[G2 General] votinh:
Here's my notes from a few years ago.

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Li-Ion Battery

(From Wiki) During discharge, lithium ions Li+ carry the current from the negative to the positive electrode, through the non-aqueous electrolyte

and separator diaphragm.[7]

During charging, an external electrical power source (the charging circuit) applies a higher voltage (but of the same polarity) than that

produced by the battery, forcing the current to pass in the reverse direction. The lithium ions then migrate from the positive to the

negative electrode, where they become embedded in the porous electrode material in a process known as intercalation.

Prolonging battery pack life (from wiki)

+ Avoid deep discharge and instead charge more often between uses, the smaller the depth of discharge, the longer the battery will last.

+ Avoid storing the battery in full discharged state.

+ Li-ion batteries should be kept cool; they may be stored in a refrigerator.

+ The rate of degradation of Li-ion batteries is strongly temperature-dependent; they degrade much faster if stored or used at higher temperatures.

+ Li-ion has no memory effect.

+ Li-ion does not need to be fully charged.

+ In fact, it is better NOT to fully charge, because high voltages stresses the battery.

+ Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off =>

+ To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible. (meaning do NOT overcharge)

+ Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and

can distort the charge cycle. Battery manufacturers advise against parasitic load because it induces mini-cycles.

What does that mean to us? Don't use when it's plugged in?

+ A portable device must be turned off during charge. This allows the battery to reach the set threshold voltage unhindered, and enables terminating charge on low current.

+ Li-ion should never be discharged too low.

+ Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week.

Simple Guidelines for Charging Lithium-based Batteries (from batteryuniversity.com)

+ A portable device should be turned off while charging. This allows the battery to reach

the threshold voltage unhindered and reflects the correct saturation current responsible to

terminate the charge. A parasitic load confuses the charger.

+ Charge at a moderate temperature. Do not charge below freezing.

+ Lithium-ion does not need to be fully charged; a partial charge is better.

+ Chargers use different methods for “ready” indication. The light signal may not always indicate a full charge.

+ Discontinue using charger and/or battery if the battery gets excessively warm.

+ Before prolonged storage, apply some charge to bring the pack to about half charge.

+ Over-discharged batteries can be “boosted” to life again. Discard pack if the voltage does not rise to a normal level within a minute while on boost.

Conclusion:

+ A portable device should be turned off while charging.

+ Avoid deep discharge and instead charge more often between uses.

+ Lithium-ion does not need to be fully charged; a partial charge is better.