Storage Temperature and Charge (Important)

roryrudy · 01-14-2008

Storage temperature and charge

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

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 1 year

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.

This was from Buchmann, Isidor (September 2006). Batteryuniversity.com

mbarry · 01-14-2008

Thanks Roryrudy. Very informative.

Th3_uN1Qu3 · 01-14-2008

Thanks for this. Now i know it's not good to leave my player charged if i won't use it in the summer, but i doubt that will happen.

iversonjack · 01-14-2008

Cool, gives me more reasons to not charge my player :P

Traps · 01-15-2008

Nice post roryrudy! Thank you!

There is also another important thing to be aware of with Li-ion batteries (citing Wikipedia on "Lithium-ion battery"):

Quote:

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.

If you look on Wikipedia, there's a bunch of other recommendations for prolonging a Li-ion battery's life, like charging it often and early, with a "deep cycle" only around every 30th recharge (necessary to prevent the fuel gauge from showing an incorrect battery charge).
Nevertheless, the temperature/charge/loss table referred by roryrudy is probably the most important factor to bear in mind for prolonging battery life.

@admin: maybe we could put up a link to Wikipedia here?