What To Do When A Li-on Battery Falls Asleep
No, wrong Li-Ion! (Hilarious, we know)
Lithium-ion batteries have a feature in which a protection circuit enters it into a sleep/hibernation of they are over-discharged. This is to ensure the battery is protected from abuse and to prevent damage.
This can occur when a Lithium-ion pack is stored in a discharged state for an extended time period, as the batteries self-discharge cycle would drain it. It goes into this hibernation mode to protect it, and to give you more use out of it in the long run.
Waking up the Li-ion
In most cases, you can boost the battery back to life.
Firstly, don’t try to do this if the battery has discharged to 1.5V/cell for 1+ week.
If the voltage does not rise to a normal level within a minute while on boost, discard the pack.
A sleeping Li-ion does not reveal the voltage, and boosting must be done with awareness. Li-ion is more delicate than other systems and a voltage applied in reverse can cause permanent damage.
When in storage, manufacturers recommend that you keep a lithium battery between 40-50 per cent charged, but this can be an issue due to over discharge. If in doubt, keep your battery stored at a high SoC in a cool place (15º - 20º preferably).