Battery research for telecommunications power supply systems at NTT

With the development of multimedia systems, batteries are becoming increasingly important for use in telecommunications systems. High energy density, safe batteries have been studied for use in portable telecommunications equipment. At NTT, lithium batteries have been studied in order to achieve a high energy density battery. The relatively large capacity of valve regulated lead-acid (VRLA) batteries makes them suitable for backup power. To ensure the reliability of power supply systems the deterioration of batteries for back-up power should be periodically measured. However, it is difficult to measure the deterioration of VRLA batteries because they are sealed. Therefore, NTT has developed a simple method for measuring deterioration. On the other hand, since the power consumption of telecommunications for multimedia systems will increase, power saving will become much more important. For example, cogeneration systems using fuel cells will produce much residual heat energy, so it will be important to transform thermal energy into electrical energy to save power. The authors explain the following: the main uses and requirements of batteries at NTT and battery trends in Japan; a method of measuring deterioration of VRLAs; new types of cells, which are a high energy density battery and a thermocell that can be simultaneously discharged and thermocharged.