A dead Timex battery is one of the few watch repairs that most owners can safely complete at home with basic tools and about ten minutes of time. The process involves opening the case back, identifying the correct battery cell, swapping it without touching the battery’s contact surfaces, and closing the case with proper gasket care. The full procedure costs roughly $3–$8 in parts versus $15–$45 at a retail watch counter, and the risk is manageable if you stop at the first sign of resistance.
This guide covers the tools, the case-back identification, the step-by-step swap, and the verification checks that confirm the job was done correctly. It also includes the common failure points that turn a simple battery change into a trip to a repair bench.
What You Need Before Opening the Case
Timex produces watches across three broad categories, and each requires a different opening approach:
| Case-Back Type | Typical Timex Models | Opening Tool |
|---|---|---|
| Snap-off (pressure-fit) | Expedition, Weekender, most analog quartz | Case knife or thin blade |
| Screw-down | Some Waterbury and higher-end models | Case-back wrench or adjustable spanner |
| Battery hatch (small screw) | Select digital and older models | Small Phillips screwdriver |
Tools that should not be used: flat-blade screwdrivers, kitchen knives, or any improvised prying tool. These slip easily and will gouge the case back, damage the gasket channel, or slice the gasket itself — any of which compromises water resistance permanently.
A proper kit includes a case opener with multiple blade profiles, a case holder or cushion to keep the watch from sliding, and a pair of non-magnetic tweezers. The Timex Men’s Expedition Scout 40mm Watch – Black Case Cream Dial with Green Fabric Strap and similar Expedition models use a standard snap-back that responds well to a case knife.
Gasket inspection is not optional. If the rubber gasket inside the case back is cracked, flattened, or dry, the watch will lose whatever water resistance it originally had. A fresh gasket costs under $2 and should be replaced whenever the case is opened — this is the single most common skipped step that leads to moisture damage later.
Identifying the Correct Battery Before You Buy
The battery code is not printed on the case back. It is printed on the movement itself, which means you must open the case to see it — or you can look up the movement caliber by your watch’s model number.
Timex movements commonly use the following button cells:
- SR626SW / 377 — used in many Expedition and Weekender analog models
- SR621SW / 364 — found in smaller ladies’ and slim dress models
- CR2016 / CR2025 — used in select digital and chronograph models
The 377 and 364 are silver-oxide cells with identical dimensions to their alkaline counterparts (LR626 and LR621) but flatter discharge curves, which keeps the watch running at consistent voltage until the battery is nearly exhausted. Silver-oxide is the correct choice for a Timex quartz movement; alkaline equivalents cost less but die sooner and can leak.
If the movement has no visible battery code, note the caliber number (usually stamped near the battery holder, e.g., “M24” or “PC32A”) and search for a battery cross-reference chart. Ordering a battery by case-back model number alone is unreliable — the same case can ship with different movements across production years.
Step-by-Step: Replacing the Battery in a Snap-Back Timex
Snap-back cases account for the majority of Timex quartz models, so this is the procedure most owners will use.
Step 1: Prepare the Work Area
Place the watch face-down on a soft cloth or watch cushion. Position a bright light source at an angle so you can see the seam between the case back and the case. A magnifying lamp or loupe helps spot the small notch where the case knife inserts.
Step 2: Open the Case Back
Insert the case knife blade into the notch between the case back and the case lug. Apply firm, steady pressure downward and twist slightly. The back should pop free with a distinct click. If it does not release after moderate pressure, stop — the watch may have a screw-down back that looks like a snap-back, or the gasket may have bonded to the case channel.
Early checkpoint: If the back resists, do not force it. Forcing a snap-back with a knife is the most common cause of scratched case backs and damaged gasket channels.
Step 3: Remove the Old Battery
Identify the battery clamp — a small metal spring or bracket holding the cell in place. Use a toothpick or plastic pry tool to lift the clamp gently, then tilt the battery out with non-magnetic tweezers. Do not use metal tweezers to touch both the battery and the movement simultaneously; this can short the circuit.
Note the battery code printed on the cell before discarding it. Cross-reference this against the movement stamp to confirm you have the right replacement.
Step 4: Install the New Battery
Inspect the new cell for any visible defects. Handle it only by its edges — skin oils on the contact surfaces accelerate corrosion and can cause intermittent contact later. Drop the battery into the holder with the positive (+) side facing up, matching the orientation of the old cell. Press the clamp back into place so the battery sits firmly with no play.
Verification checkpoint: Before closing the case, check that the battery does not move when you gently tap the movement. A loose battery will cause the watch to stop intermittently even though the cell is fresh.
