Results of Wein cell testing

[michaelk@xxxxxxxxxxx (Michael Kersenbrock)]

Greetings,

        For short attention span readers:  forget'em.


        For long attention span readers:

        Last night, I got around to opening up one of the 625/PX13 
Wein Cell packages that I got in my B&H order (which included a lot of films
all exactly as ordered and all USA made yellow-boxed and fresh dated --
and they arrived within time span they told me, etc.). 

        The Wein cells are advertised as Mercury cell replacements and state
on their package that they are "1.35 Volt"  -- just like Mercury batteries. The
625 Size had always been 'sold out' at local stores for some reason -- but B&H
sells them for $5.95, which is cheaper than local stores by a dollar or so anyway.
With Mercury cells now being illegal in the U.S., and having cameras/light meters
that use them -- it seemed to be the thing to buy for maximum light meter accuracy.
I think someone posted that the original FED stereo cameras used this cell size/type.

        What I had been using were some hearing aid batteries (size 675) which
cost about five dollars for a package of four batteries -- but those need a washer
to fit properly and their voltage measured a bit high.

        So, I took out the hearing aid battery from an old camera of mine and tested
it against the new wein cell.  Results:


                   Claimed on package               Measured
                   ------------------               --------

Mercury batteries           -           1.35V           -

625 Wein cell             1.35                         1.415

675 Hearing aid battery   1.4                          1.406   (same as measured months ago)



        Needless to say, the Wein cell appears to be the same zinc-air battery that the 
hearing aid battery is, and they had used "creative marketing" to drop the slight over
voltage rather than some chemical system tweeking as I had hoped.  I used two DVM's 
to measure the voltages and measured both batteries at the same session. Both are open circuit
measurements whereas light meters use *really* small current load levels which approximate
an open circuit (mine are that way anyway).

        What's more interesting, is that the construction of the 625 Wein cell is
that of a 675 sized battery with a press-fit washer around it to enlarge the diameter!
Good grief.  :-)  Although perhaps the washer makes it worth the extra 300% added cost,
I'm not sure why it would.

        Of course, I don't know the internal construction of the Eveready hearing aid
zinc-air cell vs. the Wein zinc-air cell.  It's entirely possible that the Wein cell has
a larger cell capacity or some other difference not externally visible.

        However, I note that the  Wein cell is built for a customer base who uses the cell
intermittantly in a camera-meter environment, while the hearing aid cell is one built for heavy
(continuous) use by the user, so if I were to guess which had the higher capacity (if they
were different)  ...

        As for use, *both* batteries work fine in the test camera -- and the light meter
on the test camera matches (when pointed at the same large 18% gray card) both my Pentax SF-1
camera's light meter and my Soligar 1-degree spotmeter.  At least at the two light levels
tested.  So from my testing, there's nothing wrong with the Wein cell other than its
price being four times that of cells available in Target, supermarkets, etc (which seem to be 
same battery minus creative camera-user labeling and minus the washer).

        My basic conclusion is a greater confidence in the hearing aid battery solution that
I had come up with a few months ago. When the Wein cell expires, I'll see if I can press-out
the battery from it's nice washer and see if I can press it onto a hearing aid battery 
(for washer neatness).  I don't think I'll be buying any more Wein cells.  Hope this info
helps someone -- would have saved me the Wein money had I known ahead of time....  

        Anybody else tested these things with different results to share?  Or is it only me?  :-)

        If it's only me, then .... "never mind!".  Back to your regularly scheduled email.

Mike K.
        


------------------------------

End of PHOTO-3D Digest 1084
***************************