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i need to build a 13.8 powersupply

Discussion in 'Electronic Basics' started by [email protected], Nov 9, 2006.

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  1. Guest

    Hello, i need to build a powersupply, i know how to regularize the ac
    current . but i need to know how i make a 13.8 volt power supply with
    at least 20 amps.

    at the shop, they have a 24 volt transformer (plus12 minus12) with 10
    amp. how i fit this ?
    And can i fit two power supply to addition the current amp ?
    Thx in advandce
  2. JeffM

    JeffM Guest

    As you haven't specified what regulation is required, I'll assume

    If you have to ask the question (and even if you hadn't),
    PURCHASING is a much better solution.
    Froogle, ebay,...
  3. Chris

    Chris Guest

    You're still a long ways away from a regulated 13.8VDC power supply,
    even with your transformer -- although that might be a start.

    The transformer you mention might be useful for a "pretty good" 13.8VDC
    power supply that'd be good for 6 amps or so. The thing is, you'll
    need other componenets to do this, which just might be more expensive
    than just buying one.

    If you have access to either a couple of 10 amp diodes or a 20 amp
    bridge rectifier, a humongous cap (how does 47,000uF, 25V sound?), plus
    various transistors, resistors and zener diodes, you might be able to
    cobble something really basic together. And if you want overcurrent
    protection (you will need this if you're working on automotive
    electronics), you'll have to add more circuitry. Building a power
    supply that will do current sharing (so you can run them in parallel)
    adds a lot more complexity, too.

    Froogle or eBay sound like the best way to go, even if you've got one
    of the parts you might need to build a power supply yourself.

    Good luck
  4. Baron

    Baron Guest

    At 13.8 V, I'm guessing that you are tring to imitate a lead acid
    bettery ! A computer PSU can/will supply 20 Amps. You will have to
    mod it slightly if 12 Volts is too low.
  5. Rich Grise

    Rich Grise Guest

    For that matter, a battery charger could do it, if it has a float

  6. Lord Garth

    Lord Garth Guest

    No, I think not.

    I'm looking at one now and it can supply 6A at 12V, 22A at 5V and 14A at
    This is a 360W power supply but it's clear that the greatest current is on
    the 5 volt
    output, followed closely by the 3.3 volt output.
  7. Baron

    Baron Guest

    Thats fairly small. 650W ones are becoming common. Just looked at mine
    and its rated 18Amp @ 12volts, 26A @ 5V, 22A @ 3.3V. I have seen 700W
    ones advertised and dual redundant chassis PSU rated @ 1400W.

    But I think Rich's suggestion, using a big battery charger could be a
    more cost effective approach !
  8. Tim Auton

    Tim Auton Guest

    CPUs (well, the switching supply on the motherboard which feeds the CPU)
    used to be powered from the 5V line. These days they (and high-end video
    cards) are powered from the 12V line.

    A random Enermax supply (the first computer PSU supplier I could think
    of, the first low-end supply I found on their site):

    3V: 20A
    5V: 22A
    12V: 20A

    The 400W 'entry level gaming system' PSU linked from their homepage has
    *two* 12V rails, providing 20A *each*, with 26A on 3.3V and 5V:

    The PSU you were looking at is old (in computer terms).

  9. Phil Allison

    Phil Allison Guest


    ** Got no idea what a 20 amp car battery charger is like, have you -
    dickwad ?

    Hint - it ain't a DC power supply.

    ....... Phil
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