answer:how’s the signal where you phone is during the day? i know the signal at my house is terrible, so my phone, although not an iphone, dies faster than when it is at work. part of the problem with mine is that it checks my work Exchange email with ActiveSync constantly, so it’s constantly using the internet. I found a setting that allows me to change the frequency of the email send/receive during peak and non-peak times, and that seems to have helped quite a bit. But, if you’re not using ActiveSync for Exchange on your iPhone, or some kind of email, then i am betting it could do with the signal. cellular phones will use more energy when they are “roaming”, or when the signal is really poor, since they are trying to find a better signal.