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regulated-output dc-dc converter

Discussion in 'Electronic Components' started by Dave, Jul 19, 2007.

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  1. Dave

    Dave Guest

    I've got an electronic device which operates, at least it used to operate,
    using a car battery as a power source. Over time it has begun to complain
    about low battery voltage which causes the unit to shut down. The battery
    voltage is fine... when I hook it up to the battery in my car and leave the
    car running (~14.4VDC while charging) the device will run indefinitely.
    So... it would appear that whatever is sensing the input voltage is sensing
    the voltage incorrectly.

    So... my options are to open up this device (it's a sealed, ruggedized,
    evacuated of air, computerized survey total station so this would be my 2nd
    choice) to have a look at the (no doubt) SMT microcircuitry within, or to
    find a device which will give me a regulated, say, 13.8VDC from my 12V wet

    Can anyone point me at a retailer who sells 12V-12V converters with
    regulated boosted voltage? I've only found one at but a) they are in
    Australia and I am in Canada and b) these units are 8A and up whereas I only
    require maybe 1A max. Otherwise the description of this device is EXACTLY
    what I want.

    Somebody must make these things, maybe for RV's or sailboats or so
    solar-powered survivalists can write their manifestos on laptop computers...

    Any help greatly appreciated.

    Sorry about cross-posting to the repair group but there's no
    sci.electronics.workaround group.

  2. Joerg

    Joerg Guest

    See if something like this could work: Series.pdf

    The PTK15-Q24-S12 from Cui is around $50 at Digikey, in stock and the
    Digikey P/N is 102-1078-ND.

    I believe TI has numerous modules as well.
  3. John Fields

    John Fields Guest

    Another possibility is that your battery is coming to the end of its
    useful life and its capacity has been diminished.

    To find out, connect a voltmeter across the load without the engine
    running and track it until your device shuts down. Track it,
    because as soon as the load shuts down the battery voltage will rise
    and you want to know where it was when shutdown occurred.
  4. Dave

    Dave Guest

    Thanks, John, but that was my first hunch too... I tried several
    fully-charged different batteries and got the same results.
    Given all the other projects I've got on the go right now, I'd as soon buy
    one as my employer will pay for it, but if I've got to build one, so be it.

    Thanks for the link.

  5. Dave -

    Yours is a common problem faced by Ham Radio Operators, as some
    transceivers are voltage-critical. There was an article published a few
    years back in the QST magazine, on how to build a DC-DC converter to
    convert a range of input voltages to a steady 13.8 Volts. I believe it
    was also offered in both kit and finished form. However, I don't recall
    the company.

    I searched Google for 13.8 dc-dc and came up with several hits. One of
    the first was
    which had two models, PST-DU500 and PST-DU700, that appear to do what
    you need.

  6. Rich Grise

    Rich Grise Guest

    Leave the car battery in the car, and get a deep-cycle (marine, golf-cart,
    etc.) battery for your device, and a proper charger.

    Car batteries are for starting car engines, and don't like long-term
    "moderate" loads, and discharging them very much shortens their life.

    A deep-cycle battery would be seriously overloaded if you tried to
    start a car with it, but they can provide a few amps for a surprisingly
    long time, and they're not damaged by a deep discharge. (well, within
    reason - the point is, they tolerate it better than a motor-starting

    Good Luck!
  7. Dave

    Dave Guest

    The device only draws a few hundred milliamps, and I've tried deep cycle,
    gel cel, and AGM over the years.

    the drain on the battery isn't the problem.

    I've got several smart-chargers for the different types of batteries and
    generally get several years out of a battery.
  8. ehsjr

    ehsjr Guest

    How about a simple "Rube Goldberg" solution -
    add a 1.5 volt battery in series. That will
    at least buy you some time until you find
    or build the DC-DC converter.

  9. kell

    kell Guest

    Go to and search for PWR1245
    here is a link if it works:

    The device puts out 1A positive and negative 15 volts (for driving op
    amps), obviously you will only use the positive.
    Only costs $9, surplus. It would cost a chitload more than that if
    you bought it retail.
  10. Rich Grise

    Rich Grise Guest

    OK, so, then, what was the question? ?:-/

  11. neon


    Oct 21, 2006
    the devu\ce care about voltage if it is wthin specs it cares about current more.
  12. Dave

    Dave Guest

    Where might I procure a voltage boosting device to feed >13V to my device
    from a 12.6V (or less) source? There were a couple of suggestions, I
    ordered one yesterday.


  13. Dave

    Dave Guest

    Thanks, Fred, that's just the ticket. Overkill with 36A continuous ability,
    but I ordered up the 500W model yesterday.

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