Why did my phone do a system update at 0% battery and how can I fix it?

[Android Central Question]

I have a galaxy S6 and when I woke up I tried to charge my phone except it wouldn't work. Later when I tried to turn my phone on it started installing a system update.

 

[B. Diddy]

Welcome to Android Central! What exactly does the screen say? Does it say "Downloading, do not turn off target"?

If the battery is at zero, plug it into a wall outlet and let it charge for at least 6 hours without disturbing it. Then try powering on normally.

 

[Rukbat]

If it's actually installing the update, just plug the charger in and let it finish - if you stop it in the middle, unless it's Oreo or Pie, you'll convert the phone into a paperweight.