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

  1. #11
    FLAC
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    No, not exactly but the full details are way more complicated.

    The LM1084 has a high voltage drop - which means many PC's will not run off it's output since the car voltage - the voltage drop is too much. You probably won't be able to combine them straight with the ITPS since the ITPS with it's extra hardware will likely have a different voltage drop and hence either it, or the LM1084's will end up trying to dominate.

    Search for my thread on using 15 2A regulators in parallel into a PW-200. It's cheaper and they have a much lower voltage drop. That's how I'm doing it. Cut out the ITPS and it's way cheaper but you have no automatic shutdown controller. But you can build your own very cheaply or buy zootjeff's which is fairly cheap.
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  2. #12
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    But the LM1084 it's the same that ITPS uses and if I join two of them together the dropout don't change, am I wrong? (yes there is the ballistic resistance but is very small 0,015 ohm.. 0,015 ohm x 12 A = 0,18 V | 0.015 ohm is the resistance of two feet of #18 wire)

    In my design the PW200 is connected directly to the 12v rail with two LM1084, then the ITPS switch on the system with a relay.

    However I'll search for your thread.. 15 regulators of 2A! impressive... 15 small heatsinks or only one very big?

  3. #13
    FLAC
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    In my design the PW200 is connected directly to the 12v rail with two LM1084, then the ITPS switch on the system with a relay.
    That's better. I thought you were intending to use all 3 together. Except for the huge voltage drop across them.

    Here are two links:
    DSX12V: 12V in 12V out 10 AMPS!
    Revised New 16A 12V Regulator Circuit Double Checking
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  4. #14
    Constant Bitrate sanbas's Avatar
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    sorry to butt in for a sec, when you guys say use 8 awg for the opus power wire do you mean all the way ot the circuit board of the opus? or just use 8 gauge until you solder or connect it to the 14 awg power wire coming out of the opus?

    b/c i was just testing my setup and I have a 4 gauge coming in to the trunk into a fused distrobution block and then i have the 14 awg opus wire connected directly into the distro. block and an amp also going in to the distro. block with 8 gauge wire.

    thanks

    P.S. i think its 14 awg that comes with the opus, correct me if i am wrong.

    Also I am waiting for my xenarc 700tsv to coming in and since i have a spare cigaratte ligter plug i might use that if i can do it neatly but if i cant i want to run it off the opus (dont know how)...will do some search on how to do that again, didnt find anything solid last time i did though.

  5. #15
    Maximum Bitrate contaygious's Avatar
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    yeah could someone help me out too please. I have an opus 90w and need help wiring it to my battery. what do I have to buy and how do I hook it up exactly?

    Thanks a lot!
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  6. #16
    Variable Bitrate kmcniece's Avatar
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    Quote Originally Posted by sanbas
    ... I have a 4 gauge coming in to the trunk into a fused distrobution block and then i have the 14 awg opus wire connected directly into the distro. block and an amp also going in to the distro. block with 8 gauge wire.

    P.S. i think its 14 awg that comes with the opus, correct me if i am wrong.
    My understanding is that you want to get the biggest pipe (4 ga. should be fine) to the distro block.

    From there you should connect the opus using the 14 ga. that comes with the PS. The Distro block just distributes the power to the smaller pipes (smaller ga. wires).

    This is of course only from what I've read and I am absolutely no expert on these things.
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  7. #17
    FLAC
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    I have 13 2A regulators connected in parallel without the diodes shown in the above circuit. Most circuits recommend a small load resistor on the output of each regulator but I decided to skip that and rely on the built-in regulation. What I find is that one or two regulators appear to be somewhat maxed out providing the 8 amps I need for my setup (getting too hot to comfortably touch but not so hot as to cause burns if you test with a finger . I estimate the one I know consistently gets hot is running about 80-90 degrees C and probably not at it's rated max operating temperature of 125 degrees - at least not where I'm touching it).

    Edit: There may be diodes inside the 2A regulators I'm using but there definitely isn't one on the ground since I fried my first attempt at this circuit by connecting the circuit to the 12V in backwards at one point . I was a lot more careful with the 2nd attempt.
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  8. #18
    FLAC
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    Oh, and I get less than 0.25V drop across my uber-regulator circuit.
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  9. #19
    FLAC shakes's Avatar
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    Quote Originally Posted by Arathranar
    I have 13 2A regulators connected in parallel without the diodes shown in the above circuit. Most circuits recommend a small load resistor on the output of each regulator but I decided to skip that and rely on the built-in regulation. What I find is that one or two regulators appear to be somewhat maxed out providing the 8 amps I need for my setup (getting too hot to comfortably touch but not so hot as to cause burns if you test with a finger . I estimate the one I know consistently gets hot is running about 80-90 degrees C and probably not at it's rated max operating temperature of 125 degrees - at least not where I'm touching it).
    Right ... but the whole point of using the load resistors is so the power usage will be more evenly distributed across all regulators. instead of two of them getting really hot because they're working hotter.
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  10. #20
    FLAC
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    Quote Originally Posted by joshthepilot
    The 2 diodes out of the regulators really are good practice or you will overload the lower regulator if it isn't putting out EXACTLY the same voltage as the first.
    How do diodes help that? I can see that power resistors could. But a diode should be largely a fixed voltage drop and hence have no effect on preventing a regulator overloading.
    Quote Originally Posted by joshthepilot
    The 3rd diode is there because this is a professional circuit. It is to elimiate people applying the power and ground backwards. It also raises the circuit .7 volts from ground to cancel out the .7 volts drop in the regulator diodes. WUT.
    I had one in my 2nd circuit to prevent me doing it again but in the end I took it out since I wasn't convinced it wasn't going to cause me unpleasant grounding issues between different components (e.g. the PC and the LCD). I originally thought it's presence might make the circuit try to put out 12.25V but removing it didn't cause the regulated voltage of my circuit to drop at all.
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