Emergency lights use rechargeable batteries to maintain continuous power during a grid failure. Here are the Common Battery Chemistries :
Sealed Lead-Acid (SLA): Inexpensive and rugged; standard 6V versions (like 4.5Ah) are widely used in traditional twin-spot lights.
Nickel-Cadmium (NiCd): Compact, long-lasting, and mountable in any position; common in slim thermoplastic exit signs and combo units.
Nickel-Metal Hydride (NiMH): Slim, cadmium-free alternatives often used in modern conversion kits.
Lithium Iron Phosphate (LiFePO4): Highly efficient, lightweight, and thermally stable, representing the newest standard for high-reliability fixtures.