another 12v dc pc goes in use.

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  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.

    It is possible to construct a very energy efficient computer on AC too. I rebuilt mine a couple of months ago, it did then have a P4 3.0Ghz CPU, three 250GB drives in RAID5 and a Radeon 9600 graphics card. Idle was about 180 watts. This computer runs 24/7 so I was concerned with the huge power draw (1600kWhs/year!).

    I rebuilt it using a 2.0Ghz Pentium Mobile CPU on a socket 479 motherboard, one internal 500GB drive (same effective size), an external 500GB for backup instead of the RAID5 system and a nVidia 6600GT graphics card.

    The new idle power draw was......67W!

    This means around 1000kWh saved per year.

    And the best part ? The P4 Mobile 2.0Ghz is faster than the old P4 3.0Ghz :)
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: another 12v dc pc goes in use.

    Matt it is an easy check to see if it is the batteries, just check their voltage as you try to start it. I would be willing to bet it is the wire run and not the batteries. Speaking of that what is the length and size of the wire feeding it?
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.

    i was measuring the voltage RIGHT at the input of the 12v power supply of the pc. i am sure the batt volts didnt go that low as everything else would have surely crapped out (webserver), which it didt. im guessing its 30-40' total length. i will measure after i replace the last 6' stretch with heavier guage

    well im using a long run of romex, maybe 10guage i think, smaller wires for about 6-8' before the pc. i can most easily change that last run of wires. the romex is 6' away, just gotta run something smaller on that run for starters. its not permanently wired anywhere i could go bigger but if its just the end id like to know.

    yes this pc is pretty efficient now with this new power supply replacing the pc's ac power supply. im idle now at 41w and thats includes running the wallwart ac to dc. i cant recall exactly but the pc's regular ac powersupply used alot more power. i changed some settings in the bios which cut the power draw (and speed a bit). this is a amd 64 3000+ i shoulda got onea the mobile processors. the notebook is the amd mobile and it runs very low, but i never run it plugged in directly just charge it on the solar and sit oin the couch w/it.

  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.

    im running off 12v!!!

    (thicker cable, just for the last leg of the wire run to the pc and it started right up)!! who hoo

    mx 60 showed 83 watts or so startup, idling around 73, thats running my webserver too (about 11w, and whatever it takes to keep the batts floating). awesome! now i have to put the other car one in so i dont have to worry about it while theyre absorbing, etc. this. thank you so much guys this is great, and keeping this pc off the drid as much as possible will really offset my houses utility usage.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: another 12v dc pc goes in use.

    matt,
    if that romex is 10-2 there are 3 wires in it. if you were to parallel that 3rd wire to either one of the other 2(but not both as that's a short circuit) it would cut the resistance of either the positive or negative wire in half making the overall run a 25% reduction in resistance. for 10-3 there are 4 wires in it and you can parallel one for each the positive and negative wire. that would yield a 50% reduction in resistance. i think that once you start running that computer with applications you will find it needing more power and the wires could then impose a severe voltage drop causing the computer to crapout. it does sound like you will need to buy the wire of choice for the locations selected for the computer and the batteries, as mickey mouse is good for disney and the government. :roll: if i were to run the calculations it would be redundant as you can see the vdrop by measuring from the battery and then measure it at the end of your wire. i do know that from the info you've indicated then 12-8=4 volts dropped and is severe. i would either get a minimum of #6 or start buying more romex to be run with what you have. ie 10-2 would have all 3 wires paralleled and would be used on one of the polarities with another romex cable setup the same way and run to the other polarity meaning each romex cable will handle a polarity. even at that you will see some large v drops, but it may be sufficient to run it.
  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.


    Hi Neil,
    I dont think im going to have any issues as we're talking only the startup thats been the issue (at least that what it looked like). the new plug wire I'm using at the end of the line is much thicker. and while i havent measured the input voltage again i have hooked the dvd drive and floppy drive backup and it still boots ok even with that extra draw on this new cable. i just ran a utility that cranks the hardrive pretty hard and its fine. i will report back,

    oh, btw yes it is 3 wire with the unused neutral , thanks for that tip i never thought of that (doubling up one of them). would i double up the positive or neg of the romex if it turns out i need to do that, or should it definitely be both? i was under the impression that most current went through + but then i really dont know much about electricity as you know.

    we're only talking a 40-50w load TOPS. its that startup draw that was killing me, and a tiny wire rated for way less amps than needed id guess ;)

    i just checked: the webserver and keeping the batts floating was 33w, now that i have the pc on its 73 w (idle) total, how cool is that!>?!

    so im down to only about 40 watts, :)

    running off ac with the same config (but needing an ac/dc adapter) was 48w idle (jumps 10-20w during heavy use under either scenario). so thats something like 17% increase in efficiency going off straight 12v. of course as jkirkebo points out its cool that ive lowered the power req's overall as i will have to run this on the ac/dc adapter winters.


  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: another 12v dc pc goes in use.

    actually it doesn't matter if it's the positive or the negative. if you do both with one wire you will short out your battery. :-o :roll: i'm glad to know it's finally working though.
  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.

    yea,

    so i tried in the computers bios to change the clock frequency (what i was messsing with to decrease the computers power draw).
    my particular bios has about 5 speed settings i can change, lately ive been running it at the slowest speed which is still much faster than my previous amd athlon processor. i tried a midway speed to go faster and it booted ok , running WAY faster (oh its hard to see how fast it could be) and it bbooted ok and was running fine (at about 55-60w now up from 40w) but it kicked off again so the voltage must have dropped. so i went back to the slower speed. now, thanks to you guys i at least know what i need to do if i want to run full speed, which id like to do in summer on sunny days at its just wasted power if i dont anyhow!

    im going to try to use the notebook more in winter too.

    minit-itx machines are incredible for low power, but of course are a little slower. i built 2 systems with a notebook hardrive (that decreases power draw alot too, which is something i may look into for this machine). i actually have one sitting idly by unused, maybe ill take its notebook hardrive for this machine.

  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: another 12v dc pc goes in use.

    The other simple thing to do is add a capacitor right at the converter, it will handle the "spikes" or surge of startup and not add any load otherwise.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.

    the voltage drop prob is all solved: looks like it was my poor wiring work with weak interconnections. I've redone one of them and also put it in a proper electrical box for interconnections and its ok. so now ive got the pc running at full speed direct off 12v, NO PROBS! :)

    hard to say the individual draw but right now the mx60 shows about 80watts to run my full sized desktop pc, the small webserver (about 14w), and keep the batts (~660 AH) floating (wattage varies). and it charges my notebook but that appears to use virtually nothing once charged up. so cool :mrgreen:
  • System2
    System2 Posts: 6,290 admin
    Re: another 12v dc pc goes in use.

    ok did some more little testing tonight..just thought id post results:

    test system is an
    amd64 (3000 i think) w/cpu fan
    ati pci video card (i hear onboard video is lower power: untested).
    seagate serial ata (SATA) hard drive
    no cdrom for testing.
    using 12v wide input fanless power supply as described previously
    powering the system off a ac to dc wallwart adapter (current use includes this inefficiency)

    system idle: downloading off the net: 44+w
    took out the 12v power supply and ran same config with a standard pc power supply: 20w increase.
    tried switching video cards for hahas as i have another: put in a AGP graphics card and usage went UP 5W!

    same config as above, directly off 12v
    40.8 to 42w !

    the dvd drive adds quite a bit, im going to test later and see if another brand/model uses less, and also considering taking it out and using a external.