Replacing old 625 batteries

[Leicakillen]

I think it is difficult to find the old Mallory PX625 1,35 V batteries nowadays. However there is a new Varta V625U available. The size is the same as the old Mallory but I think that the voltage of the newer one is 1,5V - not 1,35V. I have tried the Vartas on my M5, CL and Leicameter. Seems to me that I get about half stop smaller aperture compared to my M9. Can anyone recommend a better battery solution for my old Leicas?

Thanks,
/Anders

[roydonian]

Originally Posted by Leicakillen

I think it is difficult to find the old Mallory PX625 1,35 V batteries nowadays. However there is a new Varta V625U available. The size is the same as the old Mallory but I think that the voltage of the newer one is 1,5V - not 1,35V. I have tried the Vartas on my M5, CL and Leicameter. Seems to me that I get about half stop smaller aperture compared to my M9. Can anyone recommend a better battery solution for my old Leicas?

Thanks,
/Anders

I found the MR-9 adaptor to be a good solution. I used it in my M5 and SL2.

MR-9 Adapter. Replacement for PX625, PX13 or MR9 discontinued Mercury cells.

Best regards,

Doug

[dkpeterborough]

Have a look here .... tells you all about mercury cells and modern compatibles Small Battery Company - Watch, photo, hearing aid and other small batteries for sale on-line.

Cheers

dunk

[Artorius]

I also am using the MR-9 adapter in my MR-4 meter.

[gvaliquette]

I also have been using the MR-9 in my MR meter, in my CL and in my R6.2. They work flawlessly.

Guy

[budrichard]

Hearing aid battery and a #9 faucet rubber o-ring do the job. Batteries are less than $1 from Walgreens if you purchase a pack.-Dick

[Crex-Client]

Varta V80H NiMh accu is in PX625 form. Rechargeable, works in a Contarex Super electronic of mine.

Uwe

[giordano]

I've been reading up on this and it seems to depend very much on the model of camera how well the various substitutes work. For instance:

Some cameras use a (Wheatstone?) "bridge" circuit and the metering doesn't depend on the battery putting out an exact voltage. Cameras where metering means centering a needle on a short + | - scale (or the LED equivalent), are likely to fall into this category and should work fine with alkaline, silver, zinc-air or NiMH substitutes. Uwe, is the Contarex Super meter like this?

Other meters were designed with the constant 1.35V of a mercury cell as a fundamental assumption. In this case using any other type of cell can cause problems. But different problems with different cameras because of the way the meter is affected by the characteristics of the cell.

• Zinc-air: usually seems to work well but on some cameras, in some lighting conditions, the difference between the 1.35V assumed and the c. 1.4V delivered can put the exposure off by as much as a stop.
• Silver cell, and recalibrate the meter: the recalibration may have to be a compromise.
• Silver cell with voltage-reducing adapter: the adapters don't contain actual voltage regulators but just a resistor that will reduce the voltage to approximately 1.35V when the current drawn is that of a typical meter circuit. So they'll work perfectly with some cameras in most or all lighting, but not very well with cameras that draw more or less current than the designer expected, or whose current draw changes significantly with the light level.
• NiMH rechargeable: 1.2V: may not even be possible to calibrate the meter for this voltage, and if you do it will be way off if you run out of charged--up batteries.

So it seems to be a case of suck it and see.

[gvaliquette]

Originally Posted by giordano

• Silver cell with voltage-reducing adapter: the adapters don't contain actual voltage regulators but just a resistor that will reduce the voltage to approximately 1.35V when the current drawn is that of a typical meter circuit. So they'll work perfectly with some cameras in most or all lighting, but not very well with cameras that draw more or less current than the designer expected, or whose current draw changes significantly with the light level.

Giordano:

The MR-9 adapter uses a Zener diode to reduce the voltage, if I am not mistaken. The electronics actually require a minimal current drain to function properly. See here:
MR-9 Adapter. Replacement for PX625, PX13 or MR9 discontinued Mercury cells.

Guy

[giordano]

Originally Posted by gvaliquette

Giordano:

The MR-9 adapter uses a Zener diode to reduce the voltage, if I am not mistaken. The electronics actually require a minimal current drain to function properly. See here:
MR-9 Adapter. Replacement for PX625, PX13 or MR9 discontinued Mercury cells.

Surely it can't be the ultra-basic voltage reference circuit

(thank you Wikipedia) or the battery would discharge itself (down to 1.35v) in the adapter regardless of whether it was installed in a camera? And there doesn't seem to be either the space or the spare voltage for a more complex circuit.

Likewise I'd expect to measure 1.35V across the output with a DVM; having to put a resistor across the terminals to ensure a significant current draw in order to get the right voltage suggests to me that there might be nothing but a series resistor.

(Also, one of the sources I found said straight out that the "CRIS" adapters just used a series resistor to drop the voltage. But it's possible that the Small Battery Company does it differently.)

But I don't know much about electronics and look forward to a better explanation.

[Crex-Client]

Giordano,
the Contarex Super electronic meter is more the "adult" version, not the simple +/- thing. The reason why I try this solution is a kind of philosophically one. I do restoration on complex cameras with the aim to preserve valent technical goods.
On the other hand I hate this buying/throwing away thing. The solution with rechargeable technology fits my point of view.

