How i can save voltage battery of fipy+Board 3.1

[HAMMOUTI]

Hi i try to save voltage battery of fipy+Board 3.1 when i do test with USB cable i find save in the file "vb.txt" i create it with fonction open python but when i boot the Board 3.1 + fipy i cant find any save voltage in the file i use 2 battery 1,5 v 3V to board 3.1
Can you help me how to do correcte test battery of pycom device .

[Elizar]

@HAMMOUTI Please try to close() or flush() the file from time to time to ensure your data is really written to the filesystem. The cleanest way to do that is to always use an open(...,"a")/write/close() sequence.

If that on the long run is a good idea may be a different story. FLASH memories tend to degrade if written too many times.