[Galaxy S I9000 Android Development] richardbroder:
Battery drain was ridiculous with me. The first night I went to sleep I remember my phone was nearly fully charged, when I woke up at morning it had used around 50%... that is, 50% of the battery for around 6 or 7h just sitting in IDLE! When I actually USED the phone it could barely handle 10h with a full charge, and that's with very moderate usage. I had to leave the phone charing all the time to survive a day with it (charging in my car, charging every time I stopped near an AC outlet, etc). And yeah, the funny thing was noticing how exaggeratedly high the screen battery drain was, even though I wasn't using the screen all that much...

Some other symptoms of the high battery drain:

-Charging the phone took FOREVER with the phone being used, took a LOT of time with the phone sitting Idle, but if I turned the off the battery would actually charge very fast... that proved that the phone was draining so much energy even the AC charger (or USB outlet) couldn't effectively charge the battery while supplying power to the phone...

-The phone got HOT very easily...

How did I solve it?

Well, yesterday I decided I would reflash my device. I did a full reflash (as I always do) including a re-repartion. Now the funny thing that I noticed was that my phone actually wouldn't flash! It would always crash at the Galaxy S welcome screen... I have never flashed it using my notebook (since I'm traveling), but I used the exact same procedure I always use with my desktop back home, for some reason it wasn't working. Maybe some corrupt file? I re-downloaded ALL files (that is, Odin with the 803 pit file, and the JPC files)...

For my surprise, this time my phone hanged in a green screen, and it was really scary. I even thought perhaps the Nokia USB cable I was using was causing some kind of incompatibility problem, but that would make no sense at all... so I entered the recovery menu in my phone and reset EVERYTHING, and tried flashing it one LAST time (this time closing ALL background apps in my notebook, to avoid any problems)... and there it went, a perfect flash, as easy as they go with my desktop PC back home.

1st thing I did was a hardreset, and then I reflashed it again with Doc's RomMod V2 (was using V1 the day before), and new hardreset in the sequence. Then I changed as little as possible in the phone configurations, I just turned everything off (GPS, wifi, and even the data connection through the power button shortcut), and went to sleep...

For my surprise, the next day I checked the phone's battery use, it had drained only ~4-5% for more then 10hours, this means it would, at least in theory, be able to last for days and days in this setup...

So I installed my apps again (not that I have many), did lagfix, turned widgets and network connection back on... and it has been working like a breeze, although battery drain can still be considered high, it's nowhere close to being as bad as it was before I flashed it, now at least the battery will last a full day with a charge @ my standards of usage, that's good enough for me...

One thing I did change, I remember my screen setup was always at 10/30min for shutdown, I left it like that because I'm always using the phone in situations where the screen will constantly shut down at my face, and that annoyed me... well, this time I actally left the stock 30 seconds for screen shutdown, not sure if it has anything related, but one of the things I noticed before was that my IDLE battery-drain was as high as you'd expect from a phone that had it's screen on all the time... maybe some bug makes the phone drain screen power even with the screen turn off, let's say if you have the 30min turn-off config, your screen will continue to drain power for 30min (and there you have the reason for so much screen draw in the stats), even though the screen is turned off... despite my hardware knowledge telling me that a black screen should NOT be draining power from your phone battery, you never know how far a software bug can fck things up hardware-wise, so I wouldn't be surprise if that actually DID happen...

I could even try setting my screen back to 30min-turnoff just to check if the battery drain will go back to insane levels.. but the fact is that I'm scared of messing it up again, it's working fine the way it is, why mess it up? I figured out some things that get messed up with this phone appear to only get fixed with a new firmware flash, and I really don't feel like having to flash my phone every two days...

Either way, I hope others here can fix their battery drain... it's just my tip: try reflashing, leave everything as stock as you can (only thing I did was Doc's RomMod v2, and later Ryan ZA's lagfix, none of them seem to be related to JPC's battery drain), and see if it helps...