My balancing robot has an identical problem. But not from the beginning: At first it worked. But then the motor board failed. I can't tell if it's related to a connection via USB for loading the battery or if it just happened. But it is definitely the board that is broken.
I have noticed that the case gets warm when I try to charge it. The red LED lights up continuously, indicating a fully charged battery, but the unit won't turn on. There are no green LEDs on the motors. As I said, it worked in the beginning.
I have noticed that the IMU on the core unit no longer provides data when the motor unit is connected. It looks as if the I2C bus is blocked.
If a USB cable is connected for charging, the IC 5306 gets hot above 90°C:
By the way: Now, the red LED is no longer lit at all!
I think the board is broken. I measured the voltage of the battery when the battery is connected to the board but it shows 0V. Maybe the short circuit protection shuts down? Good to know, otherwise my flat would be on fire now....
The battery is working fine inside another M5Stack Core unit, so the battery is not broken.
I measured the Current consumption of the board without a connected battery:
Again, a further indication that the board is damaged.
Looks like I will need a new board...
Does anyone else have a problem with the board?