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Thread: Zinc-Air cells.

  1. #1

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    Zinc-Air cells.

    I just put new Z-A cells in my LunaSix and checked it against the two other meters I use regularly, a Weston Master III and a Nikkormat FTN.

    Pointed at the skylight, solid bright white featureless overcast -
    Gossen f:16 @ 1/200
    Weston f:16 @ 1/200
    N-mat f:16 @ 1/60 (*)

    Pointed at a white wall, same room -
    Gossen f:4 @ 1/30
    Weston f:4 @ 1/40
    N-mat f:3.5 @ 1/30 (*)

    * the Z-A cell in the Nikkormat has been there for 37 months. I'll get my Fluke out and measure the OC voltage later on today; I think the internal resistance has risen to the point where it is no longer useful, it used to agree with the Gossen +- 1/3 stop across the range. This is the longest one has ever lasted.

    The cells in the Gossen are fitted into "Cs" made of bare #12 AWG wire. 3 of the four airholes are blocked off by using gold nailpolish (just in case it's conductive) to glue three 1/16"~ squares of Al foil over the airholes of each cell. The needle goes to the far end of the red block on test, I replace the cells when it falls to the near end of the red block. They last 2+ years.

  2. #2

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    Man that Nikkormat is way off. I hope it's just the batteries and not a bad meter cell. I think if the cells in either of my Nikkormats went bad, it would be like a death in the family.

  3. #3
    AgX
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    But the open circuit metering won't tell you the effect of risen resistance/voltage drop under load.

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    Quote Originally Posted by Tom1956 View Post
    Man that Nikkormat is way off. I hope it's just the batteries and not a bad meter cell. I think if the cells in either of my Nikkormats went bad, it would be like a death in the family.
    It's behaving precisely as I would expect it to, with a moribund cell in it - the more current demanded from the cell, the greater the error.

  5. #5

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    Quote Originally Posted by AgX View Post
    But the open circuit metering won't tell you the effect of risen resistance/voltage drop under load.
    Correct. But it might give others some useful information, maybe. Not everyone has an assortment of resistors around, but multimeters aren't that uncommon.
    I'll see if I can find some resistors to put it under a known load.

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    Why would you even think of using a zinc-air cell after 37 months?
    [FONT="Microsoft Sans Serif"][/FONT]Chuck B

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    Quote Originally Posted by CJBo001 View Post
    Why would you even think of using a zinc-air cell after 37 months?
    Because I put it in the camera that long ago. Until a few weeks ago it was working accurately, then I began to notice that it was disagreeing with the meter in my head.
    Cells and batteries are typically used until they cease performing properly.

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    I turned the meter in the Nikkormat on and left it pointed at the skylight for about 5 minutes. Then I removed the cell and put the meter on it, it was climbing past 1.2v and after about half an hour was at 1.370v. The new cells are 1.431v.

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    Quote Originally Posted by Tom1956 View Post
    Man that Nikkormat is way off. I hope it's just the batteries and not a bad meter cell. I think if the cells in either of my Nikkormats went bad, it would be like a death in the family.
    It's back to normal, with a new 675 in it.

  10. #10
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    Quote Originally Posted by E. von Hoegh View Post
    3 of the four airholes are blocked off .
    I use a lot of zinc cells but have never done this. Does that make them last longer?

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