This would be great for trips.
Apple should have a mode where it only takes the phone charge to 80% and just keeps it there till the battery case is depleted - so it doesn't keep your phone battery pack at 100% (which is bad for battery capacity life).
Yeah, the ideal algorithm would be, with both starting at 100%:
- Deplete phone battery to 80%
- Switch to battery pack. Deplete battery pack to 0%
- After that, start depleting phone from 80% down to 0.
This gets both batteries to 80% as quickly as possible.