Hi all, the battery on my ipad 4 won't accept a charge any more. I've tried both the mains charger plug and the usb on its own, no luck. All I get is a battery symbol, red in the bottom, with a plug symbol showing a lightning flash. This appears for a second or two and then goes. I'm inclined to think u/s battery, but if that were the case it would work when plugged in to the mains wouldn't it? Any advice greatly appreciated. AG