A UPS with an energy storage function using long-cycle-life VRLA batteries has been developed. Combining the functions of UPS and energy storage is effective to enhance the cost-effectiveness of the UPS. New long-cycle-life VRLA batteries, with capacities of 1000 or 1500 Ah at 2 V, have been developed for the UPS. A cycle life of 3000 or more cycles was estimated from our cycle test. The UPS has been installed in a telecommunications building for field-testing. This paper describes the system configuration, electrical characteristics of the UPS and its components, and result of our field test.

This paper describes the characteristics of lithium-ion cells developed for stationary use, as in the case of stand-by sources in power systems. The effect of a cell-voltage-equalizing circuit developed for batteries of cells is also demonstrated. The tested lithium-ion cells were suitable to be charged by the constant-current, constant-voltage (CCCV) method and could be charged efficiently over a wide range of temperatures. They also showed good discharge performance with little dependence on the discharge current and temperature. Total capacity reduction of over 60% can be expected in batteries of lithium-ion cells. The cell-voltage-equalizing circuit was shown to be useful and necessary for batteries of lithium-ion cells in order to suppress deviations in the cell voltage and capacity loss.

A rack-mounted DC power-supply system utilizing Li-ion batteries, which have higher energy density than conventional VRLA batteries, was developed. The system was designed to have the management functions of Li-ion batteries, such as overcharge protection, over-discharge protection, and cell-voltage equalization, by taking operational requirements into consideration. The volume and weight of the entire system were decreased to one-fourth and three-fifths, respectively, of the volume and weight of a conventional system, making the proposed system ideal as a high-energy-density backup power supply. The functions, system configuration, and characteristics of this rack-mounted DC power supply system utilizing Li-ion batteries are described.

We describe a simulation method and design for a stand-alone hybrid power supply system composed of a wind turbine generator and photovoltaic modules. The system has been developed to supply power for telecommunications equipment in areas with no commercial power sources. We also report a comparison of the simulation results with actual measured data. The results show that the hybrid system can function effectively as a power supply for telecommunications equipment.