Designer & bike rider in British Columbia, Canada

Casio MQ-24 series watch battery replacement

This may also apply to other Casio models with similar snap-on back covers. I believe the following batteries codes are all compatible: SR626SW / 377 Battery / SR66. I bought the Maxell SR626SW in bulk.

Parts & tools:

  • replacement battery
  • at least one small flathead jewelry screwdriver
  • Optional second size: larger screwdriver for prying off the back cover more easily
1. Remove one strap.

Flip the watch face down on your table. We need to remove one of the straps (either side is fine) to gain access to the back cover. The strap holding pins are spring loaded: fix the end of your small-blade screwdriver on one of the pin’s end grooves closest to the watch body and press away from the watch body and into the strap, while pushing to the right slightly to disengage the pin from the hole in the body.

Careful the pin doesn’t go flying when you carefully remove your screwdriver.

2. Remove back cover.

Note the back cover is a press-fit, with two tabs acting as a spring. We need to flex these tabs over the taper of the watch body—carefully pry up on one tab with your larger screwdriver blade until it pops loose. Careful not to damage the plastic of the watch body.

If you need more leverage, hang the screwdriver off the edge of your table. Sometimes I pry from the middle flat of the cover cover, rather than the tabs—not sure which method is better or more consistent.

Slowly pull the back cover off noting if the rubber gasket (o-ring) is stuck to it—don’t break this gasket. The two tabs on the other side should more easily come off the watch body now.

3. Remove gasket.

Lay the back cover down on its face. Lay the gasket on top of the cover, keeping the same side of the gasket oriented to the back cover. Reason: the gasket may have been pressed for years against the cover, we want to maintain the same orientation and “squish” to avoid introducing potential leaks.

4. Remove the battery.

The battery is held by a small springy metal lever. Press up on this lever to release the battery. Careful as the battery can go flying (it usually pops out 4″ or so off the table). Note the bottom lipped metal arm is not flexible. Don’t pry this bottom arm.

Full disassembled. Don’t confuse your old battery with the new one.

5. Insert new battery

Insert the new battery face up (+), tapered side (-) down. First insert at an angle, with the bottom of the button tucking under the bottom angled arm.

Use your finger to snap the top edge of the battery under the top straight arm, which is spring loaded. Ensure the battery is snug and doesn’t fall out.

6. Re-insert the gasket.

Replace the gasket in the same orientation you removed it. MOST CRITICAL that it fits in the dedicated groove of the watch body and doesn’t overhang inside or out. If this gasket is improperly placed you will get moisture in your watch later. I’ve noticed, and a few have commented, that this gasket is a tad oversized—my guess is it expands and increases in diametre slightly when the pressure is released (after years of being squished?)—so it can be difficult to get it back in the grooves. Careful it doesn’t stick out and get pinched.

7. Re-insert the back cover.

Inset the strap-side tabs first and carefully press down from left-to-right until the other tabs snap over the watch body tapers. MOST CRITICAL that you don’t dislodge the gasket from its groove.

Ensure the back cover is flush and parallel with the watch body. Visually inspect every side to make sure it’s flat, and that the gasket is not pinched or protruding.

8. Re-install the strap.

With the strap pin in the strap, insert one end of the pin into the watch body, then get the other end of the pin close to the watch body. With your small screwdriver, load the spring in the pin and carefully push into the watch body, ensuring it seats fully in the watch body hole. Give your strap a few tugs to ensure its seated and the same amount of pin and its grooves are visible as when you started (or compare to the other strap’s pin).






42 Responses to “Casio MQ-24 series watch battery replacement”

  1. Hans Olof Holmberg Avatar
    Hans Olof Holmberg

    4. Remove the battery. …”Press up on this lever…”. I have misunderstood this. You mean “up” on the picture I now understand but I have first thought you ment one should lift up the lever. The result is that the lever stayed somewhat up so that the new battery is not pressed down correctly. But still there is electrical contact so that the watch is now functioning. I hope it will keep going…
    Afterwords I several times looked at this video to understand:
    “Press this lever to the side (in direction parallel to the upside of the battery) away from the battery” is my suggestion if you would like to alter the text.

  2. Mike Rogers Avatar

    Thank you for giving such clear advice and Hans for his additional tip. In the past I have bought a new watch rather than pay a shop to replace a battery, but this time I shall give it a try.

  3. Paul Avatar

    Very helpful – Thanks

  4. luis Avatar

    Thanks for the tips!
    If it wasn´t your page i wouldn´t open my watch!

  5. Unknown Avatar


  6. Stacie Avatar

    Thank you!
    Nobody in Walmart could change a watch battery. With your article I took my watch back off & changed my own battery standing at the jewelry counter!

  7. Tim Avatar

    Thank you, Jeff – from Tim in the UK.

  8. T R Black Avatar
    T R Black

    HUGE Thanks! I am a complete klutz when it comes to mechanical repairs…still take way too long to remove and replace a bike tire after over 35 years of riding, including many centuries. Your PERFECT procedural, with exacting words and fab photos is precision.

    Therefore, it is idiot proof, as I succeeded in minimal time by following each and every step with ZERO profanity…a first!

    You are a mensch and an example of what is BEST about the internet.

    Much appreciation,

    T R Black
    Irvine, CA

  9. Jeffrey Werner Avatar
    Jeffrey Werner

    T R Black: I’m a bicycle racer—I should do a post on tips and tricks in tire changing!

  10. shaind Avatar

    It seems my rubber seal doesn’t fit inside the warch groove. It looks like an oval now. Is there anything I can do for that?

    1. Jeffrey Werner Avatar
      Jeffrey Werner

      I have the same problem with one I recently changed the battery on—the seal appears to have expanded 10% and won’t fit again. I’d also like to source a replacement, but no luck finding one so far.

