Opening the case back is the first step, and it's usually the hardest part

Most pocket watches have a screw-off case back or a snap-off back. To find out which yours is, look at the back of the watch—if you see a thin seam all the way around with small notches or grooves, it's a screw-off. If the seam is smooth with no notches, it's a snap-off. The case back is where the battery sits, and you have to remove it to reach the battery compartment.

For a screw-off back, use a case opener tool (a flat metal tool with notches that fit into the grooves). Place the notches into the grooves on the case back and turn counterclockwise slowly—don't force it. If you don't have a case opener, a flathead screwdriver works in a pinch, but you risk scratching the back. For a snap-off back, slide a thin flathead screwdriver or a plastic pry tool into the seam and gently twist to pop it open. Work your way around the edge rather than prying hard at one spot.

Key Takeaways

  • Pocket watch batteries are usually small button cells (SR626, SR927, or similar) that cost between $3 and $8 and last one to three years depending on the watch model.
  • The case back is either screw-off (with notches) or snap-off (smooth seam), and you need the right tool to open it without damaging the watch.
  • When you remove the old battery, note which side was facing up—the positive side (marked with a + or flat side) must face the same direction when you insert the new one.
  • After inserting the new battery, test the watch before closing the case back to make sure it's working and the battery is making contact.

Identifying the battery type and size before you buy a replacement

Once the case back is open, you'll see the battery sitting in a small metal holder or compartment. The battery is a flat, round button cell with numbers and letters stamped on top. Write down this code exactly—it tells you the size and chemistry. Common pocket watch batteries are SR626 (1.55 volts, used in many vintage watches), SR927 (also 1.55 volts, slightly larger), and SR920 (1.55 volts, smaller). Some older watches use mercury batteries, which are no longer sold, so you may need an equivalent alkaline or silver-oxide replacement.

Take a photo of the battery code with your phone before you remove it, or write it down on a piece of paper. When you go to a pharmacy, jewelry store, or electronics shop, show them the code and they'll hand you the right replacement. Don't guess—putting the wrong size battery in can damage the watch mechanism or cause it to run fast or slow. A replacement battery costs $3 to $8 and usually comes in a small blister pack.

Removing the old battery without damaging the contacts

Look at how the battery sits in the compartment. Most pocket watches have two small metal tabs or springs that hold the battery in place. The battery rests against these contacts, and they complete the electrical circuit. Gently lift one edge of the battery with a plastic spoon, a plastic pry tool, or the edge of a plastic credit card—not a metal tool, which can scratch the contacts and break the circuit.

Lift slowly and let the battery tip out into your hand. If it's stuck, don't force it. A tiny drop of rubbing alcohol on the edge can help loosen it. Once the battery is out, look at the metal contacts inside the compartment. They should be shiny and clean. If they look dark, dull, or corroded, gently rub them with a clean, dry cotton swab or a soft cloth. Corrosion breaks the electrical connection and stops the watch from running, even with a fresh battery.

Installing the new battery in the correct direction

Before you insert the new battery, look at the old one again. One side is marked with a + (positive) and the other side is blank or marked with a − (negative). The positive side almost always faces up, toward the watch face, but check your old battery to be sure. If you install the new battery upside down, the watch won't run and you may damage the circuit board.

Slide the new battery into the compartment with the positive side facing the same direction as the old one. It should sit flat and rest against the metal contacts on both sides. You may hear or feel a small click as it settles into place. Don't force it—if it doesn't slide in smoothly, you may have the polarity backwards. Flip it and try again. Once it's in, gently press down on the top of the battery to make sure it's making firm contact with the upper contact.

Testing the watch before you close the case back

Before you screw or snap the case back on, hold the watch to your ear and listen for a ticking sound. If you hear it, the battery is working and making contact. If you don't hear anything, remove the battery and check the polarity again. Make sure the positive side is facing up. Also check that the metal contacts are clean and not bent. If a contact is bent away from where the battery sits, gently bend it back toward the battery with a plastic tool or the edge of a credit card.

If the watch still doesn't tick after you've checked the polarity and contacts, the battery may be dead (rare, but it happens), or there may be a problem with the watch itself. Try a different new battery from a different pack to rule out a defective battery. If the watch still doesn't work, the circuit board or the movement may need repair, and you should take it to a watch repair shop.

Closing the case back securely

Once the watch is ticking, you can close the case back. For a snap-off back, align the seam and press down firmly all the way around until you hear or feel a click. Start at one point and work your way around the edge, pressing evenly. The back should sit flush with the case—no gaps or wobbling.

For a screw-off back, place the case opener tool into the notches and turn clockwise slowly. Don't over-tighten—you want it snug, not stripped. A good rule is to turn until you feel resistance, then give it one more quarter turn. If you hear a grinding sound, stop when ready and back off. You may have cross-threaded the back, and forcing it will damage the threads. Back it out, line it up again, and try once more.

Common mistakes that stop the watch from running

The most common mistake is installing the battery upside down. The second most common is not cleaning the metal contacts before inserting the new battery. If the old battery leaked or corroded, the contacts will be dark or crusty, and they won't conduct electricity even with a fresh battery in place. A quick wipe with a dry cotton swab solves this.

Another mistake is forcing the case back open or closed. Pocket watches are delicate, and the case back threads or snap points can break if you use too much force. If the case back won't budge, soak the seam with a tiny drop of penetrating oil (like WD-40) and wait 10 minutes before trying again. If the snap-off back won't pop, try a different spot on the seam—sometimes one side is tighter than the other. And if you're using a case opener for a screw-off back, make sure the notches are fully seated in the grooves before you turn. Partial contact will slip and strip the grooves.

Frequently Asked Questions

How long does a pocket watch battery last?

Most pocket watch batteries last one to three years, depending on how often you wear the watch and whether the movement is quartz or mechanical. A watch you wear every day will drain the battery faster than one you wear once a week. If your battery dies much sooner than a year, the watch may have a short circuit or a corroded contact, and a repair shop can diagnose it.

Can I use any button cell battery, or does it have to be the exact model?

It has to be the exact model number stamped on the old battery. Different button cells have different voltages and sizes, and using the wrong one can make the watch run fast or slow, or damage the circuit board. The model number is small but always there—look closely at the top of the old battery before you throw it away.

What if the metal contacts are bent or corroded?

Gently bend a bent contact back toward the battery using a plastic tool or the edge of a credit card. For corrosion, rub the contact with a clean, dry cotton swab. If the corrosion is heavy or the contact is broken, the watch needs professional repair and you should take it to a watch repair shop.

Do I need special tools to open a pocket watch?

A case opener tool (about $5 to $10) makes opening a screw-off back much easier and safer. For a snap-off back, a thin flathead screwdriver or plastic pry tool works fine. You can also ask a jewelry store or watch repair shop to open it for you—many will do it for free or a small fee if you buy the battery from them.

What should I do with the old battery?

Button cell batteries contain small amounts of mercury or other metals and should not go in the trash. Take the old battery to a pharmacy, electronics store, or hazardous waste collection site. Many places that sell batteries will also take old ones back for recycling at no charge.