Graflex.org

[Henry]

I used to fire 5B bulbs reliably in my Ultima flash with folding reflector, using a 22.5 volt battery, Mallory M-215. The equivalent battery is available today from Radio Shack, Eveready M412, rated at 140mAh. I don't think current supply would be a problem with the 3x9v cells I'm envisioning!

Incidentally, that Mallory M-215 lasted forever. I must have fired off several dozen bulbs over a period of several years, and it just wouldn't quit. That's not heavy use, I admit, but believe it or not I still raise a tickle on the voltmeter with it today.

[Polaski]

I checked last night, and the Minox flashes use a 15v battery. The original is of course no longer available, but good old Radio Shack has equivilents.

And of course the Minox flashes were designed for AG1 bulbs, although I saw one recently that has a fan reflector much like that of the Tilt-a-Mite.

It's a bit odd that I am in this discussion, since I almost never depart from available light. It's just that using this old technology makes me smile.

[robcruickshank]

The problem with using 9v batteries, or 22.5v ones, for that matter for flash applications, is the internal resistance of the battery itself. These are true batteries (ie, a stack of 1.5 volt cells), and have higher internal resistance than a single cell. 3 9v batteries in series will provide 27v open circuit, but since the internal resistance of the batteries is added together in series, you will gain voltage, but not current.
I did a quick experiment, and found that an alkaline 9v battery on my desk will deliver a short-circuit current of 1.5 amps, max. This means the internal resistance of the battery is about 6 ohms. So if you stack two 9Vs, you get 18 volts, but the internal resistance of the stack is now 12ohms, and you'll still get only 1.5 amps, assuming the bulb is 0 ohms. As someone pointed out, a single alkaline 9v can reliably flash a bulb- using a higher voltage won't give you more (or less) current without a capacitor. Add a cap, however, and your current will be determined by the energy stored in the cap, rather than the resistance of the battery. That's why it's useful to use a lightweight, low-current battery, and a good cap, rather than a big heavy high-current battery.
Oh, and single malt scotch will improve the performance by at least an amp or so, two amps for an Islay.

[C. Henry]

Similar tests on a single carbon/zinc "C" cell (good but not totally fresh) gives a dead short current of 2.25 amps for an internal resistance of 0.66~ ohm, an alkaline "D" cell (also good but not totally fresh) read 3 amps for an internal resistance of 0.5 ohms.
If I recall correctly the old carbon/zinc cells (which were all we had in the 1950s) had a lower internal resistance than the modern alkaline cells but became exhausted with a lot less total use than the alkaline cells. I was surprised that the "D" cell that I tested did not have that much more dead short current than the "C" cell, probably supporting my recollection of the difference between the two types of cell.

C. Henry

[robcruickshank]

Apparently there were special zinc-carbon batteries just for flashes:
http://en.wikipedia.org/wiki/Photoflash_Battery
I've seen these referred to in old manuals, but i guess I'm too young to have ever seen one, although I remember my dad's flash with a 22.5V battery.

[Henry]

I'm concluding from this discussion, incl. the Wiki article, that fresh alkaline D cells will work just fine in my 2-cell Graflite. What say?

[robcruickshank]

[C. Henry]

Fresh alkaline "D" cells should be OK, carbon/zinc "D" cells might be better for photoflash use (Rayovac Heavy Duty is one brand) and are cheaper to buy but will not last as long.

C. Henry