laptop power source questions

notsobrightnotsobright Solar Expert Posts: 247 ✭✭
hi all, my laptop requires 19 volts. I can get a DC adaptor but it is quite expensive so Im wondering just how much power is wasted by using a suresine300 inverter and the OEM AC adaptor versus a DC to DC adaptor alone?

the OEM AC to DC adaptor gets really warm, almost hot! I know its a major consumer so Im just trying to justify the cost of the DC to DC adaptor. ($170)

the highest reading Ive seen on the kill-a-watt meter is 0.57 amp but the battery is charged and the CD or other stuff isnt running.

the OEM AC adaptor output is marked as 19v/4.22a

thanks

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: laptop power source questions

    You also need to measure the watts too (that is, for the most part, what is being removed from your battery vs Volts*Amps).

    I have from the same mfg. (HP) new laptops with Power Factor Corrected supplies and one (a netbook) with a non-PFC type supply... Depending on computer--they seem to take around 20-30 watts when doing average stuff (backight on, surfing internet/writing, no battery charging).

    From the spec. sheet (PDF), the SureSine inverter at 50-150 watts is over 90% efficient. Below 20 watts, the operating losses of the inverter (around 6 watts) becomes more dominant.

    It would not be hard to believe that the Laptop power bricks are 80-85% efficient (when loaded--mine seem to take 1 watt or less when not loaded). And the standard DC converters are probably around 85% +/-... So, you may be cutting the 10% or so losses from the inverter (when operated in its "sweet zone")...

    Then you also get into the standby losses of your DC converters vs the SureSine in standby/search mode...

    If this a serious project to conserve power--you probably have to do your own measurements with a DC Amp*Hour / Watt*Hour meter like one of these for $60...

    I don't really trust "advertised" numbers--as your actual results will almost always be less...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: laptop power source questions

    I had an DC to DC converter for an old Toshiba laptop. Measured the power used for both the DC-DC and the AC-DC. Both where about the same.
  • notsobrightnotsobright Solar Expert Posts: 247 ✭✭
    Re: laptop power source questions

    the highest watt reading I got was 60.

    intresting thing I noticed was that the kill-a-watt went to zero when I turned off the laptop. I expected it would show something when the AC adaptor was plugged in even when the laptop was off.

    I guess its probably not enough difference to justify buying the DC to DC adaptor.

    I like that Doc Watson meter! Ive been looking at those.

    thanks
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: laptop power source questions

    nsb,
    the adapter is drawing something, but it is too small to register on the killawatt meter.
  • icarusicarus Solar Expert Posts: 5,225 ✭✭✭✭
    Re: laptop power source questions

    The Apple power supplies are pretty smart, they will draw almost zero power once the device is charged. My Mac books draw a max of ~60 watts while working and charging,, down to ~20 watts while fully charged and working.

    Tony
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Re: laptop power source questions

    I think the big waste' is if the laptop is the only load on the inverter. inverters consume sigfnificant amounts of energy when running. My 1800 watt Prosine uses about 30watts running and <1watt searching.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: laptop power source questions

    Yep--a good reason to size the inverter to the loads...

    Or perhaps several inverters... A "small" TSW Inverter for electronic loads (laptop, cell phone chargers, TV, DVD player, a few CFL lights) and a larger one (perhaps MSM) for the vacuum cleaner, well pump, etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notsobrightnotsobright Solar Expert Posts: 247 ✭✭
    Re: laptop power source questions
    Photowhit wrote: »
    I think the big waste' is if the laptop is the only load on the inverter. inverters consume sigfnificant amounts of energy when running. My 1800 watt Prosine uses about 30watts running and <1watt searching.

    I do as BB mentions and only run the laptop on my SS300. it will run on an even smaller inverter I have that is not a true sinewave inverter but I have lost data (photos) durring memory card transfers this way more than once and never when using the true sinewave inverter.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: laptop power source questions

    I switched earlier this year to a netbook. I still have my big Toshiba laptop, but when in my camper I use the netbook (actually, I use it most of the time now). I used to use a small 400w inverter for my 60w laptop and now I use a 12v cigarette lighter power supply with the netbook.

