Was trying to do OS upgrade on MC-40 Device and TC700H Device. In both scenario battery level was less than 30%, but it was charging through following medium and for each medium behavior was different
1) Charging through AC Power
2) Charging through USB attach to Computer/Laptop
 
Have submitted OS upgrade through Power Manager CSP, provided path from where zip file can be read. Once xml was submitted or through barcode, device goes in to recovery mode,
1) Charging through AC Power: After going in recovery mode, check the batter percentage and successful update the OS.
2) Charging through USB attach to Computer/Laptop: After going in recovery mode, check the batter percentage, but here OS upgrade fails telling battery level is low so couldnt perform the operation. Try later.
 
In both condition device was charging, on USB it failed.
 
What kind of checks are added for checking battery level for applying any zip. Or any other details that should be kept in mind.