Power a flash with a 12v battery pack?

Discussion in 'Digital SLR' started by Evan Platt, Jul 10, 2006.

  1. Evan Platt

    Evan Platt Guest

    I'm hoping someone here has an inexpensive solution.. I have a 12 volt
    battery belt - basically a 12 volt 7 amp hour sealed lead acid
    battery. I'd like to be able to power my Promaster 5700 flash from it.

    Basically, I'd first need something to go from a cigarette lighter
    type plug (what my battery belt has) to the 4 AA cell type holder on
    the flash - I don't physically have the flash yet, but I don't believe
    it has a plug for like an external power supply.

    Any ideas?

    Thanks.

    Evan
     
    Evan Platt, Jul 10, 2006
    #1
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  2. Evan Platt

    Pat Guest

    4 AA batteries is 6 volts not twelve.
     
    Pat, Jul 11, 2006
    #2
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  3. Evan Platt

    Evan Platt Guest

    Umm.. thanks, I realize that. Obviously the device that goes from the
    flash to the battery belt would have a stepdown converter (sorry, I
    don't know the technical name). But almost anything that has a
    cigarette lighter type plug and is made for a specific device has
    this. Like say a police scanner that takes 2 AA batteries and comes
    with a DC cord, obviously the cable or the scanner has a converter in
    so it's not feeding the scanner 12 volts. That would probably be the
    simplest part, the more complex part would be basically something that
    looks like the 4 AA battery holder that goes in the flash, and somehow
    also allows the battery door to close. :-D
     
    Evan Platt, Jul 11, 2006
    #3
  4. Evan Platt

    ColinD Guest

    It might be easier to make a belt to carry 5 or 10 d-cells in a
    series-parallel configuration to give 6 volts.

    Colin D.
     
    ColinD, Jul 11, 2006
    #4
  5. Evan Platt

    C J Southern Guest

    Be careful - they do it in one of 2 ways ...

    1st way is where the belt pack may have 12v worth of batteries, but it's
    organized as 2 banks of 6v in parallel

    2nd way is some flashes accept 12 volt and use it to "speed things up" by
    bypassing much of the usual protection circuitry

    A while back someone posted some info about a retired chap who built his own
    "no-nonsence" external battery packs - he had some good info about all of
    this on his site - someone else might have the link?
     
    C J Southern, Jul 11, 2006
    #5
  6. Evan Platt

    C J Southern Guest

    C J Southern, Jul 11, 2006
    #6
  7. Evan Platt

    Evan Platt Guest

    Interesting.. That's almost exactly what I'd like to have as a setup.
    But obviously my battery pack doesn't have the M adapter. :-D
     
    Evan Platt, Jul 12, 2006
    #7
  8. Evan Platt

    Thomas Guest

    Many flashes have a connector for an external power source (and if not,
    you can create one :). The voltage may differ, but it is usually meant
    to be 5 or 6 NiCD/NiMH batteries. That would be 6 V or 7.2 V. I don't
    think a normal flash would take the 12 V you have.

    There is another problem: lead acid batteries are rather slow. They do
    not like fast charge or discharge, and they do not like cyclic use
    (taking lots of charge out, recharging, repeat) either. So NiCD or NiMH
    would be a much better choice, and they weight a lot less, too.

    You could try to get some kind of power regulator, but the current is
    pretty high (10 A maybe?). So I guess it is easier to just get a 6 cell
    NiCD high power battery pack.

    Thomas
     
    Thomas, Jul 12, 2006
    #8
  9. Evan Platt

    C J Southern Guest

    Thomes,

    Have a read at ...

    http://www.aljacobs.com/THE BLACK BOX.htm

    I think you might pick up a few useful bit of info.
     
    C J Southern, Jul 13, 2006
    #9
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