How to Test a Watch Battery with a Multimeter (Guide)

Small watch batteries also known as coin batteries and small single cell batteries can be used with various electronics. You can find these round shape batteries on watches, toys, calculators, remotes, and even on desktop computer motherboards. Commonly known as coin or button types. Usually, a button battery is smaller than a coin battery. Regardless of size or the type, you might have to test the watch battery voltage.

So, today I’m planning to teach you how to test a watch battery with a multimeter.

In General to test battery voltage, first, set the multimeter to the DC voltage setting. Place the multimeter red lead on the positive side of the battery. Then, place the black lead on the negative side of the battery. If the battery is fully charged, the multimeter will show a reading close to 3V.

Different Voltages of Watch Batteries

There are three different types of watch batteries available in the market. They have different types of voltages, and the size is different too. These variations can be identified as coin or button battery types. So, here are the voltages of those three batteries.

Battery TypeInitial VoltageBattery Replacing Voltage
Lithium3.0V2.8V
Silver Oxide1.5V1.2V
Alkaline1.5V1.0V

Keep in mind: According to the above chart, when a Lithium battery reaches 2.8V, you should replace it. However, this theory does not apply to the common Renata 751 Lithium battery. It has an initial voltage of 2V.

Things to Know Before Testing

In this section, you’ll be able to learn two methods to test battery voltage.

  • Initial Testing
  • Testing with Load

Initial testing is a quick and easy method to test the voltage of a watch battery. But when testing with load, you can observe how the particular battery reacts to the load.

discharge characteristics on load graph
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In this case, 4.7KΩ of load will be applied to the battery. This load might vary according to the type and the size of the battery. Choose the load according to the discharge characteristics of the battery. (1)

Things Needed

  • Digital multimeter
  • Variable resistance box
  • Set of red and black connectors

Method 1 – Initial Testing

This is a simple three-step testing process that requires only a multimeter. So, let’s get started.

Step 1- Set Up the Multimeter

multimeter at a reading of 2.928 vdc
Video | Sofeast Ltd

First and foremost, set the multimeter to DC voltage settings. To do that, turn the dial to the VDC symbol.

Step 2 – Placing Leads

technician holding multimeter probe and testing watch battery
Video | Sofeast Ltd

Then, connect the multimeter red lead to the positive side of the battery. Next, connect the black lead to the negative side of the battery.

Identifying the Positive and Negative Sides of a Watch Battery

multimeter's red probe on watch battery
Video | Sofeast Ltd

On most watch batteries, there should be a plain side. That is the negative side.

multimeter's red probe touches the side of the watch battery
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The other side displays a plus sign. That is the plus side.

Step 3 – Understanding the Readings

reading on multimeter at 2.928 vdc
Video | Sofeast Ltd

Now, check the reading. For this demonstration, we use a Lithium battery. So, the reading should be close to 3V, given that the battery is fully charged. If the reading is below 2.8V, you might need to replace the battery.

Method 2 – Testing with Load

This test is a little different from the earlier tests. Here, you’ll have to use the variable resistance box, red and black connectors, and the multimeter. As mentioned earlier, in this test, we are applying a 4.7KΩ with the help of a variable resistance box.

Tip: A variable resistance box is capable of providing a fixed resistance to any circuit or electrical item. The resistance level might range between 100Ω and 470KΩ.

Step 1 – Set Up the Multimeter

technician testing the watch battery with multimeter at a reading of 3.106 vdc
Video | Sofeast Ltd

First, set the multimeter to DC voltage settings.

Step 2 – Connect the Variable Resistance Box to the Multimeter

watch battery test with a variable resistance box
Video | Sofeast Ltd

Now, use red and black connectors to connect the multimeter and the variable resistance box.

Step 3 – Set the Resistance

Next, set the variable resistance box to 4.7KΩ. As mentioned earlier, this resistance level might vary according to the type and size of the watch battery.

Step 4 – Placing Leads

multimeter's red and black probes on a watch battery in a blue background

Then, connect the resistance box’s red lead to the positive side of the watch battery. Connect the resistance box’s black lead to the negative side of the battery.

Step 5 – Understanding the Readings

multimeter reading at 3.106 vdc when watch battery is being tested
Video | Sofeast Ltd

Finally, it is time to check the readings. If the reading is close to 3V, the battery is in good health. If the reading is below 2.8V, the battery is not good.

Keep in mind: You can apply the same process to a Silver Oxide or Alkaline battery without much trouble. But, remember initial voltages of Silver Oxide and Alkaline batteries are different compared to the above demonstration.

Wrapping Up

Whatever the battery type or the size, always remember to check the voltage according to the above testing processes. When you test a battery with a load, it will give a good idea of how the particular battery reacts to a load. So, it is an excellent method to identify good watch batteries. (2)

Take a look at some of our related articles below.





References
(1) battery – https://www.britannica.com/technology/battery-electronics
(2) good watch – https://www.gq.com/story/best-watch-brands

Video Reference

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.