Mercury battery replacement options...

[celerystalksme]

I just bought a Canon Demi EE 17. Now...the only problem is finding a

battery. It takes a old mercury PX625...

 

From what I understand, my replacemnt options are alkaline, zinc air,

wein cell (proprietary zinc air), silver oxide...they have direct

PX625 replacement options. OR...I can opt for a MR-9 adapter (voltage

reducing converter) with a 386 (SR43W) silver oxide battery...

 

Anyone have any insight or recommendations?

 

Thanks!

[miha_steinb_cher]

I don't know anything about your Canon.

Battery requirements depends on what is it used for. CdS resistor based lightmeters can work very well with alkaline cells, some other pieces of electronics may require more exact voltage. If I were you, I'd try an alkaline cell first, it's inexpensive and you'll be able to see the results quickly.

[rich815]

Seems like you've already outlined the main options out there. A Google search on "PX625 replacement" gives a load of links regarding this....

[lex_jenkins]

The zinc air size 675 hearing aid battery is almost always the best available replacement for the 625 mercury cell. It has almost identical output and discharge characteristics. Imagine a projectile following a straight horizontal path and then declining fairly suddenly. The only disadvantages are the smaller size and shorter life.

 

The 625 alkaline cell is usually the poorest replacement for the 625 mercury cell. It's output and discharge characteristics are almost entirely unsuitable. If it ever matches the meter with the original mercury cells it's by sheer coincidence. Imagine tossing a softball as high into the air and as far as you can throw it. The proper output is achieved only at the peak of the arc. A bit of an exaggeration but it'll do.

 

Silver oxide batteries are also usually unsuitable replacements. A meter should be designed for the characteristics of that type of battery.

 

The smaller size of the 675 cell has never been a problem in any of my cameras that were originally designed for the 625 cells. The existing battery contact spring tension was sufficient to maintain continuity. However there are several simple methods for ensuring a proper fit for the smaller 675 cells.

 

The Wein cell is little more than a 675 zinc air battery enclosed in a metal collar to make it the size and shape of a 625 button cell. For the price of a single Wein cell you can buy a packet of several 675 hearing aid batteries.

 

Once the zinc air battery is exposed to air by peeling off the tape it'll usually last no more than six months. Depending on the camera I get more or less that.

[Andrew in Austin]

The 625 Wein cell IS a 675 zinc air with an added collar and two vent holes instead of four. Each 625 Wein cell retails for $11 at my local camera shop. While the 675 zinc air cells are about a buck a piece at Walgreens or Radio Shack.

 

If one is looking for the drop-in convenience of the Wein cell, then order the non-Wein brand Z625PX equivalents from photobatteries dot com. They are $9 a pair with delivery.

[celerystalksme]

Ok...I'm a bit confused...

 

The 675 zinc air hearing aid battery is a 1.4v battery. Will that work? Seems like a pretty small difference. Will the CdS cell expose my shots well?

 

As for the WeinCell MRB625...they claim that it is 1.35v, same as the mercury PX625...so how can it be a 675 with a collar? Are my numbers wrong?

 

Thanks!

[peter_kim2]

I find the hearing aid batteries underexpose by about a stop so set my asa to that much ie instead of 400 I turn to 200...But this in exact as the dischage slope is different over time.

 

Anyone know how long they last if you stick the sticker back on the holes everytime after using the camera? Does it make it last longer or is the chemical reaction continuous once your peel it off?

[cenelsonfoto]

I use Weins with no complaints.

[celerystalksme]

Peter,

 

The 675 hearing aid batteries are zinc air...supposedly, zinc air has a constant voltage, like the old mercuries. Are you sure your 675's have a downward sloping discharge curve? It should be relatively horizontal before a sudden drop off...

[gerald_widen]

By doing a google search you should be able to find someone selling the original mercury batteries. At least I found a few sellers about a year ago. I picked up 3 for $8 each plus shipping. The mercury batteries last for years. I get about 8 years use in my Leica MR meter. If you go to your local town garbage/disposal they will dispose of them for you. Also the person who sold mine claimed on their website that they will properly dispose of them if you send them the depleted batteries. But with the batteries lasting 5-10 years who knows if they will still be around.

[walter_degroot]

humidity affects the life of a hearing aid battery

for example arizona residents would see the gel inside the battery

drying out sooner.

I blocked 2 holes on the wal-mart hearing aid battery ( they appear to my eyes as dents) and the battery ( cell) lasted 5 months

strange tho the new batteries also had died?

i bought a new 6 pack.

I would like to find a metal ring to adapt to other cameras.

lex said it better than i could.

http://www.butkus.org/chinon/camera_batteries.htm

go here for info and a pdf on how to make a adapter

 

back up to butkis.org to get interesting old camera stuff.

[walter_degroot]

humidity affects the life of a hearing aid battery

for example arizona residents would see the gel inside the battery

drying out sooner.

I blocked 2 holes on the wal-mart hearing aid battery ( they appear to my eyes as dents) and the battery ( cell) lasted 5 months

strange tho the new batteries also had died?

i bought a new 6 pack.

