What is the requirement for rechargeable batteries used in smoke alarms?

Rechargeable batteries used in smoke alarms must recharge automatically to ensure continuous operation and reliability. Automatic recharging is a critical feature that allows the smoke alarm to maintain its readiness without requiring manual intervention. This significantly enhances safety since occupants do not need to remember to recharge the alarm or replace the batteries regularly, reducing the chance of having a non-functional smoke detector due to depleted batteries.

While recharging time and lifespan are important aspects of battery performance, they are not the defining requirement for the functionality of smoke alarms. The focus on automatic recharging highlights the goal of fire safety devices: to operate effectively without additional user effort, ensuring they are always ready to respond to smoke or fire detection.