Battery type 3RZ5 — Compatible cameras

"3RZ5" is the incomplete Western spelling of the Soviet battery designation 3РЦ53 (transliterated 3RTs53). It is not a single button cell but a stack of three mercury-zinc cells of type РЦ-53, connected in series and placed in the battery compartment of the TTL prism. Each individual cell delivers 1.35 V, so the total voltage of the stack is 4.05 V. The single РЦ-53 is identical in construction to the Western PX625 (MR9). The designation consists of 3 (number of cells), Р = Ртутно (mercury), Ц = Цинковый (zinc), and 53 (size).

The 3RZ5 powers only the TTL light meter prisms of Soviet Kiev medium format cameras. Specifically, this concerns 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 do not require a battery — power is only needed for the light metering in the prism. The full compatibility list can be found at the top of this page.

The РЦ-53 cells were Soviet-made mercury batteries and were produced until the collapse of the Soviet Union. The EU Battery Directive 2006/66/EC initially exempted button cells with ≤ 2% mercury content from the ban. Only Directive 2013/56/EU removed this exception — the complete mercury ban for button cells came into effect on October 1, 2015. In the USA, a comparable ban has been in place since 1996. In Eastern Europe, some leftover stock from old inventories still circulates, but these are rare, expensive, and no longer available in regular trade. Since the РЦ-53 was only used in a niche (Kiev TTL prisms), there was never a broad Western market for replacements.

Because "3RZ5" technically means 3x PX625 mercury cells, the established PX625 replacement solutions can be used — three of them are stacked in series to reach the original 4.05 V. There is no single "best" way; each variant has strengths and weaknesses:

• Ausgeknipst 3RZ5 adapter with zinc-air cells: Adapter specially made for the Kiev-TTL prism that holds three zinc-air hearing aid batteries type 675 and adapts them to 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 3RZ5 adapter for Kiev 60 / 6C / Gold 6s plus matching zinc-air refill pack type 675.
• 3x Wein-Cell (MRB625): Factory zinc-air cells in PX625 form factor with correct 1.35 V. Stack voltage 4.05 V. Relatively expensive (3 cells instead of one), only available in specialty photo stores, lasts only three to six weeks after activation.
• 3x Alkaline battery V625U (LR9): Fits mechanically immediately without an adapter. Disadvantage: 3 × 1.5 V = 4.5 V is clearly too high, the light meter measures about 1 to 2 stops incorrectly. Also, the voltage continuously drops with increasing discharge — the measurement becomes increasingly inaccurate over the battery’s lifetime. Ideally requires recalibration of the prism.
• 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 it is also too high. Works cleanly only if the prism is internally recalibrated or an adapter with voltage regulation (Schottky diode) is used. Special adapters are expensive and hardly available on the market for the 3RZ5 form factor.

Yes, especially with the Kiev-TTL prism, because the voltage error affects the stack threefold. A higher voltage than the original 4.05 V (alkaline 4.5 V, silver oxide 4.65 V) causes the light meter to accept too much light → the camera closes the aperture more and underexposure occurs. Lower voltage, conversely, leads to overexposure. Negative film tolerates two to three stops of overexposure well but reacts sensitively to underexposure; a slight undervoltage is therefore the lesser evil. Slide film forgives neither.

Even more important than the absolute value is the consistency over the discharge curve: Alkaline batteries continuously lose their voltage and deliver fluctuating readings over their lifetime. Mercury, zinc-air (Wein-Cell and 675 hearing aid batteries), and silver oxide, on the other hand, keep their voltage almost constant throughout the entire discharge — this was exactly why the original РЦ-53 was chosen for light meters in the Soviet Union, and exactly why zinc-air adapters are today the technically cleanest replacement options.