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8907
July 25th, 2004 16:00
Details Regarding 150W Power Brick and Load to Power Inverters
I have a 150W power inverter that plugs into my truck's cigarette lighter socket and suspected that the 150W power brick that comes with the Inspiron 9100 laptop doesn't use the full 150W during normal use. I set up a test rig using my Fluke 189 logging multimeter and measured the AC current draw under two conditions: (1) Battery fully charged and laptop running various applications; and (2) Battery 50% charged and laptop off and then on and running various applications. The results are graphed in a Excel spreadsheet at http://home.earthlink.net/~fuzzypenguin/LaptopPS.xls
My initial assumption was that the power brick had a possible efficiency (power out to power in) of around 90%. That would mean that when the power brick was at its full 150W capacity, the load to a power inverter would be 150/0.9=167 Watts. My Wagan-Tech power inverter is capable of 200W continuous for 5 minutes, with suitable cooling off periods in between, so prolonged use at the full capacity would be outside the range of the power inverter.
System specs:
Inspiron 9100 laptop with Pentium 4 HT @ 2.8 GHz
512 MB RAM
60 GB 7200 RPM HDD
ATI Radeon Mobility 9700 GC w/64 MB RAM
WUXGA Display (1920x1200 resolution) [Full brightness]
Dell 1450 dual-band WLAN card (active)
Windows XP Professional
The summary of the results are as follows:
BATTERY 100%: Power requirements were all over the place with the overall sample average power draw at 86.7 Watts. Typical power draw with the desktop active and a 4-port USB-serial converter (100mA), USB game pad (100mA), USB wireless mouse (50 mA), and Echo Indigo I/O Cardbus soundcard was 50-75 Watts. Gaming draw was 100-115 Watts average and peak draw was about 120 Watts for short periods of time (see chart).
BATTERY 50%: Power requirements were stable at the limit of the power brick. When the laptop is powered OFF, power draw from the brick is about 98 Watts to charge the battery. With the laptop ON, power draw was stable around 168 Watts, regardless of application being run. This gives an approximate power conversion efficiency of 89.3%. As the battery charges, I expect the power to drop to that of the battery at 100%. Note that there is a second or two between turning the laptop off before power is drawn to charge the battery.
Therefore, it seems possible to use a 150W power inverter to power a fully charged laptop (or one with the battery removed) or to charge a discharged battery with the laptop powered OFF. Use of a 150W power inverter to both charge the laptop's battery and operate the unit is not recommended and may overload the power inverter and/or damage your power supply and/or laptop.
I hope these results help answer some questions regarding power inverters for the Inspiron 9100 laptops.
Best,
Scotty
poushag
6 Posts
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July 27th, 2004 18:00
That is a sweet meter (and I wish I had one)! I appreciate your efforts in testing the 9100. Could you perhaps run the test again while playing a DVD (no other apps need be running)? I would really like to know the power required by the 9100 with a fully charged battery (or no battery) to play DVDs for my daughter (while on a road trip). This would assist me in choosing a power supply for use in my vehicle that would be sufficient without overdoing it.
Thanks,
Andy
blueelectron9
16 Posts
0
July 27th, 2004 20:00
Yes, I will perform three additional tests assuming a full battery: (1) DVD Playback; (2) CD-R Recording; and (3) 3-D Graphics-Intensive Screen Saver.
I will perform these tests shortly and should have the results in a few hours. I'm glad it's helped someone besides me.
Best,
Scotty
Message Edited by blueelectron9 on 07-27-2004 04:12 PM
Message Edited by blueelectron9 on 07-27-2004 05:00 PM
Ozonator
4 Posts
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July 27th, 2004 21:00
This is just the information I was looking for. Thanks for your efforts.
Some have reported damaged power bricks with extended use on a modified sine wave (MSW) inverter and emphasize that you should use a true sine wave (TSW) inverter. They have not mentioned the load conditions associated with the powerbrick failure. I'm wondering if the failures occurred while the computer was being used at the same as the battery was charging (max load).
Are you using a modified or true sine wave inverter?
blueelectron9
16 Posts
0
July 27th, 2004 21:00
Results are here: http://home.earthlink.net/~fuzzypenguin/LaptopTests.xls
TEST 1: DVD PLAYBACK. High average power consumption 76 Watts.
TEST 2: CD-R BURNING. High average power consumption 70.5 Watts.
TEST 3: PLUS! AQUARIUM 3-D SCREEN SAVER. High average power consumption 108 Watts.
All tests were performed with the 1450 dual-band WLAN adapter turned OFF.
Personally, I wouldn't recommend anything less than a 150W power inverter for the Inspiron 9100 and certainly do not recommend using the power inverter with the laptop powered on and charging the battery. Maximum consumption is about 170 Watts.
Happy computing,
Scotty
blueelectron9
16 Posts
0
July 27th, 2004 23:00
I have not used the power inverter yet. I performed these tests to verify that I wouldn't excede the capacity. My inverter is a modified sine wave inverter. I've heard others use these inverters with no troubles.
Belkin makes a 300 W unit that plugs into the cigarrette lighter socket, but at 300 Watts, one would need about 25A--assuming 100% conversion efficiency of the power inverter. It is closer to 29A with an 85% efficient 300 W inverter at maximum capacity at 12V. I just don't think the cigarette lighter socket is capable of more than 12-15 A, which is why I haven't seen a power inverter greater than 150W being plugged into a cigarette lighter socket except for the Belkin 300 W unit. I am very suspicious of that unit.
Please keep me informed of any news. I plan on using my inverter and laptop on an upcoming trip in September. I'll keep you posted as to performance.
Best,
Scotty