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Stable voltage until just before discharge: SR44 silver oxide cells deliver 4 x 1.55V = 6.2V with a flat discharge curve – almost identical to the original PX27 mercury battery. No creeping drift like with alkaline (LR44).
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Original dimensions without tinkering: The adapter fits four SR44 cells to exactly 12.7 x 20.5 mm. Battery compartment cover closes cleanly, stable contact – no tape needed.
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Replacement for expensive disposable stacks with affordable standard cells: SR44 (type 357) is a standard button cell, available in packs of 10 for under 5 EUR. A battery change costs about 2 EUR – the adapter itself is a one-time purchase.
Compatibility
Fits various cameras, including:
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Minox: 35 EL, 35 GL, 35 GT, 35 PE, 35 PL, C, LX [...]
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Rollei: 35 LED, 35SE, 35TE, A110, E110
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Agfa: Optima 335, Optima Sensor Flash
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Hanimex: VEF Zoom
Not suitable for Minox 35 ML, MB, and MBC (these require a PX28 adapter).
Unsure if the adapter fits your camera? Complete list of all cameras compatible with PX27 battery type.
Scope of delivery
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Standard: 1x PX27 adapter + 4x SR44 batteries
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Set: 1x PX27 adapter + 4x SR44 batteries + 2x ISO label (replacement)
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Complete: 1x PX27 adapter + 4x SR44 batteries + 2x ISO label + 1x 30.5mm filter adapter
Technical details
- Adapter material: plant-based bioplastic (PLA+)
- 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)
- Replacement for: 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 has been 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, contacts are clean, and the battery compartment cover closes effortlessly.
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 Minox 35’s exposure automation works without an internal voltage regulator – it reacts directly to the battery voltage.
SR44 silver oxide cells deliver 4 x 1.55V = 6.2V with a similarly flat curve. The voltage remains stable until the cell’s end of life, when it drops sharply. Under normal lighting conditions, the slightly higher voltage has no relevant effect on exposure.
LR44 alkaline cells start at 4 x 1.5V = 6.0V and then continuously drop. At first, 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 is discarded. 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.
Practical tips
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Inserting: Insert batteries into the adapter, place adapter into battery compartment, close cover. The adapter ensures correct polarity.
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Transport lock: Place the included insulation disc between adapter and battery compartment contact if the camera won’t be used for a while. Prevents self-discharge.
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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 exposure.
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Reordering: SR44 batteries (also called 357, SB-B9, or SR44W) are widely available. You’re not tied to a specialty supplier.
Alternative names for this battery type: 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
Want to learn 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.
Frequently Asked Questions
“Do 4x SR44 even fit in the battery compartment?”
Without an adapter: barely or not at all. Four SR44 cells measure 21.6 mm in 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 cells are 16.8 mm, too short and wobbly. The adapter compensates for the height difference and provides the correct outer diameter. This exact fit issue is a recurring topic in analog photography forums.
“6.2V instead of 5.6V – is exposure still accurate?”strong>
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 (dusk, indoors), a slight tendency to underexposure can occur. To be safe, reduce ISO by one stop. Negative film easily tolerates this minimal difference.
“Wouldn’t 2x CR1/3N lithium cells suffice?”
2x CR1/3N provide 6.0V with a flat discharge curve – on paper a good alternative. In practice, photographers report CR1/3N cells delivering undervoltage from the start (2.7V instead of 3.0V), especially from cheap sellers and marketplace fakes. SR44 is a standard watch battery, too cheap to fake – eliminating this risk.
“Why not just buy a ready-made PX27 replacement battery?”
GoldenPower and similar PX27 replacements internally contain 4x LR43 alkaline cells 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.
