Detection of the charging state

I am using powermanagers auto calibration for the battery level. Seems to work well for the most part, but sometimes it sets offsets a little high (e.g. seemingly to early). Yesterday I had started the day on a very low charge. Bangle ran empty over night and I could only charge for about 20 minutes before leaving the house. So pretty much started the day on a close to empty battery and it was shown as such (low dual digits battery, definitely under 20%). Without having a charger with me that somehow changed to 89% somewhere around noon. It was a wrong offset for the voltage/percentage, probably set by powermanager, after resetting that offset it went back to showing 12%.

So the question is, could somehow leaking currents or something like that have triggered the charging event without having a charger present? Has anybody seen something like this?

I have tried to get incorrect values in the charging event by wiggling the charger around, but as far as I can see that works just perfectly. There do not seems to be events lost or doubled, every event changes state from the previous event. The state changes in powermanager seems to match up fine.

powermanager currently ignores the charging state on boot but in my testing that does make no difference in the behaviour. Maybe setting a timeout for recalibrating instead of using the charging=false-event would work better, but I don't know how to check it actually works better than before. Maybe someone else has an idea for testing?