Battery charge/discharge device

A battery charging and discharging device comprising:

• a main power conversion unit configured to charge and discharge multiple cells that are connected in series;
• multiple transfer switch units connected to the multiple cells, respectively, in a one-to-one way and each configured to perform a connection and separation between each cell and the main power conversion unit;
• multiple auxiliary power conversion units configured to charge and discharge the multiple cells, respectively;
• and
• a control unit configured to control the main power conversion unit so that constant voltage control is performed on the multiple cells based on a total voltage of voltages of the multiple cells and to control the multiple auxiliary power conversion units so that the voltage of each of the multiple cells is maintained at a target voltage of a corresponding cell in a constant voltage interval for the multiple cells,
• wherein each of the multiple transfer switch units comprises:
• a serial switch unit that is connected to each of the multiple cells in series;
• and
• a bypass switch unit that is connected to each of the multiple cells in parallel,
• the serial switch unit comprises first and second semiconductor relays that are mutually connected in series and first and second diodes that are connected to the first and second semiconductor relays in parallel, respectively, and
• the bypass switch unit comprises third and fourth semiconductor relays that are mutually connected in series and third and fourth diodes that are connected to the third and fourth semiconductor relays in parallel, respectively.