Battery adapter PX27 for Minox 35 GT, EL, GL & LX

• Constant exposure thanks to a flat discharge curve. SR44 silver oxide cells maintain their voltage steadily throughout their entire lifespan – almost identical to the original PX27 mercury battery. No creeping drift like with alkaline (LR44).
• Precisely made to PX27 original dimensions. The adapter fits four SR44 cells exactly to 12.7 x 20.5 mm. Battery compartment cover closes cleanly, stable contact – no tape, no tinkering.
• Replacement batteries under 1 EUR each. SR44 (type 357) is a standard button cell. Drugstores, watchmakers, Amazon – available everywhere, in 10-packs for under 5 EUR. A battery change costs about 2 EUR.

Why SR44 instead of alkaline or ready-made stacks?

The original PX27 was a mercury battery with 5.6V and an extremely flat discharge curve. The voltage remained constant until shortly before the end. The Minox 35’s exposure automation works without an internal voltage regulator – it reacts directly to the battery voltage applied.

SR44 silver oxide cells deliver 4 x 1.55V = 6.2V with a similarly flat curve. The voltage stays stable until the cell’s end of life, when it drops sharply. Under normal lighting conditions, the slightly increased voltage has no relevant effect on exposure.

LR44 alkaline cells start at 4 x 1.5V = 6.0V and then continuously drop. At first, the exposure is correct. After a few weeks, it’s not. In analog photography forums, Minox owners regularly report deviations of about one stop when using LR44 – without realizing the battery is the cause.

Ready-made 4SR44 or 4LR44 stacks offer no advantage: 5–7 EUR each instead of 2 EUR, only available from specialty dealers, and when empty, the entire unit goes to waste. GoldenPower PX27 replacement batteries cost 8–15 EUR and internally contain 4x LR43 alkaline cells in one housing – with the typical voltage drop included. Also, LR43 has only about half the capacity of an SR44. So you pay more and have to replace more often.

Scope of delivery

• Standard: 1x PX27 adapter + 4x SR44 batteries
• Set: 1x PX27 adapter + 4x SR44 batteries + 2x ISO label (spare)
• Complete: 1x PX27 adapter + 4x SR44 batteries + 2x ISO label + 1x 30.5mm filter adapter

Technical specifications

• Material: PLA+ (technical plastic)
• Color: Black
• Dimensions: 12.7 mm x 20.5 mm (identical to PX27)
• Battery system: 4x SR44 silver oxide (1.55V per cell, 6.2V total)
• Compatibility: Replaces PX27 / V27PX / 4SR43 / EPX27

Description

The PX27 mercury battery was the standard power source for the Minox 35 series and other compact cameras from the 70s and 80s. Since the mercury ban, there is no identical replacement. The typical workaround – wrapping four button cells with tape and hoping the stack fits – is error-prone and leads to contact problems.

This adapter holds four SR44 silver oxide cells and brings the stack to the exact original dimensions of the PX27. The cells sit firmly, the contacts lie cleanly, the battery compartment cover closes without force. The adapter itself is a one-time purchase – only the batteries are replaced.

Note: Not suitable for Minox 35 ML, MB, and MBC (these require a PX28 adapter).

Alternative names for this battery: PX27, V27PX, 4SR43, S27PX, PX27S, RPX27S, PX27A, 4LR43, A27PX, 4AG12, U27PX, V7150, Varta 7150, L7150, EPX27, KX27, RPX27, H-4N, MER27, HS3C, 1413MP, 4NR43, VPX27

Typical concerns – and our answers

“Do 4x SR44 even fit in the battery compartment?”

Without the adapter: barely or not at all. Four SR44 add up to 21.6 mm height. The PX27 compartment is designed for 20.5 mm – a 1.1 mm difference is enough to prevent the cover from closing. Four LR43 are 16.8 mm and too short, causing wobble. The adapter compensates for the height difference and creates the correct outer diameter. This exact fit issue is a constant topic in analog photography forums.

“6.2V instead of 5.6V – is the exposure still correct?”

Practical tests and community experience show: The Minox 35 series works at 6.0–6.2V without relevant exposure deviation in normal daylight. In low light conditions (dusk, indoors), a slight tendency to underexposure can occur. If you want to be safe, reduce the ISO by one step. Negative film easily tolerates this minimal difference.

“Wouldn’t 2x CR1/3N lithium be enough?”

2x CR1/3N provide 6.0V with a flat discharge curve – on paper a good alternative. In practice, photographers report CR1/3N cells that deliver undervoltage right from the start (2.7V instead of 3.0V). Especially from cheap suppliers and marketplace fakes. SR44 is a standard watch battery and too cheap to be faked – this risk is eliminated.

“Why not just buy a ready-made PX27 replacement battery?”

GoldenPower and similar PX27 replacement batteries internally contain 4x LR43 in a plastic housing – alkaline with a dropping discharge curve and only about half the capacity of an SR44. Cost: 8–15 EUR each, with unstable voltage and more frequent replacement. For the same price, you get our adapter plus 10 SR44 silver oxide cells – each with a flat discharge curve and double the capacity.

Practical tips

• Inserting: Place batteries into the adapter, insert adapter into the battery compartment, close the cover. The adapter ensures correct polarity.
• Transport lock: Place the included insulation disc between the adapter and battery compartment contact if the camera won’t be used for a while. Prevents self-discharge.
• First film: Use ISO 400 negative film for the first roll after battery replacement. The wide exposure latitude forgives slight deviations while you get a feel for the exposure.
• Reordering: SR44 batteries (also called 357, SB-B9, or SR44W) are available everywhere. You’re not tied to a specialty supplier.

Want to know more about battery alternatives for analog cameras?
In our FAQ article on batteries and adapters, we explain all options in detail – including voltage comparisons and recommendations by camera type.