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Thread: I want a computer in my backpack

  1. #1
    Newbie btown's Avatar
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    I want a computer in my backpack

    just to be innovative and retarded i'm thinking about wasting a grand on this instead of a laptop. Mostly for school. I need some ideas. I think i can fit a 17" monitor in there, so I would take lcd and wireless kb/mouse out of backpack to use it. Power source could be banks of D-cell NIMH batteries. I'm trying to figure out if i could run the computer for like 10hours (all day) without recharging, huge advantage over laptop. 10 D-cell in series is 12v. batteries would probably be substantial part of cost (>$100 for 10). there are 9000mah D batteries, i think weight like 15lb for 10. definitely not more than 20 batteries then, cause i have to be able to carry backpack. there must be lighter weight batteries. 40w computer power would be like 3A (rounding down), so 3 hours on 10 batteries. what kind of rig should i run? if i did VIA's thing, i could get 10w computer usage + monitor/kb/hd (not sure how much wattage 17" lcd uses). I don't know anything about idle computer power usage. May or may not go for video card. thanks for ideas.

  2. #2
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    what about old video camera batteries. like the huge vhs cameras of the 80's and early 90's. i bet they had to eat tons of power. I haven't reasearched this idea, so I don't really know if it is feasible, but its just an idea. those batteries are heavy and large, but maybe more weight efficent than D's. search for the power usage calculators, they could give you rough estimates on most devices. good luck.

    ray

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    Maximum Bitrate freestyler's Avatar
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    http://www.techkwondo.com/projects/bedouin/index.html

    check out that guy, he's doing a backpack laptop....

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    btown, I think you may want to look up the weight of batteries again. There is NO way that 10 d cells is 15 lbs. Perhaps you meant 15 ounces? They weigh about 160 grams a piece. That is about 3.5 lbs for 10. Not TOO bad. 12x9=108 theoretical watt hours. More likely, around 85-90 usable watt hours. So, if your computer is using around 60 watts, once you take into account converter in-efficiencies, it'll be using around 75-90 watts. So, you'll get about an hour of use from 10 d cells. You MIGHT get 2 hours if you have a real low power system. If you use the real small and power efficient things (I find your 10w spec hard to believe, though that is mostly because I am pretty new), you might get up to 3 hours if you are dang lucky, but not likely. A spec I found for one 15" lcd is 50 watts usage. You MIGHT find one as low as 30 watts, but I wouldn't be too hopeful.

    If you have electronics knowledge, lithium ion is DEFINATELY the way to go. The individual cells can be dirt cheap. You just need to know how they work so you can charge them and use them without burning them up. Plus they are a fair bit lighter per watt-hour than other stuff.

  5. #5
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    Ok, the quick answer to what you want to do: it isn't practical.

    Ok, you your going to have a backpack filled with something near 25-35 lbs of computer equipment (your kidding yourself if you expect less, 20 lbs of batteries alone, if not more). These batteries arn't going to be cheap either, as you noted. You would have to go the via way, using integrated graphics. Anything else would draw too much power. And for the hard drive, I would highly recommend using a laptop 2.5" drive, draws far less power. BTW, for the screen, you can go look up specs on a specific moniter, but expect 30-50 W.

    So, this is where we sit:

    10W Motherboard/CPU (trusting your numbers on this account)
    40W Moniter
    5W Laptop Hard drive
    10W CD-ROM (not sure on exact wattage)

    65W Total

    Now, take into account 70% efficiency on your power supply (and this is a fairly optimistic number), and we are up to 84.5W. At 12v, this is 7.04 A. So, in order to run 10 hours, you would need 70,400 mAH worth of batteries, or 8 of those D cell batteries you were talking about. I guess these seems managable at the moment, but I doubt it works out this nicely in practice.

    Anyways, you would probably be far better off buying a laptop in both cost and usability. If you want more battery life, apply some of your money towards building an external battery (or just buying a second battery) for your laptop. You can build a battery that will output similar voltages to the power brick the laptop uses without too much effort.

  6. #6
    FLAC Pudge's Avatar
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    Quote Originally Posted by Sinorm
    Anyways, you would probably be far better off buying a laptop in both cost and usability.
    Yeah, but where's the fun in that?
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  7. #7
    Maximum Bitrate jusatry's Avatar
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    it seems like your LCD is gonna be the biggest problem. Why not get a bare 10-12" LCD (PM my if the 12" one sounds good, ive got a sharp w/all the fixin's that im not using), and save the power on that? Plus the space. And then a touch kit would be more practicle, so you could have that wow feature....as for the battery power- no idea. what are you gonna use for a DC-DC psu? thats gonna get hot so make sure you dont light your backpack on fire....thats a funny image....the via board + laptop HDD + DVD drive (im assuming ) is not gonna take up much space....so you have LOTS of room for batteries.....i guess its doable...

    okay thats my thoughts for now. Cool idea for a project.

  8. #8
    Newbie btown's Avatar
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    ok, i did more research.
    17" lcds typically are 45w. i know laptop lcds suck compared to desktop ones cause they use hardly any power.

    http://www.zbattery.com/zbattery/gp900dhc.html
    these batteries would cost me ~$110 for 10pack. the 10pack would weigh 4.5lb (WAY less than i thought), man i could have like 4 10packs in there for 36ah and 18lb.

    opus power supply is 90% efficient as i recall.
    let's say i run it for 4hr and idle it for 6hr

    http://www.silentpcreview.com/module...rtid=19&page=1
    at this place they made a power meter and tested computer with these specs at 70w idle and 110w max:

    P4-1.6 CPU overclocked to 2125 MHz
    Gigabyte GA-81RXP motherboard with built-in LAN and sound card
    2 Seagate Barracuda IV 40G hard drives
    1 CD burner
    1 DVD drive
    512 meg DDRAM
    Enermax EG365P-VE(FCA) 350W power supply
    1 Panaflo 80mm low power fan at 5V

    obviously i don't need anywhere near that amount of peripherals. i ordered a fluke 112 multimeter so i'm going to do some wattage measuring with various setups on my carpc rig.

    now i'm trying to justify doing this considering i could install laptop in backpack and use the NIMH battery packs to run it for same time and use the 17" monitor and wireless mouse. it would be worth it only if the desktop setup was better in some way. pros could be:
    good agp video card, since all laptop video sucks.
    pci tv tuner card.
    7200 rpm hard drive WAY better performance
    cheaper

    basically i think to have it be better than a laptop it will have to consume ~100w with the screen running. so 100/12~8A so i've got 36ah in 4 10packs so about 4 1/2hr run time. Now i'm leaning toward laptop with screen and keyboard and massive battery backup. just having the external screen is enough of a wow factor.

  9. #9
    Variable Bitrate HybridMike's Avatar
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    is there a reason for not using a small form factor PC...like this one:




    or maybe one with more options like this:


  10. #10
    Maximum Bitrate jusatry's Avatar
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    not as much fun

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