Why does my iPhone 5 shuts down at 7%?

I had the same problem with my iPhone 4 and it kept doing that and every while it shuts down at 7% than 10% than 15% than 20%! And I had to sold it! I really don't want the samething to happen to my iPhone 5! Because my parents won't buy me another phone? I don't have warranty and I can't change the battery because it's expensive!

Take it to the Apple store

  • My laptop shuts down in the middle of iPhone music syncing? I've synced my music onto my iPhone 4 from my laptop before, but recently, when I try to sync my updated music onto my phone, it resyncs All of the music I already have in there and then my laptop completely shuts down sometime after syncing 100 songs… It has happened multiple times and is very irritating.
  • My iPhone 4S shuts down randomly? I just got an iPhone 4S and I will charge it full but somehow I loose battery so fast and then when it's about 50% it just shuts down randomly I checked for updates it's said I have the latest update does this mean I have to restore my iPhone?
  • My iPhone 4S shuts down 3-4 times a day. What will Apple do? I had my iPhone 4S since December 30, 2012 and it started to shut off at random times. It gets pretty annoying when I'm rebooting it. When I take it to the Apple Store, will they replace it? If so, how much will they charge me?
  • My Iphone 4 shuts down randomly when not plugged in? I've been listening to music today outside, sun was shining and suddenly it shut down, ever since it keeps shutting down if its not plugged in like in every 10 seconds, can anyone help, can sun be reason to damage battery or something? If so what can i do?