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Thread: How to wire a DC-DC PSU to a battery?

  1. #1
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    How to wire a DC-DC PSU to a battery?

    I've searched these forums for about 3 hours now on dialup and still have not found an answer. I have a computer that I'm looking to put in my car, I think its about 500 mhz.

    I was looking to put a DC-DC power supply by opus or the m1-atx in the computer. Though all the diagrams Ive seen shows a wire going from the battery to the power supply. How exactly is this done? How do you connect a wire to the battery? Is the fuse box involved at all?

    Any help would be great. Thank you.

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    The best thing is that you put an heavy power cable directly from the battery to the PS. Along the cable don't forget to put a fuse (10A should be sufficent) as close as possible to the battery. And between the cable and the PS a ITPS could be fine. If you don't have an ITPS or you need more power (ITPS allow only 5A (regulated) 5Ax12v=60W) you should use a voltage regulator 12v fixed rated of 10A. (in evidence: no voltage regulator or ITPS -> FIRE, battery is not stable at 12v... when you have ignition it drops at about 10v while when your engine is on it rises at 16v too )
    If you can't find one of 10A you could use 2 of 5A in parallel. In both cases don't forget a big heatsink.. 10A are enough to cook some eggs....

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    Quote Originally Posted by lewdog1980
    I've searched these forums for about 3 hours now on dialup and still have not found an answer. I have a computer that I'm looking to put in my car, I think its about 500 mhz.

    I was looking to put a DC-DC power supply by opus or the m1-atx in the computer. Though all the diagrams Ive seen shows a wire going from the battery to the power supply. How exactly is this done? How do you connect a wire to the battery? Is the fuse box involved at all?

    Any help would be great. Thank you.
    RUBBISH! You are not looking right. You have to think of who else connects stuff to the car battery......car audio people do! Look for amp wiring kits and the like.

    As for the advice from kodiex, i am not sure about that.

    If you are looking at the Opus or M1-ATX you DO NOT NEED AN ITPS. The Opus 90W, 150W and the M1-ATX 90W all take unregulated in from the car battery. If you put a 60W ITPS in the way then you are limiting your entire system to 60W and adding more components whcih gives lower efficiency.

    The Opus and M1 will take voltages down as low as 8V (maybe even lower, maybe a bit higher, it depends ont he model) so you do not need to worry about crankign issues if your wiring is up to the job. Most people have toruble because they try to use too small a gauge of wire. For the Opus 150 use 8 or 10 guage (i would go with 8 incase you run anything else off it) and with the 90W PSUs i would use 10 guage minimum. If you run an amp (not too hight power) as well then you can do a single run with 4 guage and then use a terminal to split off with 8 guage for the AMP and PSU.

    The advice abou the fuse is correct, kind of. You want it placed as close as possible to the battery on the +ve power lead. For a 90W PSU then 10A should be fine as you will be drawing 6.5A when the engione is running but bear in mind that during cranking and if the PC is booting you willbe running close to the 10A so if you find they are not lasting long then up it to a 15A. for the Opus 150 you will need a 15A fuse minimum of a 20A upper limit.

    For the 500mhz PC you should ge away with the 90W PSUs depending on what esle you are running. IE if you deide to run an AGP grahics card, 2 3.5" IDE drives etc then ypu will need more power. Don't forget it is also the safest option to run your screen from the PSU as these PSUs are fully regulated as they are powering your PC so they have to be. Even though the LCD may take up to 24V DO NOT RISK IT! You can searhc and read why, i shall not go into it here.

    an example wiring kit can be found at car audio wiring places, you wil find terminal blocks, fuse holders etc etc. Even linITX sells an 8 guage amp wiring kit suitable for being used with upto the Opus 150.

    Good luck and any more questions jsut ask (but search 1st obviously )

    Get some specs of your car and system up in your sig too, its always good to see what people are doing.

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    Hi S.M.! Yes you have right, for Opus or M1-ATX ITPS is not needed, however I feel me safer with additionals regulators...

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    Quote Originally Posted by kodiex
    Hi S.M.! Yes you have right, for Opus or M1-ATX ITPS is not needed, however I feel me safer with additionals regulators...
    no you are not safer. I don't think you can wire two regulators in parrallel. If you try this with most basic transistor regulator circuits you will be in a world of pain.

    The more components you add and the more connections you have the more you are asking for trouble.

    The Opus and M1 have very good regulators curcuits designed for the currents they need. The guys designing them know more abotu that kind of stuff than me, and probably you, so leave them too it. If you want to be safe use nice thick wire and a fuse.

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    The parallel is possible with a small resistor that balances the currents... this cause a drop of voltage so is necessary take care, however there are regulators rated for 7.5A I'm sure, and probably more too.
    Now I'm going to look about the schematics of Opus and M1-ATX to see what type of regulators they have built in... because they MUST have a kind of regulators.. for example the ITPS has a LM1084 rated of 5A.

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    Quote Originally Posted by Scouse Monkey
    As for the advice from kodiex, i am not sure about that.
    LMAO, I think you were completely sure about it.

  8. #8
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    Quote Originally Posted by kodiex
    The parallel is possible with a small resistor that balances the currents... this cause a drop of voltage so is necessary take care, however there are regulators rated for 7.5A I'm sure, and probably more too.
    Now I'm going to look about the schematics of Opus and M1-ATX to see what type of regulators they have built in... because they MUST have a kind of regulators.. for example the ITPS has a LM1084 rated of 5A.
    ITPS is a linear regulator. It requires something like 13V minimum to output 12V. Once it drops too low, it shuts off. So your PC wouldn't survive the crank. The other solutions contain switching regulators that can work to a much lower voltage and survive crank. The ITPS isn't comparable.
    Progress: 80% - Permanent install left.
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    Quote Originally Posted by rando
    LMAO, I think you were completely sure about it.
    well ok. i was being diplomatic

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    Quote Originally Posted by Arathranar
    ITPS is a linear regulator. It requires something like 13V minimum to output 12V. Once it drops too low, it shuts off. So your PC wouldn't survive the crank. The other solutions contain switching regulators that can work to a much lower voltage and survive crank. The ITPS isn't comparable.
    Not exactly...
    If you have unswitched power direct from battery and an another battery (for example a maintenace free gel battery) in parallel with yours power regulators your carputer survive to anything...

    And however only a PW200 + ITPS + LM1084 x 2 + Backup Battery can provide 200W. Others are far (FAR) from it.. Am I wrong? If so please tell me that I buy something else...

    LM1084 is a power regulator ((5A for each one) that can be combined in parallel, I've red the datasheets) and with a backup battery can provide a stable 12v line against any type of voltage rise/drop between 0 and 40 V, are they enough?

    Is not comparable but at the end it does the same thing, isn't it?

    Thanks to all.

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