Battery drain.

Do you have any apps running in the background? Double click your home button and see what is running in the multi-task. Technically all should be in a frozen state, as it is not really a true multi-tasking but some may not have closed right when you exit out. I'd also check your data usuage, because if your data usuage is higher than what you checked last time, it could mean that one of the app that uses the data wasn't closed properly.

When you double click the home button it shows all the apps that are still open. In theory they should all be suspended and not actually running. In fact not all apps support multi tasking any way so some of them may be completely inactive. None of them should actually be running anyway as the multi tasking on the iPhone is not in reality true multi tasking.

Lars Wikstrom wrote:
I double click the home button but how can I tell if I have apps running in the background? It shows me a list of the recent apps I have used.

to close the apps, simply hold on one of the apps until it's wiggly, and you will see a red cirle with a - on it. Just hit those until you close them all.

This does not show all apps that are still open and/or running.

Double-selecting the home button reveals a fast app switching and a recently used apps bar. A recently used app does not mean the app is still open and running. The overwhelming majority of 3rd party apps will continue to be quit when leaving the app since the overwhelming majority of 3rd party apps do not need to remain open and running in the background.

Some apps such as games will remain open and be placed in a suspended state when leaving the apo so you can resume where you left off when returning to the game instead of having to start the app and game again from scratch. A suspended app is not using an processor cycles and very little if any battery while suspended.

Some apps such as a music streaming app and a GPS turn by turn voice navigation app will continue to remain open and run in the background when leaving the app - such apps are few and far between.

http://whenwillapple.com/blog/2010/04/19/iphone-os-4-multitasking-explained-agai n/

I had the same problem last night. I fully charged (%100) my iphone 4 last night and went to sleep. When I woke up in the morning, the battery drained to %20. I have checked if WIFI, noficications, location .etc were open. But I found that nothing was left open. As clarified above I understand that open apps could be the reason. But I have never closed the apps by clicking the - sign before and never had this battery drain problem since I have been using my iphone4 for 3 weeks.

Any comments?

Do you see the little purple location-services active icon up by the battery level indicator? If so, you have an app that is still actively using location services, and that can drain a battery very swiftly. For example, right after app switching was introduced in the iOS, MapQuest had an issue where if you closed it with a route still in use, it would not release location services and kept them active. It would continue to rapidly drain the battery even though the app itself was not open (MapQuest has since fixed that little issue).

Thanks for coming back with an answer Lars.I have checked that too. But there was no pink sign next to the battery sign on the top left hand of the screen. To be honest I am a bit irritated by this problem because of having it again in the future.I was just thinking what the cause of the problem can be and realized that I used the net, app and played games last night before I fully charged and I remember that iphone4 became very hot and this has not ended while I was charging it. Can this cause the battery draining of a fully charged battery down to %20 in 6 hours.

Thanks a lot.

Sorry, thanks Michael.

When you look at your wi-fi locations, is "HPSETUP" one of them?

When i get to settings/wifi, i do not see htpsetup. Is that what you asked?

Yes...long story. I just ran into a major battery drain yesterday. Without going into specifics, the "HPSETUP" wi-fi source was somehow draining my battery like crazy (if you want more info, you can google "hpsetup" and see how many headaches this has caused over the last few years). Still no clue why it was draining my battery...but after a network restore it seems to be retaining it's power.