Electric circuit and diagnosis method

An electric circuit that switches connection among a plurality of storage cell units including a first storage cell unit and a second storage cell unit, a load of the plurality of storage cell units, and a power supply supplying power to the plurality of storage cell units, the electric circuit comprising:

• a first rectifier configured to rectify a current flowing between a first pole terminal of the power supply and a first pole terminal of the first storage cell unit with homopolarity with the first pole terminal of the power supply;
• a second rectifier configured to rectify a current being different from the current and flowing between the first pole terminal of the power supply and a first pole terminal of the second storage cell unit with homopolarity with the first pole terminal of the power supply;
• and
• a connection switching device configured to connect the plurality of storage cell units in series between the first pole terminal of the first storage cell unit and the first pole terminal of the second storage cell unit and release the series connection of the plurality of storage cell units during a period in which the power supply supplies power to the plurality of storage cell units,
• wherein the connection switching device includes
• a first contactor configured to switch connection and non-connection between a second pole terminal with heteropolarity with the first pole terminal of the first storage cell unit and the first pole terminal of the second storage cell unit, and
• a second contactor configured to switch connection and non-connection between the second pole terminal of the first storage cell unit and a second pole terminal with heteropolarity with the first pole terminal of the second storage cell unit,
• the electric circuit further comprising:
• a control unit configured to switch between a first connection mode in which the first storage cell unit and the second storage cell unit are connected in parallel and a second connection mode in which a third storage cell unit is connected in parallel to both ends of a pair of the first storage cell unit and the second storage cell unit connected in series,
• wherein the third storage cell unit is equipped in the load,
• wherein the connection switching device is able to electrically connect the first storage cell unit and the third storage cell unit in parallel, and
• wherein the control unit switches among the first connection mode, the second connection mode, and a third connection mode in which the first storage cell unit and the third storage cell unit are electrically connected in parallel.

A diagnosis method for an electric circuit that switches connection among a plurality of storage cell units including a first storage cell unit and a second storage cell unit, a load of the plurality of storage cell units, and a power supply supplying power to the plurality of storage cell units,

• wherein the electric circuit includes
• a first rectifier configured to rectify a current flowing between a first pole terminal of the power supply and a first pole terminal of the first storage cell unit with homopolarity with the first pole terminal of the power supply,
• a second rectifier configured to rectify a current being different from the current and flowing between the first pole terminal of the power supply and a first pole terminal of the second storage cell unit with homopolarity with the first pole terminal of the power supply, and
• a connection switching device configured to connect the plurality of storage cell units in series between the first pole terminal of the first storage cell unit and the first pole terminal of the second storage cell unit and release the series connection of the plurality of storage cell units during a period in which the power supply supplies power to the plurality of storage cell units,
• wherein the connection switching device includes
• a first contactor configured to switch connection and non-connection between a second pole terminal with heteropolarity with the first pole terminal of the first storage cell unit and the first pole terminal of the second storage cell unit, and
• a second contactor configured to switch connection and non-connection between the second pole terminal of the first storage cell unit and a second pole terminal with heteropolarity with the first pole terminal of the second storage cell unit, and
• wherein the diagnosis method comprises:
• performing a first diagnosis mode in which the first contactor is set to a cutoff state, the second contactor is set to a conductive state, and a voltage of a capacitor equipped in the load is determined;
• and
• performing a second diagnosis mode in which the first contactor is set to the conductive state, the second contactor is set to the cutoff state, and a voltage of a capacitor equipped in the load is determined, after the first diagnosis mode.