Mercury battery...comprehensive solutions! Sorta...

Discussion in 'Classic Manual Cameras' started by celerystalksme, Sep 17, 2004.

    Mostly has to do with the mercury PX625 cells...
    Do you have an old/classic camera whose meter was made for a mercury cell? Do your exposures never come out right because you're using alkalines or whatever?
    Well...I have found the most comprehensive resource about how to overcome the mercury cell problem! Check it out! I'll summarize and list the options here for those that don't want to read that pdf file:
    1) Find some old mercury PX625! RARE...but can be found every once in a blue moon. Check eBay...apparently there some for auction a few months ago. Otherwise, keep an eye on the following sites:
    http://www main.cgi
    The chances they'll find some more stock is slim...but possible.
    2) Find some old mercury PX675 cells! Apparently, they fit MOST PX625 compartments. Otherwise, people use little rubber plumbing grommets to make sure they fit snug! 675's ARE in stock here: main.cgi
    A rubber grommet may not work in all cases. If you're not creative/resourceful enough to figure out how to make them fit, this guy will sell you a metal adapter: /Nikon_F_meter_batteries.htm
    3) Zinc-air cells. These are not a terrible option. Voltage is the same as mercury...and the flat constant output characteristic is the same. The only real downside is they're not very cheap...and once you pull the battery tab, they typically don't last very long. And since they need oxygen to function, it won't work in a air-tight battery compartment. Once the tab is pulled and the battery takes in oxygen, the cell usually lasts 6 months or less...but it depends on humidity and temperature and sometimes it can last upto 18 months. It is recommended that you take the batter out and put the seal back on the battery when not in use. There's a zinc-air cell called a "Wein Cell"'s supposed to last longer than normal zinc-air cells because it has fewer holes for air...but people haven't noticed a big difference.
    4) Alkaline. Usually not a good option. Voltage starts too high...and the sloping discharge curve shows it ends up to low. There's a very very very narrow window when your exposure meter will expose correctly. Deviatations due to an alkalines non-constant voltage can be upto 4 light values in either direction. can work some SOME older cameras.
    5) Silver-oxide 625 replacement. This can potentially work. They have a constant discharge voltage, just like mercuries. But they're voltage is way too high. So your exposures will be off. Fortunately, since it has constant voltage, the exposure will be off by the same amount all the time. So you can adjust for that yourself on the camera. Just set the film speed off by 1-4 stops, whatever makes it right. The battery life is not as good as a mercury cell...but not as bad as a zinc-air cell. They're not as expensive as either one.
    6) Use a silver-oxide 675 hearing aid battery! These can sometimes fit without any type of adapter. Might need a rubber grommet, just like the mercury 675's. Silver oxide 675's have the same voltage as the mercury 625/675...and they discharge flat with constant voltage. So these work really well. Plus, they're real cheap. And if you can use that metal adapter made by Paul: /Nikon_F_meter_batteries.htm
    7) You can get your camera permanently fixed by a camera repair guy. This is probably the best long term solution. But you gotta find the right guy for your particular type of camera. And the initial cost can be high...could be around $100.
    8) Use the silver-oxide 625 replacement with an adapter that corrects for voltage. Silver-oxide has the same flat discharge curve as mercury...but the 625 replacement voltage is too high. So...the MR-9 seems to be the most popular adapter to reduce voltage. They work OK. Except most of these adapters are a teeny bit large so you may not be able to close you batter compartment door all the way. Also, the MR-9 only allows for a maximum drawn current of 200 microamperes...which is fine for super low draw camera's like the Rollei 35's. But most cameras draw more than that.
    To get an adapter that allows for more current draw than a can either build one yourself as outlined in the PDF file I linked above. can buy a ready-made one from the guy that wrote the document (Frans de Gruijter). He also sells a small kit so you can make it yourself. An adapter from Frans de Gruijter, with a BAT83 Schottky diode, is the best option for most applications.
    You can find the MR9 here:</ a>
  2. If anyone knows anything more...or if I've posted something wrong, let everyone know!!!
  3. 9) Build a battery adapter with appropriate diode it it. Or solder a diode inline with the wire from the battery compartment. See,

    10) Recharge your existing Hg cells. There are purpose built chargers for Hg button cells. Besides you haven't been throwing out these highly toxic batteries, or have you?
  4. I think I mentioned least the build your own part. And the very first link in my post is Frans de Gruijter's PDF document.

