When I try to boot it it shows the Apple logo for a second and then gives up, same with Recovery mode.
When I put it on quick charge it boots up and works but when I unplug it, it slows down and then shuts off.
I've managed to do a quick change from quick charge to the laptop USB port while it was in Recovery mode and am currently reinstalling the software.
Any ideas?
Best Answer
The battery is dead and needs to be replaced.
If you can only power on and use your phone while it's plugged in, then the battery can no longer hold a charge. It needs to be replaced.
"Quick charging" has to do with the current that the charger supplies. It's not a mode you can select. Laptops don't have the ability to quick charge as a typical USB port only provides 5V at 500mA max. You need at least 2.4A to quick charge (12W).
You can try doing a hard reset of the phone, but if the problem persists, it's definitely a failing/failed battery and it will need to be replaced.