What Are Watch Batteries 321? Understanding the 321 / SR616SW Battery

If you\'ve ever opened the back of a watch and found a tiny silver button cell staring back at you, you already know the frustrating part: several batteries can look almost identical. That\'s where the number printed on the battery becomes useful. So, what are Watch Batteries 321? A 321 is a 1.55V silver oxide watch battery, commonly identified by the equivalent designation SR616SW. MicroBattery lists the 321 at approximately 6.8 mm in diameter and 1.6 mm in height. The company currently carries 321 batteries from several manufacturers, including Seizaiken, Renata, Maxell, Murata, and Energizer. That sounds straightforward, but there\'s more to choosing a 321 than finding a product with “321” in the title. If you\'re replacing one battery at home, selling them online, repairing watches professionally, or maintaining business inventory, the details can save you from ordering the wrong cell.