Modifying a PX625 Battery to Take a Standard AG13/SR44 Cell

[John Seaman]

The other day I acquired a nice Gossen Lunasix 3 exposure meter, which runs off two obsolete Mercury batteries. I started to think about replacements, which led me to retry an idea I had some years ago - to gouge out the innards of a currently available 1.5V PX625, which has the same flange as the Mercury battery, and use the shell to carry a standard 1.5V cell. I found it was possible to slice off the top with a junior hacksaw, when it was revealed that these are just cases with a standard flangeless cell inside. It wasn't too difficult to prise this out leaving an empty shell, into which can be fitted a standard SR44, AG13 or whatever else they are called. Or a Zinc Air hearing aid cell, if you need the lower voltage.

 

 

In the event I found two still working Mercury cells for the Lunasix which is performing well. Of course it's possible to buy commercially made adaptors online.

A warning though - I did the same thing with an actual Mercury cell when I tried it previously, they are MUCH harder to open up, and do indeed contain harmful Mercury ...

Edited October 6, 2020 by John Seaman

[rodeo_joe1]

....when it was revealed that these are just cases with a standard flangeless cell inside.

LOL!

 

My Lunarsix 3 showed a variable error when fed with 1.5 volt cells. Not far off in the middle of the scale but increasingly less accurate at the high end.

 

I took it apart and managed to re-calibrate it, but it wasn't easy. The circuit isn't very logically designed and there's a lot of interaction between the adjustment potentiometers. Anyone venturing down that path should prepare for some hair-tearing along the way! :eek:

Edited October 6, 2020 by rodeo_joe|1

[Sandy Vongries]

Even here on occasion.

[m42dave]

This article below has instructions on how to make your own adapter (the author also sells kits and ready-made adapters). Donations to the Butkus site suggested too, of course.

 

https://www.butkus.org/chinon/batt-adapt-us.pdf

 

New old stock Russian RC-53 batteries (same size and voltage as the original PX625) also occasionally come up for sale online.

[steve_gallimore1]

My Konica Autoreflex TC runs happily on a pair of zinc-air hearing aid cells. I'm not using any adaptor, I'd always intended to find the correct sized o-ring, but never got around to it, so they're just balanced in there with the lid holding them in place. I used this camera during the 2005 G8 protests in Edinburgh. The camera took a good few hits, but survived (lens hood didn't), the batteries never shifted. Used it a few weeks ago (with new batteries, still just balanced in there), still works fine.

[John Seaman]

The article makes me wonder if the author did a PhD. thesis on Mercury battery alternatives! Actually I tried drilling to expose the internals, and couldn't control it well enough without a drill stand. I found it quite easy to partly slice of the top with a small hacksaw, then peel it off completely with pliers.

 

Yes, you can often get away with a flangeless battery, depending on the holder. Some devices have plastic battery holders with contact to the edge of the flange. though.

 

My own approach, if it needs a Mercury battery:

 

1) Don't bother with it in the first place.

 

2) Fit a hearing aid battery (if it's not too loose).

 

3) Fit a 1.5V PX625 cell, and see what happens. Some cameras have compensation circuits and might give correct readings (as long as nothing else is adrift). Some can be corrected by setting the ISO faster or slower (e.g Nikkormats) - at least at certain light levels - given that the meters drift over time anyway.

 

4) Sell it.

[Niels - NHSN]

New old stock Russian RC-53 batteries (same size and voltage as the original PX625) also occasionally come up for sale online.

I have actually seen Russian mercury cells regularly advertised on this site. Even if it is not illegal to sell them privately(?), I feel it is ethically questionable to import them. There is a reason why most civilised countries has banned them, and there are plenty of ways we can use our old equipment without these toxic batteries.

[John Seaman]

most civilised countries has banned them

 

And many uncivilised ones.

[rodeo_joe1]

There is a reason why most civilised countries has banned them....

Which is?

And yet mercury-amalgam tooth fillings are still legal and commonplace. As are mercury-vapour fluorescent tubes.

 

Time our legislators had some technical or scientific training..... or at least a modicum of common sense!

[dan_fromm2]

Hmm. Lunasix 3 = Lunapro in the US. I have one. Gossen made an adapter that accepted two LR44s. Now discontinued, alas.

 

Back when, I bought two of the adapters, one for the Lunapro and another for a Canon S8 camera. Both did what they were supposed to do.

