At 1641hrs Dorchester Central dispatched units for A “Reported STRUCTURE FIRE” at 4645 MAPLE DAM RD in the Cambridge 1-5 Box Area. Chief 1 arrived on location with A light haze and electrical smell inside the structure and established command. Units after an extensive investigation found the source to be A bad computer battery. Ventilations was performed and Command was terminated with all units being placed in service without incident.