Hello,
I had a calibration problem but only after receipt of the Max2. The battery was at 80% when i was reading. I put the system in standby, then the system powered off at some moment and I had to plug the wall charger when I wanted to use it. At reboot the battery was at 5%.
After a full charge I never had any other battery problem.
I never power off the Max2, I put it in standby (or automatically after 1 hour) and I can use it for more than a week (reading books or music scores and annotating, playing some music with earphones).
I suppose your battery has a serious problem and you should ask for a replacement unit.
Denis