I recently replaced the battery myself in my out-of-warranty 3GS. All was going well (though the percentages were a bit off) until I noticed a new update for iOS (4.3.3). As I was on 4.2.1, I figured it couldn't hurt to upgrade.
Please note, I didn't care about nor was I jailbroken. I upgraded as normally and was prompted with a couple of errors including "error code 29". Apparently "error 29" indicates that the hardware is incompatible - the circuit board attached to official (read: stock) batteries is different than that attached to aftermarket batteries and iTunes will detect this, locking out the upgrade and throwing your device into a DFU loop.
Whoops.
Please note, I didn't care about nor was I jailbroken. I upgraded as normally and was prompted with a couple of errors including "error code 29". Apparently "error 29" indicates that the hardware is incompatible - the circuit board attached to official (read: stock) batteries is different than that attached to aftermarket batteries and iTunes will detect this, locking out the upgrade and throwing your device into a DFU loop.
Whoops.