PX625 rechargeable battery with USB-C charger

• Voltage close to the original: Operating voltage of 1,25–1,30 V instead of the excessive 1,5 V of an alkaline, correct metering with CdS light meters, no incorrect exposures on negative film.
• Direct replacement instead of an adapter ring: The V80H sits directly in your camera's battery compartment, without an MR-9 adapter and without a diode for voltage adjustment.
• Rechargeable instead of single-use: A V80H battery, rechargeable via USB-C, replaces expensive zinc-air cells that dry out after a few weeks.
• Ready-made charging station instead of DIY: Custom PCB, USB-C port, housing with spring contacts. Plug in, charge, done.

Safety notes

Please charge the V80H battery only in this dedicated charger. Charging indicator: the blue LED shows that the USB-C cable is connected. There is no battery-full indicator; a full charge takes approx. 9 hours.

Conversely: only the Varta V80H belongs in this charger; smaller NiMH button cells such as the V15H or V40H must not be inserted. The charging current is fixed to the 80 mAh of the V80H (C/7) and does not switch off when the cell is full. A V15H would receive a good five times this charge rate, a V40H twice as much. Both overheat and can leak.

Compatibility

Replacement for the 1,35 V PX625 mercury battery (IEC designation MR9). Suitable for various cameras and light meters, including:

• Canon: Canonet series (QL17, QL19, 28, G-III), F series (F-1, FT, FTb, FX), Demi / Dial series (Demi, Demi S, EE17, Dial 35 II) [...]
• Nikon: F series (F, F Photomic, FTN), Nikkormat / Nikomat series (FT, FTN) [...]
• Minolta: SR-T series (100-303, MC, SC, Super), SR series (1, 7, 100-505), Hi-Matic series (7, 7S, 9, 11) [...]
• Olympus: OM-1 series (OM-1, MD, N), 35 series (RC, RD, SP, DC), Pen series (F, FT, D2, EED) [...]
• Pentax: K series (K2, KM, KX), Spotmatic F, H series (H1a, H3v) [...]
• Rollei: 35 series (35, 35S, 35T, Classic), SL35 series (SL35, SL35M, SL350), XF35 / A26 [...]
• Gossen: Luna-Pro / Lunasix series (Luna-Pro, Luna-Pro S, Luna-Six 3, Lunasix 3S), Sixtomat Electronic, Sixtar / Sixtar 2, Super Pilot / Super Pilot SBC [...]
• Sekonic: L-98 Micro-Leader, L-218 (Apex, Autorange), L-228 Zoom-Meter, L-248 Multi-Lumi, Marine Meter series (L-164, L-184C, L-1484) [...]

Light meters often need two cells, cameras usually just one: the Gossen Luna-Pro, Luna-Pro S, Luna-Six 3, Lunasix 3S and Sixtomat Electronic run on two. The Pro Pack contains two rechargeable batteries. Don't confuse them: the Luna-Pro F and Luna-Pro SBC run on a 9 V block battery, so this cell won't fit there.

Not sure whether the battery fits your camera?
Here is a complete list of all cameras and light meters that take the PX625 battery type.

Scope of delivery

• Standard: 1x USB-C charger + 1x V80H rechargeable battery (PX625-compatible)
• Pro Pack: 1x USB-C charger + 2x V80H rechargeable battery
• Pro Pack + battery compartment tool: 1x USB-C charger + 2x V80H rechargeable battery + 1x battery compartment coin tool for opening the battery compartment

Technical details

• Rechargeable battery: Varta V80H (Low Self-Discharge NiMH, 80 mAh)
• Nominal voltage: 1,2 V (according to the manufacturer)
• Operating voltage (plateau): 1,25 – 1,30 V
• Capacity: 80 mAh, enough for weeks at the microampere draw of a CdS meter
• Charging method: gentle slow charging (C/7) via USB-C
• Charging time: approx. 9 hours (charging overnight recommended)
• Charger material: engineering plastic
• Connection: USB-C, fixed 5 V without PD negotiation

Description

In short: The Varta V80H is a rechargeable replacement for the discontinued 1,35 V PX625 mercury battery (IEC MR9) and is charged via USB-C. With a working voltage of 1,25–1,30 V, it keeps your CdS light meter accurate, with no adapter ring and no diode, right in the battery compartment. Fits the Rollei 35, Leica CL, Olympus OM-1, Canon F-1 and Minolta SR-T, among others.

For a long time, the classic workaround for the 1,35 V PX625 mercury battery (IEC MR9) was an adapter with a diode that lowers the voltage. It was necessary because classic analog cameras such as the Rollei 35, Leica CL, Olympus OM-1, Canon F-1 or Minolta SRT were designed for exactly this battery. Since the production ban, there has been no replacement that covers voltage, form factor and shelf life all at once. The most common alternative (1,5 V alkaline) delivers too high a voltage, which leads to incorrect exposures, especially with CdS light meters.

