Mercury Battery Replacements

Might work...

Might work...

spyder2000 said:
Since the zinc cell is air activated, could one not cover the air holes when not in use and shut the battery down to save life? I haven't tried it, but has anyone else?
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...if you knew it would be out of service for awhile. I've also heard of folks covering all but one hole with clear nail polish.

I just make sure the camera's meter is off. I don't worry about the Gossen because it's always off until I take a reading.
 
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venchka said:
...if you knew it would be out of service for awhile. I've also heard of folks covering all but one whole with clear nail polish.

I just make sure the camera's meter is off. I don't worry about the Gossen because it's always off until I take a reading.
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Turning it off can't hurt, but it won't help the usual early-expiry problem with zinc air, which is that they actually dry out inside. That's what covering the holes when not in use (or plugging all but one) is meant to prevent.
 
I had a Wein in an M5 for a couple of years and it was still working when the camera went to Sherry K for CLA. Conversely, I tried regular hearing aid ZA cells in the Wein ring and they were NG, mostly because their voltage was in the 1.45-1.5 range and the meter simply didn't run right. The Wein cell had only two air holes, which may be why it ran longer...not sure why its running voltage was lower, unless that's also the holes, though I'd think that once it was activated it would run at whatever its spec'd voltage was.
 
I compared the Wein 1.35 V zinc air battery directly to a drug store 675 1.4V hearing aid battery, and saw absolutely no difference in meter readings on my Canonet QL-17 GIII or a Yashica-MAT 124G. Physically, they are different in two ways. The Wein cell has a ring around it to make it larger in diameter. In the Canonet, this ring is not needed, but it is needed in the 124G. The other difference was in the number or air holes. The Wein cell had two air holes and the hearing aid batteries have four.

From this testing, I found no reason to buy more than one Wein cell. When it dies, you can pull the ring off of it and place it over a 675 hearing aid battery and get the same meter readings. The difference in air holes might cause the hearing aid battery to run down faster, but considering that they cost about 1/7 or 1/8 of what a Wein cell costs, I think it's still a good deal.

I don't use the Canonet too often, but when I do, I just check that the meter is working and make sure I have an extra battery.

Paul


ps...I just read JNewell's post above, so I guess my findings don't carry over to every camera. But, I think the hearing aid batteries are so cheap, it's woth buying some to make your own comparison.
 
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Alkalines and zinc-airs

Alkalines and zinc-airs

Doug said:
Some cameras that use mercury batteries have a circuit that accomodates variations in battery voltage. Pentax Spotmatic is an example. These will run fine on modern silver cells that fit the battery compartment.

Also, some cameras can be modified by adding a diode in the meter circuit to deal with the voltage difference, then they work fine with silver batteries. This would be my choice wherever possible, I think. I use zinc-air batteries in my hearing aids, and they're a royal pain, very short life.
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If a camera can use variable voltage cells, then even alkaline cells can be used. There is a direct alkaline replacement for the PX625. It is called PX625U or LR-9. Works at least in all Praktica LTL series SLR's, which use that battery size. It is readily available in Europe as it is made by Varta, but I have heard that it is more difficult to find in the US.

Which brand of zinc-air batteries you use, Doug? The Rayovac 675 (PR44) zinc-airs I use in cameras regularly last at least 3 months after activation and the average life is around 6 months. I have one that was activated in the beginning of December 2006 and it still works!

The zinc-airs are used in hearing aids since no other cell can provide the capacity of a zinc-air cell. The 675 for example has capacity of 630 mAh, which is four times the capacity of a similar sized silver-oxide cell (MS76 a.k.a SR44). So I suspect that your hearing aid zinc-air batteries might actually become depleted simply because hearing aids are used continuosly for long periods and they draw much more power than for example watches, but the zinc-airs might last a lot longer in other devices.

That said, I also know that the life after activation of zinc-airs does depend on the air intake design. The Wein cells are just zinc-air batteries with a single small air intake hole. Wein cell marketing material also says something about a "propietary oxidizer", but I am almost certain it is marketing bs -- after all, my Rayovacs last almost as long as the Wein cells...
 
vladhed said:
Still, I guess the optimal solution is the Ag2O battery with a 1.25 volt Zener diode, since it will allow the battery to drop quite a bit in voltage before effecting exposure. Not sure what the discharge curve looks like but I suspect by the time a Ag2O battery gets to 1.25 volts it's dead dead dead.
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Yes. The voltage curve of silver-oxide cells is similar to mercury, zinc-air and lithium cells. The voltage is initially about 1.6 V, then it will drop rapidly to about 1.55 V and after that the voltage will drop slowly to about 1.5 V, after which it will drop rapidly to below 1.2 V. Nominal cutoff voltage is usually listed at 1.2 V, but the drop from 1.5 to 1.2 is very rapid.
 
JNewell said:
I had a Wein in an M5 for a couple of years and it was still working when the camera went to Sherry K for CLA. Conversely, I tried regular hearing aid ZA cells in the Wein ring and they were NG, mostly because their voltage was in the 1.45-1.5 range and the meter simply didn't run right. The Wein cell had only two air holes, which may be why it ran longer...not sure why its running voltage was lower, unless that's also the holes, though I'd think that once it was activated it would run at whatever its spec'd voltage was.
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I find it very strange that a zinc-air cell would produce a voltage above 1.45 V. I have measured the voltage of a couple of them and it was always between 1.4 and 1.45 volts half an hour after activation. The Wine cells are just zinc-airs with smaller air intakes, so they should produce the same voltage as the hearing aid batteries. Here is the spec sheet of a Duracell zinc-air and for most part of the discharge curve the voltage is actually less than 1.3 volts:

http://www.duracell.com/oem/Pdf/new/ZA675_Dur.pdf
 
I agree, but I had a whole pack of them that were all 1.45v or higher, and they gave the (expected) poor results in the M5. The Wein cells by comparison were all ~1.35v or a little over when checked.

