Canon F-1 (Classic): Changing the battery, PX625 alternative with Type 675 hearing aid batteries and an 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, environmentally friendly, and affordable alternative is Type 675 zinc-air hearing aid batteries together with a small spacer (rubber O-ring) or a professional PX625 adapter. These provide a constant voltage close to 1.35 V, and your light meter will work again just like it did on the first day.

Disclaimer: We sell some of the products linked here ourselves.

Important: The New F-1 requires a completely different 6 V battery than the classic F-1 and F-1n. Our Canon F-1 vs F-1n vs New F-1 comparison explains which model you have and how they differ.

Why the old batteries are a problem

Many film cameras used to run on mercury batteries. Their ingenious feature was their extremely constant discharge voltage, which is why many light meters are calibrated precisely for them. Since mercury batteries are now banned and hardly available, you need a replacement that delivers exactly the same electrical characteristics.

Why Type 675 (zinc-air) is a good choice

• The nominal voltage under load is around 1.35–1.4 V, which is 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 significantly more environmentally friendly than the old PX types.

What you need

• Canon F‑1 (Classic) with an intact battery compartment
• Type 675 zinc-air hearing aid battery (available from various manufacturers)
• Small rubber O-ring as a spacer or a suitable PX625 adapter
• Contact cleaner and, if necessary, a small tool (a coin to open it, a fine blade or screwdriver for cleaning)

Step by step: Replacing the battery

1. Open the cover: Simply use a coin to unscrew the battery compartment cover on the bottom of the camera.

1. Check and clean the contacts: Old contacts are often somewhat oxidized. If they look heavily soiled, carefully brush them with a small screwdriver or fine blade, then apply some contact cleaner.

1. Remove the old battery: Take out the old battery. Be sure to check the compartment for any residue or corrosion.

1. Activate the zinc-air battery: These cells react with air. After removing the protective tab, the battery sometimes needs 1–2 minutes to reach a stable full voltage. So wait a moment before continuing.

1. Attach the spacer / O-ring: The Type 675 cells are slightly smaller than the original PX625 and would move around in the compartment. Use a small rubber O-ring as a spacer: Simply slide it onto the battery so it sits securely and makes contact.

1. Observe polarity and insert the battery: The positive side (plus) goes facing upward. Insert it, close the compartment, and screw the cover back on securely.

Practical tips

• If the light meter behaves strangely after installation, first check the contacts and the voltage of the new battery.
• Zinc-air batteries discharge more quickly when they are continuously exposed to air. It is best to store unused cells with the protective tab on or in their original packaging.
• Remove the batteries if you will not be using the camera for a longer period to prevent damage from leakage or aging.
• 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

Although zinc-air batteries do not contain mercury, they do not belong in household waste. Please dispose of used cells properly by returning them to a battery collection point at a retailer or your local collection facility.

Conclusion

For the Canon F‑1 (Classic), Type 675 batteries together with an O-ring or adapter are a brilliant, affordable solution for replacing the old mercury cells. They provide the correct voltage, are better for the environment, and allow your light meter to continue working accurately.

Good luck with the replacement, and “good light”!

Yours, Vladi