modern equivalent for mercury button-cell battery?

[JAPster]

<p>Hello folks,<br>

Greetings again to the wide photo.net viewing community.</p>

<p>I have a question about batteries.</p>

<p>An acquaintance just gave me his old Sears Auto TLS 35mm film SLR, with 50mm f/1.4 normal lens and a 135mm f2.8 telephoto. A bit of research on the camera turns up this camera is actually a Ricoh Auto TLS camera, but flying under the Sears banner. A bit more research turns up the original owner's manual for the Ricoh Auto TLS, courtesy of Mr. Butkus & his fine collection of manuals. A quick download and printing of the manual were accomplished w/o problems.</p>

<p>The manual says this camera uses a single mecury cell, type Eveready EPX625 or Mallory RM625 or equivalent. The voltage rating is not stated. That's about all that's said about the battery.</p>

<p>I'm anticipating I will not be able to find or buy either of these types at the places I usually get camera batteries (Walmart, Radio Shack, Best Buy, etc, etc), since this camera is obviously about 30+ years old.</p>

<p>So, I guess my question is, for very knowledgable vintage camera users, what's the best modern equivalent replacement battery for this type mercury cell?</p>

<p>BTW, this camera model uses a Cds type light meter, if that makes any difference.</p>

<p>Thank you,<br>

AP</p>

[Mike Gammill]

<p>Closest equivalent would be a 625 Wein cell, which uses zinc-air chemistry to generate a similar voltage to mercury cells. Mercury cells had a constant 1.35 volts for most of their lifespan with general purpose zinc air cells coming in at 1.4 volts. The Wein cells are tweaked to give closer to 1.35 volts. A cheaper alternative is to buy the zinc air cells in a multipak and use a #9 o-ring to make it fit (since the largest zinc air cells are 675 size.)</p>

[paul_wheatland]

<p>My solution involves using a silver oxide button battery 1.55 volts with an "O" ring to take up the slack. Then reset your ISO to one stop slower ie. 400 print film set ISO to 200. Before loading film compare it with a known meter reading just to be comfortable with my advice. If the battery does not make contact you might want to place a wad of "tin foil" under the battery cover to take up the slack.</p>

[michael_madio]

<p>I use 1.4V zinc-air hearing aid batteries. They're inexpensive and close enough to 1.35 volts for use without compensation.</p>

[john_shriver]

<p>There are many pages on this subject. One common approach is a 675 zinc-air hearing aid battery, with an O-ring as a spacer. Same electrochemistry, so the same voltage, which is important. But you have to be sure to not leave it in the camera when not in use, since they can corrode a LOT worse than the mercuric-oxide/zinc batteries, and faster too.</p>

[david_smith110]

<p>Try this for a slightly more expensive but permanent and easy solution.</p>

<p><a href="http://www.criscam.com/mercury_battery_adapters.php#gotohere">http://www.criscam.com/mercury_battery_adapters.php#gotohere</a></p>

<p>The MR-9 adapter fits in your battery compartment and allows you to use modern silver oxide batterys and adjusts the voltage for you. I plan on getting one shortly to swap between my SRT 102 and Canon FTb. I have read good reviews of this online.</p>

[walter_degroot]

<p>If you or a friend are handy with electronics<br>

and taking things apart<br>

a 50 cent shotky diode can be put inside the camera in series with the silver-oxide cell<br>

to reduce the 1.5-1.55 volts to close to 1.35 volts<br>

this would also be a permanent fix.<br>

the WORST is an alkaline cell that the companies TELL YOU<br>

is an exact replacement. As an alkaline cell ages the voltage gradually declines<br>

and gives false readings<br>

the other cells silber zinc-air and the banned mercury<br>

all keep the same voltage until the very end, then quickly die.<br>

I think it is possibkle the silver 1.55 v cells with an ISO adjustment will work<br>

and last two years.</p>

[jim_momary]

<p>The offset method for ISO/ASA does work, but know the relationship is NOT linear across the EV range.</p>