 

More recently I bought a Horseman Exposure Meter that wants 4 MR9s, Both of my Gossen adapters are in it and I use PX675 zinc-air cells in the Lunapro. I wrap them in paper to keep them roughly centered in the battery compartment. The cells pass battery check for about two months in it after the seals have been broken. There are worse punishments.

[Niels - NHSN]

Which is?

And yet mercury-amalgam tooth fillings are still legal and commonplace. As are mercury-vapour fluorescent tubes.

 

Time our legislators had some technical or scientific training..... or at least a modicum of common sense!

You are right, as almost always in your own contrary kind of way (which I enjoy, BTW) ;-)

However, I thought the mercury vapor lights were banned in EU a handful years ago? Or was that only for commercial use?

The use of amalgam fillings has been restricted for a number of years in my country but why it is even possible to use it still is beyond me. Of course banning it completely would scare half of the population, which could be quite profitable for the dentists and expensive for the health care systems.

[BeBu Lamar]

I would simply use the 625A battery which is alkaline and has the same physical size. Some camera/meter works fine with it some doesn't then I don't bother.

[Rob_the_waste]

I just used a couple of 675 hearing aid cells and wrapped a couple of o-rings arouind them. They fit and they worked. Then I broke the meter.

[Vincent Peri]

...Then I broke the meter.

 

That's because this is 2020, the worst year I've ever lived through.

[Mike Gammill]

I can't speak for all meters, but the Gossen Luna Pro I once had was very sensitive to battery voltage. I traded it to someone a few years ago since I already had a couple of working meters. After mercury cells were not available I had fairly good luck with the Wein Cells (zinc air). I would think if I could put a hearing aid zinc air (much cheaper than Wein) that would have been a workable solution. Some users of hearing aid batteries recommend covering two of the four air holes on the cell so that it won't dry out as fast. Never tried it myself.

[glen_h]

Fluorescent tubes have a fairly small amount of mercury.

 

Until LEDs, the efficiency was worthwhile.

 

Incandescent lamps powered by a coal power plant emit more mercury, for the total amount of light

(that is lumen hours) than the mercury in a fluorescent tube. That is, there is mercury in coal.

 

By they way, coal power plants also emit more radiation than is legal for nuclear power plants,

again due to what is in the coal. I am not sure what fraction of that is K-40, which we all have

inside of us anyway.

 

If you are reliable at taking used Hg batteries to the hazardous waste station, then it

probably isn't much of a problem. Though cadmium is pretty bad, too, and there are a

lot of NiCd batteries around. I am pretty good at making sure mine go to the right

place, but not everyone does that.

[rodeo_joe1]

However, I thought the mercury vapor lights were banned in EU a handful years ago?

And yet CFL lamps (horrible things) that use exactly the same technology as the old fluorescent tubes, were being pushed as 'eco friendly' a few years ago.

 

A cynical person might come to the conclusion that many of these 'energy saving' initiatives were more about selling new, and more, needless crap than about saving the planet. That's what a cynical person might think.

[glen_h]

It is about 5mg per lamp, and people are often enough reminded about safe disposal.

 

On the other hand, I never see signs warning about safe disposal of mercury batteries,

which I suspect have a lot more than 5mg.

 

There are a fair number of reminders for proper disposal of rechargeable batteries,

especially lead and NiCd, though when they are inside products I suspect that many

people don't even think about it when putting them in the trash.

[chuck_foreman1]

If you are reliable at taking used Hg batteries to the hazardous waste station, then it

probably isn't much of a problem. Though cadmium is pretty bad, too, and there are a

lot of NiCd batteries around. I am pretty good at making sure mine go to the right

place, but not everyone does that.

 

I think this says a lot. The ban came about just as envirnmental concerns were becoming de-jure. I think in this age..at least everybody in Germany .. is well aware of the danger and (all) even regular batteries are collected for disposal. The drugstores and the grocery stores have boxes for colelction. "Only you can prevent for...XX ...toxic contamination"

Edited October 11, 2020 by chuck_foreman|1

[Mike Gammill]

I think if all the mercury (II) oxide in a mercury battery is reduced to mercury that the cell would have about double the mercury as a typical CFL. In many locations people just toss CFL's in the trash along with everything else. The average user of mercury cells, however, is more likely to dispose of them properly, IMHO.

[glen_h]

One site says 450mAh

0.45Ah/26.8Ah/mol = 0.017 mol electrons

0.017 mol * 0.5 Hg/e = 0.0085 mol Hg

0.0085mol Hg * 200 g/mol = 1.7g = 1700mg

That is for 100% efficiency, which usually isn't true.

 

1700g/5g = 340 fluorescent lamps