My device: Original Samsung Q1, 1G Ram, XP Tablet and Vista Ultimate dual bootable. I am currently experiencing a large difference in battery life between the two for the same use case.
Ok here is what I know...
I gave up on running full battery life discharge tests and I installed NHC (notebook hardware control) so I could watch the power being consumed as measured by the battery itself. This was very enlightening. Note: I'm only using NHC for monitoring. The CPU dynamic switching and voltage adjustment features are useless with the Celeron M. I found that nothing you do with the min / max processor % have any impact on power use. Setting max to 50% screws up the scale in task manager however and doubles you reported proc usage. Also with some tools (NHC included) leaving set like that makes it assume your proc frequency is moving around when it isn't. My recommendation is to just set min and max to 100% to disable all the monkey business. That's what I did for these tests.
For starters, yes it turns out my standard 3 cell battery is seriously messed up. Nasty wear factor, voltage that sags as the battery drains causing the power used to gradually increase. (Due to efficiencies dropping as the voltage falls below norms). It has a pretty non-linear discharge. Bottom line here, the 3 cell battery is a gonner, time to switch to my shiny new 6 cell that recently arrived. Its too bad because I like the form factor and weight with the 3 cell. Anyway this explains why my total run times don't align with the results others have had, but it still can't explain the repeatable battery life delta between XP and Vista on the same hardware, same battery with the same test cases. So time to just pay attention to power draw and do some direct comparisons.
I took lots of data with each battery, at different points with different settings etc. But rather than bore you with that, I'll attempt summarize in my usual rambling, long winded fashion.
Notes and disclaimers:
Power draw fluctuates a lot (more with Vista than XP) so I had to let things settle, and shoot for an average. I didn't bother trying to get actual data logging enabled since this was supposed to be a quick sanity test. The data was taken at minimum brightness, after the adaptive dimmer kicks in using my brand new 6Cell topped off. I am attempting to just measure battery life at idle. So I'm shooting for a best case here, not a worst case. And another disclaimer - I've disabled lots of services in my quest so my results may not match your system. The results are pretty consistent for me across multiple runs however. And yes I fully acknowledge that this could just be my hardware / configuration. Since others have reported similar battery life losses, however, so maybe this time I'm not just being an idiot.
Vista: wifi on, bluetooth on, hard wired lan disabled: minimum brightness after auto-dim. Attempted to let the HD settle:
Typical min power use: 10.3 - 10.4 Watts
XP: wifi on, bluetooth on, hard wired lan enabled, minimum brightness after auto-dim. Easier to let the HD settle:
Typical min power use: 8.3 - 8.5 Watts.
That is a pretty serious difference. After a lot of playing around with settings and enabling / disabling stuff I found the biggest contributor to Vista's power use (on my Q1): Bluetooth!
Vista: wifi on, bluetooth disabled in device manager, lan disabled, min brightness after auto-dim...
Typical min power use: 9.2 - 9.3 Watts.
So over 1 watt used just to have the bluetooth radio on? I didn't even have any bluetooth devices connected so it should have been idel. I also have BT sharing and auto device connection turned off which should help.
My first thought was that I had something messed up with the drivers so I un-installed them, and re-installed them - same results.
Something is obviously wrong. Driver? OS install? Implementation? As usual just when I start to think maybe my hardware is messed up I remind my self that XP doesn't exibit this same behavior on this system. When I disable the Bluetooth on XP it only drops only a small amount and is lost in the noise (.1 - .2).
So turning bluetooth off gets me closer to XP power draw, but still nearly a 1 watt more. -Trying to find the source of this missing watt is a problem for another day.
Exchanging Bluetooth for battery life is not going to be an option for me since I have a large assortment of BT goodies I use with my computers. (Too numerous to list here, although it might be fun to line them all up someday for a photo shoot. Then again, no need to give my peers yet another reason to mock me).
I need someone else to help verify these results. Could there be a bluetooth power bug in Vista similar to the old XP USB bug?