Canon F-1 (Classic): Changing the battery — PX625 alternative with Type 675 hearing aid batteries and O-ring adapter
Summary
The classic Canon F‑1 originally uses mercury batteries (PX625), which are no longer available. But don’t worry: a practical, eco-friendly, and affordable alternative are Type 675 zinc-air hearing aid batteries together with a small spacer (rubber O-ring) or a professional PX625 adapter. These provide a steady voltage close to 1.35 V and your light meter will work like on the first day again.
Why the old batteries are a problem
Many analogue cameras used to run on mercury batteries. The clever thing about them was their extremely constant discharge voltage, which is why many light meters are precisely calibrated to it. Since mercury batteries are now banned and hardly available, you need a replacement that delivers exactly the same electrically.
Why Type 675 (zinc-air) is a good choice
- The nominal voltage under load is about 1.35–1.4 V — very close to the old PX625/mercury voltage.
- Zinc-air batteries have a relatively flat discharge curve, keeping your light meter stable.
- They are completely mercury-free and much more environmentally friendly than the old PX types.
What you need
- Canon F‑1 (Classic) with intact battery compartment
- Type 675 zinc-air hearing aid battery (available from various makers)
- Small rubber O-ring as spacer or directly a suitable PX625 adapter
- Contact cleaner and possibly a small tool (coin to open, fine blade or screwdriver for cleaning)
Step-by-step: Changing the battery
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Open the cover: Simply unscrew the battery compartment cover at the bottom of the camera with a coin.
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Check and clean contacts: Old contacts are often a bit oxidised. If they look very dirty, gently brush them off with a small screwdriver or a fine blade and then wipe over with some contact cleaner.
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Remove old battery: Take out the old battery. Be sure to watch for residue or corrosion in the compartment.
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Activate zinc-air battery: These cells react with air. After you pull off the protective tab, the battery sometimes needs 1–2 minutes until the full voltage stabilises. So wait a moment before continuing.
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Attach spacer / O-ring: The Type 675 cells are a bit smaller than the original PX625 and would rattle in the compartment. Use a small rubber O-ring as a spacer: just slide it onto the battery so it fits snugly and makes contact.
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Observe polarity & insert: The positive side (plus) goes up — put it in, close the compartment and screw the cover back on tightly.
Practical tips
- If the light meter behaves oddly after installation, first check the contacts and the voltage of the new battery.
- Zinc-air batteries discharge faster if they are constantly exposed to air. Store unused cells best always with the protective tab or in the original packaging.
- Remove the batteries if you don’t use the camera for a long time to avoid damage from leaking or ageing.
- The rubber O-ring is often the simplest DIY solution; but there are also special PX625 adapters made of metal that are even more durable.
Safety and disposal
Even though zinc-air batteries contain no mercury, they do not belong in household waste. Please dispose of used cells properly — simply hand them in at battery collection points in stores or at your local collection centre.
Conclusion
For the Canon F‑1 (Classic), Type 675 batteries together with an O-ring or adapter are a brilliant, affordable solution to replace the old mercury cells. They provide the right voltage, protect the environment, and your light meter continues to work precisely.
Good luck with the change — and “good light”!
Your Vladi
