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Souping up a classic flashlight


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#1 Mathew Rudenberg

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Posted 12 April 2009 - 01:27 PM

I'm doing a music video where the loosely structured narrative involves kids wandering through a spooky house. Art Dept is renting some old school flashlights, which unfortunately I don't think will read at all on camera regardless of how much haze I put up. Since this is a music vid, I'd like the lights beams to be pretty extreme.

I found some mention on the forums of using 12v MR-16 globes wired to batteries which sounds like an excellent idea, but I have a couple of questions:

Does anyone know where in LA could I potentially rent these SLAB or whatever 12V batteries. (I haven't been able to find anywhere so far) If they can't be rented then where could they be bought?

What gauge wire should I use to hook them up to the globe, would zip cord (18 gauge) be too thin and overheat?

How long should I expect the batteries to last if I'm using a 50w NSP 12v mr16?

I would greatly appreciate any help in this matter.
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#2 John Sprung

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Posted 12 April 2009 - 02:32 PM

18 gauge will be fine for a 50 watt load. The lamp will draw just a tad over 4 Amps, so in theory, a 4 Amp-Hour battery should run for an hour. For color temperature, best to play safe and only use the top half, get 8 AH per hour of run time. You can use smaller batteries, keep several on chargers, and swap them out often if the problem is concealing them.



-- J.S.
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#3 Dan Salzmann

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Posted 12 April 2009 - 03:07 PM

18 gauge will be fine for a 50 watt load. The lamp will draw just a tad over 4 Amps, so in theory, a 4 Amp-Hour battery should run for an hour. For color temperature, best to play safe and only use the top half, get 8 AH per hour of run time. You can use smaller batteries, keep several on chargers, and swap them out often if the problem is concealing them. -- J.S.





+1 on all of this, I've done it many times. Just make sure you turn them off between takes as they heat up. Also remove the plastic "lens" in front of the flashlight bulb because those tend to melt fast.
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#4 Mathew Rudenberg

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Posted 13 April 2009 - 03:54 PM

Thank you for your help gentlemen!

I have all the parts except the batteries, if you know where to rent or buy them in LA, or at least at what kind of store they would most likely be stocked (eg computer/hardware/etc) that would be very helpful.

I see SLAB batteries at 12v and 8ah are often used in UPS devices, but I don't have time to have them delivered... I doubt best buy carries them though.
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#5 Bruce Taylor

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Posted 13 April 2009 - 08:09 PM

I see SLAB batteries at 12v and 8ah are often used in UPS devices, but I don't have time to have them delivered... I doubt best buy carries them though.


A specialty computer store may have the UPS batteries. I get my sealed lead-acid gel cell batteries from Interstate Battery. They mostly sell car batteries wholesale, but they have a very good selection of smaller gel cells and appropriate chargers.
Interstate Batteries Of Santa Monica
(310) 445-3246
2321 Pontius Avenue
Los Angeles, CA 90064

Of course you could use a car battery too. You can get them at any auto parts store, obviously.

Bruce Taylor
www.indi35.com
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#6 Ralph Keyser

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Posted 14 April 2009 - 01:15 PM

Another good source for SLAB is any company that sells security systems. Those batteries are used as the back-up batteries in commercial and household security systems (much like the UPS systems).

You might also checkout Magic Gadgets flashlight insert (http://www.magicgadg...htm#superbright). It drops into a (largish) standard flashlight and gets the power from a flock of AA cells in the flashlight.
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