Casio F-91W Battery Extension MOD (CR2032)

This project was conducted to extend the battery life of my Sensor Watch Lite Board and add the ability to recharge the battery as I did not want to constantly burn through CR2016 batteries. I did not develop the sensor watch. The sensor watch was developed by Joey Castillo (Oddly Specific Objects) and his team. I highly recommend you check out the crowed supply page if you’re interested into adding more functionality to your F-91W. If you’re reading this I think this would be right up your alley. The sensor watch page is linked here : https://www.sensorwatch.net/

The First Image : The first image shows the voltage reading on the sensor watch face from the new battery.

The Second Image : The second image shows the tools that would be required to preform this mod. The oils are a Dremel with a metal cutting wheel, and a small Philips screwdriver. Not shown but highly recommended are a par of needle nose pliers for easier removal of the case back clips.

NOTE : This Mod when completed might hinder water resistance, furthermore assembly of this watch mod will be very tight. There is no space between the case back and the positive side of the battery this sandwich will have to be screwed on very tightly. For this reason I assume the contact between the gasket and the case back is minimal. Another compromise is that this mod renders the buzzer useless as the original buzzer uses the case back as the positive terminal and the bottom spring bar as the negative terminal. In the case of this mod the positive terminal is in contact with the negative terminal of the buzzer rendering it useless. There could be a work around to this but I have yet to find it.

All you need for this mod is the casio F-91W, A CR2032 battery (I opted for a rechargeable one), and the tools required.

The first thing you need to do is remove the watch from the watch housing by un screwing the screws. The second thing you need to do is remove the 593 module back metal retainer by unclipping the side clips (pliers help in this regard).

The next step is to use the Dremel to cut the retainer in half and then slowly cut away chunks from it until the horizontal component of the retainer is shaved away. This is more complicated that I can show with just two pictures but you essentially want to slowly follow the vertical wall of the retainer clip. While you do this make sure not to cut away the clips some areas are thinner than others where the clips are located. I know this because this isn’t the first attempt I had at preforming this mod.

Assembly is pretty straight forward all you need to do is to attach the separate retainer clips on each side and insert the battery inn the middle. Add the gasket to the back of the watch, Then screw on the case back to tightly enclose the whole assembly. I know in the image there is no faceplate but yours should have a faceplate. This is why I haven’t tested the water resistance. I hop this helps in your projects. If you read this long and c found the information useful don’t hesitate to drop a like.