Most important:
- never discharge it completely (discharging a cell completely before charging is only useful for Nickel-Cadmium and, in some circumstances, for Nickel-Metal Hydride chemistries, but it's definitely harmful for Lithium-Ion batteries)
- never keep it at high states of charge (say, above 60%) at high temperatures (above 50°C)
Less critical:
- keep it cool, in general
- don't charge it completely, stop when cells are at approximately 4.0V -- this battery has two cells in series, and you can check the pack voltage in sysfs, e.g.
root@brigitte:~# cat /sys/class/power_supply/BAT0/voltage_now 7657000this is the pack voltage in µV. I guess the “smart battery” chip included in this battery actively balances the cells, so you can assume reasonably close voltages and just divide this number by 2 to get an estimation of a single cell voltage
- charge it slower (I’m not sure if it’s doable with the Librem 13, but maybe limiting the input current at the DC jack could work)
- before storage (if you were to buy a replacement, e.g.) charge it at 40% and then keep refrigerated (4°C). Check state of charge periodically (every 6 months), restore if necessary
The battery assembled in the Librem 13 is manufactured by Sunwoda in Shenzhen, model name is “TU131-TS63-74”. More information at: http://www.cvc.org.cn/swf/UN2014-0607-1.swf. You can also buy a replacement, see for instance http://www.aliexpress.com/item/New-and-original-The-Tablet-PC-battery-for-TU-TU131-TS63-74-7-4V-45Wh/32314737489.html. As it appears unlikely that Purism will offer any kind of support or replacements, I think I’ll buy one soon (as long as it’s still in production) and keep it in the fridge.
Sources: professional background. This guide: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries is also quite comprehensive.
Cheers
дядя Вова