Power a flash with a 12v battery pack?

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Evan Platt - 10 Jul 2006 23:37 GMT

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

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Pat - 11 Jul 2006 00:29 GMT

4 AA batteries is 6 volts not twelve.

> 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
[quoted text clipped - 10 lines]
>
> Evan

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Evan Platt - 11 Jul 2006 00:46 GMT

>4 AA batteries is 6 volts not twelve.

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

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C J Southern - 11 Jul 2006 04:03 GMT

> 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).

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?

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C J Southern - 11 Jul 2006 05:39 GMT

Found it ...

http://www.aljacobs.com/THE%20BLACK%20BOX.htm

If you haven't done so already this is very entertaining (and informative)
to read.

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Evan Platt - 12 Jul 2006 18:26 GMT

>Found it ...
>
>http://www.aljacobs.com/THE%20BLACK%20BOX.htm
>
>If you haven't done so already this is very entertaining (and informative)
>to read.

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

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ColinD - 11 Jul 2006 01:14 GMT

> 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
[quoted text clipped - 10 lines]
>
> Evan

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.

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Thomas - 12 Jul 2006 19:30 GMT

> 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.

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

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C J Southern - 13 Jul 2006 05:16 GMT

> > 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
[quoted text clipped - 13 lines]
> pretty high (10 A maybe?). So I guess it is easier to just get a 6 cell
> NiCD high power battery pack.

Thomes,

Have a read at ...

http://www.aljacobs.com/THE%20BLACK%20BOX.htm

I think you might pick up a few useful bit of info.

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