There may be an issue with your battery, and you can use these steps to troubleshoot it
- Click ( www.apple.com/batteries/iphone.html) for tips on how to prolong iPhone's battery life.
- Try turning iPhone off and then on again.
- Connect iPhone to iTunes and restore iPhone.
- If the screen shows a low-battery image, the battery is low on power and needs to charge for up to ten minutes before you can use it.
- When charging iPhone, make sure to leave it charging until it is fully charged. You'll know the battery is fully charged when the battery icon in the upper-right corner of the screen looks like this .
Note: When charging using a computer, don't connect iPhone to a keyboard. Also, the computer must be turned on and not in sleep or standby mode. If iPhone is connected to a computer that's not turned on or is in sleep or standby mode, the iPhone battery may drain.
When you restore, set it up as new and see if the issue persists with nothing on your device
http://support.apple.com/kb/HT1766?viewlocale=en_US <=== to backup your content
http://support.apple.com/kb/HT4083?viewlocale=en_US <=== to import your photos (YOU WILL WANT TO DO THIS)
http://support.apple.com/kb/HT1414?viewlocale=en_US <=== to restore your iPhone
Thanks. I have done all these in past month.
What I did right now is that let the iPhone drained to 0 % and now I have put it on charge.
Besides the sudden drop , I also witness this that after charge, the battery percentage is not accurate. Like for example it's on 96% but 3rd oarty battery apps shows 100. when I turn off and on again iPhone, the battery percentage goes back to 100.
If you change the battery yourself, you may not be eligible for the out-of-warranty fee if anything goes wrong and you'd have to buy a phone at full retail value.
It sounds like there is an issue with the battery percentage reader, so you can try to restore it to see if that does anything, but if it doesn't you will need a reaplcement