309 Energizer Battery. Brand New & Guaranteed Factory Fresh. The shelf life on Energizer batteries is 5 to 10 years. These batteries are commonly required for Swatch, Fossil, Timex and Casio popular brands. Energizer's reported failure rate is far less than 1/1000 of 1%. This devotion to consistent quality has led it to control over 70% of market share in Switzerland, one of the world's leading watch producing countries. Energizer is respected world wide for its uncompromising quality and consistent performance. Energizer's technological leadership produces a variety of miniature batteries which are trusted for use by the best names in watch, computer, keyless entry, consumer electronics and hearing aid industries.