Trouble restoring Ipad 3

Hello, I've had to resort to asking as I cannot find for the like of me anything along the lines of my problem!

The other day I decided to give my Ipad it's long awaited system update, alls good, it starts installing I go to bed, however during the night it must have run out of charge as it died. Now I am stuck in a loop of it charging, turning on, asking to be restored and then running out of battery again (or so it says).

I reckon the problem is the brightness is at max and the restore screen does not seem to turn off, so it sits there draining what little battery my ipad has accumulated in a never ending loop. My charger isn't apple branded but it runs at 5.1 volts (I believe that's just over 2 amps?) I think that is enough although I could be wrong? I was hoping you good people would be able to tell me.

If it is meant to be enough, is there any way I can turn the ipad off during this loop at any point while still charging it? All advice is greatly appreciated!

Thanks in advance for the help!