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Thread: My idea for powering carpc off wall at home (cheaply!)

  1. #31
    Constant Bitrate
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    so what's the non ghetto way to power a carputer off the wall outlet? There's got to be AC to DC converters, no?

  2. #32
    Variable Bitrate billmee's Avatar
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    MPJA sells a 13.8Vdc 11 Amp supply for $59.99

    I've been thinking about installing one in the trunk ( permanently ) and hooking up an AC line when parked in the garage. This will power the pc and charge my second battery.

    http://www.mpja.com/productview.asp?product=16780+PS

  3. #33
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    Seriously, dude. I do this all the time. All you need is a simple automotive battery charger. Easy to find, easy to use and works on any car.

    If you want more convenience, just add a quick plug-in type connector behind the grill, under the bumper or something. Yes, a battery charger is noisy, but tying it directly to your battery goes a long way in filtering the noise out. A little audio interference while in the garage is not a big deal. In my case I usually don't hear it. Attaching through the cigarette lighter will be noisier.

    Also, if you have a dead battery someday, the charger will pay for itself. A cigarette lighter plug is fused 20A at most, so you can't charge a battery quickly through it. In fact, most of the plugs you find that plug into them melt with 10A or less sustained draw. A PC power supply is great at regulating the voltage but poor at surge loads. Depending on brand, you could smoke it by attaching when the battery is too low or turning the key on and off.

  4. #34
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    What I've always wanted to set up is a separate 12V gell cell to power the computer. It would be set up in a standard dual battery system with a solenoid or isolator (lots of products available). Then you can keep the computer running while the car is off with no risk of killing the main battery. Maybe you could have a switch to "keep-alive" before you turn the key off. Ideally you would have some provision to auto power-off the PC if the second battery gets low.

    Actually, I would be surprised if somebody here hasn't already done this.

  5. #35
    FLAC
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    Why use an external 12volt if you are going to be using it at home? You would need a fairly large battery (expensive) and you would still need to buy a battery charger for it. For less money, do you guys think a simple high current power supply would work (just connect it in parallel with car electrical system and set it to ~14v)? Such as this:
    http://www.partsexpress.com/pe/showd...number=120-548

    Only a bit over $100 and can provide 22A. For a bit more, there are even models that are capable of higher currents. I also found this thread which talks about converting just a single AT psu into a battery charger:

    http://www.mp3car.com/vbulletin/powe...pc-supply.html

    My original design (3 psu's in series) didnt handle loads over 10A that well, so I might consider this mod because I have a ton of old psu's laying around.

  6. #36
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    There's no reason why a bench-top power supply wouldn't work. It would also be great for powering up equipment and working on it outside of the car.

    A basic car battery charger would work though for what you were originally trying to accomplish: http://www.harborfreight.com/cpi/cta...emnumber=31207

    Both are good basic tools to have.


    Maybe I didn't explain my "second battery" idea very well. It eliminates the need for an external power supply unless you are running the PC for extended periods. The battery gets charged by your alternator as you drive. Everything is automatic. Just google dual battery, battery isolator, etc, but in this case the second battery would be smaller.

  7. #37
    cheap custom title JC-S60's Avatar
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    Use an old pc power supply and connect only your carpc to the 12v output.

    You can find plugs that, when you connect them, another connection gets disconnected (like when you plug headphones into your stereo, it shuts of the speakers), could be an easy way to do it (or with a relay and a diode, so the pc gets disconnected from the car once it receives power from mains)...

    Many ways to accomplish what you want

    Joachim

  8. #38
    cheap custom title JC-S60's Avatar
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    Quote Originally Posted by ticketmagnet View Post
    There's no reason why a bench-top power supply wouldn't work. It would also be great for powering up equipment and working on it outside of the car.

    A basic car battery charger would work though for what you were originally trying to accomplish: http://www.harborfreight.com/cpi/cta...emnumber=31207

    Both are good basic tools to have.


    Maybe I didn't explain my "second battery" idea very well. It eliminates the need for an external power supply unless you are running the PC for extended periods. The battery gets charged by your alternator as you drive. Everything is automatic. Just google dual battery, battery isolator, etc, but in this case the second battery would be smaller.
    Attention: a battery charger is often a very simple device, not regulating the power very well - it could damage your carpc.

    Joachim

  9. #39
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    The problem with battery chargers is that only the really expensive ones will be high current enough to power the entire car electrical system. Unless maybe someone has a link to a cheap one that is capable of 20+ continuous (not just cranking) amps?

  10. #40
    lez
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    Quote Originally Posted by ticketmagnet View Post
    Then you can keep the computer running while the car is off with no risk of killing the main battery. Maybe you could have a switch to "keep-alive" before you turn the key off. Ideally you would have some provision to auto power-off the PC if the second battery gets low.

    Actually, I would be surprised if somebody here hasn't already done this.

    I have.

    Gel cells are cheap now as they use those in 'jump starters' (ebay) they usually have a little air pump built in etc, the battery fitted is usually 12v17ahr

    When I'm indoors with it I just plug the battery charger on it, the gel cell protects the PC supply (m1atx) from any spikes/dips from the charger etc.

    Also its guaranteed to survive even the longest crank (15+seconds!)to start my diesel on a cold morning
    Lez, more widely known as flez1966

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