    Here's what I'm using now (literally, using it to write this):

    Acer Aspire One 751h: (ZA3):

    http://us.acer.com/acer/productv.do?LanguageISOCtxParam=en&kcond61e.c2att101=60841&sp=page16e&ctx2.c2att1=25&link=ln438e&CountryISOCtxParam=US&ctx1g.c2att92=843&ctx1.att21k=1&CRC=1896186187

    2g ram, 250 hd, 11.6" screen at 1366x768 resolution with a "just about full-size" kb. It's a decent solid little machine and works fine dual-booting Win7 and BackTrack linux. I can bog it down with too many apps running, but that doesn't happen often. There's no CD/DVD drive, but I have a little 12v DVD player so I don't miss it. I like this little computer quite a lot. I got it used from a guy who bought it last November at a ""Black Friday" sale. He paid $250+tax, and I bought it from him for $150 cash. I wanted this model specifically for the bigger kb.

    The battery life with the stock 3-cell battery was only about 2.5 hours, and a lot less if I was using my high power Alfa WIFI card:

    http://www.data-alliance.net/-strse-73/Alfa-AWUS036H-1000mW-USB/Detail.bok

    So, I picked up a 7200mah 9-cell off Amazon for 50 bucks:

    http://www.amazon.com/Acer-Replacement-battery-UM09B31-UM09B34/product-reviews/B002TPWQWE/ref=cm_cr_dp_all_helpful?ie=UTF8&coliid=&showViewpoints=1&colid=&sortBy=bySubmissionDateDescending

    See the review on that product by "umv" - I wrote it. The bottom line is I get 8+ hours out of that battery without the Alfa hooked up, and 6+ with the Alfa.

    And then I added the 12v power supply:

    http://www.amazon.com/Car-Charger-Acer-Aspire-One/dp/B002GENZXW/ref=pd_rhf_p_t_4

    Also see the review on that product by "umv" - again mine. Bottom line, first one melted down after about two hours, but the replacement is working fine.


    If I'm driving, I charge off the cigarette lighter, and if I'm running the generator I charge off that - but when I'm not doing either one I just run off the big 9-cell battery.

    As for power consumption...well, who knows? I still haven't bought a Kill-O-Watt, but that wouldn't help me when plugged into the cigarette lighter anyway. Here is what I *do* know:

    * The AC power brick is rated at 30w.
    * In Linux (without the Alfa), the apci reports that when the battery is charged, the machine is using between 9,000mw-13,000mw (Depending - it jumps up when the CPU speed jumps up, which seems to happen mostly when something video intensive is going on...like moving the mouse. Mostly, the CPU runs at 800mhz and the power consumption shows around 11w.
    * In Linux (without the Alfa), when the battery is charging, the acpi reports that the machine is using 714,930mw (!?!?). Well...that *can't* be right.


    Bottom line; It's a great little computer for surfing the net, watching videos, writing and the odd bit of Linux hacker stuff. The video chip will NOT play modern games, but otherwise the computer is perfectly usable. And with the big battery it'll run all day (and take half the night to re-charge).

    And it uses a LOT less electricity.
  • notsobrightnotsobright Solar Expert Posts: 247 ✭✭
    Re: laptop power source questions

    9,000mw-13,000mw? wow thats a neat system dwh! and dualboot w/backtrack linux... nice!

    I should start looking for a used netbook instead. there are some great CD emulators out now so thats no big deal. my main requirement would be it would have to be able to run XP (I havnt trimmed win7 down yet) and boot up from USB flash and optionally from micro SD card. I love that ;-)

    In running a 700mb WinXP right now and have a microXP down to 480mb! also have a live version that runs totally in RAM!

    this laptop has wireless USB (WUSB) and the USB drives are just becoming available for these. I want to get one just to see if I can boot it up wireless!
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: laptop power source questions
    and boot up from USB flash and optionally from micro SD card. I love that ;-)

    Mine will do that, but I rarely do it. Usually only when I'm making a bootable flash for someone else and I need to test it.

