Random iphone 3g battery drain ... appears to be a background mail check

Question

Phone Info: Model: 16GB/Black, 3g ON, OS 2.0.1, Mail: Push On and Manual Fetch, Location SVCs ON, LCD auto bright, Own this phone for 20 days.
I noticed (twice) that my phone battery drained up overnight after a full charge 5 hours earlier. It happened once with OS 2.0 and other time with OS 2.0.1. I started suspecting background apps (while the phone is in standby - blank screen) probably doing some unnecessary work and draining the battery juice.
I did some investigation during last week to turn on/off various parameters to close on which app is causing trouble. It appears to be Apple mail program! If I turn off all mail accounts, phone "Settings->General->usage meter" goes up by approx. 1min/hour when the phone is in standby. With my 3 mail accounts (2 yahoo and 1 gmail) on, usage meter goes up anywhere from 4-12 mins/hour or lot longer in some cases. This translates to about 100-250 mins of phone usage time/day without really opening up the phone. On 3G phone, 4 hrs of usage is where battery goes from full to 10% charge.
Details: The above problem doesn't happen always! This happens only when mail application spins in the background for a *long time* to fetch or sync mail. When it happens you see a rapid battery drain in standby. This is a most common scenario when you have a network connection (web browsing OK) but somehow the mail sync up (thru' SSL POP) takes forever. This is what I tried to reproduce: Goto mail->open account1->open inbox .. when it is spinning to fetch mail manually.. 30-45sec later give up and try another mail account..repeat above and press home button finally(at this point as a typical user you waited 1-2 mins to get mail on Wifi and gave up.. we are talking about your inbox having zero new in/out mails!. This is just for syncing your phone with the server). You can press standby and turn off the phone screen. Check couple hours later and usage meter goes up by how long the mail was spinning in the background.
I think the right implementation is Apple Mail should turn off background check when the user closes the app! OR at the least detect the phone is in standby and stop spinning after a small timeout.
Mail Push on or off has no effect on the problem. No other settings (3g on/off, GPS...) have any effect.. they don't increase background battery usage!
Appreciate your posts on any workarounds or fixes to this problem.

Answer 1

I'm flying blind here, a little, because I'm not currently using a 3G iPhone. However, I use MobileMe on my iMac, MacBook Pro and a Windows Vista laptop. Keep in mind that MobileMe syncs not only your email, but your calendar, contacts, bookmarks, etc. If possible, turn off MobileMe at night when you don't need to sync. See if that stops the spinning globe. When Apple changed from dotmac to MobileMe--offering "push" email, calendar updates, etc.--battery drain on the iPhone was bound to happen, because it takes battery power to connect to the MobileMe server. That's true of BlackBery's as well as any other mobile device using "push" technology.
Turning your POP and other email accounts off probably doesn't change MobileMe's synching with calendar, contacts, bookmarks, etc. I've noticed when I make a change on my MacBook Pro or iMac that the change does not take place immediately, unlike a BlackBerry connected to an Enterprise server. I'm assuming you're not using ActivSync with an Enterprise server. Neither do I since I use the BlackBerry Internet Service (BES). Emails, using BES, usually hit my BlackBerry before hitting Apple Mail on my Macs, but BEST is only pushing email.
Best answer to problem? Turn off your iPhone at night and save battery power. Not a perfect solution if you want to take phone calls at night. But until AT&T improves its 3G network (more towers, more 3G radios, etc.), that's the easiest way to keep your battery powered.
I explain the battery power situation in my V1 iPhone review. Google "Mobile Telephony Innovations iPhone" and you'll see the review listing.