Look, G-Shocks are tanks. You bought one because you wanted a watch that could survive a drop from a building or a dip in the ocean without flinching. But eventually, that rugged digital display starts to fade. Maybe the backlight flickers and dies when you press the button, or the "Recover" (RECV) indicator starts haunting your screen. It’s annoying. You think about taking it to a jeweler, but then you realize they’ll probably charge you thirty bucks for a five-minute job.
So you decide to do it yourself.
Changing the battery is actually pretty straightforward, but if you mess up the reassembly, you lose the one thing that makes a G-Shock a G-Shock: the 200-meter water resistance. Honestly, most people who try to change battery on G Shock units end up pinching the O-ring or forgetting the AC reset. If you don't do the reset, the watch might just stay "dead" even with a fresh cell inside. It's a heart-stopping moment when you think you've fried your favorite Mudmaster or DW5600, but usually, it's just a sequence error.
The Stuff You Actually Need (Don't Wing This)
Don't use a kitchen knife. Seriously. I’ve seen so many mangled case backs because someone tried to pry things open with a butter knife or a flathead screwdriver that was way too big. You’re working with tiny, precision screws.
You need a PH00 Phillips head screwdriver. A set of plastic tweezers is also a lifesaver—metal ones can short out the battery if you grab it across the positive and negative poles. If you only have metal tweezers, just be careful to only touch the sides. You also need a bit of silicone grease. Not WD-40. Not olive oil. Pure silicone grease is what keeps that rubber gasket supple so water stays out of the circuitry.
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And the battery? Most classic "square" G-Shocks like the DW5600 take a CR2016. The beefier, solar-powered models use a CTL1616 rechargeable cell. Check your specific case back before you buy anything. It's engraved right there in the steel.
Cracking the Case Without Total Destruction
Start by laying the watch face down on a soft cloth. You don't want to scratch the crystal while you're wrestling with the back. If your model has the resin "protector" or the straps curve inward over the screws, you might have to pop the spring bars out first. It’s a bit of a pain, but trying to work around the straps usually leads to a stripped screw.
Unscrew the four corner screws. Do it in a cross pattern, like you're changing a tire on a car. This keeps the pressure even. Once the steel plate is off, you’ll see a rubber spacer. Lift it gently. Underneath is the white plastic movement cover and the battery itself, usually tucked under a metal tension clip.
The Great G-Shock Reset Secret
This is where everyone gets stuck. You swap the battery, put the back on, and... nothing. The screen is blank. You panic.
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Every Casio module needs an AC (All Clear) reset after a power swap. Look for a tiny hole on the back of the module labeled "AC." You need to take your tweezers or a paperclip and bridge the contact inside that hole to the top of the battery (the positive side). Hold it for two seconds. You’ll see the digital display spring to life. If you skip this, the microprocessor might stay in a "locked" state, or the internal logic will be so glitched that the buttons won't work.
Protecting the Seal or Saying Goodbye to Waterproofing
The gasket is a thin, black rubber ring. It might stay in the groove of the case or stick to the metal backplate. Pick it up. Clean it with a lint-free cloth. If it looks cracked or flat, replace it. If it looks okay, coat it in a tiny, tiny amount of silicone grease. You want it to look shiny, not goopy.
Place the gasket back into its channel perfectly. If even a hair-thin part of that ring is out of place when you screw the back down, the watch will leak the next time you wash your hands. It’s that sensitive.
Dealing with Solar Models (Tough Solar)
If you're trying to change battery on G Shock models that feature Tough Solar technology, stop for a second. These don't use standard lithium batteries. They use specialized secondary cells (usually the CTL1616 or ML2016). They are significantly more expensive—often $15 to $25 compared to a $2 standard cell.
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Common mistake: putting a regular CR1616 into a solar watch.
Don't do it.
The watch's charging system will try to push a current into a non-rechargeable battery, which can cause it to leak or explode inside the module. If your solar G-Shock isn't holding a charge, sometimes it just needs three days on a sunny windowsill rather than a new battery. These cells are designed to last 10-15 years.
The Finishing Touches
When you put the metal backplate back on, make sure it’s oriented correctly. Most Casio plates have a "top" and "bottom" indicated by the text direction. Screw the four screws back in, again using that cross pattern. Tighten them until they are snug, but don't crank them down with all your might. You're screwing steel into a resin (plastic) case. If you over-tighten, you will strip the threads in the plastic, and then the watch is basically garbage because it will never seal again.
Once it's closed up, check the functions.
- Does the light work?
- Does the beep sound when you switch modes?
- Is the time actually advancing?
If the alarm doesn't beep, you probably lost the tiny "alarm spring." It's a microscopic gold-colored spring that sits in a hole in the module and touches the backplate. If it falls out while the case is open, your watch goes silent. If that happens, you’ll have to find it on the floor (good luck) or fashion a replacement from a tiny piece of conductive wire.
Actionable Steps for a Successful Swap
To ensure your G-Shock survives the operation, follow this workflow:
- Verify your battery type: Look at the four-digit module number inside the box on the case back and Google the manual to confirm the battery code (e.g., CR2016, CR1220).
- Clean your workspace: Dust is the enemy of digital modules. Work on a clean, light-colored surface so you don't lose the tiny screws or the alarm spring.
- Perform the AC Reset: Use a metal tool to bridge the AC contact to the battery (+) for two seconds. This is non-negotiable for 90% of Casio models.
- Lubricate the Gasket: Use pure silicone grease to maintain the water seal. If the gasket is stretched out, buy a new one specifically for your model number.
- Test the Alarm: Before you tighten the screws all the way, trigger the alarm or the hourly chime to make sure the spring is making contact with the piezo element on the backplate.
By taking these steps, you maintain the integrity of the watch without paying the "jewelry store tax." Just be patient with the tiny parts, and remember that the AC reset is the most common fix for a watch that seems dead after a battery change.