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Thread: power options

  1. #1
    Join Date
    Nov 2008
    Las Vegas

    power options

    I'm pretty sure I'm asking for trouble just thinking about this, but I'm rolling around some ideas in my head... so let the berating begin.

    I'm trying to figure if it's feasible to power my carpc from the cigarette lighter... hopefully only temporarily. Though, I would love for everything to be easily removable.

    I have a VIA PX10000G pico board (roughly 19watts max)
    a lilliput 701 (9 watts?)
    + the touch screen drawing power from USB
    A Garmin GPS18X (<1 watt)

    a couple of low current USB devices (up to 3) and one high current USB device for a total of ~5 watts....

    I'm missing what the power supply would lose in heat, but that should still keep it under 35 watts

    these numbers are pulled from manufacturer tech specs... and using 100mA/500mA max draw for USB devices.

    35 watts @ 12 volts is 2.9A

    The 12v accessory line is fused at 20A (240 watts)

    Assuming that nothing else is on this line this is more than adequate... This is also assuming that it was wired for the full current. Even if wired for half that is enough.

    I realize that doing it this way is no replacement for dedicated wiring, but is it acceptable or in any large way hazardous?

    (I suppose I could use the factory inverter, but that's just wasteful as I could use it for other stuff).

    Like I said, I'd like to be able to remove everything quickly if needed. It also gives me easy access to pull the plug for an extended period of time.


    part 2:

    If this works, how much worse would it be to put a battery in between, charging while on and providing power for proper shutdown when the key's removed and power to acc is cut?

    I don't really have the best understanding of circuitry/electrical but I pick up quick and would love to see this work.

  2. #2
    Fusion Brain Creator 2k1Toaster's Avatar
    Join Date
    Mar 2006
    Colorado, but Canadian!
    usually it is a bad idea, but you have a very low draw system, it will be fine.

    does your cig lighter shutdown immediately with the car, or is it always on?

    You can always wire the cig lighter to a constant source, then get an ignition cable and attach to a quick connect of somesort. Then it is just 1 extra thing to plug/unplug but gives you all the advantages of a SDC
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  3. #3
    Join Date
    Nov 2008
    Las Vegas
    I'm 99% sure it gets cut with the rest of the accessories, but i'll have to double check.

    For continued power after the car is off, I was thinking a second small battery able to cover it for a few minutes while it shuts down... or maybe a deep cycle to cover it for a while and just trickle charge the battery from acc when the car's running. I know it can be done, I'm just not all that clear on how to go about it.

    My reasoning behind not wanting to run wires, splice in to others, etc: brand new car, under warranty so I don't want to leave anything in there should I have to take it in for something and have them say that voids it. Of course, I don't really want to overload and start a fire either
    But, I reason that the factory lines "should" be well protected from the "avg" consumer accidentally overloading it.

  4. #4
    Maximum Bitrate FusionFanatic's Avatar
    Join Date
    May 2007
    a better option than using the cig lighter socket/plug would be to use fuse taps and wire it into your fuse box. this allows you to run the system off your factory wiring without having to splice into it, and without having to use an ugly cig lighter plug. if you ever wanted to remove your wiring (prior to dealer service) all you need to do is simply unplug it from the fuse blox.

    fuse taps like this "add-a-circuit" are best, as they integrate a 2nd fuse holder into the tap itself. they make them in both ATC and min blade fuse sizes. you can get them online or at your local autozone, advance auto, pepboys, etc. use a multimeter or test light to check for the "hot" side of the fuse.

    your fuse box has both constant 12v and ACC (switched 12v) circuits, so you can hook up a PSU/regulator with a startup/shutdown controller. with a SSC, there is no need to hook up an extra battery as the PSU has power available even with the car's ignition off.

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