Same problem here, with an 11gen and 13gen intel.
Original charger, original cable.
After months of this problem, I decided to keep track of the charging power with node_expoter and prometheus.
Turns out, even when fully charged, the battery will sometimes report charging of a couple mW (from 20ish to 200ish). This doesn’t seem to have a hard correlation with system usage.
But another very interesting thing I noticed after playing around with the official ubuntu battery life guide: I turned off boosting of the CPU completely with TLP. And the “battery chargin / discharging” desktop notifications are now completely gone. So the main culprit of the flipping seems to be the very short bust of required power during clock boosts.
Here’s a quick graph showing the charge value (calculated with node_power_supply_current_ampere * node_power_supply_voltage_volt from node_expoter.
There’s a tiny bump in load when the battery ist charging for a bit, but it’s not a lot