An emergency ballast for a fluorescent lamp includes a rechargeable battery. The emergency ballast also includes a circuit for receiving an electrical current and providing a recommended charging voltage to the battery. The electrical current is one of two amplitudes, and the circuit provides a charge to the battery without regard to the amplitude of the electrical current. The first amplitude of the electrical current can be 120 volts, and the second amplitude can be 277 volts. The emergency ballast includes a capacitor electrically coupled to the circuit that provides an additional voltage to the rechargeable battery when the electrical current is 120 volts. The emergency ballast also includes a switch for electrically decoupling the capacitor from the circuit when the electrical current is 277 volts.