First, consider the problem of charging cable or charger, you can find another quality no problem charging cable and charger to test and exclude;
Two: It may also be the problem of mobile phone charging port, if the problem is still tested with a new charger and line, it should be considered that the problem of mobile phone charging port (charging small board)!
Three: Finally, the problem of the mobile phone motherboard, this possibility is relatively small!
The above is millet mobile phone fast charge how to slow charge the answer
The fast charging of Xiaomi mobile phones suddenly slows down, generally due to the charging protocol mismatch and power decline caused by not using the original charger to charge
The reasons for the slow charging of Xiaomi mobile phones are:
1, Millet mobile phone battery aging, resulting in slow charging speed.
2, the charger head problems, replace the new charging head can be.
3. USB has a problem.
4, charging speed can not keep up with the power consumption speed, it is recommended to standby charging.
I think your batteries are failing. I suggest you replace them one by one