Step 5: Close the Case
Clean the gasket channel with a lint-free cloth. If the old gasket shows any sign of compression loss, replace it. Seat the gasket evenly in the channel, then align the case back with the case. Press down firmly around the entire circumference — do not press on one side only, as this can pinch the gasket and create a gap.
You should hear a second click when the back seats fully. Run a fingernail around the seam; if you feel any lip or raised edge, the back is not fully seated.
Step 6: Verify the Watch Runs
Pull the crown out to the time-setting position and set the time, then push the crown back in. If the watch has a hacking movement, the seconds hand should stop when the crown is pulled and resume when it is pushed back.
Success check: The watch should run continuously for at least 24 hours after the swap. If it stops within that window, the battery is likely loose, the movement may have been damaged during opening, or the battery code was incorrect for the movement.
Screw-Down and Battery-Hatch Models
Screw-down case backs require a case-back wrench with adjustable pins. Place the pins in the notches or slots on the back, turn counterclockwise, and lift the back straight off. These backs are less common on Timex quartz models but appear on some Waterbury and dive-style watches. The same battery identification and handling rules apply.
Battery hatch models use a small screw on the case back that opens a dedicated battery compartment. These are the easiest to service — no gasket channel to manage, and the battery is exposed directly. The tradeoff is that hatch models are rarely water-resistant beyond splashes.
When to Stop and Call a Professional
The DIY path stops being the right choice at specific, identifiable points:
- The case back will not open after reasonable effort. A bonded gasket or corroded seam requires professional tools and technique.
- The movement shows visible corrosion or white residue around the battery holder. This indicates a leaked battery, and the movement may need cleaning or replacement.
- The watch runs briefly then stops. This suggests a movement fault, not a battery issue.
- The watch was advertised as water-resistant to 50 meters or more and you cannot replace the gasket with a correct-size part. A compromised gasket on a water-resistant watch is a moisture-damage incident waiting to happen.
A professional battery replacement typically costs $15–$45, which includes a new gasket and pressure testing. For a watch with sentimental value or meaningful water resistance, that cost is justified insurance.
Common Mistakes That Make the Job Fail
Mistake 1: Touching the battery contacts. Skin oils on the cell’s contact surfaces create high-resistance points that cause the watch to stop intermittently, even with a fresh battery.
Mistake 2: Skipping the gasket check. A gasket that looks fine but has lost its elasticity will not seal. The watch may pass a quick water test and fail weeks later when temperature changes cause the case to flex.
Mistake 3: Using the wrong battery code. The 377 and 364 are physically identical in diameter but differ in thickness. Installing the wrong one either leaves the battery loose (intermittent contact) or forces the clamp to over-compress (movement stress).
Mistake 4: Closing the case without verifying the battery is seated. The watch may run initially and stop when the crown is adjusted or the watch is worn. This is the most common “failed” battery replacement that is actually a seating problem.
Mistake 5: Forcing a snap-back that is actually screw-down. Some Timex models use a screw-down back with a very shallow seam that resembles a snap-back. Forcing it with a knife damages the case back and the gasket channel.
Frequently Asked Questions
How long should a Timex battery last?
Most Timex quartz movements run 2–4 years on a fresh silver-oxide battery, depending on features like chronograph functions and backlight usage. Indiglo models draw more current and may need replacement closer to the 2-year mark.
Can I use an alkaline battery instead of silver-oxide?
Alkaline cells with the same code (e.g., LR626 instead of SR626SW) will physically fit and run the watch, but they have a shorter lifespan and a declining voltage curve that can cause the watch to run slow before the battery is fully dead. Silver-oxide is the correct choice for consistent timekeeping.
Will opening the case void my Timex warranty?
Timex’s warranty covers manufacturing defects, not battery replacement. Opening the case does not void the warranty for covered defects, but damage caused during the battery change — scratches, broken gaskets, damaged movements — is not covered.
How do I know if my Timex is water-resistant after a battery change?
Unless the gasket was replaced and the case was pressure-tested, assume the watch has no meaningful water resistance. A watch rated to 30 meters before the battery change may still handle hand-washing, but submersion is a risk without a proper seal verification.
The We Know Watches editorial team brings together over 40 years of combined watch collecting, trading, and repair experience. Our editors have owned and handled watches from every major brand — from entry-level Seiko 5s to Rolex, Omega, Patek Philippe, and independent Swiss watchmakers. We’ve bought and sold at auction, worked with authorized dealers, visited manufacturing facilities in Switzerland and Japan, and serviced hundreds of movements ranging from the Seiko 7S26 to the Longines L888. Every guide and review we publish is based on hands-on experience, original research, and consultation with professional watchmakers. We do not accept payment for reviews, and we clearly disclose when we use affiliate links.