Abstract: A battery casing is formed of a flame-retardant thermoplastic composition that includes a blend of a homopolymer, copolymer and ammonium polyphosphate. The ammonium polyphosphate is in an amount to impart flame-retardance to the thermoplastic composition. Other components include polyol, intumescent char-forming agent, and melamine, which acts as a blowing agent. Antioxidants, release agents, carbon black, reinforcers and other additives can be included. Alternatively, the battery casing includes a polymer composition with a halogen-containing fire-retardant component and a polypropylene component.