wifi drains 5% of battery per hour in SLEEP MODE

It sounds like something is corrupted in the OS, or you have a hardware problem. Try doing a Restore in iTunes and set up as a new phone (do not restore your backup). If that doesn't fix it take it to an Apple store for exchange.

You can check to see if your WiFi is remaining connected by pinging your iPhone from another computer on the same network. Wait about 10 minutes after putting your iPhone in sleep mode. If you can successfully ping it, your WiFi is connected. If this is the case, you have a problem with your WiFi because it should turn off to conserve battery power. A side note: The WiFi should stay on if your iPhone is connected to a power source.

First get the IP address of your iPhone: Settings/Wi-Fi touch the greater than icon (>) to the right of the name of your WiFi network. The IP address will be listed.

Next if you have a Windows PC or laptop, open a command prompt window: Start/Programs/Accessories/Command Prompt.

Finally type: "ping" followed by your iPhone's IP address. For example, if the IP address is 192.168.0.50, you would type: ping 192.168.0.50 and press the enter key.

If your iPhone is connected to WiFi you should get valid reply data. If not, you'll get unreachable messages.

To be on the safe side, if you haven't already done so, repeat the pinging with your iPhone active and verify that you get reply data.

I suggest turning off Celluar Data (Settings/General/Network) and see if that helps. If it doesn't turn off Wi-Fi (Settings/Wi-Fi) one last time. If that does stop the battery drain, you might want to make an appointment with the Genious Bar at the closest Apple store.

When you have cellular data off and wi-fi off while you sleep, it is normal that you still lose some % during the night. Even in standby mode, it still needs some power to keep the phone running. I too experience that with cellular data off and wi-fi off, during the night, I, too lose 2-3% of battery, as it is completely normal, and I don't have a problem with it.

Have you tried turning on airplane mode while you sleep? Surely you don't notice any % drop over night.

Kwopau,

2-3% overnight is certainly reasonable. However, RiverCrab reports a 5% loss per hour in sleep mode. This seems excessive.

RiverCrab, I have the EXACT SAME problem as you.

Moreover, it seems specific to my home router (a DLink Dir-655). When I am at work (on wifi), the battery only drops about 1% every ~2 hours, which is fantastic (that would be 200 hours, or ~8 days, on standby).

When I am at home, however, the battery drains like a sieve, maybe 3-5% per hour.

By checking my router, I can see that my iPhone4 is maintaining a persistent connection to "nwk-st-courier009-03.push.apple.com". Which is interesting because I have all Push notifications disabled.

I also have a 3G, and an iPad. They drop off my router's wireless connections list within seconds of going to sleep, whereas the 4 just stays connected to Wifi forever.

Disabling wifi immediately fixes the battery drain. Have tried upgrading my router's firmware as suggested elsewhere but it didn't make any difference.

I guess I need to completely reset/restore my device, and pray that actually does something?