I would like to find a metal ring to adapt to other cameras.

lex said it better than i could.

http://www.butkus.org/chinon/camera_batteries.htm

go here for info and a pdf on how to make a adapter

 

back up to butkis.org to get interesting old camera stuff.

[peter_kim2]

Hey J. I heard that they have a faster and uneven discharge slope. I rememebr seeing a chart somewhere before but I dont know where now. In any case I only use BW films like Tri-x with my camera (a minolta himatic) so variable dischrage doesnt seem to be a big deal for me. Slide film is another matter all together!

 

Gerald, Know any place specific we can get Mercury batteries? I tried a google seach but was unable to find anything except abotu replacement batteries not the real deal.

[peter_kim2]

OH heres that chart I was talking about. The discharge is similar but the zinc are discharge slightly faster and at an angle. Not exactly constant.

 

http://rick_oleson.tripod.com/index-111.html

[berk_sirman2]

www.px625.com still has some (original mercury) px675's in stock. px625's are out.

 

I was very lucky and bought 6 px640's for my Yashica Tl-Electro for $9.99 on ebay about 7 months ago. I am expecting them to last quite some time. That is, if they do not start leaking before they are out.

[peter_kim2]

Hey Berk let me know if you ever want to part with a pair! :)

[celerystalksme]

Lex,

 

What are some of the simple solutions to ensure that a 675 battery fits in a compartment made for 625?

 

Thanks!

[charles_stobbs3]

In some applications (like Canonets) all that is needed is a plumbing rubber o-ring (frome Home Depot, Lowes, True Value, etc) of a suitable size. For Oly 35 ED, EC stack two zinc/air cells in a plastic tube made from an aspirin desicant container in one cavity and a wooden dowe, cut to length, with a hole drilled through the middle and a nail, cut to length and inserted down the hole to complete the circuit in the other cavity.

Another recent thread somewhere said that zinc/air cells might outgas with time and cause problems. I have never had a problem but I have never left batteries in the camera more than two weeks at a time. I have an old but pristine appearing Yashica Electro 35 GSN which was corroded at several electrical junctions within the camera. I suspect some previous owner had left a mercury battery in far too long.

[gerald_widen]

I just did a search and also couldn't find any. I guess the world wide supply is out. I would check ebay from time to time as they were available as recently as a year ago on the internet. As I said I bought 3. One for my Leica meter, one for the Canonet and an extra. I guess the extra goes to the fridge for when the one in my meter dies.

[Matthew Currie]

I use zinc-air hearing aid batteries in my Konica T3. They work very well with the ASA setting offset by a couple of notches. But if you go that route, get quantities. They really don't last very long, and seem to fail pretty quickly when they go. I don't mind that, because they're so cheap, but it's important to keep spares on hand.

 

I don't know about the Canon, but if the system is not sensitive to precise voltage, or if it can actually be recalibrated, I'd go for silver oxides, because they last longer and stay consistent.

[jim bob]

I use hearing aid batteries that cost less than a dollar apiece. I use a rubber O-ring grommet (size 9, I believe, that you buy for pennies each. The O-rings provide a snug secure fit for the batteries in the camera. Works fine! and cheap!!!

[kaiyen]

I currently use Wein cells. My problem was that, for my Canonet 1.7, the difference in shape made it pop out of the right location a lot, and I'd lose metering. i could solve that with an o-ring, but I've been lazy so far. Plus, I had some Wein cells lying around for when I thought I'd actualy use the meter in my Yashicamat 124.

 

I think the o-ring method would work fine with the 675's. I would suggest you consider doing that rather than just throwing the 675 in there, though I believe Lex hasn't had the same problem I've had.

 

Finally, I've seen the Wein's online for more like $3.50 each (esp. if you buy like 10 at a time), and they last quite a long time. the one in my canonet has been in there for probably 6 months.

 

allan

[graham_patterson1]

It looks like I am in the minority for using the MR-9 adapter for 386 batteries. I have three, two are used in my old Soligor spot meter which sees constant use with the medium and large format equipment. The third is used when I need the meter in one of my OM-1s or in the Rollei 35.

 

This is not a cheap solution, and I trust I won't throw the adapters out by mistake, but they do work. The 386 cells are in most local drug stores and are not expensive. The lifetime is less than the old 625s - maybe 50%?

[lex_jenkins]

My "solution" for making sure the smaller diameter 675 zinc air battery fits in a 625 compartment without slipping around and losing continuity was so primitive it's laughable. So far the only time I've had to resort to the was with a Canon TX we used at an office I worked for as an inspector.

 

I used a toothpick to gently pry up the copper contact springs in the compartment to increase pressure. Then I popped the 675 button cell in the compartment. Then I broke off a bit of the toothpick and jammed it in sideways to keep the 675 cell from slipping around. The main thing I was concerned about was using a non-conductive material as a shim to prevent shorting out the contact.

 

Don't snicker - it worked.

 

I haven't needed to use the same trick with a Canon FTbn, OM-1, Canonet GIII QL17 (actually the easiest of the bunch to fit with a 675 cell), and others.