    Windows 7 though has a neat feature - it can use the flash (USB or SD card) as extra virtual RAM. I have 2gb of real ram in my netbook, and another 2gb card in the flash drive. Haven't really noticed yet though if it makes much of a difference as I don't really load up the netbook to the limit.
  • lamplightlamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    Re: laptop power source questions

    interesting.. but thats a big inverter. Mine is 1500w sine wave, it uses about 30 watts running my webserver (a small netbook) and the inverter, with the macbook plugged in (but already charged/not being used) off the inverter. the macbook uses about 15-20 watts when on (the super efficient macbook pro 13").
    Photowhit wrote: »
    I think the big waste' is if the laptop is the only load on the inverter. inverters consume sigfnificant amounts of energy when running. My 1800 watt Prosine uses about 30watts running and <1watt searching.
  • lamplightlamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    Re: laptop power source questions
    niel wrote: »
    nsb,
    the adapter is drawing something, but it is too small to register on the killawatt meter.


    yep, and while its charging is probably when theres more loss in the conversion. if you have a very small system and/or not much power to spare it is worth getting a dc converter. i run my little webserver off 12v directly with a dc car charger and it is definitely less power, i forget but i did measure it once. You can do better than $170! I think i got one for $80. yes they arent cheap. but like people are saying, if you have an inverter running already anyhow...
  • lamplightlamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    Re: laptop power source questions
    dwh wrote: »
    I switched earlier this year to a netbook. I still have my big Toshiba laptop, but when in my camper I use the netbook (actually, I use it most of the time now). I used to use a small 400w inverter for my 60w laptop and now I use a 12v cigarette lighter power supply with the netbook.

    Here's what I'm using now (literally, using it to write this):

    Acer Aspire One 751h: (ZA3):

    http://us.acer.com/acer/productv.do?LanguageISOCtxParam=en&kcond61e.c2att101=60841&sp=page16e&ctx2.c2att1=25&link=ln438e&CountryISOCtxParam=US&ctx1g.c2att92=843&ctx1.att21k=1&CRC=1896186187

    I just bought one! (still waiting for it to come in) the atom processors are super efficient. I switched to using a netbook a couple of years ago (from the via processors on mini itx platform) for my web server (http://florenceit.net and http://lamplight.no-ip.org both on the same "server", run off of 12v battery bank directly). recently decided to upgrade and did a ton of research on the various new atom processors that are out now and found that the atom Z series processors are THE most energy efficient (but of course they are NOT the fastest either), so I went for a aspire one to use as my new server. there's not too many out with the z530 (except dell which i dont buy) so i went with the z520 and this netbook has the right specs. you got a great deal, i paid about $280 with shipping. i expect it will use even less power than the atom i bought last year, when idle (which it is a lot as a small business web server).

    http://www.netbookmarket.net/intel-atom-n-series-vs-z-series/
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: laptop power source questions

    Yea, I've played with the Acer netbook with the 10" screen and the 280 (270?) processor, and there is a very noticeable difference in processing speed. The 520 (what mine has) is not as powerful, but I don't mind (normally in power save running at 800mhz anyway) and it does use less watts.

    That extra inch of screen real estate makes quite a difference, and of course the keys are big enough that typing is not a chore.

    What I don't like, is that the screen is HIGHLY reflective - literally smooth as glass - which is a never-ending pain.

    For a webserver running Linux (or BSD) and without X running, 800mhz with 2gb of ram is more than enough power.


    FWIW, I have noticed that the big battery seems to be slowing *increasing* in charge capacity...the first couple of weeks Win7 would report 8-8.5 hours at 100% charge, lately it's reporting 9-9.5, and sometimes as high as 10.

    But then...Windows measurement code has always been a bit flakey, so pass the grain of salt please.


    EDIT: Oh, and the Acer has an Atheros wifi chipset (at least mine does) so the default ath5k drivers work great and support packet injection just fine.
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