625 mercury battery

[colyn]

I'm well aware of the (mostly false) information about how dangerous mercury batteries are.

I've been using silver oxide battery adapters, diodes, wein cells, etc but was wondering if there are still any viable sources for new 625 mercury batteries and if so where might I obtain a few??

I'm not even interested in the useless alkaline replacements.

 

[cosmonot]

Why not have your gear converted to take common silver 1.5 V batteries? By installing the proper diode (I have used 1N6263 to give the proper 1.35 V) inside your camera/meter/whatever you effectively have the adapter built in. And you can buy much cheaper batteries.

 

[colyn]

Why not have your gear converted to take common silver 1.5 V batteries?

Because it is converted to 1.5v alkaline not the actual 1.55v of the silver oxide battery which doesn't sound like much but does in fact affect accuracy..

By installing the proper diode (I have used 1N6263 to give the proper 1.35 V) inside your camera/meter/whatever you effectively have the adapter built in. And you can buy much cheaper batteries.

As stated in my post I use the various alternatives but it would be nice to get to use the battery these cameras/meters were made for. Some battery chambers require modifications such as my Gossen CDS Super Pilot in order to use the smaller battery while others lose the battery check because of the diode.

The 625s batteries available at some websites don't have the constant voltage needed to power these cameras/meters as they are supposed to be.

 

[Bob Michaels]

The source used to be www.px625.com but you could see their price go up and their supply dwindled. The website no longer exists which says something.

I only have two of them left. One is now in my Canonette QL 17, the other is my spare. When that spare is gone, I'll have to convert to a 1.5V battery

 

[colyn]

The source used to be www.px625.com

This is where I used to buy them.

I've seen a few Chinese 625 mercury batteries pop up on eBay but they usually start at $35+ which in my opinion is stupid since nobody bought..

 

[Tuolumne]

You could try the zinc-air hearing aid battery replacements. They last longer than people say, especially if you don't open all of the holes.

/T

 

[colyn]

You could try the zinc-air hearing aid battery replacements. They last longer than people say, especially if you don't open all of the holes.

/T

I've tried them with no success. They die within a few weeks to a month. I've had better luck with Wein cells which I can usually squeeze 2 months max of effective use out of..

 

[cosmonot]

Because it is converted to 1.5v alkaline not the actual 1.55v of the silver oxide battery which doesn't sound like much but does in fact affect accuracy..



As stated in my post I use the various alternatives but it would be nice to get to use the battery these cameras/meters were made for. Some battery chambers require modifications such as my Gossen CDS Super Pilot in order to use the smaller battery while others lose the battery check because of the diode.

The 625s batteries available at some websites don't have the constant voltage needed to power these cameras/meters as they are supposed to be.

I respectfully disagree. I believe using small signal schottky diodes to drop the voltage of a silver oxide battery is acceptable for my gear, even if it just allows the device to be calibrated to offset any difference between the battery+diode and a good old mercury cell. I also believe that any device designed to use mercury cells likely needs a good calibration after all these years anyway. The 357 cells in my cameras & meters seem to have a very flat discharge curve and are more than suitable for the task considering how easy they are to get, and how cheap they are in quantity.

That's just after throwing my EE degree at the problem, and consulting with a couple camera repair shops that do these conversions regularly, often including them in the price of a standard CLA. But I suppose paying the $$ for a single mercury cell of questionable quality makes sense, for some.

 

[colyn]

I respectfully disagree. I believe using small signal shottky diodes to drop the voltage of a silver oxide battery is acceptable for my gear, even if it just allows the device to be calibrated to offset any difference between the battery+diode and a good old mercury cell. I also believe that any device designed to use mercury cells likely needs a good calibration after all these years anyway. The 357 cells in my cameras & meters seem to have a very flat discharge curve and are more than suitable for the task considering how easy they are to get, and how cheap they are in quantity.

You misunderstood what I said.

Every repair person I've talked to including George at QLM will calibrate these meters to take 625 alkaline. I have mine serviced and calibrated to factory specs so I can use either Wein cells or add the shottky diode.

The 357 silver oxide cells have a nearly identical voltage curve as the original mercury batteries and are ideal replacements BUT.... some meters will need internal battery chamber modifications to take the smaller battery. Not because of the overall smaller size which can be shimmed with a "O" ring or other method but because of the smaller diameter negative end which is to small for some battery chamber negative contacts.

