Watch batteries—types replacement and environmental regulations.

A small button cell battery does not take up much space but it contains substances that must be handled correctly — both for the environment and for the watch's own electronics. Battery change is one of the most common tasks at a watchmaker's and that is why many of the trade's environmental and safety rules come into play in everyday life.

• 01Silver oxide batteries (SR) maintain stable voltage for most of their lifespan and are often used in classic analogue quartz watches
• 02Lithium batteries (CR) typically have a longer lifespan and are often used in watches with multiple functions or higher power consumption
• 03Older mercury batteries have been phased out and can no longer be used due to their toxicity

Mercury is harmful to health and the environment, so EU rules strictly limit its content in batteries. Batteries that still contain more than the set limit values for mercury, cadmium or lead must be marked with the chemical symbol for the substance — namely Hg, Cd or Pb — so both consumers and waste management can see what the battery contains.

Used batteries must not be thrown in ordinary household waste. According to the Environmental Protection Agency's rules on producer responsibility for batteries, they must be handed over via collection schemes, e.g. in shops or at recycling centres. Retailers selling batteries are generally obliged to take back used batteries from customers — a duty that also applies to watch shops that sell and change batteries.

A correct battery change is about more than putting a new battery in. The watchmaker checks the battery's reference number against the watch's specifications inspects the sealing around the back or crown and pressure tests the watch afterwards if relevant. This way a simple battery change is also an opportunity to catch other beginning problems before they become expensive.

Beyond the battery itself, many modern watches contain a circuit with electronic components. When such a module is no longer functional it falls under the rules for electronic waste (WEEE) and must be kept separate from ordinary waste when disposed of. As a professional, the watchmaker helps ensure that both batteries and electronics end up in the right place in the waste system.

Environmentally sound handling of batteries and electronics is not bureaucracy for the watchmaker — it is a natural part of the professional standard that distinguishes a professional service from a quick battery replacement at a kiosk.