Battery type 3RZ5: Compatible cameras

“3RZ5” is the incomplete designation commonly used in the West for the Soviet battery designation 3РЦ53 (transliterated as 3RTs53). It is not a single button cell, but a stack of three mercury-zinc cells of type РЦ-53, inserted in series into the TTL prism’s battery compartment. Each individual cell supplies 1.35 V, so the stack’s total voltage is 4.05 V. The individual РЦ-53 is dimensionally equivalent to the Western PX625 (MR9). The designation is composed of 3 (number of cells), Р = Ртутно (mercury), Ц = Цинковый (zinc), and 53 (size).

The 3RZ5 exclusively powers the TTL exposure-meter prisms of Soviet Kiev medium-format cameras. Specifically, this applies to the models Kiev 60 TTL Prism, Kiev 6C TTL Prism (Cyrillic 6С), and the later special edition Kiev Gold 6s TTL Prism. The camera bodies themselves are purely mechanical and require no battery. Power is needed only for exposure metering in the prism. You can find the complete compatibility list at the top of this page.

The РЦ-53 cells were Soviet-designed mercury batteries and were produced until the dissolution of the Soviet Union. The EU Batteries Directive 2006/66/EC initially exempted button cells with a mercury content of ≤ 2% from the ban. Directive 2013/56/EU finally removed this exemption. The complete mercury ban for button cells came into force on October 1, 2015. In the USA, a comparable ban has been in effect since 1996. In Eastern Europe, some remaining stocks from old inventories are still circulating, but they are rare, expensive, and no longer available through regular retail channels. Since the РЦ-53 was also used only in a niche application (Kiev TTL prisms), there was never a broad Western market for replacements.

Because “3RZ5” technically means 3× PX625 mercury cells, the established PX625 replacement solutions can be used, with three of them stacked in series to reach the original 4.05 V. There is no single “best” method; each option has advantages and disadvantages:

• Ausgeknipst 3RZ5 adapter with zinc-air cells: An adapter specially made for the Kiev TTL prism that holds three type 675 zinc-air hearing-aid batteries and matches the dimensions of the three РЦ-53 cells. Voltage: 3 × 1.4 V = 4.2 V, close enough to the original 4.05 V for most prisms. Available as the 3RZ5 adapter for Kiev 60 / 6C / Gold 6s plus a matching type 675 zinc-air refill pack.
• 3x Wein-Cell (MRB625): Factory-made zinc-air cells in PX625 form factor with the correct 1.35 V. Stack voltage: 4.05 V. Relatively expensive (three cells instead of one), available only from specialist photography stores, and each cell lasts only three to six weeks after activation.
• 3x alkaline V625U batteries (LR9): Fits mechanically right away without an adapter. Disadvantage: 3 × 1.5 V = 4.5 V is significantly too high, causing the light meter to measure approximately 1 to 2 stops incorrectly. In addition, the voltage continuously drops as the battery discharges. The measurements become increasingly inaccurate over the battery's service life. Ideally, the prism needs to be recalibrated.
• 3x silver-oxide SR43/SR44 with adapter ring: Silver oxide provides a very stable discharge curve, but at 3 × 1.55 V = 4.65 V, the voltage is also too high. It only works properly if the prism is recalibrated internally or an adapter with voltage regulation (Schottky diode) is used. Specialized adapters are expensive and are hardly available on the market for the 3RZ5 form factor.

Yes, especially with the Kiev TTL prism, because the voltage error enters the stack threefold. A higher voltage than the original 4.05 V (alkaline 4.5 V, silver oxide 4.65 V) makes the light meter assume there is too much light → the camera stops down further, resulting in underexposure. Lower voltage leads to overexposure, conversely. Negative film tolerates two to three stops of overexposure well, but reacts sensitively to underexposure; slight undervoltage is therefore the lesser evil. Slide film forgives neither.

More important than the absolute value is the consistency across the discharge curve: Alkaline batteries steadily lose voltage and provide fluctuating readings throughout their service life. Mercury, zinc-air (Wein-Cell and 675 hearing-aid batteries), and silver-oxide batteries, by contrast, maintain a constant voltage over almost the entire discharge period. That is precisely why the original РЦ-53 batteries were chosen for light meters in the Soviet Union, and precisely why zinc-air adapters are technically the cleanest replacement options today.