Maxell Watch Battery Button Cell SR920SW 371. Maxell is a worldwide leader in small electronics batteries. Maxell offers a full line of Watch Electronic Specialty Batteries for applications used in precision engineering tools to power a wide variety of small electronic devices. Maxell batteries are used in home health devices such as glucose monitors, blood pressure cuffs and digital ear thermometers. Also, button cells can be used in keyless remote entry systems for cars and homes. Hand held electronic devices also use batteries in calculators, watches, photo camera, computers, audio books, games, toys and more.