Choosing the right watch battery is essential when you need a replacement. If you've got the original battery that needs to be replaced, then the process is very simple. If you don't, you may have to take a trip to the jeweler. Watch batteries are defined by a set of codes and standards. Varying combinations of these numbers will identify the appropriate watch battery for your time piece, as well as compatible models.
Turn the watch upside down and use a screwdriver to pop off the back plate. There should be a notch that will accommodate the end of the screwdriver; just slide the end underneath and gently pop off the back. In some cases, there will be small screws that need to be removed, which you can do with a jewelry screwdriver.
Find the battery in the back of the timepiece. It's a very small, silver disc that should have engraved numbers on it. Use the tweezers to pop this out of the back and lay it down on a table with the numbers facing up. You may need a magnifying glass to see all the engraving.
Write down the information on the back of the battery. As an example, it might say something like this: SR626SW. It may also have the name of the watchmaker and the country where the piece was made.
Compare these numbers to a cross-reference chart to discover the battery you'll need to purchase for your watch. When you compare the number in our example, SR626SW, to the chart, you'll find the following: The International Electrotechnical Commission code for this battery is SR66; Energizer, Rayovac, Renata, and UCAR all make a compatible battery and its code is 377; and Maxell, National, Panasonic, Sony, and Toshiba sell the exact code as SR626SW. Some manufacturers also have their own brands that fit their watches taking an SR626SW. Bulova's version is a 606, Citizen's version is 280-39, Duracell's is D377, Seiko's is SB-AW, Timex's is BA, and Varta's is V377.
Decide where you want to buy your battery by comparing the prices of the compatible models. If you want to purchase the brand specific for your watch, then locate the brand at the top, scroll down to the SR626SW and write down the brand specific code for the battery you want.
Order online or take your code to a jeweler and tell him which battery you want. As insurance, consider taking the original battery with you in case you've used an outdated chart. Replace the battery and pop the back of the timepiece back on.
Tips
If you've lost the original battery, take the watch to a jeweler or horologist to see if they can identify your need. The specifics are not written on the inside of the watch, only on the battery.