My 4s is 3 years old and the battery is just about shot. I'm on limited time. I get 2 hours if I'm lucky. It often discharges as it's plugged in. Today I'm struggling to get it to 100% from 87% and it's been plugged in for 4 hours! I have it in airplane mode w/ wifi on (so my son can contact me if need be). I looking on ifixit.com and it looks pretty easy to change the battery. I have an old 4 I will take apart first to check it out then will try my own phone. Is there just one Mah hours I can buy or are there other sizes? I would love to go a little more but I'm sure if I just got the "regular" size i'd be fine. What is the "normal" mah for a 4s battery? I have no money to buy another (used) 4s or even a 5 so right now my only option is to change the battery. If I wasn't planning on moving in a few months I'd just buy a 6 outright but that money is spoken for already. Any help/advice would be appreciated. Thank you.