Guide: 35mm Film Camera PX625 Mercury Battery Alternative

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If you own an old 35MM Film Camera, you may find you need a PX625 1.35V battery. A 1.35V button battery was common in 35mm cameras from the 1960s-1980s. I wasn’t a photographer during that time, but I do have a vintage Minolta SRT that I bought on eBay that needed a PX625 battery for the light meter. There’s a full list of cameras that use 625 batteries here.

The bad news is that PX625 batteries are not available anymore. Mercury-based batteries were banned in the US in 1996 (and around the same time elsewhere around the world).

The good news is that there are alternatives to PX625 button batteries!

Best Option: PX625 Replacement

The easiest option is to use these mercury-free Zinc Air batteries MRB625. You can get a two-pack for under US$10 on Amazon and they are rated 1.35V. While you can buy cheaper 1.5V alternatives that “will work,” the higher voltage may throw your light meter out. These batteries work on my Minolta SRT and are rated to work with cameras such as Nikkormat F, Canon F1, Leica M5, Olympus OM-1, Pentax Spotmatic F, and Glossen Luna-Pro.  This may get expensive over time, so while it’s the best and quickest option, may not be ideal if you burn through batteries and plan to shoot film regularly.

Advanced Option: MR9 Adapter (and MR9 Voltage Reducer)

MR9 AdapterIf you go through batteries regularly and want to save money long term, it will require an investment up front in an MR9 Adapter. What is an MR9 Adapter? It is basically a housing for a battery that converts the size, so it will work where a PX625 fits. See the image on the right to get a better idea of what they look like. There are two types of MR9 Adapters, cheap ones (convert the size) and more expensive ones (convert the voltage).  Remember, a higher voltage may throw out the accuracy of your light meter. There is an even spread of people who claim no issue with 1.5V batteries and others who complain, so your mileage may vary.

MR9 Adapters (not a voltage reducer)
Your options here are either to get a cheaper non-voltage converter adapter (this one is US$10 on Amazon) and use it with a 1.5v LR44 battery,  although some people recommend using these 1.45v hearing aid batteries. Remember that this MR9 adapter is NOT a voltage reducer, and I can’t vouch that using a higher voltage won’t cause damage to vintage electronics that power your camera, flash, etc. Notwithstanding that, exposure and light readings may be wrong because the voltage is out.

Update: I did find this person who hand makes battery adapters, he sells them in 2 packs for ~US$13 delivered. The site looks old and low-fi, but various forums have shared positive experiences, and it works with cheap 1.55v Zinc Air hearing aid batteries. It’s not a voltage converter but ensures cheaper batteries “fit.”

MR9 Voltage Reducer Adapters
The more advanced way is to buy an MR9 Adapter that IS a voltage reducer, these cost around US$40 and are sold by C.R.I.S Cam. There’s also this KantoCamera version out of Japan, that sells for ¥2,762 (~US$20). The prices for both don’t include shipping, but they do pop up on eBay from time to time. These adapters will reduce 1.5V batteries to 1.35V so that you can use cheap and readily available SR43 (386) silver oxide batteries.

Cheap/Emergency Option: 675 Hearing Aid Battery + Spacer

I am reluctant to share this, given the caveats but if you’re in a crunch and need a solution, some people (haven’t done this myself!) suggest you use 675 Zinc-Air hearing-aid batteries, which are rated at 1.55v (less than US$1 a battery), and use a #9 Rubber O-Ring as a spacer. I have not done this, but I did find the suggestion buried deep in a forum somewhere and figured I should share, especially as hearing aid batteries can be bought anywhere in the world.  You need to do this because the 675 is smaller than the 625.

Note: If you’re doing this on a Minolta SRT, there is a non-conductive decal in the inside center of the SRT’s battery caps, which shows the proper battery orientation. That decal should be removed, so the smaller 675 battery makes contact. Larger 625 batteries make contact with the edges of the chamber cap on the outside of the decal, while the smaller 675 battery needs to contact the center area of the cap.

Final Tips

If you have no option but to use a 1.5V battery and are concerned about exposure issues, a simple workaround is to adjust the film speed set on the camera to compensate for the different metering results. This should not be an issue if you’re shooting film for prints. The success of 1.5V batteries, I think, depends on the age and reliability of your equipment and how well the vintage electronics have held up over the passage of time.

Hope this helps!

Important: I am not affiliated with any of the manufacturers, brands, services, or websites listed on this page and this is my personal experience.  If you find this helpful and want to say thanks, please buy me a coffee or take a look at my book on Amazon. It keeps this page ad-free. Thank you!

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