1. Over discharge protection: when the battery is about to run out, when the voltage reaches a required minimum value, the protection board will also close and cannot discharge. Therefore, the product will automatically shut down, forming an over discharge protection function.

2. Overcharge protection: when charging the product, when the voltage reaches the maximum battery voltage (4.2V), the protection board will automatically power off and close, indicating that charging is not continued. A kind of overcharge protection.

3. Short circuit protection: when the battery is inadvertently short circuited, the protection board will automatically close within a few milliseconds and will not be powered on. At this time, it is OK even if the positive and negative electrodes touch one. A short circuit protection will not cause explosion.

4. Overcurrent protection: when the battery is discharged, the protection board will have a maximum limiting current, which is different for different products. When the discharge exceeds this current, the protection board will automatically close.