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 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 like new again.

Important: The New F-1 requires a completely different 6-V battery than the classic F-1 and F-1n. Which model you have and how they differ is explained in our Canon F-1 vs F-1n vs New F-1 comparison.

Why the old batteries are a problem

Many analog cameras used to run on mercury batteries. The genius of these was their extremely constant discharge voltage, which is why many light meters are precisely calibrated to them. Since mercury batteries are now banned and hardly available, you need a replacement that delivers exactly the same electrical output.

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 manufacturers)
• Small rubber O-ring as a spacer or 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

1. Open the cover: Simply unscrew the battery compartment cover at the bottom of the camera with a coin.

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

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

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

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

1. Observe polarity & insert: The positive side (plus) goes up — insert it, 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 with the protective tab on or in the original packaging.
• Remove the batteries if you won’t use the camera for a long time to avoid damage from leakage or aging.
• The rubber O-ring is often the simplest DIY solution; however, 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 take them to battery collection points in stores or your local recycling center.

Conclusion

For the Canon F‑1 (Classic), Type 675 batteries combined with an O-ring or adapter are a brilliant, affordable solution to replace the old mercury cells. They provide the correct voltage, protect the environment, and your light meter continues to work precisely.

Good luck with the battery change — and “good light”!

Your Vladi