m5paper charging issues?

gcormier

I plug m5paper into a USB-C PD charger, but I seem to have intermittent issues. It won't charge, or it won't fully charge. Has anyone else had this issue? No charging indicator appears when it is plugged in. Also, The voltage jumps to almost full sometimes when plugged in, so the battery reports 100% charged.

Basically, I can't figure out how to charge this thing.

felmue

Hello @gcormier

Unfortunately M5Paper doesn't have a charging indicator (eg. LED) and as you already noticed yourself the reported voltage is of almost no use either.

The thing is that the charger IC used in M5Paper has two outputs (charging and standby) which would indicate if the battery is being charged or not. Sadly though the M5Stack engineers decided to not use those outputs.

I did some measurements with my M5Paper and on average it did not take more than 3 hours to fully charge the battery.

So I suggest you keep it charging for at least 3 hours and it should be full.

Thanks
Felix

sj3fk3

@felmue Do you have an idea what the lowest (device still working) voltage is and what the maximum is? It's a 3.7V battery? But I think when it's fully charged it can be 4.2V? I've tried to find something of a table to convert voltage to % power left, but failed to find anything useful. In example code that I saw, they used something like 3.3V as lowest possible voltage, but my initial test told me that it craps out around 3.8V / 3.7V?

Or are the measurements that you get from the api just not worth while to use?

felmue

Hello @sj3fk3

I am currently running a discharge experiment where I measure the battery voltage with a multimeter and compare the value to what M5.getBatteryVoltage() returns.

M5Paper is in deep sleep and I wake it from time to time and check the values.
So far the values are quite comparable. You can find the data here.

The battery in my M5Paper is a 3.7V type with an end charging voltage of 4.35V. You'll find some additional information in the above link.

Thanks
Felix

felmue

Hello again

Update: in the above experiment my M5Paper successfully came out of deep sleep for the last time at about 3.31V (multimeter value) / 3.284 (ADC value). Next time I checked it died during boot.

Thanks
Felix