Alternative to PX625 battery

Pieter12 · Apr 19, 2025

I just became aware of the Varta V80H rechargeable NiMH battery. It delivers 1.2-1.3 volts. Would it be suitable as a replacement for the mercury PX625, rated at 1.35 volts? Has anyone used these?

pbromaghin · Apr 19, 2025

PX625 battery is 1.5 volts, so no.

The guy who converted my Minolta SRT-201 circuits put in a Vinnic L1560. It died and Google gives several equivalents. I just today I ordered this off Prime:

Amazon.com

ags2mikon · Apr 19, 2025

Why not just use the mr-9 adapter and use a 357 silver oxide battery? I'm using them in a lot of my old junk and they work fine.

Pieter12 · Apr 19, 2025

Both of those batteries are 1.5 volts. That won’t work for meters without recalibration. The PX625 is 1.35 volts, the V80 is closer at 1.2-1.3 volts. I am aware of the Wein zinc oxide batteries but they don’t last long.

pbromaghin · Apr 19, 2025

Oops. Senior moment. I both forgot and remembered that the conversion allowed mine to use 1.5 instead of 1.35. Never mind.

mshchem · Apr 19, 2025

I just switched to a non-meter prism on my F. Problem solved

4season · Apr 19, 2025

That NiMH cell might be worth a try, as NiMH maintains fairly constant voltage through much of it's discharge cycle.

But I was puzzled by how cameras designed for mercury batteries sometimes lacked any sort of on/off switch, save for the photocell itself. And one such camera in my collection (Konica S3) even has a "Mercury battery only" sticker. Curious, I queried Microsoft's AI, and it said that mercury batteries can "recover" somewhat, in a way that other battery types don't. And maybe that's the #1 reason why Konica didn't simply modify their meter to use 1.5 volt alkaline or silver batteries: Other battery types likely would need more frequent replacements, and customers would complain.

reddesert · Apr 20, 2025

I have not tried it so have no answer to the original question. It's not very expensive, considering, so interesting to try.

The genuine MR9 battery adapter contains a diode (probably a Schottky diode) to drop the 1.5v 357 battery to around 1.3v. The voltage drop would depend on current draw, but people who use these generally report good results.

Most of the original cameras using mercury batteries used a CdS photoresistor as the photosensitive element. These can have resistance of hundreds of kilo-ohms to several megohms in the dark. So depending on the meter circuit, if you stored your camera away with the lens cap on or in a dark environment, the current draw of the meter could be down to microamp levels, and the mercury battery would last a long time.

I think the cameras labeled "for mercury battery only" were related to the favorable discharge curve of the mercury battery (fairly constant voltage until it dies, unlike alkalines), under the assumption the average amateur user wasn't going to replace their batteries until obviously dead. Many cameras of that era didn't have a battery check indicator.

Paul Howell · Apr 20, 2025

I might give it a try, although 625 will be too large for my Konica ts which a take mercury 675 the zinc air 675 fits just fine. At the end of a shooting session I take the zinc air out and tape over the air holes. Topcon Uni also uses 675. Pentax Spotmatic does not matter much almost any battery will work. I have cardboard sleeves that I made for my Minolta 101 and 102 so I might try the rechargeable. One odd note, my Miranda EEs, the screw in battery compartment door is so tight I had to drill holes for the zinc air to breath.

KevinW · Apr 29, 2025

I have several of these that I use with 675 zinc-air hearing aid batteries:

PX625 PX-13 replacement Nikon F Leica, Gossen, Canon etc

A re-usable adapter for true PX625 PX-13 compatibility. Buy online with PayPal USPS Worldwide. 1000's sold worldwide est.2004, Nikon,Leica,Gossen and many more.

www.paulbg.com

It might seem like a lot of money for a 'washer' but they are a perfect fit. I use them in a Luna Pro light meter, a Luna Six 3 light meter, a Pen FT camera and a Yashica Mat 124G. They fit and work perfectly.

As an aside, I've had the zinc-air batteries last anywhere from 3 to 9 months (never less than 3 months in any device). They are pretty cheap to buy however, and they can be found literally everywhere (I've even seen them in larger gas station chain stores).

As another aside, here is an article from the March '95 issue of PopPhoto testing Mercury, Wein Cell and off the shelf Zinc-air hearing aid batteries. They found no more that one third of a stop difference between all three when using a Luna Pro light meter.

Disconnekt · May 3, 2025

Ive been using a MR-9 adapter with a 386 battery in my Sears TLS & its worked fine with it, the film negatives have come out fine.

2ndGenNikonian · May 12, 2025

Seconding the MR-9. I use it for my Spotmatic. It does sometimes get a little fiddly and require a re-seating in the chamber, but it works just fine otherwise.

Jbennett68 · Sep 16, 2025

I bought a pen FT recently off marketplace. There was an old PX 625 mercury battery that came with it. I figured there no way this battery is good but I put it in and boom. Meter is working. Months later and it’s still working.

ags2mikon · Sep 16, 2025

Mercury, the gift that keeps on giving.

wiltw · Sep 16, 2025

Jbennett68 said:
I bought a pen FT recently off marketplace. There was an old PX 625 mercury battery that came with it. I figured there no way this battery is good but I put it in and boom. Meter is working. Months later and it’s still working.

Help it...take it out if not using the camera!!!! And then get an MR-9 adapter, and use the mercury cell only as a 'gold standard' for comparison testing any other substitute against.

benderscameracorner · Sep 17, 2025

Jbennett68 said:
I bought a pen FT recently off marketplace. There was an old PX 625 mercury battery that came with it. I figured there no way this battery is good but I put it in and boom. Meter is working. Months later and it’s still working.

The mercury battery in my Nikomat FT is years - nay, decades old - and is still going strong and metering accurately. It'll be a sad day when it finally dies.
You can understand why camera manufacturers in the 60s and 70s spec'd them instead of alkaline/silver oxide batteries until they were basically forced to.

Chan Tran · Sep 17, 2025

benderscameracorner said:
The mercury battery in my Nikomat FT is years - nay, decades old - and is still going strong and metering accurately. It'll be a sad day when it finally dies.
You can understand why camera manufacturers in the 60s and 70s spec'd them instead of alkaline/silver oxide batteries until they were basically forced to.

Back then they could't design a metering circuit that doesn't depend on steady battery voltage. In the late 70's when they switched to silicon cell camera meters would read the same from 3V down to 2.5V or so.

wiltw · Sep 17, 2025

Chan Tran said:
Back then they could't design a metering circuit that doesn't depend on steady battery voltage. In the late 70's when they switched to silicon cell camera meters would read the same from 3V down to 2.5V or so.

Wheatstone Bridge circuits were never Voltage dependent, they operated comparing Resistance values.
And the CdS cell used at the time are resistive devices with resistance changes in proportion to the amount of visible light. In fact, in my senior year in high school, my project for Physics class illustrated Wheatstone Bridge principle in action in a lightlevel-dependent circuit using CdS (Silicon Blue had not yet been invented!).

Why a 'constant' Voltage circuit was employed instead I have no particular insight. Perhaps someone else might elaborate.

Saganich · Sep 17, 2025

I use MR9 with silver oxide 1.55 battery in Rollei 35T. Matches my spot meter and lasts a while if I keep camera in case. The Varta V80H rechargeable reportedly works fine... but how do you recharge them??

Alternative to PX625 battery

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