    But...I did NOT know you could recharge mercury cells! That's news! I have not been throwing them out...cuz I've never used a mercury cell...yet!
  5. I have been using #675 zinc/air cells (hearing aid batteries) in Canonets, Oly 35RCs EDs and ECs. They are less than $1 each which I think is pretty cheap compared to the cost of film and processing.I don't know what their life span is expressed in rolls of film or months but at least 2 or 3 rolls of film in a 2 month period. I don't have any experience much below freezing. They are stocked in most drug stores and are no danger to you or the environment. In the above applications o-rings, plastic sleeves, and a little aluminum foil will fit them properly.
  6. To my chagrin, just found another thing about zinc-airs: unmasked, as they charge up they may expel oxidation by-products through those breather holes. If you use zinc-airs, let them charge up out of camera.
  7. 11) Disregard all the above and buy a decent lightmeter.
  8. Gary,

    Yeah, that works too...sometimes. But sometimes it's not convenient to always carry a light meter in addition to the camera. And sometimes I need to shoot fast...just focus, shoot...focus, shoot...focus shoot. I don't want to have the point the light meter, get the values, adjust the aperature, adjust the shutter speed, focus, and shoot. For some situations, that takes way too shot is gone.
  9. Mercury batteries are no more toxic than lots of other forms of mercury, chemical companies pour mercury into our rivers and oceans every day, thats why you are advised to ration your input of fish. There is mercury in your tooth fillings and people are buried with them every day. Mercury is used in thermometers and many many other products. I would not be worried about disposing of your mercury batteries.
  10. Um, Gary, I have three decent lightmeters, two of them fairly freshly overhauled (both last spring/summer) and working. Weston Master V, Gossen LunaPro. The Master has a selenium cell, doesn't need external power.

    Relevance to this thread? The LunaPro (also known as LunaSix III) uses mercury batteries. Bogen, Gossen's US distributor, sells a little cylinder, presumably with diode, that holds 2 SR44 cells and fits the LunaPro (and all LunaSix) battery compartment. Works like a charm. Also fits my Canon 814LS' (814AZ adapted to diabolical B&H double system sound) battery compartment and works well there too. Around $20 at retail. Can't imagine why the C.R.I.S. single cell adapter costs $30.

    I use the Master mostly as a sanity check on the LunaPro, and I use the LunaPro quite a bit with the narrow angle attachment. Not sure why, they're both good meters and neither has bad ergonomics.

    My dud is a LunaSix II. Functions, smells of cooked electronics, is very inaccurate, clearly needs service. Haven't been able to justify the expense because the III works well AND accepts attachments.


  11. "Mercury batteries are no more toxic than lots of other forms of mercury, chemical companies pour mercury into our rivers and oceans every day, thats why you are advised to ration your input of fish."

