Recently my iPhone has started dieing overnight when it is not being used. I turned off most apps using location services. I set e-mail to fetch. I turned off WiFi and Bluetooth. None of these helped. I checked usage levels and there was very littel use of the battery by apps and what there was didn't correspond to any changes in the battery charge level which was basically a straight line from 80% to 0% overnight. I put the phone in Airplane mode and the battery stayed fully charged all night. Since I had already turned off WiFi and Bluetooth, and there were no apps using the battery I conclude that the Verizon modem is eating the battery. What else could it be?
I forgot to mention that it was doing this with the origina battery, even though the battery status tool said it had over 90% of its capacity remaining. I took a shot and replaced the battery. No change.
Hi, awaschka! From what you say, it sounds like your device has a software issue (like repeating a function in the background a thousand times). I say this because it only happens at night. Does your device have the most recent operating system update on it?