What is Inside a Laptop Battery Pack?

Wanna know what secrets lie in a laptop battery pack? If your IBM ThinkPad Battery used to hold around 4 hours but now the laptop battery can only hold about 1 hour after using for 3 years. May I replace the cells inside? Let's open the case and see what is the anatomy of a Li-Ion notebook battery:

If the temperature reaches a high level for whatever reason, the electronics cut off the current to isolate the laptop batteries from charging or discharging to avoid overheating. There might be temperature sensors in the battery compartment, feeding its own safety systems.

For some laptop battery, like IBM laptop battery or Lenovo laptop battery, 4 cell or 8 cell AA Li-Ion cell are wired together within a typical battery pack. Cell Sensor Wire is routed between cells and cells are insulated with special insulating paper.

This regulates the voltage supplied by the battery during charging and discharging to ensure consistent current. Therefore, make sure the voltage is correct before buying a replacement battery is always important.

This is shrouded and designed to minimise the risk of short circuits when the battery pack is separate from the main equipment. Even if the plastic shroud is damaged, the circuitry inside the pack should detect short circuit conditions and protect the cells from rapid discharge.

Most consumer equipment treats a stack of cells as a single battery, but this can be dangerous in lithium ion. As the cells age, some will lose capacity faster than others ¡X and if one cell becomes flat before the others, it can actually start to charge in reverse, which is a highly dangerous condition. The internal circuitry of the battery pack thus has to monitor cells separately and shut down the whole pack if one cell is too far out of balance.

Many lithium ion packs have a built-in meter consisting of a row of LEDs and a button. To check battery charge, press the button and the number of LED lights that appear will tell you charge status. If all lights appear, you have a fully charged battery. This can become more inaccurate over time; more modern cells will recalibrate themselves.