I periodically do what you say, P2 motors turned on for a long time to almost fully discharged them. No way.
This new P3, first charge: 96% displays the app.
For my first tests and firmware upgrades I have near 80%. It is welcome the new that I plugged the charger and it is charging.
My P2 batteries don't charge if 4 leds are green (more than 75% of charge)