M5Core2, M5StickC and M5StickC Plus all use AXP192 as power management and have an RTC with backup battery. If I am not mistaken all three products use the same RTC backup battery (e.g. MS614SE), which, according to its datasheet should be charged with 100uA.

In the M5StickC and M5StickC Plus source code the charging current is set correctly to 100uA, however for M5Core2 the current is set to 400uA which I think is incorrect.

I've made a pull-request which corrects the charging current for M5Core2 and set it to 100uA.

Thanks
Felix