Hello @Zontex
thank you for checking with your engineers regarding possible long term damage for the RTC backup battery. It's good to know there is none expected.
This M5StickC Plus was part of order M5-8036 and the serial number is (I think):
0_1606915658442_M5StickCPlusSerial.png
In case that is not the serial number, then please kindly let me know where I can find it.
Thanks
Felix