Why is my iPhone's battery draining so fast?
If I had a nickel for every time someone complained to me about the battery life of their iPhone I'd have, well, a lot of nickels.
Lets get one thing out of the way right up front:
Remember how long the battery on your old phone used to last (days, a week)? If you think back you'll recall that your old phone had a tiny little black and white screen and the only thing you used it for was to make phone calls and send/read text messages. In comparison your iPhone has a big, beautiful colour screen, a built in GPS, a video and still camera, an iPod music player, motion sensor, gyroscope, multiple cellular antennae, and will also let you make phone calls or send/read text messages when you get around to it. And what's more, that iPhone in your pocket has more computing power than existed in the entire world before 1969 (Yes, really).
And you're wondering why it's battery doesn't last as long? One doth protest too much, methinks.
So, its a new world and until battery technology catches up with "Cool Features" technology we're going to have to accept that we need to charge our iPhone every night. Having said that, we shouldn't have to accept having to charge our iPhone every hour. So if you still think the battery is draining faster than it should then read this article (and the article I link to at the end) and I'll describe some reasons why it might be doing that and how you can remove or minimise the problem.
First up, who can tell me one of the main features of your iPhone? (Hint: it's in the name) Yep, to use it as a phone (crazy eh?). And to do that your iPhone has to be connected to the mobile phone network. But not all phone networks are created equal, and not all areas have good reception. If you're in an area with poor reception (or "competing" reception*) your iPhone will need to work harder to maintain a good connection. And if you are in an area that occasionally gets just one bar of reception then you're iPhone is going to be working REALLY hard to keep that connection up. When you're in those areas your battery will drain very quickly. If you're waiting on a call then there's very little you can do to mitigate this except to have your iPhone connected to mains power. But if you don't need to make calls, send text messages, or connect to the internet but still want to have your iPhone turned on (to look at photos or take photos, check your calendar, play games, etc) then put your iPhone in "Airplane Mode". Some of my customers live in rural areas with no phone reception. Since they can't make/receive phone calls anyway, they put their iPhone into Airplane mode when they are at home so it will still have plenty of battery life when they get to town. The trick is to remember to turn Airplane mode off when you get to town. 😊
* What's "competing" reception?
I was once staying in a hotel that was located exactly halfway between 2 cell towers (I only knew this because I did some geeky testing). So my iPhone was constantly switching from one tower to the other and back again. My battery strength went from 100% to 20% in less than 2 hours (which is what prompted the geeky testing). How did I fix this? Well, I didn't. I just had to leave my iPhone plugged into its charger while I was in the room and only unplug it when I was ready to leave. Sometimes there isn't "an App for that". Importantly, unless you did the geeky testing I did, there was no way to tell why my iPhone battery was draining so fast.
The bottom line is that cellular reception plays a very big part in your iPhone's battery use. And this can make troubleshooting your battery life very tricky.
I should point out at this point that I was prompted to write this article after reading another article written by Scotty Loveless that was linked to from Jim Dalrymple's web page; The Loop. That article does a great job of prioritising and then resolving the various "battery sucking" issues I have come across. Scotty didn't mention the two issues related to cellular reception I mentioned above so I've described those here. But since he did such an excellent job of communicating the other problems I can do no better than refer you to his article.
(EDIT: Scotty has now added a section on phone reception)
Of course you should never forget another major cause of iPhone battery drain; Using your iPhone. Never discount the possibility that your battery is draining fast because you're using your iPhone a lot. And if this is the real cause of battery drain then you need to start looking at an iPhone battery case. I've never used one, so you're on your own there.