How to Change a Watch Battery

Determine the Battery Type

To change a watch battery, first determine what type of battery you need.

• In many modern watches, the type of battery is often engraved directly on the rear cover or case back. Look for three digits starting with “3,” such as 371 or 395. There may also be a string of four to seven letters and numbers beginning with “SR,” “LR,” or “CR.”
• If there’s no engraving, look for the model number. With that information, a quick internet search should turn up the required battery type.
• If you don’t know the model number or can’t find the battery information on the internet, the dead battery will have the model number in it.

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Open the Watch

Before I begin working with my watch face down, I place a piece of painter’s tape over the face to prevent scratches. Additionally, I lay a dark colored towel or T-shirt under the watch to make small metal parts more visible. And I wear nitrile or laytex gloves before touching anything inside the movement.

The case back of a watch can be attached several ways. Most Casio, Timex and other readily available watch brands use a screw-down or pressure-fit back.

• Screw-down backs are easy to remove with a #0 or #0-2 Phillips head screwdriver. Just loosen the four corner screws.
• Pressure fit backs, however, have no screws or indentations. Look for an inconspicuous tab to pry the case back off.

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When you find the case back tab, slide the blade of your pocket knife underneath it and twist your wrist to pry the case back off the watch. I’ve used other tools for this, like a mini flathead screwdriver, but I find that the fine blade edge of a quality pocket knife most effective.

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Replace the Battery

Gently open the watch case back and view the battery.

Some watches may have a plastic spacer and/or rubber gasket that must be gently removed to see the battery. These are not all symmetrically shaped. To ensure you reinstall them properly, note how they sit inside the watch. Take a photo for a visual reminder.

• Using a plastic tweezers or gloved hand, remove the dead battery, noting the side that faces upward.
• Insert the replacement battery into the cavity so it’s situated the same way as the battery you removed.
• Before replacing the back and any gaskets or spacers, peak under the painter’s tape or listen to the movement to verify the watch is working again.

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Reassemble the Watch

Replace the gasket and/or spacer in the same manner as you found it initially. If your watch has a screw-on back, secure with the four Phillips head screws in each corner.

For pressure-fit backs, this task is more difficult.

• Fold your cloth over so you have two or three layers under the watch face.
• Use any text written on the back, or battery indentation on the inside of the case back, to align it on the watch.
• Press the watch case back against the table (and cloth) with your thumbs until you hear a faint snap. If you’re having trouble, use something cylindrical roughly the same size as the case back, like a wooden dowel or quality flashlight, to apply more even pressure until it snaps into place.

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