An example is my Gossen CDS Super Pilot meter. The negative contact prongs are too large in diameter and extend past the batteries negative cap and come into contact with the positive edge therefore I cannot use a Wein cell or my homemade adapter with diode in this meter unless I modify it..

 

[plummerl]

I'm not sure why you have such a hesitancy to using the Schottky diode approach. It certainly does lower a silver-oxide voltage to 1.35 volts. Have you seen the exhaustive document on this subject:

http://butkus.org/chinon/batt-adapt-us.pdf?

I have quite a few Olympus OM-1s that have been converted and they are as accurate as the OMs I have that do not use the former PX625. For my Gossen Luna Pro, I have the Gossen silver-oxide adapter and it works perfectly.

I'm not sure where you are getting the "(mostly false) information" spin, but it couldn't be farther from the truth.

 

[Fotohuis]

The above mentioned document is the best source on the internet and technically the best solution for the replacement of the mercury batteries.

All other options are less stable and very limited in lifetime.

Best regards,

Robert

 

[David Murphy]

The MRB625 Wein cell works just fine and it's short life problems are exaggerated -- recommended

 

[Murray Kelly]

You can allegedly recharge mercury cells provided they aren't absolutely discharged.
Do a Google on recherge mercury cells.

It might be the answer you want.

Murray
Brisbane, Oz

 

[cosmonot]

An example is my Gossen CDS Super Pilot meter. The negative contact prongs are too large in diameter and extend past the batteries negative cap and come into contact with the positive edge therefore I cannot use a Wein cell or my homemade adapter with diode in this meter unless I modify it..

Admittedly, I've never seen the inside of a Super Pilot, but I could think of several ways to solve the problem. If it was mine, I'd try to solder a small contact onto the center of one "prong" (or both if necessary) to get good contact with the negative side of the battery, and keep them farther away from the sides.

As far as spacers go, o-rings work. My OM-1 has a teflon spacer that I turned on my lathe to be a snug fit for the battery compartment, but a loose fit on the battery. I've also heard of people reusing the metal rings from wein cells on some of the silver oxide batteries.

 

[kuzano]

The MRB625 Wein cell works just fine and it's short life problems are exaggerated -- recommended

I agree with this, plus, although its a bit of a PITA, I have made them last much longer than most by taping the air holes shut during periods when the camera is not being used a lot.

 

[Peter_Jones]

My latest OM1 needs the germanium diode mod, just a case of having the time 🙂

 

[colyn]

I'm not sure why you have such a hesitancy to using the Schottky diode approach. It certainly does lower a silver-oxide voltage to 1.35 volts.

Actually I was and am still using the diode approach when most were saying "it doesn't work". But that was not my question. I asked if sources were still available for mercury batteries.

Varta still makes the 625 and 675 mercury cells but only for Military use. I was able to obtain a couple from a friend who is in the Military but they are for the most part hard to get..

 

[colyn]

The above mentioned document is the best source on the internet and technically the best solution for the replacement of the mercury batteries.

You can download it from my website too.

http://www.colyngoodson.com/manuals.html

 

[colyn]

Admittedly, I've never seen the inside of a Super Pilot, but I could think of several ways to solve the problem. If it was mine, I'd try to solder a small contact onto the center of one "prong" (or both if necessary) to get good contact with the negative side of the battery, and keep them farther away from the sides.

I'm afraid that fix won't work on this meter. The only way is to open the meter remove the original contact and fashion a new one and since the cap is plastic positive contact is made deep in the chamber around the largest diameter of the battery.

Wein cells do not work in this meter due to the small diameter of the negative cap of the battery.

In other words my only options are to use a 625 or do the extensive modification

 

[colyn]

The MRB625 Wein cell works just fine and it's short life problems are exaggerated -- recommended

I have a couple of unconverted Weston Ranger 9 meters which takes 2 cells each and both meters eat Wein cells within 1 1/2 - 2 months. My SRT's get 3-4 months. My Leica MR4 meter gets 3-4 months also.

These batteries cost $8-9 each including tax depending on where I buy which does not make them cost effective..

According to the maker covering the holes when not in use does nothing to prolong their life..