Converting 1.8V NiZn to 1.5V

[Djedi]

Hi!
I am appealing to all you electronic geniuses out there for a solution to my problem. I am a photographer and use alot of AA's in my flash equipment. Recently, the Powergenix NiZn's have come to my attention. In some flash units they work like a charm, cutting the recycle time down by 20 to 50%, but in other units, they wreak havoc and the flash dies after little or no use.
My newest flash manufacturer (Metz) does NOT recommend NiZn's due to the higher voltage output. They have no trouble at 1.5V (alkalines) but one user reports killing the flash shortly after loading these batteries.:fail:
So, my question- is there a resistor I can install wired to one (last in series of 4) battery that would reduce the voltage of the entire set to 6 or so volts? I think it would just be a matter of soldering the resistor to the side of the button, insulating the top of that button, then bringing the other end of the resistor up to the flash contact. If possible- what would be the value of that resistor and would I still see a benefit in flash recycle time?
Thanks
Wolfgang

 

[Djedi]

Re: Converting 1.8V NiZn to 1.5V-another idea

Say couldn't I use a 7806 or 7906 voltage regulator for this task? :thinking: If so, do I need to use any caps?
Thanks

 

[Illum]

nope...78xx series require a differential of about 1.5V to work, in this case theres only 0.3V to work with.

Look up LT1963 from Linear Tech, the Lt1963 is about as simple as it gets
http://eedatasheet.com/pdf/LT1963,LINER,30937.pdf

Drops out at 0.9V
Comes in an S8 package

 

[Glasstream15]

Eneloops work fantastically well in Canon Speedlights. Really quick recycle and good life. Rechargeable of course. And they are Low Self Discharge so the ones I charged the first of June are still ready to go today.

I don't know about Metz flash units, but I can safely recommend Eneloops in Canons.

I just don't believe in trying to complicate something simple.

 

[Djedi]

nope...78xx series require a differential of about 1.5V to work, in this case theres only 0.3V to work with.

Thanks so much, but if I were using 4 in series (as most flashes do) wouldn't my actual voltage drop be from 7.2V to 6V? meaning 1.2 volts? Sometimes these beasties actually charge to 1.85 or more. But during use, they will even out at about 1.6V+ EACH
Wolfgang

 

[Djedi]

Eneloops work fantastically well in Canon Speedlights. Really quick recycle and good life. Rechargeable of course. And they are Low Self Discharge so the ones I charged the first of June are still ready to go today.

I don't know about Metz flash units, but I can safely recommend Eneloops in Canons.

I just don't believe in trying to complicate something simple.

People who have used the NiZn's in Nikon SB800s have found refresh rates cut almost in half! That's under 2 seconds at FULL power .When shooting fast action, this can make the difference between getting the shot and not. Only thing is, the fast rate can damage the flash tube since it recycles so fast (heat) - so you cannot do so more than 3 times in succession without giving the flash a rest. But when you need it, the power is there, because of these batteries' high throughput.:twothumbs
I currently use eneloops myself, so I concur that they are great batteries, but I have missed several shots due to trying to anticipate action and it happening right after I have just taken a shot.
Wolfgang

 

[Illum]

Thanks so much, but if I were using 4 in series (as most flashes do) wouldn't my actual voltage drop be from 7.2V to 6V? meaning 1.2 volts? Sometimes these beasties actually charge to 1.85 or more. But during use, they will even out at about 1.6V+ EACH
Wolfgang

well, if you're using alkalines, under any appreciable load over 200ma AA cell voltage will sag a bit, while its not all that apparent in NiMH...I can't say for NiZn because I never used it before. IIRC a flash circuit works by using a transformer to induct power from a battery to charge a capacitor, then using the energy accumulated to feed a second transformer that supplies the starting current necessary for the flash to go off. If this is the case, the current pull would be peanuts and I don't think cell voltage will sag much at all.

the only quick and minimum solder "drop-in" I can think of is the slightly expensive and mysterious DC-DC controller marketed as "anyvolt micro" that can buck/boost any voltage between 2.6V to 14V into any output you want between 2.6V to 14V, adjusted via onboard trimmer, it mimicks TO-220 packages so it'll drop in where 78XXs are used and requires no additional caps.

 

[Djedi]

Wow! That's a nice unit! Only small issue is that I don't know how much amperage that flash draws. That may be the limiting factor, since the Anyvolt only is rated at .5 amp. The big plus of these batteries is their high throughput, so I am afraid the regulator might limit amperage, negating the advantage of the NiZm's. However, it is worth looking into. Thanks:thumbsup:
Wolfgang