Actually, yes. At least anecdotally– I _had_ to do this when my iPhone 5's lightning port was damaged.
When traveling overseas a cheap charger died, partially frying my lightning port. The phone completely refused to charge and I grew more and more desperate as the battery slowly drained over the next day before eventually dying. Now trying again to charge the dead phone had a surprising result: it actually charged enough to boot up! Ridiculously: it then stopped charging once booted and drained again in about 2 minutes.
The solution I developed was to plug it in _then_ power it off and it would charge (slowly) while completely powered down. Removing power for even a moment would boot the phone and stop charging.
I'd absolutely guess that, in a pinch, you could charge your modern iPhone with a non-working cable if you did the same procedure: plug in, power off, let charge while off.
Unlikely, even if you shut the device down when you attach a charger it goes into either a semi-on state or just turns on entirely. Even if you shut it down while it’s plugged in.
I thought the “semi-on” state with the battery display was still just firmware and not full iOS. If not, what exactly is it booting to display that? Surely not an ordinary kernel?
My experience is with the MTK platform but Apple may be similar; in which case the battery display is done by neither "firmware" nor the full OS, but an intermediate component:
I believe they are just one of the things you can "boot", alongside regular iBoot in the boot partition and loaded appropriately by SecureROM. I'm pretty sure the images at least ship inside IPSWs.
This is correct. That's because the "Charging" screen also sometimes has OEM or carrier branding on, and error messages that might need to be i18n translated eg. "battery failure", "overheat". It's much easier to do that with a separate component rather than give every OEM the ability to flash and recompile firmware.
Side note: I wish that feature could be turned off. Sucks to turn your phone off for the night, plug it in to charge, and it boots back up (it's not the semi-on battery display either, it does a full boot to iOS).
> To enable full current, 0x74 request must be issued by Tristar and processed by HiFive. For SecureROM/iBoot that's enough
I wonder if that means, in a pinch, you could turn off the device to use an uncertified charger that iOS would block.