A lighting system (10) is provided that includes at least one lighting device (14A,14B,14C), a plurality of external power sources (20,22,24,26,27) and an internal power source (16) applying a first electrical current to illuminate at least one lighting source (18A,18B,18C), wherein the internal power source (16) supplies the first electrical current. Further, a fuel gauging system and method (1230) detects an electrochemical composition of a power source (16,20,22,24,26,27), which can be at least one of the internal power source (16) and the external power source (20,22,24,26,27), and then determines a state of charge of the power source (16,20,22,24,26,27) based upon the determined electrochemical composition of the power source (16,20,22,24,26,27).