Pentax Spotmatic SPII battery query

Discussion in 'Pentax' started by Eric V, Aug 6, 2003.

  1. Eric V

    Eric V Guest

    I have read varying responses on the web to the question of a
    replacement battery for the Pentax Spotmatic SPII light meter.
    Recently got one of these cameras, sans battery, and tried a Energizer
    Silver Oxide #392 per some suggestions. Although it's not an exact
    fit, it is the right width, and fit fine. I compared it to another
    camera's meter readings, and it seems right on, although I didn't
    shoot film yet to see about the exposure. The voltage of the 392 is
    1.55, which is higher than the original mercury 1.3, but I have read
    some entries saying the Spotmatic has a "bridge circuit" with the
    light meter, which corrects for voltage discrepancies, etc. Any
    thoughts on this? I could get a Wein Cell, but I have heard that they
    have a very limited life, and are more expensive and less available
    than Energizer Silver Oxide Watch/Electronic batteries. Thanks!
    Eric V, Aug 6, 2003
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  2. Eric V

    Jeremy Guest

    x-no-archive: yes

    I've used the alkaline replacement batteries in my Spotmatics for years, and
    have had no problem. If voltage concerns you, try the h-b adapter. Check
    the following link:

    I'll probably get around to getting a few (I have 3 Spotmatic bodies--so it
    can get a bit costly) but for now everything works fine. Just be sure to
    replace the batteries at least annually--don't wait for them to become
    exhausted--because these replacement batteries don't have the same flat
    voltage output as did mercury batteries. They tend to drop voltage as they
    age, as opposed to mercury batteries, which put out their rated voltage
    until they just went dead.
    Jeremy, Aug 6, 2003
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  3. Yes. That's it. You should stick with the silver oxide batteries
    as they last longer and die more gracefuly than the alkeline.

    Geoffrey S. Mendelson, Aug 6, 2003
  4. Eric V

    Avogadro Guest

    ....which matters naught, because the meter is not voltage-sensitive.
    Should be worth it for only a quarter of a cent, but I have had good
    luck using a silver oxide battery without any such appurtenance. That
    battery, BTW, happened to be the wrong polarity. So I just turned it
    over, easy to do because it was much smaller than the intended

    As the battery weakens, you will notice that the needle moves more
    slowly to its position. It still seeks the correct position, because
    of the bridge circuit. However, with an almost exhausted battery, the
    sluggishness of the needle can make metering difficult. A mercury
    battery keeps its performance right to the end. Other batteries will
    show gradual degraded performance once they get to the end of their

    Avogadro, Aug 6, 2003
  5. Eric V

    Colyn Guest

    The meter is not sensitive to minute variations in voltage but it is
    as the voltage starts to drop..
    The difference between the silver and the alkaline batteries is the
    silver holds its voltage till the end. The alkaline starts to decline
    as soon as you start using the meter.. So the spotmatic meter will
    perform per specs without the above sluggisness you mention..
    If you take a look at the below url, you'll find the silver oxide
    battery performance is nearly identical to mercury batteries..

    Colyn Goodson

    Ft. Worth, Texas

    625 and 675 mercury battery fix

    Camera manuals

    For Sale
    Colyn, Aug 7, 2003
  6. Eric V

    Avogadro Guest

    The Spotmatic meter will continue to operate accurately as the voltage
    drops. It will do that through long persistent voltage declines. But
    after a long time, when the voltage becomes too low, its response will
    become slower to the point of inconvenience. This is noticeable... so
    just replace the battery when this becomes a nuisance.
    Okay, but the alkaline starts at a voltage of 1.5. It has quite a bit
    of room to discharge before it gets to the Spotmatic design voltage of
    1.35 -- and the meter will continue to work below that voltage too,
    but after a long time, the response becomes so slow as to pose an

    Agreed though that silver oxide is a better choice.
    Yes, very good URL.
    I guess my point is that with the Spotmatic, it's not that important
    what battery you use. Sure, there are performance differences, but
    they will all give good readings. So shop on price or use what you
    have at hand.

    I'm still using mercury batteries in my Spotmatics, and the last time
    I replaced them must be... I don't know, 2 years ago at least. So
    replacing batteries is not much of an issue, IMHO.

    If you do find you go through them fairly fast, buy hearing aid
    batteries. They are cheap. Buy 'em a half dozen at a time, and replace
    as they die.

    Avogadro, Aug 7, 2003
  7. Eric V

    Jeremy Guest

    x-no-archive: yes

    I am using alkaline replacements (387S--available by special order at Radio
    Shack--mine took 4 days to arrive) and have had no problem whatsoever. I
    just replace them every year. I never had my meter recalibrated--all the
    meters in my 5 Spotmatic/ES bodies still work as they always did.

    The loss of the mercury battery's availability was not really much of an
    issue for me. I never paid attention to how long it took the needle to
    move--it is slower using the alkaline, I never noticed it.
    Jeremy, Aug 7, 2003
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