@Redlunn
Sounds like a neat solution with the AMT21s. I see that you found a solution to the turns count problem as well, with the battery. Another solution would be to modify the firmware for the Teensy slightly, to store and retrieve the turns count from the EEPROM (non-volatile memory). Preferably, you would only store it on shutdown, to alleviate the issue of exceeding the maximum rated (100,000) write cycles of the EEPROM in the Teensy board.