An apparatus, comprising: first and second input terminals (10, 12) configured to be connected to a charging power source for charging a backup power supply for an emergency lighting system and to receive an input voltage from the charging power source across the first and second input terminals (10, 12), the input voltage corresponding to an applied nominal operating voltage of the charging power source among a plurality of nominal operating voltages for the emergency lighting system; a temperature detector configured to determine whether a temperature in a vicinity of the backup power supply exceeds a backup power supply temperature threshold; and a heater including a plurality of heating elements (182, 184); the apparatus being characterized in that the temperature detector is configured to produce a temperature signal indicating whether the temperature exceeds the backup power supply temperature threshold; in that the heating elements (182, 184) is configured to be selectively activated to heat the backup power supply; and in that the apparatus comprises: a voltage level detector configured to produce, in response to the received input voltage, an input voltage level signal indicating the applied nominal operating voltage of the charging power source to which the input voltage corresponds; a switching circuit configured to activate the heater; and a logic circuit having a first input configured to receive the input voltage level signal from the voltage level detector, and a second input configured to receive the temperature signal from the temperature detector and in response thereto produces an output signal to the switching circuit for controlling the operation of the heater; wherein the temperature signal determines whether the heater is activated, and when the heater is activated the input voltage level signal determines which of the heating elements is/are activated. first and second input terminals (10, 12) configured to be connected to a charging power source for charging a backup power supply for an emergency lighting system and to receive an input voltage from the charging power source across the first and second input terminals (10, 12), the input voltage corresponding to an applied nominal operating voltage of the charging power source among a plurality of nominal operating voltages for the emergency lighting system; a temperature detector configured to determine whether a temperature in a vicinity of the backup power supply exceeds a backup power supply temperature threshold; and a heater including a plurality of heating elements (182, 184); the apparatus being characterized in that the temperature detector is configured to produce a temperature signal indicating whether the temperature exceeds the backup power supply temperature threshold; in that the heating elements (182, 184) is configured to be selectively activated to heat the backup power supply; and in that the apparatus comprises: a voltage level detector configured to produce, in response to the received input voltage, an input voltage level signal indicating the applied nominal operating voltage of the charging power source to which the input voltage corresponds; a switching circuit configured to activate the heater; and a logic circuit having a first input configured to receive the input voltage level signal from the voltage level detector, and a second input configured to receive the temperature signal from the temperature detector and in response thereto produces an output signal to the switching circuit for controlling the operation of the heater; wherein the temperature signal determines whether the heater is activated, and when the heater is activated the input voltage level signal determines which of the heating elements is/are activated.