The problem with this project was to find a suitable charging solution. Those accus are part of consumer products like wireless headphones and are charged in this products. After searching a lot I found a solution that I am testing right now. A crazy accu charger built in the German democratic Republic in the 80s to charge accus for something like a hearing aid (I hope this is the right word). Measuring the accus gives 1.27 Volt. I am not good in electronics at all, my world is a mechanical one. We will try the accus in the next months on some Rollei 35s and other cameras to see if the thing works.

Uwe

[Ron (Netherlands)]

Please note that hearaid batteries will be empty after about one or two months.
Alkaline batteries are also not fit, because during their lifetime they don't provide a stable current.
zinc-air batteries are ok and provide the correct voltage of 1,35 almost during total lifetime, but will only last for about one year (the socalled Weincell batteries).

[masjah]

Originally Posted by giordano

Surely it can't be the ultra-basic voltage reference circuit

(thank you Wikipedia) or the battery would discharge itself (down to 1.35v) in the adapter regardless of whether it was installed in a camera? And there doesn't seem to be either the space or the spare voltage for a more complex circuit.

Likewise I'd expect to measure 1.35V across the output with a DVM; having to put a resistor across the terminals to ensure a significant current draw in order to get the right voltage suggests to me that there might be nothing but a series resistor.

(Also, one of the sources I found said straight out that the "CRIS" adapters just used a series resistor to drop the voltage. But it's possible that the Small Battery Company does it differently.)

But I don't know much about electronics and look forward to a better explanation.

I wonder if it uses a zener (or other voltage reference diode of that ilk) at all. I wonder if it's just got a forward biased diode in series with the cell, so that you simply lose the forward voltage drop across the diode junction? What's the diode withe smallest forward voltage drop? Anybody know if there's one at about a.15V? Just a thought.

[giordano]

Originally Posted by masjah

I wonder if it uses a zener (or other voltage reference diode of that ilk) at all. I wonder if it's just got a forward biased diode in series with the cell, so that you simply lose the forward voltage drop across the diode junction? What's the diode withe smallest forward voltage drop? Anybody know if there's one at about a.15V? Just a thought.

I'd thought of this and dismissed it, assuming that there wouldn't be a diode with forward voltage drop less than about 0.5V. Turns out I'm wrong and that Schottky diodes can be made with 0.15V drop, though I can't find one in the Maplin catalog.

[masjah]

Originally Posted by giordano

I'd thought of this and dismissed it, assuming that there wouldn't be a diode with forward voltage drop less than about 0.5V. Turns out I'm wrong and that Schottky diodes can be made with 0.15V drop, though I can't find one in the Maplin catalog.

Now that does ring a vague bell! Ages ago I remember seeing a web page showing how to construct your own adapter. I don't remember whether it was from some supplied components, or whether you were supposed to scavenge an od cell. But I rather think it might have employed a Schottky diode.

[doubice]

Originally Posted by masjah

Now that does ring a vague bell! Ages ago I remember seeing a web page showing how to construct your own adapter. I don't remember whether it was from some supplied components, or whether you were supposed to scavenge an od cell. But I rather think it might have employed a Schottky diode.

A Schottky diode it is indeed. I found a pdf file with the instructions as to how to make the adapter, deeply burried inside my PC........ Anybody interested - send me a PM with your email address and I'll be happy to email it to you.

Best,

Jan

[masjah]

Originally Posted by doubice

A Schottky diode it is indeed. I found a pdf file with the instructions as to how to make the adapter, deeply burried inside my PC........ Anybody interested - send me a PM with your email address and I'll be happy to email it to you.

Best,

Jan

Jan, is this the article:

http://www.buhla.de/Foto/batt-adapt-US.pdf

[doubice]

Originally Posted by masjah

Jan, is this the article:

http://www.buhla.de/Foto/batt-adapt-US.pdf

Yes, it is. Whenever I find an interesting tidbit of information, I file somewhere in the depths of my PC and never look at it again until an oportunity arises.

It seems that the time has come....

Best,

Jan

[NZDavid]

Try: Wein Cell MRB625 replacement for PX625, MR-9, S625PX

[bobs]

Originally Posted by Leicakillen

I think it is difficult to find the old Mallory PX625 1,35 V batteries nowadays. However there is a new Varta V625U available. The size is the same as the old Mallory but I think that the voltage of the newer one is 1,5V - not 1,35V. I have tried the Vartas on my M5, CL and Leicameter. Seems to me that I get about half stop smaller aperture compared to my M9. Can anyone recommend a better battery solution for my old Leicas?

Thanks,
/Anders

Use the Wein CEll MRB 625 as it has the correct voltage (1.35v) I use them in my SL and it is great and gives correct readings. Don't fiddle around with resistors or incorrect voltages, you need a linear response at a constant voltage for the Wheatstone bridge. Contact Micro-Tools, Camera & Watch Repair Tools - Home for supplies. They are about Aus$12.00 Australian

Regards

Bob Showers