Ni-MH batteries and EDLCs hybrid stand-alone photovoltaic power system for digital access equipment

The authors propose a hybrid stand-alone photovoltaic power system with cylindrical photovoltaic (PV) modules that uses nickel metal hydride (NMH) batteries and electric double layer capacitors (EDLCs). This system is a potential power source for digital access equipment. The battery volume and weight can be reduced to about half those of a conventional PV power system and the installation area can be reduced to about one tenth. This paper describes the system configuration charging control technique for the Ni-MH batteries using the EDLCs, and the Ni-MH battery monitoring method. It also introduces a prototype PV power system. Experimental results show that this prototype system can operate with the desired control and monitoring characteristics