The Varta V80H solves this problem with a working voltage of 1,25–1,30 V, which is much closer to the original. It is not an ordinary NiMH battery: the V80H comes from Varta's industrial “Robust” series (built for server RTC and medical technology) and uses LSD NiMH technology (Low Self-Discharge). Its self-discharge is comparable to the Eneloop series.

The idea of using a V80H as a PX625 replacement comes from Troeszter.net. Building on that, we developed a standalone product: our own PCB, USB-C instead of a lab power supply, and a housing with spring contacts.

On cameras like the Rollei 35 or Leica CL, the battery compartment sits in the film chamber, so every battery change means: film out. With the Pro Pack (2x V80H), you simply swap the battery every time you change film.

Frequently asked questions

“1,2 V is too little. The original had 1,35 V”

The nominal voltage on the datasheet is the average over the entire discharge cycle. Our measurements in a Rollei 35 show: freshly charged, the V80H delivers 1,30–1,32 V. After two weeks, it still delivers 1,27–1,28 V. The deviation of 0,05–0,08 V is within the tolerance range for negative film.

“Only 80 mAh capacity. That's not enough”

A CdS light meter draws microamps. At this current draw, the stable voltage plateau of the V80H lasts not hours, but weeks. 80 mAh is little for AA batteries, but for a camera button cell it is sufficient.

“But NiMH discharges on its own”

Standard NiMH loses 10–20% of its charge in the first few days. The V80H is not standard NiMH. As an LSD cell (Low Self-Discharge) from the Varta “Robust” series, it still retains approx. 80% of its capacity after one year at room temperature, comparable to the Eneloop series.

“Can't I just use an alkaline and compensate with the ISO dial?”

The problem with alkaline is not so much that the voltage is too high, but that it drifts: it starts at just under 1,6 V and drops to about 1,2 V over its lifetime. So the metering error doesn't stay put: the correction that is right today will be wrong in four weeks. Then there's the direction: too much voltage means underexposure, and that is the one direction negative film doesn't forgive. In bright light, a fresh alkaline can leave you up to two stops short, because the CdS response curve is not linear. The V80H, on the other hand, holds its plateau at 1,25–1,30 V. Whatever deviation remains goes towards overexposure and is less than a third of a stop. You won't see that on negative film, and if your camera has a compensation dial, you set it once and leave it there.

Practical tips

• Battery check: Many cameras (OM-1, Minolta SRT) have a battery check calibrated to 1,35 V. With the V80H, it will show “empty”, even though the light meter works perfectly. This is normal.
• Cold: Below 5 degrees Celsius, NiMH becomes unreliable. For winter shooting in freezing temperatures, a zinc-air cell or alkaline + ISO correction is the better choice.
• After charging: Let the V80H rest for 1–2 hours after charging before putting it in the camera. The resting voltage stabilizes during this time.
• Power source: You'll get the most reliable charging from an old, simple USB power adapter with a fixed 5 V or from a USB port on a laptop. Newer USB-3.2 and PD power adapters and many power banks negotiate the voltage first or shut off again because of the tiny load. Then no current reaches the charger, and it doesn't charge.
• Leica M5: The screw cap on the M5 fits more tightly than on other PX625 cameras, so the V80H can get stuck there. If you can't get it cleanly into the compartment, use a type 675 zinc-air cell for the M5. It is smaller and fits straight into the M5 without an adapter.

Detailed comparison of all PX625 alternatives (alkaline, zinc-air, Schottky adapter, V80H and DIY solutions) with measurement data, practical tests and community feedback: Go to the complete PX625 guide.

Independent video test

The US channel Camera Talk bought the set on its own and tried it out in four devices: Gossen Super Pilot, Nikon F Photomic, Rollei 35 and Contarex Super. In the video he states explicitly that he received neither a discount nor free samples from us. We are leaving his criticism as it is: the price, and the fact that the LED doesn't show when the battery is fully charged.

Video: Camera Talk, “A Rechargeable Alternative to the Mercury Cell” (English)

External test reports

Thomas Raatz of analoge-fotografie.net received the charger with two batteries from us for testing and labels his article as advertising. He describes how it handles in practice, including criticism: despite the guide groove, the cell can be inserted the wrong way round, and there is no automatic charging cut-off. Read the test report on analoge-fotografie.net

Joshua Lowcock received the Pro Pack with two batteries from us for testing and tried it out in his Minolta SRT 201. His result: with our battery, the light meter shows the same readings as with the WeinCell MRB625 he used before. The SRT's battery check still reports the cell as empty, because this check is calibrated to 1.35 V (see practical notes). Read the test report on joshualowcock.com (English)