Of course, not all battery systems adopt the scheme shown in the above figure. In some cases, there may also be a design of a charging controller within the battery pack. For example, many laptop computers have a charging controller attached to the battery rod. This is because laptop computers generally have a charging controller built into the computer, only providing consumers with an adapter. Therefore, the external battery pack of notebook computers must have a charging controller to ensure the safety of the external battery pack when charging with an adapter. In addition, products that use car cigarette lighters for charging sometimes also have a charging controller installed inside the battery pack. The Last Line of Defense

　　If all electronic protective measures fail, the last line of defense will be provided by the battery cells. The safety level of battery cells can be roughly distinguished based on whether they can withstand external short circuits and overcharging. Due to the fact that before the battery explodes, if lithium atoms accumulate inside the material surface, the explosion power will be greater. Moreover, the protection against overcharging often leaves only one line of defense due to consumers using inferior chargers. Therefore, the ability of the battery cell to withstand overcharging is more important than the ability to withstand external short circuits.

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