Battery icon has a question mark in it I checked a lot of forums, like a lot, but no one had my exact problem. I have an ASUS Tablet with Android 4.2.2 and the battery icon in the notification bar has a question mark in it. At least when it turns on cause ocasionally it crashes on boot and reboots itself before even reaching the lockscreen. 
Anyways, when I'm lucky and it turns on, it eventually crashes and reboots after a few minutes. If it is on and I try to get to the battery settings, it crashes and reboots.
I didn't manage to get to the battery to check the contact, like most forums say, but I don't think it's the case as it's getting juice from it to turn on...

I tried reseting it by the way.
There can be three reasons for this:


Your battery is dead or the Battery Status Indicator (BSI) pin on your battery is faulty. In either case, you have to replace the battery.
The BSI pin head on your phone hardware is faulty.
The firmware on your phone has a bug, and is unable to properly read the battery charge.


The third one is very less likely. The second option is less likely, but in my case (a Samsung Galaxy On7), both 1 and 2 had occurred at the same time.