10 min battery life

  • Re: M5Paper EPD power consumption

    Sorry to deviate a bit from the current discussion. Do you guys also have a battery life of around 10 mins? I just received my M5Paper and it is of no use as "e-ink" display if it can't last a day with a full charge. Thank you very much in advance.

  • Hello @rahulthakurms

    just curious

    • how long did you charge the battery?
    • how did you determine the battery has been fully charged?

    I have not yet had the chance to do measurements myself, but from the results of others it seems that running some of the examples the current is around 150mA.

    This should result in a runtime of roughly 7 hours from a fully charged battery (which is rated 1150 mAh according to the specification).

    So I suspect that either the battery in your M5Paper is defective or maybe it has not been fully charged?


  • It's confusing to tell if its fully charged using the example code as the battery icon is just calculated by looking at voltage.. so it'll jump to 100% quickly after the USB-C is connected.

    It will not however be full though. (the voltage is increased by the USB not by the battery being charged)

    Leave it charging for a few hours.

  • @sambartle the battery voltage increase is actually because of the charging - the PMIC reports the charging voltage, and without the load of running the M5Paper from battery. Just by using the battery instead of an external power source, voltage can drop by 0.1-0.3V as well. The PMIC in this device is incredibly dumb, and some of the features (e.g. the charging/charged indicators) aren't even hooked up.

  • Hi guys

    I've just cracked my M5Paper open and I am currently measuring the current going into the battery. Even though the charger IC (according to its datasheet and M5Paper schematic) is setup for 1000mA my measurement so far shows about 420 mA within a couple of minutes after starting to charge an empty battery.

    BTW: the voltage already shows 4250mV. As @sambartle and @fonix232 pointed out, the voltage is no indicator about whether the battery is already full or not.

    The battery is rated 1150 mAh which means the charge time will be at least 3 hours, most likely more as the current will drop further. I'll update this post with more numbers when the charging current has dropped to zero, eg. the charging has finished.

    Update: the charging dropped to 200 mA after about 2.5 hours, then dropped to zero after about 3 hours. I don't think that was enough to charge the battery completely - but I might be wrong. Could there be a 3 hours maximum charging limit? Anyhow, I need to do more experiments to gather more information.


  • Thank you very much everyone for your time and response.
    I was charging only for 15 mins as the battery percentage is showing 100% within 15 mins. Even I found it odd. Thanks for pointing out that It might be showing battery 100% even when it isn't. I will keep it connected for 6-7 hours and test it again.

  • @rahulthakurms please let us know the results :)

  • @rahulthakurms Are you running the FactoryTest firmware? If yes, go to the test page while charging and watch the battery item - it should show ~4.25V while charging. Then unplug the charger and check what the voltage drops to. Around 3.5-3.6V the battery is basically discharged completely. The percentage calculation of this firmware is quite simplistic (linear relation between voltage and percentage, which is mostly incorrect - you'll see that under the same load, the first 10% drop, i.e. 100% to 90%, will take roughly twice as long as, say, 30% to 20%).

    @Zontex I hope all these issue reports are logged for future reference for a V2 of the M5Paper. We definitely need a better charging IC, and a simplified circuit of voltage regulators to reduce power consumption in deep sleep mode. Possibly even a switch to a PMU that supports digital control. And of course better power control of the components (e.g. turning off the touch screen, or at least hooking it up to an interrupt on the ESP32). The current implementation of the M5Paper feels a bit rushed and untested, closer to a v0.4-0.5 than a v1 release.

  • @fonix232 said in 10 min battery life:

    touch screen, or at least hooking it up to an interrupt on the ESP32

    Hello @fonix232

    I think the touch screen interrupt already is connected to the ESP32, eg. TOUCH_INT which is connected to GPIO36 of the ESP32 according to the schematics. Or am I missing something?

    BTW, I fully agree with you, the M5Paper power control system certainly has room for improvement.


  • @felmue

    I think the touch screen interrupt already is connected to the ESP32, eg. TOUCH_INT which is connected to GPIO36 of the ESP32 according to the schematics. Or am I missing something?

    It is, but once the M5Paper goes to deep sleep via power cut (M5.shutdown()), the touch panel is disabled, thus it cannot wake the device up. I see now why my comment might have been slightly misleading.

  • Hi @fonix232

    thank you for the clarification. Yes, being able to wake up the system from shutdown mode via touch would be nice (like it is already possible using an RTC timer or alarm).