The PX625 (also referred to by other names such as PX13) is a small button-shaped 1.35volt mercury battery which great number of camera models were designed to use.
Before the manufacture of mercury batteries was banned, many cameras were designed to use them. Because mercury batteries produced a constant and reliable voltage, many cameras were built without any voltage regulation in the metering circuitry. Unless preventative measures are taken, use of other kinds of batteries gives erratic exposures and meter readings.
Devices requiring PX625Edit
Many cameras and light meters were designed for and require a 625 mercury cell: 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), and so can use the higher-voltage (and less voltage-stable) alkaline (PX625A, 1.5v) or Silver-Oxide (S625PX, 1.55v) cells. Devices without regulation circuitry (or some method of compensating for other voltages) can use Zinc-Air type cells made especially - with the correct 1.35v potential - to replace the mercury cells.
- Suggestions from Rick Oleson (based on ideas from Leon Schoenfeld) to make classic cameras give acceptable meter readings using modern alkaline batteries.
- The mercury cell problem and its solutions (PDF file) by F. de Gruijter. Also discusses PX675 and other mercury batteries.
- The mercury oxide battery problem, at Konica SLR system, providing information about the PX625 and PX675 battery that is not specific to Konica models
- Russian mercury px625 battery Seller of Mercury Batteries specializing in the Original Mercury px625.