This question came about:
The middle power band starts at 3.7 V according to the user manual.
We have a trip that is below 3.7 V (3.692 V) and the units still reports as per medium level.
Why is that?
The thresholds are correct in the user manual. The subtlety is that the firmware samples the battery voltage 200 ms after waking up, and then uses that sample to make power decisions until it sleeps again. The battery voltage that is logged with the GPS points is at the time of the fix, which could be slightly different from the wake up sample.
What you are seeing is the battery voltage recovering during sleep – probably above 3.7 V. Then when it has been loaded by the GPS for a few seconds, it comes down slightly, and that is used with the log.
This approach has been found to be most consistent (that is, take a sample on wake up, and use that for the session). It is more confusing if the behavior changes because the device is moving into different bands in the same session. It makes your testing harder though – this could be worked around using a more verbose debug setting on the OEM Server?