<p>There may be 2 or 3 stops of error under very bright conditions and only one stop for dim scenes. But, using a negative film with broad characteristics does mitigate this substantially, so it's not a huge issue.</p>

<p>Like Walt said, Schottky diodes inserted inline with the battery wire below the baseplate really do a decent job dropping the silver oxide cell's 1.55V down to just about 1.4V, and they are stable across their entire life. For my older cameras that I've done this to, they all have no issues with modern batteries.</p>

<p><a href="http://www.ihagee.org/batt-adapt-us.pdf">http://www.ihagee.org/batt-adapt-us.pdf</a></p>

<p>Search thru archives here on photo.net and you'll pull up dozens of discussions.</p>

<p>Jim M</p>

[michael_linn]

<p>For a camera with a nicely aged 40 year old cds cell I would say that some checking on it's accuracy even with the correct voltage on board would be a good idea. As I recall, the meter adjustment on this model is pretty straight forward, if necessary. If the light seals and mirror bumper are original, they will need to be replaced before using the camera.</p>

<p>The copal shutter rarely gives any trouble. Inside, it looks a lot like a Nikkormat FT.</p>

<p>I owned one of these in the early 70's and it was my beater camera, going to europe for a month. The f1.4 normal lens was huge but performed very well.</p>

[bjscharp]

I use the MR-9 adapter in my Leicameter. Works ok, but because the 'cap' of the silver cell ( the minus pole) is smaller than the cap of the real mercury cell would be, how well it works will depend on the design of the battery compartment. In my Leicameter, I had to tape off part of the contact for it to work well.

[walter_degroot]

<p>Thank you jim I had wodered about using silver-oxide cells<br>

and adjusting the ISO. I wondered why it was not ever suggested.<br>

now, from a practical aspect I know why.<br>

In the early years, I was "fat dumb and happy" I believed what the camera stores told me and used Alkaline cells in my sensorex. THEN someoe woke me up.<br>

Now I have had a "second awakening"<br>

I can see to frame and focus<br>

but not to do "small stuff" I will let my son do that.<br>

To let others know, a semiconductor diods has a fixed drop<br>

The most common are silicon and germanioum. the drop is not correct for this.<br>

however a Shottky doide, because of it's construction, when used in series with a 1.55v cell<br>

drops the voltage to anout 1.4v, just right to replace a mercury cell.<br>

It is wierd that the mercury cell has been banned,<br>

but now they are pushing CFL ( compact flourescent bulbs)<br>

that contain mercury and NOTHING is being said, and there are NO provisions for recycling them.<br>

Honestly they DO NOT last as long as they say they should.</p>

[Mike Gammill]

<p>Good point about the CFL's, Walter. A mercury cell may have about twice the mercury of one CFL, but an informed mercury cell user would probably be more likely to dispose of a mercury cell properly than the average CFL user. <br>

Anyway, Alan, you've got lots of good solutions to choose from. </p>

[JAPster]

<p>Thanks for all the practical advice. This is the kind of thread its good to revisit every once in a while. I ended up going to wally-world and getting a RayOVac pac of 8 zinc-air cells, with an average cost of about $1 a cell. Seems to work ok in my Minolta Srt101, so I hope it will also work ok in this sears slr.</p>

[steve m smith]

<p>It's worth doing some investigation to see if the meter circuit is sensitive to cell voltage. If it is, you will need to use a zinc air cell as you are doing now or use some other means to reduce the voltage such as the diode already mentioned.</p>

<p>If the camera has a bridge circuit then the voltage is not critical. Cameras with bridge circuits have meter needles which go to the middle of their travel when exposure is correct and also rest at that place when the meter is switched off. Non bridge circuits which are voltage critical tend to need a secondary needle moved to line up with the meter's needle. THey also rest at one end of the travel when switched off.</p>

<p>If your camera has a bridge circuit then just about any cell which you can fit and make contact will work.</p>

[arden_lindsey]

<p>Try a Wein 1.35V zink/air...try ebay if you can't find one anywhere else...WEIN PRODUCTS INC. 115 W. 25th St. Los Angeles, CA 90007 Battery #MRB625</p>