So I got an N900 on Monday the 23rd, played with it for a few days and noticed the battery would drain in under 6 hours with very moderate use.
Before you ask here is the setup:

• No Wifi Use AT ALL / Even set Internet Connection to Always Ask
• No Skype/IM even set up
• Turn off the Internet Connection Manually when not using it
• Make 1 or 2 phone calls, send 20 texts or so, and surfed the internet on 3G for maybe 2 hours
• Yes, I charged the phone according to specs (let it almost die the first time, recharge without interruption for the first charge etc)

...and dies after 6 hours.

So of course I looked into all the issues people mentioned and came up with nothing.

I sent the phone back to Nokia to get a replacement unit thinking I had a defective phone.

So now it is the 4th of December and I got my new Nokia. Without charging the phone at all yet it went from the half battery it had when I opened the box to dead in about 3 hours, it is currently sitting on the charger and Im not touching it until the light turns green lol

So seems like I still have the same issue but of course I won't jump to that conclusion until after I get a full charge and use it for a bit (3 hours for a half should equal 6 hours for full approx., no?).
So I'm going to head to the T-Mobile store and get a brand new SIM card (as some have said this solves their issue with battery life) and see if I'm as lucky.
I will post back here soon as I get the new SIM and test the life a bit.

I just wanted to start a thread for anyone else who has this issue or is aware of it to post and let me know if they have any solutions and I'll be happy to try them so maybe we can narrow this down and help everyone out (or maybe bring some attention so the Maemo team/Nokia will fix this if it is a software issue in their next OTA update.

If you have any suggestions or have the same issue, please post.
And can we try to refrain from mentioning "proper charging" techniques, how the Wifi router in my house is killing my battery (since Im not using Wifi), etc. unless you truly think it could be causing this issue with all that I mentioned above.

Thanks guys! Love this phone, just scared to use its awesome features for fear the battery will die a few hours later

It will take several charge/discharge cycles before the battery controller is able to report accurate state of charge information. Look at the other threads about battery life, run your battery through several cycles, and if you're still unhappy, then trade your N900 in for a Palm Pre. That phone gets about 3 hours per charge - should make you very happy.

Given all you've tried, I will be surprised if the SIM isn't the issue since most people aren't having that short a battery life after ruling out those issues you listed..

Goodluck!

Is there a file for detailed battery infos? /proc/acpi or /sys/class does not show anything battery related.

Bye

Since you arent on a 3g network, (well since you arent on tmobile) can you also try and set the network type to GSM alone.
Trying to rule out the machine "searching" for 3g connections, if it does something like that.
My piece also seems to have something of a short battery lifetime.. but i havent had a proper chance to measure it.

Thanks for posting this.
I today got my N900 and i am about to get 6 hours as from what i can say about the status right now. Maybe less.
I have had 3G on half of the time at least. No wifi, though a 5 hr bluetooth session of data sending(cant get a normal cable transfer session with ovi suite working right now) and half of the time browsing and personalizing. It looks messy but i hope with 3G, BT and wifi off in standby, with no widgets on and all services updating almost never, brightness on 2(for when the screen is on) i will get more than 15 hrs.
I am very certain it has to be able to do that.

Did your previous phones behave pretty much the same? You might stay in an "unlucky" location, from coverage point of view: even if your signal bar is full, you might be in a "noise" location because of bad network topology. Try staying for several hours in a remote location, see if it behaves the same. Also try GPRS instead of 3G. The modem is the biggest battery consumer.

Any 3rd party applications installed / running?

Nope, made a point not to so I could test it.

So ya the new phone has the same issue.
I got excited for a while but then it dropped really quick and it is at 1/4 after taking it off the charger at 3pm and its 730.
And I got a new SIM.

BUT I think you might be right Onutz, I think when I was running around getting the SIM and showing the phone off at the (TMo store lol) and was excited about the battery looking better it was because I had better coverage. maybe. Then when I got home (where signal is not so good) that is when the battery started to drain quickly.
Now my old phones never had the same issue but both N900s did.
Hmmm, so do I sit and pray for a fix in the next OTA update?