E6400 - Why such poor battery life?

I've had my E6400 for about 3 weeks now, and am fairly disappointed with the battery life.

System specs are:

P9500
Nvidia GPU
LED Screen
4GB Ram
160GB 7200rpm HDD
5300 Intel WiFi
9-Cell Battery
XP Pro

I'm getting less than 4hrs life, doing nothing more than surfing the web, one page at a time.

In contrast, T400's with the less efficient "T" series proc. and dedicated GPU are getting 6+ hours from a 84WHR 9-cell, running the ATI GPU (and a faster 2.8ghz chip).

The big question is.......why the huge disparity in system efficiencies?
The review here at NBR shows the T400 pulling 10-13 watts. My system is pulling 16-20 watts AT IDLE!

I'm pretty sure this Dell is going back and I'm getting the Lenovo, but I would like to hear some ideas here on why the Dell is so inferior in this area.

 

I would point my finger towards the nVidia GPU, but that can be only part of the problem, since other forum members have reported getting at least 4 hours with the nvidia GPU and a 6 cell battery (6 hours from a 6 cell battery plus intel GPU is just about achievable). Don't forget that the T400 has switchable graphics and was probably using the Intel GPU when running on battery.

We need to trouble-shoot this further since 16W or mere is high.

1. What display brightness are you using? There is several watts difference between maximum and minimum brightness.

2. What CPU utilisation does Task Manager show on the performance page? It should be no more than 10% under light usage.

3. Are you running wireless and Bluetooth? Both use power.

4. Have you tried using the power management options in Dell ControlPoint?

John

 

P8400, 2GB, NVS160M, 64GB SSD, LED WXGA+, 1397; with minimal brightness at full idle, I pull 13 watts at the outlet and RMClock estimates 10 watts internally. Maximum brightness raises the outlet power draw to 16 watts.

I'd say the biggest extra power-hog in your system is going to be that 7200RPM HDD, though I'd also venture that the P9500 (despite its rated TDP) and the 5300 pull a bit more current than their less powerful siblings.

Depending on your screen brightness, I'd say your power draw isn't totally unreasonable, but battery life on your battery does seem to be a bit low. Check for like flash ads raping your CPU from time to time?

I get about four and a half hours browsing on the 55WHr battery... what's the rated capacity of the nine-cell?

 

See if the HDD is on the Tom's Hardware chart for the power consumption. You can check the P9500 voltages using RMClock and perhaps try undervolting.

Good point which I forget about since I have been running Firefox with Flashblock for the past year or two for exactly this reason.

The specs in the user guide say it 85WHr, so it's a full 50% bigger than the 6 cell battery.

John

 

Wow, thanks for the quick replies. To answer some of your questions....

-Display brightness is set around 20% to 25%.
-WiFi and Bluetooth are alway on (need 'em).
-Task Manager shows 0% to 7% on idle and while browser is open.

-My 16-20 watt idle estimate was taken from RMClock.
-RMClock shows Total cpu load at idle of about 10%-25%, with spikes about every 10-15 seconds going up to 222,345%

I've found DCP to be completely useless on this machine for managing power. I've manually disabled all network connections (except WiFi) and the CDROM through device manager.

Thanks in advance for any more advice!

 

Thanks for the additional info.

With wireless and Bluetooth both running then the power drain will be increased. You can see by how much by temporarily turning them off.

What voltage range does RMClock show for your CPU (make sure you have enabled Mobile CPU on the advanced settings page)? RMClock CPU utilisation can be higher than Task Manager's because it is calculated relative to the current CPU speed.

What model HDD do you have? What temperature are you seeing for the HDD (HD Tune will give this info). My HDD (WD5000BEVT) is at 38C having been on all day in an ambient temperature of 22C.

John

 

I have the 9 cell battery, my machine is 3 weeks old, and I still get the same battery life. If I stretch the system, I could have 9 hours of battery life. But normally, using Vista 64-bit with power saver setting in Vista, I get ~8hours. At worst, like pushing the system at max, (ie playing a game like Far Cry 2 or Crysis), I get 3 hours. Recording class using good software (direct recording and compression as MP3), having the wireless on, screen brightness at lowest settings, having Word open and Firefox with PDF document (using Adobe) open, I get 7 hours a half (despite having Windows showing 5 hours and half (jumps between 5.5 hours to 7 hours). (Note that Aero with transparency is on). Disabled card reader and contactless card reader.

My system (latitude E6400):
- P8500
- backlite keyboard
- DVD burner
- Digital Mic, no webcam
- Intel Wireless N 5100
- Nvidia Quadro NVS 160M (using latest geforce drivers)
- 1440x900 LG LED backlite screen
- 160GB 5400 RPM HDD (Hitachi)
- 4GB of RAM
- Vista Business 64-bit

 

Some additional info:

-RMClock shows my cpu running at the lowest multiplier 6 (.925 v), occasionally going up to 1v while browsing.
-My HDD is a ST9160411ASG, which I believe is a Seagate Momentus 7200.

I turned both Wifi and BlueTooth off last night and set the display to min. brightness. After 15 min. RMclock was showing a watt draw of 17 !! With VERY light browsing, I barely squeeked by with 4 hours total life.

Perhaps this battery is defective? Either way, I do think I'm going to be returning this and getting a T400.

Still, I appreciate all suggestions to fix this problem.

 

It's not the battery. Something is using too much power.

Tom's Hardware shows the Seagate 7200.3 as having a maximum power consumption of 3.03W and an idle power consumption of 0.95W, which are OK for an up-to-date 7200rpm HDD and only about 0.5W higher than for a good 5400rpm HDD.

The CPU voltages look fine - the 0.925V is the same as my P8600. However, can you now look at the idle temperatures for both cores. These are an indication of the leakage currents. Mine are 32C and 36C in an ambient temperature of 22C. The Intel power specs have a wide range and perhaps your CPU is near the upper end of what is permitted. The same probably applies to the GPU.

If this particular Dell is giving abnormal power consumption (and other people's posts suggest it is abnormal, then perhaps you should ask Dell to either replace the whole computer or change the CPU and main board). If they don't agree then it's time to consider taking your business elsewhere.

However, can you first check the power consumption on idle with no web browser open.

John

 

Thanks again for your help, John.

-My core and ambient temps are exactly the same as yours.
-With the machine at idle, display at min. brightness, all network devices off (including BT and WiFi), cpu showing less than 3% in task manager, CDROM off, EVERYTHING OFF (more or less), RMclock is still estimating a draw of 17-19 watts! I could pretty much let the machine sit idle like this and the battery will die in less than 4.5 hrs.

Also, those cpu "spikes" I mentioned above, shown in RMclock.........are those normal? Every 10-15 seconds there's a spike in utilization, showing 234,768% or something crazy like that. The graphs also show it as well.

I actually just ordered a T400, as I think the switchable graphics will be better suited for my needs.
I may pass this E6400 down to one of my employees or return it to Dell.

Thanks again,

Charlie