Balancing device and electrical storage device

Abstract

There is provided a balancing device that equalizes voltages between storage cells of a battery composed of a plurality of series-connected storage cells or voltages between electrical storage modules composed of a plurality of series-connected storage cells of the battery. The balancing device equalizes voltages between the energy storage modules by transferring electric power between the electrical storage modules through an element to which all of the electrical storage modules are connected, the transferring being realized by on-off control of current supply to each of the electrical storage modules, the on-off control being performed with a first duty cycle. Further, the balancing device introduces a period in which the on-off control is performed with a second duty cycle, the second duty cycle being different from the first duty cycle. Furthermore, the balancing device measures a voltage applied to each of the capacitance elements Cand Cwhich connect between the terminals of the electrical storage modules respectively. Furthermore, the balancing device determines the presence of an open circuit in lines which connect the capacitance elements Cand Cand the electrical storage modules, the determination being performed based on change of the voltages during the period which are applied to the capacitance elements Cand C