px625 replacement battery

How to Adapt a 675za Hearing aid Battery for use as a px625 replacement

The old 1.35v mercury px625 batteries are no longer available. There is a modern equivalent px625 replacement batery, made as far as I can tell exclusively by wein but they aren’t especially cheap. The advantage they do have is that they are the correct 1.35v. LR44 batteries can be used in the way I am about to describe but at 1.5+v they are often likely to throw the meter of your camera out. This can be corrected by applying exposure compensation, but that isn’t always a practical solution!

Adapting 675za for use as a 625

My solution to this problem, although also not 100% ideal is very cheap and provides the camera with a much closer voltage to that what is required. My Olympus 35rc appears to meter perfectly with these batteries, so if you have a camera that requires a px625 this might well be worth a go! I should add though, if you can justify the cash for a Wein cell, it is probably the best option … This is really just for the sometimes-miserly among us 🙂

It’s very simple, firstly, you want to get yourself a pack of 675ZA hearing aid batteries. Even from places like Boots they can be had for as little as £3 for a pack of six. That is in fact cheaper even than the very common LR44 batteries!

Make your self a little sausage of blu-tak, plasticine or in my case play doh (I have a 2 year old, this stuff come to hand easily) and wrap it round the very edge of the battery making sure it doesn’t intrude on the flat [+] end. Then simply place it in the battery cap.

Adapting 675za for use as a 625

Making sure none of your chosen malleable material is encroaching on the thread of the cap, screw it into the camera.

Job done, happy shooting!



(edit: since writing this I have discovered the MR-9 battery adapter)


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10 thoughts on “How to Adapt a 675za Hearing aid Battery for use as a px625 replacement”

  1. Pingback: The Olympus 35rc – yet another classic Oly

    1. Daniel VanDurmen

      I too use the 675ZA batteries and an o-ring for this and many other cameras. Yes, Wien cells fit without adapters and deliver the correct 1.5v under load (don’t try to measure without load, it will say 1.5v+), they last 6-10 months, versus 1-2 months for the ZAs, but I have so many cameras that I’d be swapping the Wien cells from camera to camera. The ZA cells are like 25¢ each and if I forget and leave one in a camera, no big deal, plus, I’ve never had a 675ZA leak.

  2. How’s about making a holder out of Sugru? This material can be moulded like bluetak, but sets into a permanent reusable shape. Here’s a link to the maker’s website, Sugru can be obtained direct, or from lots of suppliers including Amazon:


    Hope this helps :o)

  3. As an Olympus 35SP owner myself for some years, I have always used the Wein cells (available via eBay supplier for lower prices, including the shipping, than quoted above). I measure the service life of a battery in months.

    I am curious why there are so many many posts on the Internet on how to make substitutes for the Mercury PX625 batteries. If you consider camera cost, the lifetime cost of film, chemistry, etc.. that you will pay with this camera is it important to save a couple dollars/euros/pounds on a light meter battery?

    To contrast, in the last months I bought another classic that claimed to have a good PX625 battery in it. When I opened the battery compartment, I found a Chinese PX625 inside. Measuring this with my digital voltmeter, it was reading 1.55v. So not Mercury and not 1.35v either. The seller claimed the light meter was faulty and the camera was sold as-is. So I replaced this with a Wein cell and about 5-6 rolls of film later every shot perfectly exposed.

    I do admire the creativity of the alternate solutions proposed above but still ask why?

  4. It might be helpful just to mention that some cameras moved over to 1.5 volt cells while others persisted. The Nikon F2 Photomic and its derivatives all take the silver cells, the Nikkormat FT2 & 3 take the 1.5 volts and the Canon EF (1973-77) takes 2 PX 625 1.5 volt cells as it has an internal circuitry that allows it to work with 1.35 and 1.5 volt cells.

  5. Having started to use Leicaflex SL cameras and lenses, and having sold off my old Canon F1 & FTBn, I found myself once again facing the mercury PX625 battery issue. The 3 SL bodies all came with a PX625 alkaline 1.5v battery in them. Tests I had done before indicated that the slightly increased voltage indicated a stop of under exposure. With the Canons, I used to halve the ISO and found that this gave readings that matched my Gossen Lunalite (9v PP3 battery). I’m not tempted by the Wein cells. Lots of people report that when the battery goes flat, it oozes a nasty and highly corrosive fluid that buggers up the battery chamber and can permeate the inner recesses of the cameras. My God! Perhaps even the shutter itself might be at risk.

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