Tips tell you how to prevent a Li-ion battery to fall asleep

Li-ion batteries contain a protection circuit that shields the battery against abuse. This important safeguard has the disadvantage of turning the battery off if over-discharged. Storing a discharged battery for any length of time can do this as the self-discharge will gradually lower the voltage of a battery that is already low on charge. The protection circuit will eventually cut off between 2.20 and 2.90V/cell.  

Some battery chargers and analyzers (Cadex), feature a wake-up feature or “boost” to reactivate and recharge batteries that have fallen asleep. Without this provision, a charger would render these batteries unserviceable and the packs would be discarded. The boost feature applies a small charge current to first activate the protection circuit. If a normal cell voltage can be established, the charger will them start a normal charge.

Do not boot lithium-based batteries(like LENOVO ThinkPad X1 Carbon (3460)Series )back to life that have dwelled below 1.5V/cell for a week or longer. Copper shunts may have formed inside the cells that can lead to a partial or total electrical short. When recharging, such a cell might become unstable, causing excessive heat or showing other anomalies. The “boost” function by Cadex halts the charge if the voltage does not rise normally. 

When boosting a battery, assure correct polarity. Advanced chargers and battery analyzers will not service a battery in reverse polarity. With a sleeping Li-ion, the voltage cannot read and the service must be done with this awareness. Li-ion is more delicate than other chemistries and a voltage applied in reverse may cause an electrical short or do other damages. 

Storing lithium-ion batteries presents some uncertainty. On one end, manufacturers recommend to keep them at a state-of-charge of 40–50 percent, and on the other end there is the worry of losing them due to over-discharge.There is ample of bandwidth between these criteria, and if it doubt keep the battery at a higher charge in a cool place.DELL Alienware M17x R4

As part of a study, Cadex examined the cause of battery failure in mobile phones. Out of a large population of returned warranty batteries, 91 percent could easily be restored, of which 30 percent failed due to over-discharge. Only nine percent were non-serviceable. The restored batteries went back to service. Lack of test devices at customer service levels is in part to blame for the high exchange rate.

Source from Internet.