iPhone Stuck in a Restore Loop? Maybe it's your battery

This one was a real doozy.  So I was playing with a new iPhone 4 I got off eBay, seeing if I could downgrade the IOS from version 5.0.1 to 4.3.5.  Somewhere along the line, the phone went to restore mode and was completely stuck there, commonly known as a "restore loop".  I tried everything possible to get the software restored - loading both stock and custom IPSW files in iTunes, re-jailbreaking with redsn0w, but nothing worked.  iTunes would give errors 3194, 21, or -1.  RedSn0w would exploit with GreenPois0n and start the jailbreak process, but midway through, the phone would just reboot and I'd be back to the recovery screen.

It really looked like I had bricked it.  In desperation, I looked to a program called iRecovery, which is designed to get the phone out of recovery mode without doing a restore.  That didn't exactly match my problem, but figured it was worth a shot.  Getting iRecovery working in Windows 7 seemed impossible, so I just installed it on an old laptop running Windows XP.  Running iRecovery in shell mode, I see lots of error / warning messages, notably this:

gas gauge read timed out

Hmm.   Googling this error message indicated and issue with the battery.  I found a new battery for $7 off eBay, and sure enough, was then able to restore IOS and get the phone back up and running.

This was a good 3-4 days of frustration.  Would have nice if iTunes (or RedSn0w) indicated a battery or hardware issue, but both kept pointing towards software as the problem.  Anyway, thanks iRecovery - without you, I would have never figured this out.