3RZ5 Battery: Compatible Cameras

"3RZ5" is the incomplete spelling of the Soviet battery designation 3РЦ53 (transliterated 3RTs53) that is common in the West. It is not a single button cell but a stack of three mercury-zinc cells of type РЦ-53, which are inserted in series into 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 individual РЦ-53 is structurally identical to the Western PX625 (MR9). The designation is made up of 3 (number of cells), Р = Ртутно (mercury), Ц = Цинковый (zinc) and 53 (size).

The 3RZ5 exclusively powers the TTL metering 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 do not need a battery. Power is only needed for the light metering in the prism. You can find the complete compatibility list 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 closed this exemption. The complete mercury ban for button cells came into force on 1 October 2015. A comparable ban has been in place in the USA since 1996. In Eastern Europe, some remaining stock from old inventories is still in circulation, but it is rare, expensive and no longer available through regular retail. Since the РЦ-53 was also only used in a niche (Kiev TTL prisms), there was never a broad Western market for replacements.

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

• Ausgeknipst 3RZ5 adapter with zinc-air cells: Adapter made specifically for the Kiev TTL prism that holds three zinc-air hearing aid batteries type 675 and brings 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 the matching zinc-air refill pack type 675.
• 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 (3 cells instead of one), only available from specialist photo shops, and each lasts only three to six weeks after activation.
• 3x alkaline battery V625U (LR9): Fits mechanically right away without an adapter. Drawback: 3 × 1.5 V = 4.5 V is clearly too high, and the light meter reads roughly 1 to 2 stops off. In addition, the voltage drops continuously as the battery discharges. The readings become increasingly inaccurate over the life of the battery. Ideally requires recalibrating the prism.
• 3x silver oxide SR43/SR44 with adapter ring: Silver oxide delivers a very stable discharge curve, but at 3 × 1.55 V = 4.65 V it is also too high. Only works properly if the prism is recalibrated internally 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, and especially with the Kiev TTL prism, because the voltage error enters the stack three times over. 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. Conversely, a lower voltage leads to overexposure. Negative film tolerates two to three stops of overexposure well but is sensitive to underexposure; a slight undervoltage is therefore the lesser evil. Slide film forgives neither.

Even more important than the absolute value is consistency across the discharge curve: alkaline batteries lose voltage continuously 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 constant over almost the entire discharge, which is exactly why the original РЦ-53 cells were chosen for light meters in the Soviet Union, and exactly why the zinc-air adapters are the technically cleanest replacement options today.