Battery system

A battery system comprising:

• a battery circuit group in which a plurality of battery circuits connected in parallel, each including a plurality of battery units connected in series, each including a positive electrode end, a negative electrode end, a battery and a switching unit;
• and
• a control unit that determines a charge state of the battery and controls the switching unit based on the determined charge state,
• wherein in each of the battery units, the switching unit switches a state of the battery unit between a first state, in which the battery is connected between the positive electrode end and the negative electrode end, and a second state, in which the positive electrode end and the negative electrode end are connected without the battery,
• wherein when discharging of the battery circuit group, the control unit controls the switching unit such that the state of the battery unit including the battery determined to be not fully discharged becomes the first state, and the state of the battery unit including the battery determined to be fully discharged becomes the second state,
• wherein each of the battery circuits has a diode connected in series with the plurality of battery units such that a discharge direction of the battery is a forward direction, and
• wherein the control unit controls the switching unit such that when charging of the battery circuit group, the state of the battery unit including the battery determined to be not fully charged becomes the first state, and the state of the battery unit including the battery determined to be fully charged becomes the second state.