteries therefore feature an internal safety circuit which will prevent charging in this state, and the battery will be for all practical purposes dead.

 

In circumstances where a second Li-ion battery is available for a given device, it is recommended that the unused battery be discharged to 40% and placed in the refrigerator to prolong its shelf life. While the battery can be used or charged immediately, some Li-ion batteries will provide more energy when brought to room temperature before or during use.

 

Guidelines for prolonging Li-ion battery life 

 

  • The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible.
  • Unlike Ni-Cd batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a long time, they should be brought to a charge level of around 40% - 60%. Lithium-ion batteries should not be frequently fully discharged and recharged ("deep-cycled") like Ni-Cd batteries, but this is necessary after about every 30th recharge to recalibrate any external electronic "fuel gauge" (e.g. State Of Charge meter). This prevents the fuel gauge from showing an incorrect battery charge.
  • Li-ion batteries should never be depleted to below their minimum voltage, 2.4v to 3.0v per cell.
  • Li-ion batteries should be kept cool. Ideally they are stored in a refrigerator. Aging will take its toll much faster at high temperatures. The high temperatures found in cars cause lithium-ion batteries to degrade rapidly.
  • Li-ion batteries should not be frozen (most lithium-ion battery electrolytes freeze at approximately −40 °C; however, this is much colder than the lowest temperature reached by household freezers).
  • Li-ion batteries should be bought only when needed, because the aging process begins as soon as the battery is manufactured.
  • When using a notebook computer running from fixed line power over extended periods, the battery should be removed, and stored in a cool place so that it is not affected by the heat produced by the computer.

 

Storage Temperature and Charge

 

The following table shows the amount of permanent capacity loss that will occur after storage at a given charge level and temperature.

 

Permanent Capacity Loss versus Storage Conditions
Storage Temperature 40% Charge 100% Charge
0 °C (32 °F) 2% loss after 1 year 6% loss after 1 year
25 °C (77 °F) 4% loss after 1 year 20% loss after 1 year
40 °C (104 °F) 15% loss after 1 year 35% loss after 1 year
60 °C (140 °F) 25% loss after 1 year 40% loss after 3 months