I have had the app display 100% a few times, Its really not my goal.
I have a non DJI branded three battery bar / hub / strip, circuit board, well I don't know what it is, but I bought it for my P2V+.
I can charge up all three the day before, etc. Then usually before a fly, I will power on the battery I'm going to use first. Plug the charger in, if not already, and appears to top it off, like about 10 mins. This has been the only way I have seen 100%.
Now why the long story.
If I power on more than the one battery, the two or three batteries will so to speak, try to charge from each other. Don't try this in the car or at home. This strip doesn't have any protection against this, no diodes, etc.
The battery actually melted the solder holding the tab to the circuit board.
I bought it because it said it was three battery charger strip for DJI Phantom 2 series.
About 2 months later, DJI started selling their version.
Rod