A battery condition monitoring system for an emergency lighting system including: measuring means connectable to a battery and operable to obtain an indication of an impedance of the battery; reference impedance value storage means for storing a reference impedance value of the battery; and monitoring means configured to operate a battery charger connectable to the battery condition monitoring system and periodically operate the measuring means to obtain the indication of the impedance of the battery, the monitoring means further configured to compare the indication of the impedance of the battery to the reference impedance value, and to estimate the battery condition in dependence thereon; wherein the measuring means is operable to provide the reference impedance value by being connected to the battery during an initial usage phase of the battery to acquire an initial indication of the impedance thereof during the initial usage phase, or wherein the reference impedance value is an estimation of the impedance of the battery during an initial usage phase; characterized in that in order to perform an impedance measurement: the monitoring means is configured to activate the battery charger to apply a charge current to the battery for a first time period, and then deactivate the battery charger and, immediately after, cause discharge of the battery by a discharge current for a second time period, and the measuring means is configured to measure a first voltage of the battery while the charge current is applied, measure a second voltage of the battery straight after the inversion from charging to discharging, calculate a voltage drop straight after inversion from charging to discharging as a voltage difference between the second voltage and the first voltage, and divide the voltage drop across the battery straight after inversion from charging to discharging by a sum of the charge and discharge currents, thereby obtaining the indication of the impedance of the battery. measuring means connectable to a battery and operable to obtain an indication of an impedance of the battery; reference impedance value storage means for storing a reference impedance value of the battery; and monitoring means configured to operate a battery charger connectable to the battery condition monitoring system and periodically operate the measuring means to obtain the indication of the impedance of the battery, the monitoring means further configured to compare the indication of the impedance of the battery to the reference impedance value, and to estimate the battery condition in dependence thereon; wherein the measuring means is operable to provide the reference impedance value by being connected to the battery during an initial usage phase of the battery to acquire an initial indication of the impedance thereof during the initial usage phase, or wherein the reference impedance value is an estimation of the impedance of the battery during an initial usage phase; the monitoring means is configured to activate the battery charger to apply a charge current to the battery for a first time period, and then deactivate the battery charger and, immediately after, cause discharge of the battery by a discharge current for a second time period, and the measuring means is configured to measure a first voltage of the battery while the charge current is applied, measure a second voltage of the battery straight after the inversion from charging to discharging, calculate a voltage drop straight after inversion from charging to discharging as a voltage difference between the second voltage and the first voltage, and divide the voltage drop across the battery straight after inversion from charging to discharging by a sum of the charge and discharge currents, thereby obtaining the indication of the impedance of the battery.