Dr. Strangelove said:
I find it very strange that a zinc-air cell would produce a voltage above 1.45 V. I have measured the voltage of a couple of them and it was always between 1.4 and 1.45 volts half an hour after activation. The Wine cells are just zinc-airs with smaller air intakes, so they should produce the same voltage as the hearing aid batteries. Here is the spec sheet of a Duracell zinc-air and for most part of the discharge curve the voltage is actually less than 1.3 volts:

http://www.duracell.com/oem/Pdf/new/ZA675_Dur.pdf
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lena.87 said:
Does anyone know where I can get the best deal on an MR-9 adapter and cell, preferably in the UK?

Lena
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Maybe I caught them on a bad day, but the Criscam people were less than customer friendly, so I got all my adapters (MR-9, etc.) from the most helpful people at Kanto in Japan: http://www.kanto-cs.co.jp/english/index_english.html

I've used them and silver oxide batteries in all my cameras and have had zero problems.

Bill
 
There's a good article called "The mercury cell problem and its solutions", the PDF is linked at http://www.butkus.org/chinon/batt-adapt-us.pdf. It has comparisons of various batteries and their replacements, including discharge curves and circuit diagrams, as well as instructions for making various kinds of battery adapters. The author is aforementioned Frans de Gruijter, who is also selling some adapter DIY kits and readymade adapters.

vladhed said:
Still, I guess the optimal solution is the Ag2O battery with a 1.25 volt Zener diode, since it will allow the battery to drop quite a bit in voltage before effecting exposure. Not sure what the discharge curve looks like but I suspect by the time a Ag2O battery gets to 1.25 volts it's dead dead dead.
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And this is exactly the reason why using a Zener diode is a Bad Idea.

You are probably suggesting a circuit with the Zener diode parallel to the metering circuit (otherwise voltage stabilisation makes no sense) - the idea being that the Zener diode stabilises the voltage to 1.25 volts. That's indeed what it does, but it does so by burning away all the excess voltage. So your Zener diode will suck the battery empty and convert the excess voltage into heat, until the battery voltage has dropped to 1.25 V, at which point the battery is indeed dead dead dead for our purpose.

Philipp
 
lena.87 said:
Does anyone know where I can get the best deal on an MR-9 adapter and cell, preferably in the UK?

Lena
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John Neal, a member of this forum from the UK, used to make adapters for using silver cells to replace mercury cells. Not sure if he still does. HTH
 
Most of my older cameras (except my Spotmatic) require 1.35 volts. I use the zinc air hearing aid batteries. They are slightly smaller in diameter, to rectify this I use a thin piece of form cut to fit (around). I tried the 'O' rings and the adapters this seems to work the best. Just be sure you carry them with you.
 
I don't know who came up with this idea originally, but I've made these adapters for my own use for years. Anyone who bought a Canonet from me probably found one in there. For a conversion from hearing aid (675) to PX-13 battery, they work great, and since each cell is vented, they're infinitely stackable. You can read about them here: http://nelsonfoto.com/v/showthread.php?t=11131 (scroll down a bit past the last image to see the final one with the foam spacer installed).
Jon
 
rxmd said:
There's a good article called "The mercury cell problem and its solutions", the PDF is linked at http://www.butkus.org/chinon/batt-adapt-us.pdf. It has comparisons of various batteries and their replacements, including discharge curves and circuit diagrams, as well as instructions for making various kinds of battery adapters. The author is aforementioned Frans de Gruijter, who is also selling some adapter DIY kits and readymade adapters.


And this is exactly the reason why using a Zener diode is a Bad Idea.

You are probably suggesting a circuit with the Zener diode parallel to the metering circuit (otherwise voltage stabilisation makes no sense) - the idea being that the Zener diode stabilises the voltage to 1.25 volts. That's indeed what it does, but it does so by burning away all the excess voltage. So your Zener diode will suck the battery empty and convert the excess voltage into heat, until the battery voltage has dropped to 1.25 V, at which point the battery is indeed dead dead dead for our purpose.

Philipp
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The diode used is a Shockey diode, like in a crystal radio set, not a Zener, the diode is in series, and does not alter battery life, it drops the battery voltage.
Noel
 
Only for purposes of reference, I have a Rollei E-110 and the 5.6v mercury is replaceable with a newer siver 6v silver cell if one replaces the 'steering' diode which is germanium (not schottkey) with a silicon 1N914 signal doide or similar. It lives just outside the battery holder. The diode prevents damage with accidental placement of the battery round the wrong way.

The extra .4v voltage drop places the silver cell exactly in the range required for the E-110 metering to work perfectly.

It does require some skill in working with tiny parts but the new diode is smaller than the original and is working in the right current range when the shutter closes - an important point with diodes. The voltage drop of a sand state diode depends on the current at very low currents and apparently the electronics use enough to to get the required .4v drop for metering.

I am very happy with the E-110 now, and am getting great pleasure useing it.

Just an aside to the topic, but maybe useful to someone who has trouble with that camera and can't get mercury cells!

Murray
 
For what it's worth, I have an (older) Gossen N-100 hand-held meter that also originally used the 1.35 mercury batteries. Two, in fact. When I had to replace the batteries and the 1.35s were no longer available (thanks to another coup by the enviros), I e-mailed the Gossen company about it. The reply was that the Wein batteries were slightly higher voltage and might give a slightly higher reading (possibly leading to a bit of under-exposure). I used the meter for color slide film, so that could have been OK, since slide film likes slight under-exposure. But other than that matter, they said there was no reason not to use the Weins - in other words, no harm done to the meter.
 
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