Why does my iPhone 4 keep dying at 20% battery?

The battery life has decreased significantly. When I'm using it, it only lasts about an hour? Can the hardware not keep up with the software? Is it a problem with the battery itself? Just normal wear and tear?

If it is jailbroken, then chances are themes and extra tweaks are driving your battery down.
If not, check your brightness. You will be surprised how it doesn't need to be on the highest brightness in order to work. Also, check your 3G/Bluetooth/Data/Wi-Fi. When you aren't using it, turn them off.
The reason that the 20% battery death happens is because it needs enough power to keep the clock/idle setting running, like all your information.

  • Why is my IPhone4s battery dying so fast? I've had my IPhone 4s for a little over a year, and I charge it every night and when I wake up it's at 100%. When I take it off the charger, it starts going down. I wake up at around 9 AM every day and by 1 PM it's already at like 40%. I still have the old software (haven't updated to I0s7 yet) and have like 2,500 pictures so is that maybe why it's dying so fast? Please let me know!
  • Why is my iphone dying at 15% battery life? It started with my phone dying at 5%. I could handle that. But then it started dying at 7%, 10% and now it is dying at 15%. I have no clue what to do now! I have an Iphone 4 and I have NOT updated to IOS 7. What could be the issue of this?
  • Why is my iPhone battery dying when I'm not even using it? Last night I went to sleep at 10 and my phone was fully charged. I wake up at 7:30 and my phone was dead. I didn't even use it. It just dyed. Just like that. Why? I have an iPhone 5s iOS 9.1
  • Why is my iPhone battery dying so fast? I just bought an unopened iPhone 4S, because I prefer the smaller phones, and the battery drains in less than 5 hours. The phone was never used before, but is the age of the phone the reason it's dying so fast? Will replacing the battery make a difference? As those are old as well even if I but an unopened one. bought* My previous iPhone 4S is just as old, but was used constantly. And that has much better battery. Lasted two days, even if being used a lot.