I have several kitchen timers that are just sitting around not being used in my house because they run on those tiny little coin-cell batteries, which are expensive to replace, making them more bother than they're worth in my opinion. So I got to thinking today that LR44 batteries are 1.5 volts, same as "AA" batteries, so I should be able to run any one of my timers on a "AA" with a little work. Now I'll show you how to do that as well.
Step 1: Tools and Materials
For this project, you will need:
- A timer that runs off of a coin-cell battery
- Small screwdrivers
- A soldering iron and basic soldering skills
- A "AA"-type battery holder, preferably one that holds the battery in with clips
Optional if you want to give the contacts a good cleaning while you've got the sucker open:
- Rubbing alcohol
- A cotton swab
Step 2: Open It Up
Look on the back of the timer and find where the screw holes are; there should only be a few, and it's unlikely that any of them will be hidden. Remove these screws, and then gently pry around the edge of the timer to get the two halves of the case open. You may need to use a screwdriver to get the case open, and you will probably crack a few of the tabs that hold the case together, but if you are gentle, you can minimize this.
Once you have the back of the timer off, start removing screws from the circuit-board. Make sure that you don't lose any of these screws, you will need all of them later on when you put it all back together.
Step 3: Optional Step: Cleaning the Contacts
The other problem that I run into with these timers is that the contacts for the buttons get all dirty, and then the buttons stop working well. This particular timer has not had power in a few years, so I don't remember if it was having this problem, but I figure that it can't hurt, and if it does, it's just a $10 timer that hadn't had power anyway.
So, get your swab and alcohol and rub any crud off of the button contacts, then wipe up any excess alcohol.
Step 4: Adding the Battery Clip
Now, look at the circuit-board and identify where the positive and negative leads from the battery attach to the board. At least one of these should be labeled clearly on one side or another.
Once you know where the leads connect, it's just a matter of soldering on the proper leads. There should be enough solder globbed on the board that you don't need to add any extra, just heat it up and poke the proper wire into each side. Make sure that you stick the wires through the battery hole in the case prior to soldering them on.
Step 5: Finishing Up
Now that you have the clip soldered on, screw the circuit-board back onto the front half of the timer. Make sure that you tighten the screws all the way or the LCD screen's contacts won't all connect and it won't work properly. Before you put the back of the case back on, put in a battery and make sure that the thing works properly. If everything is in order, put the back back on, screw it down, and take a second to admire your handiwork.
As a finishing step, coil any excess wire from the battery clip up inside the timer in the battery hole and fill it over with some hot glue. Finally, glue the battery clip to the top of the timer where it is easily accessible, and everyone can see how you have cleverly avoided buying fiddly little batteries for such a common, useful device.
Step 6: Future Improvements
If I were to do this project again in the future, which I no doubt will, there are a few things that I would do differently. First, I would cut the leads from the battery clip shorter so that there is less excess wire running around that needs covering over. The second thing I would do is to rout out a little space in the top of the case so that I could just run the wires on the inside of the case, which just makes it look a lot neater.