Mercury cells

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Mercury cells (also referred to as mercury batteries) are batteries with a mercury oxide electrode. The manufacture, transport or sale of these batteries is banned or restricted in many jurisdictions, though some are still made in Russia. Before such bans, many cameras and lightmeters were designed to use them. Because mercury batteries produced a constant and reliable voltage, these devices were built without voltage regulation circuitry. Unless remedial measures are taken, use of other kinds of batteries gives inaccurate meter readings and therefore incorrect exposures.


Devices requiring a PX625 battery

Many cameras and lightmeters where designed for and require a 625 mercury cell (see a list of cameras and list of exposure meters). Some cameras and exposure meters were designed for 625 sized cells but include voltage regulation circuitry and thus do not require a PX625 to function properly (list of devices).

Cell names and sizes

Mercury batteries came in number of different sizes including the 32, 400, 625, 640, 675 and the like. Most of the mercury batteries are a single electrolytic cell - usually small and circular. However, the 32 is a set of 4 stacked 640 cells. The greatest number of cameras, finders and light meters were designed for the PX625.

Common number Alternative names Diameter (mm) Height (mm) Weight (g)
625 1124MP, MR9, PX625, PX13, EPX625, RPX625, KX625, HD625, PN625, RM625, 625, H1560, H-D, MR9 15.6 6.05 4.5
675 1128MP, MR44, PX675, HD675, KX675, RPX675, H-C 11.6 5.35 2.6
400 1116M, MR42, E400N, EPX400, KX400, PM400R, PX400, RM400, T400N, V400PX 11.6 3.6 1.4
640 1105M, NR52 16 11.2 8
32 1404M, 4NR52, PX32, E164, TR164, 4NR52, 1404M. HM-4N, V164PX, PX32A, PX32B 17 44.5 36

External links


Popular Photography, October 1993, p. 130; January 1994, p. 144; September 1994, p. 144; and August 1995, p. 66.

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