I had left my HTC M8s phone on my PC by the USB cable, both switched off. I intended to give it some charging the next day. When I tried to switch on my phone the next morning it did not respond at all. I tried charging both on the PC and on the mains, I just kept having a blinking orange light, no matter what and how long I tried. I just checked the manual, it indeed signifies a very low battery level.
I got very worried, thinking that the battery might have been fully drained by the PC, killing the battery! I even started to look about replacing the battery. I found instruction movies about the M8. I can tell you, you do not want to try that at home! So I was afraid it needed to go to repair. Only wondering if there would be any guarantee, and in what shape it would get back.
Then I stumbled on this thread, it saved my day!
I tried the reboot by power + volume down. To my great surprise it did start up! I had already rooted this phone, so I could go to recovery and restart to system from there. That went flawlessly, and it showed a 100% battery!! WTF?
You do not need to take out anything like SIM or SD, just reboot.
I am astonished about this situation. What happened? The starting button is fiddly and is not easy to use, but I tried several times. Anyway, the LED signalled plainly WRONG.
I am very worried that people may end up with repair costs that are totally unnecessary!