Hi, I'm just sharing my experience, just in case it may help someone else.
I recently upgraded the iOS on my iPhone 4s - long story short - it transformed into an unattractive paper weight. After, hours on the phone with Apple; they said it was a hardware issue and basically it's an old phone and it has died.
My partner wasn't happy with that - after searching on the web he found a reference to a repair man suggesting a problem with after market battery. Yes, my partner had indeed changed the original battery, so he swapped the original battery back into the phone & we were able to update it and boot it back to life! I am now using the same phone to write this post. All's well.
As an asides, the newer battery was swapped back in and the phone works.
Hope this helps someone else.
Thanks
nice :)