Also having battery drain issues on my iPhone 5 - was 100% last night and 40% this morning and it was turned off. But something else strange happened this morning. Got in the car and the phone connected to the Bluetooth and it looked like there was an open phone line. I have been having the battery draining problem since I used the personal hotspot feature a week or so ago - just wondering if it is the software causing the battery problem.
The responsible thing for me to tell you is to allow an authorized Apple repair person to do it for you. Now that I've got that out of the way......I don't know which iPhone version you have, but the iMore Blog has an excellent tutorial on replacing the battery of an iPhone 3G, 3GS, 4 and 4S. You can check it out via the following link. Maybe it will give you insight on whether or not the effort is worthwhile.Everything I've read applies to my phone... I was given it by a colleague just out of its 1 year guarantee... it was a business phone so had quite heavy usage, so I'm not surprised that the battery life isn't great to be honest. Now I have the dilemma of either replacing the battery myself or getting Apple to do it. I've found a battery on the appleipodparts online shop for ?24.99 versus ?55 (+?7courier) with Apple. A friend has said that Apple should do it to ensure it's heat/vacuum sealed afterwards. Is that necessary? My main fear is that a cheaper battery may short out and damage the phone and I'd have no comeback.