Precision M4600 Battery Life with FirePro

I am a bit baffled by the conflicting information about this. Before the laptop was released, havoctex made the following comments:

The numbers I posted are for the M6600 with a 9-cell, 97WHr, battery installed with Optimus turned on running MobileMark 2007 Battery Life. With Optimus turned off in BIOS and running the same benchmark the M6600 has 348 minutes, 5.8 hrs.
and
AMD battery performance should be real close to the Optimus OFF times on NV.

From this, I gather than the battery life with the AMD FirePro should be in the neighborhood of 5-6 hours. Unfortunately, in real life web browsing by people who already have the M4600, it appears to only get 2-3 hours (see the owner's lounge thread in the neighborhood of this page). What gives?

I can think of a few explanations for the discrepancy. First, MobileMark is not doing a good job simulating real life usage (i.e. people on battery will probably be using the wireless card and the display will be at viewable brightness). This is possible, but it doesn't strike me as very likely. Second, the M4600 somehow manages to consume more power than the M6600. This makes no sense at all. Third, there is a bug somewhere in the settings. Maybe Dell's default power plan (which people in that thread used) isn't lowering power consumption or maybe there is something wrong with the GPU drivers.

Does anyone know why the battery life would be so low? It's a huge battery and Sandy Bridge is quite efficient. If somebody who has the machine and cares about having a 4 hour battery life (most people appear to use it as a desktop replacement), would you be willing to play around with the settings a little? Maybe use Windows' power plan rather than Dell's?

 

if you tell me what specifically you want me to test i dont mind trying. i.e which setting to test out etc

5 hours would be amazing if i could get it

 

ok i tried some basic testing, surfing this forum with chrome having 10 tabs open including gmail and facebook, plus streaming a radio station and working on ms word, windows calculates that if i select the maximum battery mode i get 3hr45min and under ultra performance i get 3 hr.

 

The time i gave earlier about 2.5 hours is actual usage and not windows calculation. Windows always over estimate the remaining battery life.

Going to try playing game (civ5) after this and see how long can it last. need to use maximum performance else the game won't run.

 

actually in my experience it always underestimates it. i suppose one could always download a utility and manually calculate.

 

I guess I'll also post here. I have a M4600 with the Quadro 2000M. I don't have the IPS so I can turn Optimus on and off. Just let me know what tests I need to run and I will.

 

after turning the GPU off, what kind of life can you get on medium brightness and surfing the web/chatting/doing office apps

i'll try the same with my firepro then we can compare

lets try the maximum battery power setting dell has

 

This is going to be a really dumb question, but where do I set this?

 

click on the battery icon in the system tray (next to the clock) and click more power options

then you can select which power plan you want

 

Ok, playing CIV5 continuously 1 hour 35 min and the laptop battery dropped to 5% and auto sleep. GPU utilization 99% all the time but CPU only at about 12% and 0.8 Ghz most of the time. LCD brightness at 50%. Yet to find way to keep CPU running 3.2 Ghz when battery is in use.

Windows did over-estimated the battery remaining time of > 2hrs at the beginning.