100% battery is useless if your device isn't on

[michael.koppelman]

I really love the M5 Stack. But then you run across things really hard to understand. Like, I dunno, this:

You must set GPIO4 high within 100ms of the device powering on.
If your code has delays before setting the pin, the device will
shut down.

So if you are powering down with 100% battery, it's BY DESIGN.

Your first two lines in setup() must be:

pinMode(4, OUTPUT);
digitalWrite(4, HIGH);

They are going to protect that battery even if they have to halt your code.