where Psys is the total power supplied by the battery bank, during emergencies, to a load of specific Watts per hour given by Ld. Vbattery and 'battery are the voltage and current ca-pacities of a single battery, in volts and amperes-per-hour re-spectively, which creates a complete emergency system, with identical (NBseries+NBparailel) batteries connected in series and parallel respectively. Hence, AEM is the amount of time in hours, that the emergency system can keep Ld watts per hour running, while the primary sources are restored.