I am having a problem with the battery in my Mom's old iPhone 4.
She recently had to replace her phone because it was showing this screen: That isn't her phone, but that is what it was showing. When we unplugged it, the phone completely died so we left it to charge for a while.
It then showed the connect to iTunes screen:
I went to unplug it and plug it into my computer, but it instantly turned off. I plugged it into the computer and when it started, it showed the same screen. iTunes found it and said that I needed to update or restore the phone. I tried, but I got error 21 (some online researched said that this meant the OS couldn't boot because it had a bad battery). I ordered a new battery online and attempted to replace the battery myself. I had no problem and when I was done and plugged it in to the computer, it showed the same screen. I should also mention that there was never (from the start!) a screen that indicated that the battery was dead.
At this point I was pretty upset because my mom had years and years of photos that were never backed up.
Any help would be very much appreciated.
EDIT: My questions are A) Why would the iPhone allegedly not detect the battery B) are there any fixes that would not require me to take the device in (not on warranty anymore) and C) If it isn't the battery (because I have replaced it), what could be causing this?