What kind of coin cell batteries are there?

There are several systems. The properties are tailored to the most important applications.

Silver oxide (watches, cameras): High constant voltage, self-discharge less than 5% per year.

Alkaline (electrical appliances): Supplies large currents, voltage drops during use, self-discharge less than 3% per year.

Lithium (cameras and electronic devices): Self-discharge less than 1% per year, not suitable for heavy loads.

Zinc air (hearing aids): High capacity, self-discharge 3% per year (if not activated).

Mercury oxide (electrical appliances, hearing aids and cameras): Supplies large currents, self-discharge 2% per year, environmentally unfriendly 15% mercury.

Mercury-containing batteries have not been manufactured since 1998 and have not been supplied by factories since 1999. A replacement zinc air battery is available for a small number of these batteries.