Abstract: A battery system for supplying electric energy from a primary battery or a secondary battery to a load. This system includes a battery consisting of the primary battery or the secondary battery, an electric double layer capacitor for storing electric energy from the battery, a limiting resistor for limiting the electric energy supplied from the battery to the electric double layer capacitor, and a discharge controller for controlling the electric double layer capacitor. The discharge controller causes the electric double layer capacitor to discharge the electric energy to the load intermittently in predetermined cycles while charging the electric double layer capacitor. A discharging time for discharging the electric energy from the electric double layer capacitor to the load is shorter than a charging time for charging the electric double layer capacitor with electric energy. At this time, a discharge current is greater than a charge current.

Abstract: A solar cell system stores electric power generated by solar cells and supplies the electric power to a load. This system includes a solar cell assembly having a capacity for generating electric power in a quantity consumed by the load in one day, the quantity being determined from an estimated quantity of solar radiation available on a rainy or cloudy day, and an electric double layer capacitor having a storage capacity corresponding at least to the quantity consumed by the load in one day.