    Actually THE biggest single source of mercury is from coal fired electricity plants and those plants continue to pour out mercury and lots of other pollutants world-wide. My guess is that mercury batteries were banned because they were a convenient target with no organized defenders. The elimination of button mercury batteries maee it look like government officials had had accomplished something.
  12. Hi Dann,
    "Bogen, Gossen's US distributor, sells a little cylinder, presumably with diode, that holds 2 SR44 cells and fits the LunaPro (and all Also fits myLunaSix) battery compartment. Works like a charm."
    Have you ever tried this in one of the old Nikon F FTN or FT Photomic heads? Just a thought.
  13. FWIW, there were two chemistries used in mercury batteries. One, designed for light meters, voltage references, and other measurement applications, produced exactly 1.35 VDC. You could pick any one off the shelf and calibrate with it, knowing the result would be withihn a few millivolts of the nominal value. The discharge curve was almost perfectly flat. They can last a decade or more with almost no degradation. I haven't seen these for sale or NOS for ages. The other chemistry is similar, but produced a slightly higher voltage (1.4ish I think). It was designed for power applications, and though it worked ok for light meters, it wasn't as perfect as the correct chemistry. The last available foreign cells I've seen used this chemistry. Most of this is from memory, but if anyone is interested I can get the exact info from my battery books. I've recalibrated a couple meters for akalines, and the voltage drop problem isn't as serious as some claim, *if you do a battery check periodically*. The diode trick works, but the current draw of the meter and the diode type are important. This is best worked out for a particular meter by someone willing to check it over a wide range. The zinc-air cells work rather well, and I use that in some meters, but they don't really match the mercury battery voltage as closely as claimed. Be sure to check the readings and find your own personal film speed. You should do that anyway, regardless of what you're using. I'd have to agree that the environmental problem caused by mercury batteries pales in comparison to other sources of mercury- power plants and fluorescent light tubes, for example, not to mention the problems caused by NiCads, but we're stuck with the ban and just have to use the alternatives.
  14. Steve, I haven't tried the Bogen adapter in a Nikon F metered prism. I've never owned an F.

    Back when I bought my Nikkormat FTn and got all invested in Nikon gear, I was in the Army and the $50 difference in price between Nikkormat FTn and Nikon FTn bodies (this was at the RCAF IV Wing's base exchange's or whatever the Canadians call 'em spring 1970 photofair. The deals were wonderful.) meant a lot. Also, after hefting a Nikon FTn with a 50/1.4, I decided it felt worse in the hands -- too front heavy -- than the Nikkormat. Since then I've stuck with Nikkormats and their spiritual heirs. Ought to get an F3, can't bring myself to do it.

    For my money, the Nikkormat FTn was one of the best cameras ever made. Making the shutter speed control concentric with the lens mount was a stroke of genius; it makes the Nik'mat is a much faster-working camera than otherwise equivalent cameras with shutter speed dial in the conventional place on the top cover. I regret that my newer Nik'mat equivalents -- FM2n, FG -- and my wife's ELW have the conventional layout.


  15. I have an FTn and I was shelling out for Wein Cells and wondering why they were
    dying so soon, and I suspected a short circuit somewhere inside the camera... In fact,
    I was just about to crack it open in a desparate attempt to fix it. I tended to rely on
    the sunny 16 rule (exposure=f16@ 1/film speed ) which works fine as long as there
    aren't any clouds in the sky, and indoors/on cloudy days I just used an external
    meter. What got me thinking after reading this is, couldn't one simply use the 1.5v
    'replacement' battery, and just determine how many f stops off of the actual exposure
    it is? Would it always be a constant number of stops off?
  16. No, from what I've read, the error is not linear with the increased voltage, so tricks like changing the zero adjustment and moving to a different iso to compensate for the different readings do not work.

    I've just purchased a Lunasix 3 myself, and with a few small washers, I actually made the raw ZA 675 batteries function in it (with a *lot* of playing around) . I'm off to buy some grommets or rubber o-rings tomorrow, but it's nice to know that the meter works properly. Note that I measured 1.4 volts off the batteries (not under load) but the battery indicator goes right to the middle of the rod zone.

    Note also that with the 7.5 degree attachment, I was able to obtain a very decent almost spot meter (7.5 is much closer to a spot than 30 degrees) without having to take out a second mortgage. This is the reason that these meters, even with their battery troubles, are still worth tracking down.
  17. Andrew, there's a better solution than those infernal zinc-air cells.

    If you're in the US, send your meter to Bogen for the overhaul it almost certainly needs. That it functions doesn't mean that its right; non-linearity is a problem. Bogen will return it working to specifications and with an adapter for a pair of SR-44 cells.

    Been there, done that, recommend it highly,


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