Mercury Batteries

msbarnes

msbarnes

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So I understand that many of the FL rangefinders were designed for mercury batteries, so my question is, just how inaccurate are these meters? I understand that they won't be as accurate with modern-day alternatives, but are they consistent? e.g. will they consistently overxposed/underexposed by the same amount? If this is the case, then can be accounted for with the ISO/ASA dial.
 
Its a real nuisance! I have found that the (replacement) battery for my Praktica is at least a full stop out and yet a CdS exposure meter is almost spot-on! Whatever happened to extinction meters??
 
It depends on the meters and what battery you use as a replacement.

Zinc-Air "hearing aid" cells have identical characteristics, but run flat all on their own within months or even weeks - apart from their short life (and the lack of big, high capacity versions) these are perfect plug in replacements.

Silver Oxide have 0.2V higher voltage, but a fairly similar discharge pattern - with some meters that creates a negligible constant error below one stop, on others it will still be within the range that can be compensated on the sensitivity dial. But in some cases, the resultant offset goes past the (usually limited) range of sensitivities, and you will need to insert extra electronics (a drop diode) to make it work.

Alkalines have very different, non-linear discharge characteristics, so that measurements at various discharge stages need a different correction - making a circuit designed for mercury or silver cells work with alkalines usually requires significant rebuilding of the electronics.
 
I spent $36.95 on a CRIS MR-9 adapter (for my Canon 7S), and I'm happy about it. In fact, i bought six more of them, for my various older items that took the old Mercury batteries. I also just bought a dozen #389 batteries from China for $1.00 including shipping :) http://www.cris-store.com/servlet/the-5/MR9-MR-dsh-9-Mercury-Battery/Detail

I actually have a working Mercury battery in good shape, and have personally done my own tests (at differing exposure levels) and the output is identical with the MR-9. So good enough for my uses, and no camera modification or guesswork of any kind required.
 
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All of my mercury powered cameras/meters were anywhere from 1-2.5 stops off with the alkaline replacements.

The fix I used was to add a schottky diode inline with the circuit then use a silver oxide battery(s). Meter readings were then accurate. I've even converted my Weston Ranger 9 by using two schottky diodes.

To get an idea check out this site for the Minolta SRT. http://www.rokkorfiles.com/conversion.htm
 
For now I will use the few remaining mercury batteries I have left...when they are dead I'll probably go with the CRIS MR-9...
 
Another vote for the CRIS adapter. They're worth the price: mine has given at least 5 years of perfect service.

Regards,
D.
 
I've used Zinc-Air "hearing aid" cells and have been very pleased. That said, they don't last long - which is bothersome. The only reason I haven't bought a C.R.I.S MR-9 adapter is because they are $45 after shipping costs. That seems like a a lot for a single adapter? Of course, I know nothing about the complexity of these things and perhaps its really a bargain? I suspect I'll end up buying one eventually...
 
there are some on ebay u.k ,replacement for px625 but they need an adapter which I made a ring out of baco foil how accurate they are i do not know,they are cheaper than Weien cells,i think I have spelled that wrong
 
I have used 675 hearing aid batteries in an adapter sold by Jon Goodman (JGood21967@aol.com) - $14 for adapter and one 675 battery. It fits in most of my cameras that need this battery, but not in my Yashica Mat 124 or Zeiss Ikon Contaflex Super BC. This supplies the 1.35-1.4 volts. In 2009 I purchased a better adapter that fit in all my cameras from camera-care.com in Pennsylvania but the owner died and they are no longer in business.

If you remove the battery when not in use and cover the + side, 675 batteries last a decent amount of time, and they are inexpensive to begin with.
 
mwoenv said:
If you remove the battery when not in use and cover the + side, 675 batteries last a decent amount of time, and they are inexpensive to begin with.
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I don't bother with that any more. Even if I don't treat them any way special, they do seem to survive two or three months in all my cameras. And they are dirt cheap, to the tune of 1.50€ for six - compared to using one 5€ silver oxide battery every two years, hearing aid batteries still are cheaper. And that calculation does not even consider the adapter cost (where the plain ones are half to one quarter of the voltage reducing ones).
 
Don't buy from CRIS, they are very rude/unhelpful in my opinion. Get the same adapters from Kanto in Japan, the manufacturer.
 
Just adjust the film speed to compensate for the underexposure from using the 1.5V batteries. If shooting 400 speed, set the camera to 200, etc.
 
I've used 675 batteries in adapters that make them the same size as the original mercury battery. The 1.4 volts is very close to the original 1.35 volts of the mercury batteries and exposures are very good. If you remove the battery when not in use and cover the + side, the batteries last. However, they are very inexpensive to begin with.

I originally got an excellent adapter for $20 from camera-care.com in Pennsylvania but they are no longer in business. Jon Goodman (JGood21967@aol.com) sells one for $14 but I found it doesn't fit into one of my cameras (Zeiss Ikon Contaflex). I've just ordered two adapters for $12 + $2 shipping from a seller on ebay in Hong Kong ("manycases") that look well made.
 
You can stop or slow the chemical reaction....

You can stop or slow the chemical reaction....

I use both Wein Cells MBR625 from eBay and 675 hearing aid batteries local pharmacy.

The hearing aid type are very inexpensive... four to a card for $5, while the Wein MBR625 are two for $8.95 or larger quantity for less per item. eBay sellers... three or four of these sellers.

I typically on the Weins, take them out of the camera if not using it for extended periods and put the sticky seal back on the battery. This either reduces or stops the chemical reaction and I get good life out of them. I go to this trouble for two things, Near Correct voltage at 1.4 volts and flat discharge curve.

I use them in Olympus OM-1, Canon GIII and other mercury battery models. No fudging with the ISO/ASA needed.

I use a loop of wire around the 675 button batteries as a spacer to hold them in the same position as the original PX625 mercury would have been.
 
mwoenv said:
I've used 675 batteries in adapters that make them the same size as the original mercury battery. The 1.4 volts is very close to the original 1.35 volts of the mercury batteries and exposures are very good.
Click to expand...

No wonder. The core electrochemical reaction - and hence the voltage - in mercury and zinc air batteries is exactly the same. 1.35 vs 1.4 is a matter of labelling, not what is going on inside.
 
I am using 1.4v hearing aid batteries to all my cameras with cheap less-than-1-dollar adapters and noticed no differences to the exposure.
 
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