PX625 rechargeable battery with USB-C charger

• Voltage close to the original: Operating voltage of 1.25–1.30 V instead of the excessively high 1.5 V of an alkaline battery, ensuring correct readings with CdS light meters and preventing incorrect exposures on negative film.
• Direct replacement instead of an adapter ring: The V80H fits directly into your camera’s battery compartment without an MR-9 adapter or diode for voltage adjustment.
• Rechargeable instead of disposable: A USB-C rechargeable V80H battery replaces expensive zinc-air cells that dry out after a few weeks.
• Ready-made charging station instead of DIY work: Custom PCB, USB-C port, and housing with spring contacts. Plug it in, charge it, and you’re done.

Safety instructions

Please charge the V80H battery exclusively in the charger intended for it. Charging indicator: The blue LED shows that the USB-C cable is connected. There is no full-charge indicator; a complete charging cycle takes approximately 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 for the V80H’s 80 mAh capacity (C/7) and does not switch off when the cell is full. A V15H receives roughly five times this charging rate, and a V40H twice the rate. Both can overheat and leak.

Compatibility

Replacement for the 1.35 V mercury battery PX625 (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, while cameras usually need only one: Gossen Luna-Pro, Luna-Pro S, Luna-Six 3, Lunasix 3S, and Sixtomat Electronic use two. The Pro Pack contains two batteries. Do not confuse them with the Luna-Pro F and Luna-Pro SBC, which run on a 9 V battery and are not compatible with this cell.

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

Scope of delivery

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

Technical details

• 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, sufficient for weeks with the microampere consumption of a CdS meter
• Charging method: gentle trickle charging (C/7) via USB-C
• Charging time: approx. 9 hours (overnight charging 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 mercury battery PX625 (IEC MR9) and is charged via USB-C. With an operating voltage of 1.25–1.30 V, it keeps your CdS light meter working correctly, without an adapter ring or diode, directly in the battery compartment. It fits, among others, the Rollei 35, Leica CL, Olympus OM-1, Canon F-1, and Minolta SR-T.

For a long time, the classic workaround for the 1.35 V mercury battery PX625 (IEC MR9) was an adapter with a diode to reduce the voltage. This was necessary because classic analogue cameras such as the Rollei 35, Leica CL, Olympus OM-1, Canon F-1, and Minolta SRT were designed specifically for this battery. Since production was banned, no replacement solution has covered voltage, size, and longevity at the same time. The most common alternative, a 1.5 V alkaline battery, provides too much voltage, which leads to incorrect exposures, particularly with CdS light meters.

The Varta V80H solves this problem with an operating 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 RTCs and medical technology, and uses LSD-NiMH technology (low self-discharge). Its self-discharge is comparable to that of the Eneloop series.

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

In cameras such as the Rollei 35 or Leica CL, the battery compartment is inside the film chamber, so every battery change means removing the film. With the Pro Pack (2x V80H), you can simply change the battery whenever you change the film.

Frequently asked questions

“1.2 V is too little. The original was 1.35 V.”

The nominal voltage in the data sheet is the average over the entire discharge cycle. Our measurements in a Rollei 35 show that the V80H delivers 1.30–1.32 V when freshly charged. 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 isn’t enough.”

A CdS light meter consumes microamps. At this level of power consumption, the V80H’s stable voltage plateau lasts not hours but weeks. 80 mAh is little for AA batteries, but sufficient for a camera button cell.

“But NiMH batteries discharge by themselves.”

Standard NiMH batteries lose 10–20% of their charge in the first few days. The V80H is not standard NiMH. As an LSD cell (low self-discharge) from Varta’s “Robust” series, it retains approximately 80% of its capacity after one year at room temperature, comparable to the Eneloop series.

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

The problem with alkaline batteries is less their excessive voltage than its fluctuation: They start at just under 1.6 V and drop to around 1.2 V over their service life. The metering error therefore does not remain constant: The correction that is right today will be wrong in four weeks. The direction is also important: Too much voltage means underexposure, and that is the one direction negative film does not forgive. In bright light, a fresh alkaline battery can leave you up to two stops underexposed because the CdS response curve is not linear. In contrast, the V80H maintains its plateau at 1.25–1.30 V. Any remaining deviation results in slight overexposure and is less than one-third of a stop. You will not see this on negative film, and if your camera has a correction dial, you set it once and leave it there.

Practical notes

• Battery check: Many cameras (OM-1, Minolta SRT) have a battery check calibrated for 1.35 V. The V80H will show “empty” there even though the light meter works perfectly. This is normal.
• Cold temperatures: Below 5 degrees Celsius, NiMH becomes unreliable. For winter photography in freezing conditions, a zinc-air cell or an alkaline battery with ISO compensation 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: The most reliable option is an older, simple USB power supply with fixed 5 V or a USB port on a laptop. Newer USB 3.2 and PD power supplies and many power banks negotiate the voltage first or switch off again at the tiny load. In that case, no current reaches the charger and it does not charge.
• Leica M5: The M5’s screw cap fits more tightly than those of other PX625 cameras, and the V80H may get stuck there. If you cannot insert it cleanly into the compartment, use a Type 675 zinc-air cell for the M5. It is smaller and fits directly into the M5 without an adapter.

For a detailed comparison of all PX625 alternatives (alkaline, zinc-air, Schottky adapter, V80H, and DIY solutions), including measurement data, practical tests, and community feedback: Read the complete PX625 guide.

Independent video review

The US channel Camera Talk bought the set themselves and tested it in four devices: Gossen Super Pilot, Nikon F Photomic, Rollei 35, and Contarex Super. In the video, they explicitly state that they received neither a discount nor a free sample from us. We are leaving their criticism intact: the price and the fact that the LED does not indicate when the battery is fully charged.

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

External reviews

Thomas Raatz from analoge-fotografie.net received the charger with two batteries from us for testing and labels his article as advertising. He describes how it performs in practice, including some criticism: Despite the guide groove, the cell can be inserted the wrong way around, and there is no automatic charging cutoff. Read the review on analoge-fotografie.net

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