Reasons why the foot grinder cannot be charged

1. Caused by long-term non-use. Due to the self-discharge phenomenon of the lithium battery pack, long-term non-use causes the battery core to be under-voltage and cannot be charged.
2. The charging head has poor contact. In addition, the battery charging head and the charger head have been peeled off for a long time, resulting in poor contact between the contact surfaces, which will also cause the failure to charge.
3. If the protective board is damaged and the battery cannot be charged, just replace the protective board.