Energy storage batteries for emergency lighting systems are designed to provide immediate, reliable power during outages, ensuring safe egress in public buildings, hospitals, factories, and transportation hubs. These batteries must meet strict safety and performance standards (e.g., UL 924, EN 50171), delivering consistent illumination for at least 90 minutes as required by most building codes, while maintaining readiness for years with minimal maintenance. Their design prioritizes long shelf life, quick activation, and resistance to environmental factors like humidity and temperature swings.  

Lead-acid batteries are the traditional choice for emergency lighting due to their low cost and suitability for intermittent use. Sealed lead-acid (SLA) batteries, including AGM types, are preferred for their maintenance-free operation—eliminating the need to check electrolyte levels, which is crucial in unattended systems. A typical emergency light might use a 6V or 12V SLA battery with 1–5 Ah capacity, enough to power LED lights for the required duration. Their slow self-discharge rate (1–2% per month) ensures they remain charged during standby, and built-in trickle chargers maintain readiness when connected to the grid.  

Lithium-ion batteries are gaining traction in high-end emergency lighting due to their longer lifespan and lighter weight. Lithium iron phosphate (LFP) cells offer 3,000+ charge cycles, far exceeding lead-acid’s 300–500 cycles, making them ideal for facilities that require frequent testing or have strict reliability demands, such as hospitals or data centers. Their compact size allows integration into slim emergency light fixtures, and smart BMS features can alert maintenance teams to battery degradation via wireless connectivity. However, lithium-ion systems must include overcharge protection circuits to prevent safety risks, which adds complexity.  

Safety is paramount in emergency lighting batteries. They must be housed in fire-retardant enclosures and include thermal fuses to prevent overheating. Some systems use nickel-cadmium (Ni-Cd) batteries for their extreme reliability in cold environments, though their higher cost and cadmium’s toxicity have limited adoption. As LED lighting becomes more efficient, emergency batteries are shrinking in size while maintaining performance, with advanced chemistries and intelligent monitoring ensuring they meet life-saving requirements when seconds count.