A power management system is disclosed for providing power to one or more computers having provisions for communication with an external data source. A source of backup power, including a bank of batteries, is provided which is provided to the power bus during a utility power interruption. A microprocessor monitors the utility line and the energy remaining in the batteries and provides data signals to the computer in response to utility power interruption and to predetermined battery energy levels. The data signals enable the computer to transfer data to non-volatile media to prevent data loss. In one embodiment, two way data links are provided between the computers and the microprocessor, which also controls power cutoff switches connected to each computer. Each computer may signal the microprocessor to cutoff backup power after data has been transferred to non-volatile media.