  11. Ramon Avatar

    I have this watch and there is some different plasic shit movement signed CASÏO HKA-b inside, your one looks like Miyota.

  12. steven coggans Avatar
    steven coggans

    Great stepby step instructions!
    Just changed 2 dead casios

    Thanks Jeff

  13. Kate Avatar

    Thank you so much! I never would have had the patience to figure this out on my own.

  14. Sean Eno Avatar
    Sean Eno

    Thank you – perfect instructions.

  15. GD Avatar

    Any updates on sourcing a gasket replacement? Mine is also expanded about 10% and the case won’t close without the gasket bulging on one side or another. Seems like a shame to throw out a working watch for such a fiddly little part.

  16. Ads Avatar

    I have just done this, and the best way to get the cover off is to insert a sharp knife under the cover (round part) adjacent to the clip, and gently lever.

    Easy as pie

  17. Kathryn Hall Avatar
    Kathryn Hall

    Great tutorial, thank you.

  18. Bradford Blake Avatar
    Bradford Blake

    Thanks! I never would have figured it out on my own.

  19. Peter N Avatar
    Peter N

    Excellent. Much better than a YouTube video that you have to keep pausing and rerunning.

  20. JW Avatar

    As an Englishman in France, I echo the previous posts – good, clear instructions with precise photos. Success at first attempt!
    Suggest pushing spring clip ‘away’ from the battery to release it.
    Thanks for the time and effort neded to post this

  21. Wendy Free Avatar

    Just successfully replaced my battery using your instructions – thanks so much! Delighted I don’t have to buy a new watch or pay someone to change the battery. Hooray for DIY and sustainability! Really, really appreciate your help! Take care!

  22. James Nelson Avatar
    James Nelson

    Accurate and clear still photos of the process. Thank you

  23. Andy L Avatar
    Andy L

    Hi Jeff,

    Would greatly appreciate if you’re able to take measurements of your gasket so that those of us seeking a replacement know exactly what size to get.

    Thank you kindly in advance!

  24. Max Zhang Avatar
    Max Zhang

    Awesome blog Jeff. You are awesome.

  25. Nick B Avatar
    Nick B

    Excellent clear instructions – mission accomplished successfully. Thanks

  26. Paul Avatar

    This is such a good tutorial! Thanks for putting it up!

  27. Kay Avatar

    Awesome instructions! You accomplished turning an impossible task into a simple and straightforward one. Thank you for posting!

  28. Cip Avatar

    Great instructions and modeled photos. Thank you and many blessings!

  29. R.Ward-Jackson Avatar

    I’ve changed my battery a few times and managing to get the back back on without the gasket bulging out at the sides. I failed this time so I’ll have to see how it does without it .

  30. Legris Bourgeois Avatar
    Legris Bourgeois

    My wife and I have worn this and similar Casio models for some 25 years and follow a procedure much like Jeff’s to change batteries. One thing I notice in the last few years is that the gasket (after the watch is opened) is often distorted in shape, and it seems impossible to put back into its correct position. And (sadly) thereafter, it seems the watch collects water or humidity and quickly stops working.

  31. Patrick Henry Avatar
    Patrick Henry

    Excellent and clear instructions. Your close-up photos well illustrated your text. Like others I am not handy. I thank you for getting the watch ticking again.

  32. Daniel Avatar

    Thanks ! Worked a treat

  33. Paul Gately Avatar
    Paul Gately

    Thank you for this really well done description of how to change the battery in my cheap Casio watch. Happened to have one of the 377 batteries left over from another battery replacement so it only took a few minutes following your instructions. Thank you for posting, I love my inexpensive watch as it is low profile and doesn’t get in the way when working etc……glad to keep it a bit longer with the new battery. Thanks again.

  34. Peter Bowen Avatar
    Peter Bowen

    Thank you so much, Jeff. This is brilliant. I marvel at how unselfishly you and others like you share expertise. One can do almost anything by watching a video or other information on the Internet. I haven’t tried brain surgery yet. Well done and may you be blessed!

  35. K. Kambara Avatar
    K. Kambara

    Thanks for this info and clear photos. I was able to change my battery today and I’m happy. I didn’t have to remove the strap on my Casio 1330, so you can re-phrase that as an option.

  36. Mike W Avatar
    Mike W

    Thank you for such a well-written and clearly photographed account. Such a pleasure to see that someone knows how to focus their camera. Very helpful, and well explained. And yes, I can confirm that the old battery does fly almost exactly 4 inches!
    Best wishes.

  37. Michael Avatar

    Thank you for this excellently written and illustrated guide. I was gifted the watch through the Buy Nothing Lynn Valley group. I really like the low profile and minimalist simplicity of its design and materials.

  38. Peter Compton Avatar
    Peter Compton

    Many thanks for the help, like others I bought a new watch as the battery change looked beyond my capabilities but now I hve two working watches.



  39. Gabriela Avatar

    I am so used to having the time on my wrist that I was feeling lost without it!
    Such a simple solution with your clear instructions.
    You made my day :)
    Thank You!!! ✨

  40. Stephen Zecher Avatar
    Stephen Zecher

    I have a casio MQ 24 for which I need to change the battery.

    I removed the the battery is labeled 384 Rinata which measures 6.5 mm in diameter.

    Will battery labeled 377 that you show work?

    The reason why I ask is that photo of the replacement battery you show seems larger than the one from my MQ 24.

  41. Lucas Avatar

    Wanted to say I replaced the battery on mine and could NOT get the gasket to fit back in. Tried several times and it was always poking out. Casio gasket replacements were too expensive so I tried ordering a generic multi pack of different sizes of watch gaskets and none of them fit. Right when I was about to give up and order another, I had one last idea. I put the gasket in the fridge overnight! Worked like a charm.

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