Energizer SR521SW Button Battery, 1.55 V, 5.8 mm Diameter

The Energizer Low drain watch battery uses a zinc/monovalent silver oxide chemical system and delivers a nominal voltage of 1.55 volts with a capacity of 16 mAh, tested under a 47 kΩ discharge at 20°C down to 1.2 volts. It operates effectively within a temperature range of -10°C to 60°C and features a low self-discharge rate of less than 5% per year at 20°C. Weighing approximately 0.23 grams, this battery provides reliable, long-lasting power for small precision timepieces.

Equivalent mercury containing battery range