iPhone 4 Won't Turn On After Attempted Restore
For the past year, my iPhone 4 locks up every now and then (it does not let me slide to unlock) but it always began to work again after 4 or 5 force restarts. A couple days ago, this happened, but it did not work after many force restarts. I restored it to factory settings, and I got to the part where it says to let your phone restart, but after it did, the iPhone turned off and now it will not turn back on. iTunes cannot see it and I have tried charging it and it does not work. It had iOS 5.1.
What happens when plugged into mains power? Your Battery main have just DIED or at best gone fully flat. Which can only be recovered by the mains power. Do you get a flashing red Battery symbol with a lightning bolt? Leave for 1 to 2 minutes to see if it gaining a charge and pull the plug. If it shuts straight off then time for a new Battery.
You can purchase from here.
I hope that gives you some direction.
Replacement 1420 mAh battery for iPhone 4. Compatible with all iPhone 4 GSM and CDMA models (Not 4S). Does not require soldering. 3.7 Volts (V), 5.25 Watt Hours (Whr). — 37 available at 19.95 each.