Wein EPX-625 (MRB625)
This is a direct $4.50 replacement for mercury EPX-625, PX-13 and MR-9 cells.
It's a zinc-air cell with a washer around it so it fits perfectly. Supposedly the air holes are slightly smaller to increase the life in light meters over a hearing aid zinc-air cell.
Electrically, it seems to be a perfect match, too.
I can't believe I'm such a cheapskate. I obsessed for years reading all the hacker sites about why these won't work because they might be a few millivolts off from a mercury cell. When I finally broke down and spent my $4.50 and stuck it in an old camera (a Leica MR meter), it works great.
Now all our old Nikon F (FTn), Nikkormat and Luna Pro meters, Minolta SRT-102s and Leica Meter MR-4s will work swell, forever. Yippee!
It measures 0.094 oz. or 2.7g.
You peel the green sticker off the air holes, and it wakes up by the time you can stick it in your camera or meter.
Supposedly, if you're a real cheapskate, you can put the green air sticker back over the holes when you're not using it.
Measured Open Circuit Voltages
Degreed EE that I am (you can't speed "geek" without EE), here are my measurements.
This is all needless analysis paralysis, since the meters' battery checks are all perfectly happy, and nowhere near as precise as my Tektronix TX3 digital voltmeter with which I measure this.
as shipped, sticker still on: 1.000 V (20 Feb 2009 07:15AM)
10 seconds after sticker removed: 1.075 V
30s: 1.165 V
50s: 1.250 V
1 minute: 1.2275 V
1:24: 1.3 V
1:45: 1.31 V
2 minutes: 1.315 V
4:30: 1.331 V
5 minutes: 1.333 V
13 minutes: 1.350 V
21 minutes: 1.355 V
35 minutes: 1.360 V
45 minutes: 1.362 V
1 hour: 1.365 V
10 days: (01 Apr 2009): 1.416 V
3.5 weeks (16 Apr 2009): 1.411 V
10 weeks (30 April 2009): 1.409 V
9 Months (17 November 2009): 1.403 V
10 Months (19 Dec 2009): 1.410 V
11 Months (30 Jan 2010): 1.400 V
13 Months (29 March 2010): 1.112 V
9:34AM 29 March 2010: 1.01 V.
6:49PM (9 hours) 29 March 2010: 1.370 V.
5 Months: (09 September 2010): 1.418 V.
?Cell marked 4/09 in LEICAMETER MR-4 measured 03 November 2010: 1.419V.
Got an old meter or camera?
No more whining about finding mercury batteries; just get some of these and get back to shooting.
If you're shooting slide film, as always, check your meter and adjust the ASA slightly as needed to get the results you want. This is the same as always; no two perfectly fine meters ever agree, regardless of what batteries you use. I set my brand-new state-of-the-art electronic Gossen Digisix off by 2/3 of a stop; that's just how I like my images as shot with that meter. No meter is perfect, regardless of how new it is.
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