But seriously, folks. This "critical battery" error has occurred to me before on my Kindle 2. It happened when I ran out of juice on a sailboat in the middle of the Whitsundays thereby leaving me stranded with no reading material for several days.
At the time I did some searching from my phone for a solution because the instructions on the screen that tell you to connect your Kindle to a power source and it will only take "a few minutes of charging" were complete and utter bullshit.
According to many sources, the best way to reset your Kindle after this confusing and frightening error is to plug it into the mains charger and let it rip for a few hours. After you leave it alone, you simply press and hold the power button to the right for 30 seconds. Then wait for another 20-30 seconds for the magical flickering of the screen. At this point, if it has enough juice, it will hopefully restart.
I would like to state for the record that this method did not work for me (that time or this time). I even ended up calling Amazon customer service and they swore to me that plugging it into the mains was the best and only way to reset it. Turns out that after I tried that and failed I decided to try plugging it into the USB. And guess what? Yes, of course, that is what worked. I didn't even have to do the power button slide.
How can one avoid this situation to begin with?
I find that if you don't manually turn on the screensaver, despite the fact that the screensaver will turn on, it somehow drains the battery. If you manually turn on the screensaver, by sliding the power button to the right quickly, then it seems to conserve the battery power much better.
Good luck and may the forced be with you.