Casio DW-721: low battery problems

In today's article, we will address a common issue that some users of the Casio DW-721, also referred to as Casio W721, have encountered – low battery problems that can arise unexpectedly. We aim to provide a step-by-step guide on how to identify and resolve these issues.

First, we apologize for the poor quality of the photos. It seems that day I had shaky hands...

The Casio W-721, with its renowned 549 module, is a classic model that offers dual time, alarm, stopwatch, countdown, and the now obsolete REM function, known as the "Casio REM". It's a reliable timepiece that many enthusiasts treasure.

One day, when taking this classic out of storage, I noticed the screen appeared as follows:

Clearly, this was not normal. My first attempt to fix the DW 721 issue was to press all four buttons simultaneously, hoping for a "reset" that would bring the watch back to its normal state without needing to open it.

Unfortunately, this was not one of those models where such a reset works, and the watch did not respond to pressing any button or combination of them. Therefore, the only option left was to open it up and attempt a traditional reset.

Disassembly begins

Carefully, I removed the four screws that secure the back cover and checked for anything unusual inside the watch. The battery was the original one from when I purchased the watch, and I hadn't paid much attention to the "Casio low battery warning".

After removing the plate that holds the battery in place within the module, I checked to ensure it was in perfect condition with no leakage that could cause irreparable damage.

Using a multimeter, I tested the battery's charge and observed an unusual behavior. Initially, it showed a correct voltage level, but within seconds, it dropped below 1 volt.

This behavior was a clear sign that the battery was nearing the end of its life, so I proceeded to replace it to avoid any risks.

After placing the new battery in its compartment, I performed a "reset" by connecting the "AC" contact with the positive side of the battery. Flipping the watch over, I confirmed that everything had returned to normal operation.

I took the opportunity to clean and re-lubricate the rear seal with silicone grease for better sealing.

I then carefully replaced the back cover, ensuring the gasket remained in its proper place, and tightened the screws in a crisscross pattern to avoid stripping them.

It's essential for Casio 549 module owners to be aware of the signs of a low battery. If you experience similar issues with your Casio W721 or even the Casio 549, consider these steps to troubleshoot and potentially resolve the low battery warning. Always remember, regular maintenance and timely battery replacement can keep your classic Casio timepieces, like the DW 721, functioning optimally for years to come.

If you're as passionate about watch repair as I am, be sure to check out more in the Restorations category, where you'll find in-depth articles similar to Casio DW-721: low battery problems. Keep honing your craft with us!