Abstract: An uninterruptible power system has two current conversion units coupled between a line voltage and a load in parallel, wherein each current conversion unit has a rectifier and an inverter connected in series. The two rectifiers and inverters are further connected to form a cross configuration. At least one battery set is coupled to the output terminals of the two rectifiers, wherein a battery monitor controller is applied to monitor the battery information which is then transferred to a remote host. When either inverter or rectifier is faulty in one of said current conversion modules, the normal inverter or rectifier in the same module is still operated and controlled by the other current conversion module.

Abstract: A method of checking power status of the batteries is disclosed. New batteries are first prepared for discharge tests with different discharge rates, and the standard discharge data for different types of batteries are recorded in a data base for use in power estimation. Afterwards, the battery set installed in an uninterrupted power supply (UPS) system is connected to a monitoring device for continuous monitoring of the test discharge data and discharging time in repeated random discharge tests. The characteristic data including current output, operating temperature, and terminal voltage of the tested battery are then collected and compared with the relevant standard discharge data retrieved from the data base to produce a true estimation of the remaining power of the tested battery.