An Uninterruptible Power Supply (UPS) is a standby power arrangement system. UPS can be used for providing backup power to any electrical equipment, but mostly they are used as a standby power arrangement for PCs. In places where power outages are frequent and supply is not guaranteed UPS can also be used for running electrical equipment like fans, lights, TV sets etc. A UPS is also used in medical and telecommunication equipment or places in the industry where power outages can result in loss of life or can cause financial losses. A UPS comprises of battery system which stores electric charge. It also has a charging system to charge these batteries and means of converting the stored Direct Current (DC) to Alternating Current (AC). Modern UPS are intelligent devices and can manage the charging system, that is they shut off the electric power to the batteries when they are fully charged and turn off the UPS when the batteries are close to being discharged completely, thus preventing permanent damage to the batteries.