Every battery counter knows the moment: the old cell reads one number, your drawer is labeled with another, and the customer is watching. Battery brands use different numbering for identical cells, and translating between them is a daily bench skill. Here is the logic, plus the equivalences that cover most of what walks in. (For the buying side of this topic, see our guide to buying watch batteries wholesale.)
Why the numbers differ. There are two systems in play. The IEC code (like SR626SW) describes the cell itself: chemistry, diameter, height. Brand numbers (Renata 377, Energizer 377, Maxell SR626SW) are catalog names layered on top. Decode the IEC and every brand’s version of that cell becomes obvious.
Reading an IEC code. Take SR626SW: S = silver oxide, R = round, 6.8mm diameter (the 6), 2.6mm height (the 26), SW = low-drain for analog watches. Once you read one, you can read them all… and spot at a glance that a 377 and an SR626SW are the same cell wearing different name tags.
The workhorses. A short list covers a remarkable share of repairs: 377 (SR626SW), 371 (SR920SW), 364 (SR621SW), 395 (SR927SW), 321 (SR616SW), and the lithium CR2032/CR2025 family for fobs and specialty pieces. Stock these deep in a quality brand and the drawer answers most days by itself.
Low-drain vs high-drain. The SW/W suffix matters: SW cells serve standard analog movements; W (high-drain) cells serve chronographs, alarms, and backlights. Swap them casually and you get short life or weak function… the classic invisible cause of a comeback.
Keep the chart, buy in bulk. Print a cross-reference and tape it inside the battery drawer… then stop paying retail per cell. Wholesale strips of Renata, Energizer, Maxell and Murata from one supplier keep your cost per change low and your brands consistent.
Want the full cross-reference and trade pricing on every size? Visit our wholesale battery page or call (210) 341-7783… we will set your counter up properly.