Power supply device

A power supply device comprising:

• a battery module in which batteries are connected in series;
• a negative electrode output terminal to which a negative electrode terminal of the battery module is connected;
• a positive electrode output terminal to which a positive electrode terminal of the battery module and a connection point between predetermined batteries are individually connected through switches;
• an output voltage detecting circuit for detecting an output voltage between the positive electrode output terminal and the negative electrode output terminal;
• a charging current adjusting circuit for adjusting a charging current of the battery module;
• a state-of-charge detecting circuit for detecting a state-of-charge of each battery of the battery module;
• and
• a control device for controlling charge and discharge of the battery module,
• wherein the control device includes:
• means for controlling the switches, so that the output voltage is within a specific range;
• and
• means for controlling the charging current adjusting circuit on the basis of the state-of-charge of each battery of the battery module.