Watch Batteries
The technology used for watch batteries has matured very well. Silver Oxide is the most common chemical system used in watch batteries. It has a number of outstanding features which are ideally suited to powering watches:
- Small - Silver Oxide chemistry literally packs a lot of power into little space. It has one the highest energy densities of all battery systems.
- Steady Voltage - Quite distinct from the very common alkaline battery technology, Silver Oxide batteries feature a near constant voltage of 1.55V over their life.
The vast majority of watches which run on batteries, take one of the 300-series of watch batteries. All of these are button cells, and they all use Silver Oxide technology. They all have a voltage of 1.55V, and last for a long time, both in use and while stored.
Compared to other battery technologies, Silver Oxide technology features one of the greatest capacities to store electricity for a certain volume. This obviously matters in a watch, where the battery is often not easily accessible, and there's no space to waste. Silver Oxide technology also provides a near constant voltage over the entire life of the battery. This is essential to ensure watch accuracy, and could not be attained easily with alkaline battery technology.
Unfortunately, battery manufacturers have never agreed one standard convention for battery labels. The 300 numbers are a very common way to identify a battery, but for example a Type 377 battery could also be labelled SR626SW (e.g. by Maxell), 606 (Bulova), BA (Timex), 280-39 (Citizen), SB-AW (Seiko), and SR66 or SR626 by the IEC. It gets tricky once you discover that a 626 (Bulova) battery, is a Type 389 battery, and not an SR626 or Type 377. Fortunately, our database has cross-referenced most of these labels, so you can find the right battery for your watch by using the label on your old battery in our battery search. For help with battery designations, take a look here.