Battery refilling

ATTENTION!

Li-Ion cells are a fire and explosion hazard. By tampering with a battery pack, you also tamper with its protection capabilities, which may not be designed to handle Li-Ion cells with different specs. Don't risk your health and that of those around you to save a few bucks. You have been warned.

A battery pack can be revived by exchanging the spent Li-Ion cells by equivalent ones. Changing them for higher capacity cells is absolutely not recommended unless you are capable of designing battery packs and have changed the pack's protection circuitry to the new design values. Due to the lack of factory calibration, the refurbished battery pack may not have the full performance of a brand new one from the factory.

Always use Li-Ion cells with the exact same characteristics of the ones you are replacing (same manufacturer and model), unless you have the datasheets and knowledge required to know it is safe to do otherwise.

Except for the extremely old models, a ThinkPad battery pack is an Smart Battery, following the SBS design specs. This means the battery has an internal fuel gauge, a charging monitor, and security fuses. It is not just a bunch of power cells thrown together.