Trivia Facts About Lithium-ion Batteries: 4Qs to Test Your Knowledge

Should you recharge only when the battery is totally flat?

Answer: No.

Some studies have found that a lithium-ion battery can last 50% longer if it is charged at 20% remaining capacity rather than when it is fully discharged. Also, you should try to keep the battery at between 20% and 80% capacity as this can help extend its life.

Does frequent shallow charging hasten the aging of lithium-ion batteries?

Answer: No.

For example, unplugging after charging the phone from 30% capacity to 40% does not speed up the aging of the lithium-ion battery. On the contrary, charging the lithium-ion battery when it is fully discharged, or to its full capacity frequently will accelerate its aging. Therefore, it is not advisable to leave your device plugged in and its battery fully charged for a long time. Some computers and mobile phones have battery protection features which can limit the charge level to approximately 60% when the devices are left plugged in, or prevent mobile phones from being fully charged for too long by reducing the charging speed. Consumers should consider enabling such features.

Can fast charging hasten the aging of lithium-ion batteries?

Answer: Yes.

The temperature of the lithium-ion battery is usually higher during fast charging, which accelerates its aging. Try to charge at a lower voltage and amperage if possible.

Does low temperature affect the lifespan of lithium-ion battery?

Answer: Yes.

Temperature that is too high (e.g., > 35ºC) or too low (e.g., < 0ºC) can shorten the life of a lithium-ion battery. Therefore, in freezing cold places, you should store lithium-ion batteries that are not in use (such as backup batteries for cameras) and devices with built-in lithium-ion batteries inside bags to keep them warm.

Other useful tips on battery safety and disposal

Product selection	Choose original manufacturers or reputable brands when selecting your lithium-ion battery, device with built-in lithium-ion battery, charger and charging cable. Make sure that the charger is of appropriate wattage.
Proper maintenance	Store it in a cool and dry place and avoid putting it near garments or flammable objects. Do not crush or drop the lithium-ion battery to avoid damage. Ensure that the operating system of the electronic product is updated to the latest version as it may include new functions to protect the battery.
Handle with care	If the lithium-ion battery, charger or charging cable is deformed, damaged or overheated, stop using it immediately and unplug the charger.
Responsible disposal	Used lithium-ion batteries and devices with built-in lithium-ion batteries should not be discarded as general waste as crushing the lithium-ion batteries during the disposal process may result in short circuiting or the release of harmful substances. The Environmental Protection Department (EPD) has set up the ‘Rechargeable Battery Recycling Programme’ and "Computer and Communication Products Recycling Programme" to help consumers in the proper disposal of, and the recycle and reuse of such products. For details, please refer to: https://www.wastereduction.gov.hk/en/waste-reduction-programmes.html

For more information, please refer to the article ‘6 Ways to Extend the Life of Lithium-ion Batteries’ (Chinese version only) in issue #541 of CHOICE Magazine.

Further reading: To better understand batteries and chargers

In addition to lithium-ion batteries, we also use conventional batteries and chargers from time to time. Do you know the difference between alkaline and carbon batteries? Which is faster: Quick Charge vs Super Charge? To find out the answers, please refer to the article ‘To better understand your chargers and batteries’ (Chinese version only).