Danke @felmue ,

Your answer pointed me in the right direction.
The voltage between GND and BAT pins was indeed 4.0V+, so I went back to check my code.

I noticed that the official documentation for the AXP on the M5StickC only mentions M5.Axp.GetVbatData() (which is what I used and what gave me weird readings) but the AXP code example uses M5.Axp.GetBatVoltage() and the latter actually gives me the correct number.

What's the difference between these two? Is it just the *1.1/1000?

Cheers,
Flo

Hey folks,

I'm having a bit of an issue here. I have both a M5StickC and a M5StickC Plus and I wrote a simple little Arduino program that displays both the battery voltage and also the percentage charged.
My problem: they don't charge to more than 3.7V. I would like them to be topped off at 4.2V

I tried:

• charging with my PC (5V/0.5A) / charging with my phone charger (5V/3A)
• charging while turned off / charging while turned on
  Nothing seems to do anything.

In all the above cases, I'm charging it via USB-C. If I'm supposed to charge it via the pins, let me know, haven't tried that yet

Any help appreciated,
Flo

EDIT: The problem was that I didn't read the voltage correctly. I was using M5.Axp.GetVbatData() / 1000.0 and that's off by a factor 1.1. The correct way to read the battery voltage is M5.Axp.GetBatVoltage().

How do you guys track the amperage draw of the stick when sleeping? Do you take it apart, cut a power line, hook up a multimeter in between, and later resolder?

Also have you guys experimented with the difference between
M5.Axp.DeepSleep();
and
esp_deep_sleep_start();?

AFAIU Axp.DeepSleep is only supposed to turn off "external devices" (gyro, screen, etc.) but not the ESP itself, right?

And @Morris45 what does the Wire.begin(32, 33); line do in your code above? And why are we commenting out M5.begin()? What's the battery life you're getting from your watch? I'm trying to do a simple infrared remote (that only wakes up when you first pres the main button) and even in full deep sleep, I'm only getting 2 days.