In posts like this, and from other sources, I have heard that the handset should be fully charged before flashing or installing a customer ROM. I assume this is because the calibration for the battery is kept somewhere within the ROM, but I don't know for sure. Is this really necessary?

  • For most ROMs if you are over 50% battery you'll be alright
    – Juan Gomez
    May 6, 2011 at 13:49
  • 2
    I always just leave my phone plugged in while I make backups or flash a new ROM. If you're concerned with battery calibration you can manually reset it by fully charging your phone and then letting it run down to the point where it shuts itself off twice in a row with no charging between 100% and 0%.
    – newuser
    May 9, 2011 at 15:07
  • @JonnyP Thanks, I'm definitely familiar with the calibration reset method, but I am more concerned with whether or not it is even necessary. Seems like this is more a measure to prevent borking the rom than anything else.
    – shambleh
    May 9, 2011 at 15:34
  • That's my feeling as well. Better safe than sorry when the consequences are so drastic.
    – newuser
    May 9, 2011 at 15:36

1 Answer 1


It's just because, under some circumstances, flashing can take a while. You really don't want your device shutting off while it's being flashed; it can brick the device.

The calibration for the battery is stored, yes, but usually it gets adjusted within a few charges of the phone. It might be a little inaccurate for a while, but it's not a major concern.

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