Olympus OM-1 Battery - Mercury Battery Replacement Options

The Olympus OM-1 used a 1.35V MR-9 mercury battery, which is no longer available. Since the camera’s release in 1972, the batteries have been banned. They are are no longer being manufactured due to mercury damaging the environment.

There are replacement batteries available for the OM-1. WeinCELL MRB625 and alkaline 625A are the most popular mercury battery replacement types.

Modifications with a shotkey diode can also be done. This will alter the voltage from the battery and allow the camera to meter light correctly.

From the Olympus OM-1 Manual
From the Olympus OM-1 Manual

The original battery for the Olympus OM-1 was a 1.35V mercury battery, specifically the MR-9 (H-D, PX13, PX625). However, these batteries are no longer produced due to negative environmental impact from containing mercury.

Replacement Battery Alternatives:

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  1. Zinc-air batteries: The WeinCELL MRB625 is a zinc-air hearing aid battery. it produces the same voltage as the original mercury battery. This makes it an excellent drop-in replacement. They can be found on Amazon.
  2. Alkaline batteries: These batteries are easily available but deliver 1.5V instead of the original 1.35V. This difference may cause your light meter to give false readings. 625A batteries are available on Amazon.
  3. Silver oxide batteries: Like alkaline batteries, they also provide 1.5V, but they have a more stable voltage output over their lifespan. 303/357/76 batteries are available on Amazon.
Battery Type Voltage Stability Availability
Zinc-air 1.35V High Limited
Alkaline 1.5V Moderate High
Silver oxide 1.5V High High
  • Preserve accurate metering: By ensuring that the voltage reaching your camera’s metering system is 1.35V, it replicates the conditions under which the OM-1 was originally designed to operate.
  • Are widely compatible: They can be used with any camera or device that originally used an MR-9/PX625 battery.
  • Protect the environment: Silver oxide batteries are less harmful to the environment than the mercury cells that were originally used.

An MR-9 battery converter is a smart and efficient solution for Olympus OM-1 users. It allows the use of modern 386/SR43W silver oxide batteries (which output 1.55V) to replace the original 1.35V MR-9 mercury battery while retaining accurate meter readings.

The MR-9 battery adapter is a small metal shell that fits over the silver oxide battery, reducing its size to match the original MR-9 battery and introducing a built-in voltage reducer. This voltage reducer ensures that the battery outputs the correct 1.35V voltage required by the camera’s light meter.

eBay is the best place to find MR-9 adapters. They can be expensive and will likely be shipped from Japan.

While the Olympus OM-1 was initially designed for a 1.35V mercury battery, it’s possible to modify the camera to meter accurately with a 1.5V battery, such as the more readily available alkaline or silver oxide variants.

Battery choice will not affect the shutter speed of the camera.

A simple trick that doesn’t involve altering the camera is to adjust the ISO setting on the camera to compensate for the increased voltage. This method doesn’t require modifying the camera.

The process is as follows:

  1. Determine the adjustment: Typically, you need to set the camera’s ISO setting a third of a stop lower than the film’s actual speed. For example, if you’re using ISO 200 film, you would set the camera to ISO 160.
  2. Shoot and develop: Shoot your photos and develop the film. Check the results to see if the exposure is correct. You might need to adjust the ISO setting slightly based on the results.

Please note that this method may not be perfect, as it doesn’t account for the discharge curve differences between battery types.

Another method is to modify the internal circuit of the camera. This method should be done by someone experienced with camera repair or electronics, as it involves working with small parts and requires soldering. Here’s a general idea of the process:

  1. Open the bottom of the camera: Remove the screws and take off the bottom plate.
  2. Locate the battery wire: You’ll find a wire running from the battery compartment to the camera circuitry.
  3. Insert a Schottky diode: By soldering a Schottky diode (which has a voltage drop of about 0.15V) into the circuit, the 1.5V battery will effectively be reduced to 1.35V.
  4. Close the camera: Reattach the bottom plate and test the camera to ensure it’s working correctly.

Keep in mind that this modification permanently changes the camera and could affect its value or cause damage if not done correctly. Always consult with a professional if you’re unsure about making these modifications yourself.

The Olympus OM-1 is primarily a mechanical camera, which means that the camera’s core functionality – namely, its ability to take pictures – operates entirely mechanically and thus, can work without a battery. However, the battery is needed for the light meter to work.

  • Mechanical operation: The OM-1’s shutter, aperture settings, and film advance are all mechanical and do not require battery power.
  • Light meter: The battery powers the camera’s light meter, a tool that measures the light in a scene to help you choose appropriate settings for optimal exposure.

While the camera will work without a battery, taking properly exposed photographs without the built-in light meter could be challenging, especially for beginners or those not well-versed in manual exposure photography.

Checking the battery life in an Olympus OM-1 is a simple task. You can use the battery check button on the front of the camera, to the right of the lens. When you press this button, the needle in the viewfinder should move to the “BC” mark if the battery is good. If the needle doesn’t move to the “BC” mark, it’s time to replace your battery.

Corrosion of batteries can be a common issue in vintage cameras like the Olympus OM-1. Luckily, distilled white vinegar can be used to clean this corrosion. Here’s how:

  1. Remove the corroded battery: Be careful not to let the corrosion get on your skin or eyes.
  2. Apply the vinegar: Use a cotton swab or a small brush to apply the vinegar to the corroded parts. The vinegar will neutralize the battery salts, making them safe to remove.
  3. Scrub gently: After letting it sit for a few minutes, gently scrub the area to remove the corrosion. You may need to repeat

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