Sjors created a terrific G-Shock battery replacement video and guide. However, I have some tips that I've discovered on my own, that I'd like to share with you to help deal with any problems that you might encounter in the process.
- Sharp metal tweezers
- Micro Philips head screw driver, watch wrench, or thin rubber mat depending upon watch type
- Micro flat head screw driver
- Plastic tweezers for handling batteries
- A set of quality micro screwdrivers
- Blue painter's masking tape
- Wristband spring pin removal tool
- A soft smooth mat for doing work upon
- A magnifying glass for inspection purposes
- A small positionable desk lamp or flash light
- A small mirror to check the LCD without turning it over
* Battery replacement always requires removal of the back plate. It with be either a metal plate held on with 4 screws, or a large metal disc (screw-back) that screws into the casing.
* If your watch has 4 screws, they will be the kind that can accommodate a Philips head or flat head screw driver. I find the Philips head is easier to use, as it's harder to slip when turning the screws. With either type, make sure you use the right size screw driver to prevent accidentally stripping screws. If you plan on owning several G-Shocks, I can't recommend enough that you buy a good set of micro screw drivers. Do not buy a cheap set, as they tend to wear down and may cause screws to strip.
* If your watch has a circular metal disc backing, you will need a special 3 prong wrench tool to remove it. But if your backing has been removed before, it may be possible to remove it with a swatch of grippy rubber (the previous removal would have broken the rigid tightness that happens naturally over many years). Before using the wrench, it's a good idea to put pieces of blue painter's masking tape over the notches, then use a small screwdriver to break the tape over the notches. This will help minimize inadvertent scratches.
* Band removal: Some G-Shocks have wristbands that do not obstruct the case back. If you've got one, you'll be spared the tedious task of taking off the bands. Some models will allow you to stretch back the bands just enough to let the case back edges sneak past the band edge. Others are not so forgiving (like screw-backs) and the bands must be removed. However, you can sometimes find that only one band needs to be taken off (like the G-2000).
* Remove the back plate, either by removing the 4 screws or screw-back. I like to remove the screws diagonally from each other in consecutive order, rather than doing one side and the next.
* After the backing is removed, you will have one or two more layers to remove. If two, the topmost one will be a plastic disc. It has gaps and holes in it for the alarm spring and or/clips that are asymmetrical, so you can't get mixed up on how to put it back in. Still, make note of it just for reference. All G-Shocks have a rubber mat that directly covers over the module. It also has gaps and a hole in it for the alarm spring. Also, one side has raised bumps that always face the back plate.
* Sometimes the case gasket will remain in place after removal of the back, but sometimes it will lift off when you pull up the backing. You will have to put it back in place upon reassembly, which shouldn't be a problem, but there are some things to be aware of. I'll be mentioning those later on.
* On 4 screw plate G-Shocks, the module will have a tiny spring on it. This makes contact with the piezo speaker on the case back, which is activated when the alarm goes off or when changing modes. On screw-back cases, there is no alarm spring but instead metal "prongs" that touch the piezo speaker. The prongs are fixed in place, but the spring can come loose. Just try not to touch it if you can. If by some horrible chance you snag it, pop it off, and then it falls into a floor crevace or drain of a sink, there is some hope. I've not yet done it, but I've heard you can pull apart a spring-bar (the pins that hold on watch bands) and extract the spring inside as a substitute. But, it's no easy task (I tried one that was broken on one side), so it's best not to have to resort to this. And last time I checked, Casio does not sell this spring separately.
* Removal of the battery requires unlatching a metal clip that holds it in place. Your best bet is to use fine pointed tweezers to detach it. Sjors took a painstaking effort to describe it in detail, and even drew some diagrams, so it's best to refer to his write-up. On some watches, the clasp is anchored to the module and detatches only on one side. However, some lift completely off. On those, you'll need to remember the orientation of the clip where one end has a small metal piece sticking out.
* Replacement of the battery is obviously the reverse of removal, however you won't need tweezers to put the clip back in place. It is designed so that if you press down on it, it should snap into place. If you can't get it to latch with your finger, use a small flat head screwdriver to assist you. If you mistakenly try installing it in backwards, it won't latch (that's your clue).
* If you look carefully at the back of the module, you will see an "AC" label etched into the metal. It stands for "All Clear". Nearby the "AC" will be a small gold colored disc. When you touch metal tweezers to the AC contact and the battery, it will perform a reset on the module. Why do this? Sometimes when installing a new battery, the module will get some bad data in it that will make the module perform strangely or not at all. I've seen some that will behave as if the battery was dead. Activating the AC will usually get the module working again. On some older G-Shocks it does not always work the first time. I've seen some take several tries until the module comes back to life. And only once, where the module never came back to life... but it was a very old watch. The AC is not at all harmful to the module. If you have a telememo/data bank watch, I do not know if the data is retained for some period of time between battery changes. If it is, the AC will probably clear it. Refer to your module instructions for more details.
* Install the rubber mat (and plastic disc, if one was removed) back in place.
* If the gasket lifted up out of the case when you removed the case back, it'll be best to coat it with silicon grease before installing. You don't have to use "watch specific" grease. Anything designed for O-rings will do (I use Magic Lube II, for pool pump gaskets). If the gasket remained in place, check to see if it dried out. If you do plan to submerge your watch at any future point, I highly recommend removing the gasket and lubricating it. Otherwise, leave it as-is.
* Reinstall the case back. The screw-back requires gentle placement on the threads and a light turning motion (clockwise) to catch the threads. Be gentle and don't force it, as you don't want to risk stripping the threads. A wide rubber band is helpful for getting a good grip on the smooth surface. Once it feels like the threads are caught properly, finger tighten the backing and then follow-up with the wrench for final tightening. Do not try making it as tight as you can possibly get it, because in the future you'll have to do another battery change. If it's too tight, it could become locked in place enough to risk stripping the grip points on the case back when trying to open it. And in reality, the seal will be good enough for most purposes. If you dive with your watch, then go ahead and tighten it as much as you feel necessary, but be careful. With the screws, you'll want to be careful not to get them threaded on an improper angle, because you'll partially strip the threads inside the case (little black fragments on the screw threads are a sign of this). I like to initially turn them counter-clockwise until seated straight, then gently screw in clockwise. Again, do it gently. Don't tighten them all the way at first. Put the screws in following diagonal sequential order, while pressing on the case back with your thumb to ensure it stays in place and flush to the case. Once the screws are all in place, then follow-up with tightening. Do not tighten as hard as possible, just until the screws are snug.
* The part I don't enjoy is installing bands, because of the difficulty in getting the spring pins back into place. Some bands are soft enough to flex sufficiently for the spring pins to snap effortlessly in place. Others are frustratingly rigid and make it much more difficult (like on the composite bracelet). The best way to get a band back in place is as follows: Put the spring pin partially into the band hole (about 1/4 of the way). Position the pin into the hole on the bottom lug as the watch faces you. Holding it steady, guide the band down to the lug, being careful not to let the spring pin move out of place. Now push the band end the rest of the way into the lug space, until the top of the spring pin pushes against the upper lug. Now, you'll need to use a screw driver or wristband pin removal tool to push the spring pin down, while applying pressure on the band. Once the pin clears the lug, it will allow the band to position into place. Finally, you'll need to use a small screwdriver (or equivalent) to nudge the pin into the lug hole. If it's a particularly stiff band, you may need to use a magnifier to see where the pin is in relation to the hole. On softer bands, all you'll have to do is push down and wiggle the band a little, and the pin will find the hole naturally.
So... those are my G-Shock watch battery replacement tips. I hope you find them useful.