Casio MQA-100G Battery Change (Module 333)

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 Casio MQA-100G Battery Change  

 (Module 333)

Hello fellow Casio enthusiasts from around the World, I hope you are all well.

In this post I am going to change the battery in my MQA-100G. The watch had been running well (for over 3 years), until I noticed that the second hand had stopped running and the LCD section had become very faint leading me into a panic to change the battery. I had presumed (wrongly as it happened) that I had a spare battery but I couldn't remember which type it took so I checked an old post to see if I had mentioned it there, but I never mentioned it nor took a picture of the new battery. So that led me to open the watch up to see what type of battery the watch needed.

Let me begin...


The picture above shows the LCD section is very dim. The second hand has also stopped moving, leading me into panic mode to change the battery. I say panic mode because if the battery starts to leak (and it would have, which I will reveal later in this post) it would cause catastrophic damage to the delicate components in the watch leading to cause the watch to stop working. It was time to open the watch up and remove the old battery...


I removed the watch from it's display case and placed it face down on a soft towel.


I then took off the strap from the watch. I always find removing the strap makes it easy to work on the watch.


I then removed the watch back to reveal the battery that was clipped in place.


I then removed the plastic insulator and placed it to one side. I then loosened the small screw and unclipped the contact that holds the battery in place (of which I forgot to take a picture). With the battery removed from the watch, (which had not leaked, to my delight) I checked the new batteries I had in stock but I didn't have the correct type. 


As I didn't have the correct type cell to replace the old one, I replaced the back of the watch to prevent damage to the delicate components inside the watch and I started to look for a replacement battery online which lead me into...

A small chemistry lesson for myself


During my search for a new battery, I couldn't seem to find a standard LR927 battery, the only battery that was available was an SR927 battery so I did some research about the batteries. It turns out that the batteries are of an identical size, however the chemical make up of the batteries is different. The standard LR927 is an alkaline battery and the SR927 is a silver oxide battery. The standard LR927 is a 1.5 volt battery whereas the SR927 has a voltage of 1.55 volts. The difference doesn't stop there, apparently the silver oxide battery (SR927) has a more stable voltage output over its lifespan, where the alkaline battery (LR927) voltage tapers off or lowers during it's lifetime. Another downside to the LR927 (alkaline battery) is that alkaline batteries tend to leak when they are at the end of their useful working life, which is why I have ordered the SR927 (silver oxide) battery and why it was important (although I didn't know at that time that the battery in the watch was an alkaline) that the battery in my watch was removed as soon as possible. My panic of removing the battery quickly was justified and warranted. 

With my chemisrty lesson over, I placed an order for a Sony SR927 battery which cost me £3.25 including delivery.


With the new Sony SR927 at hand, I installed it into the battery compartment.


Once the battery was in it's position, I clicked the battery holder down and then a tightened the retaining screw. I then installed the battery insulator (the white plastic part to the right of the watch), ensuring it was oriented correctly, and then I replaced the back of the watch, this time ensuring the rubber seal was in the correct position.


Once the back of the watch was securely fitted, I turned the watch over and checked it was running, and everything was fine!! The LCD section is now well defined and the second hand was running perfect! Happy days!!


Another close up of the watch...


Once I was happy with that the watch was running correctly, I set the time on the analogue hands and then I set the time and date on the digital section of the watch and then I gave the watch a polish with a clean cloth to remove any fingerprints.


Once the watch was polished, I placed it back on it's holder and took some further pictures of it.


After taking a couple of more pictures of the watch, I replaced it into the display case for safe keeping until the next time it needs the battery changing. 

This watch is one of my favourite watches in my small collection. It is a fully metal cased watch and I can only imagine it would have been an expensive watch back in the 1980's. Casio certainly don't make watches like they used to. I would think, that if this watch were rereleased they would sell a lot of them. I would definitely buy another and wear it as I dare not wear this watch today incase I lost it. The watch may not be valuable to other people, but to an avid collector like myself this watch is worth at least a couple of hundred pounds, maybe more to the right person. This watch is not perfect, but it is in excellent condition and valuable to me!

Well my Casio friends, this is the end of this post and thank you for reading.

Please feel free to have a look at my other Casio watch posts.

Take care my friends and thank you for visiting!!

casiotribe 2026




Hello, my name is Mr.B. I have started this blog as I have owned and loved (and still do) Casio watches for more than 40 years. I would like to explain the many reasons why I still own and wear a Casio Watch. I want to share details, upgrades and maybe a vintage Casio watch restoration post. I will also show you my humble, but very cherished Casio watch collection . I will also show my beloved and aged GW-M5600, I have owned and worn for the last 17 years. I will also be adding further watches to the collection and adding a detailed post for each and every watch. I also want to show you how to avoid a fake watch and what to look for when purchasing a Genuine Casio from any seller.

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