Here's a method you could try. I copied it from the link at the end of the post.
The remedy is quiet simple, follow these steps to get the iPad to home screen to power it down so it has sufficient time to charge up and boot normally and get off the endless loop.
- Plug into wall socket to get it charging.
- Wait until the apple logo appears
- QUICKLY hold down home button and reset/ sleep button at the same time until it reboots.
- Release buttons now.
- Repeat step 3 for at least 30 to 40 times which is about 10 minutes in duration every time you see the logo on the screen.
- Now Let IPad boot up fully, should see home screen with about 2% battery life
- QUICKLY hit the rest/ sleep button down for about 2 to 5 seconds.
- Swipe the screen to when slider appears to switch off the ipad.
- This will power down the IPad which now will not reboot by itself so it can now charge without any interruption’s.
- Allow battery to charge for a least an hour or two without trying to put it on.
- Switch the IPad on
- You should now have about 10 to 20% battery Life
- Power it down again by holding the reset/ Sleep button down again and swipe the screen to power down, let it charge fully to 100% now which will take few hours