Battery control device for homogenizing battery cells
A battery control device that controls a battery assembly includes a first determining unit that determines whether a voltage difference between minimum and maximum values of OCVs of battery cells constituting the battery assembly and having an SOC-OCV characteristic curve including a flat region is equal to or larger than a predetermined voltage value, a second determining unit that determines whether the OCV of each battery cell is lower than a lower-limit voltage of the flat region, or is equal to or higher than the lower-limit voltage and lower than an upper-limit voltage, or is higher than the upper-limit voltage, a controller that executes control selected from SOC raising control, SOC lowering control, and SOC keeping control of the battery cells, based on determination results of the first and second determining units, and a processor that homogenizes the SOCs of the battery cells controlled by the controller.
1. A battery control device that controls a battery assembly, the battery control device comprising:
a processor programmed to:
perform a first determination of whether a voltage difference between a minimum value and a maximum value of open circuit voltages of a plurality of battery cells of the battery assembly is equal to or larger than a predetermined voltage value, each of the battery cells having an SOC-OCV characteristic curve including a flat region in which a rate of change of an open circuit voltage with respect to a power storage amount is smaller than that in an adjacent region;
perform a second determination of whether the open circuit voltage of each of the battery cells is lower than a lower-limit voltage of the flat region, or is equal to or higher than the lower-limit voltage and lower than an upper-limit voltage of the flat region, or is higher than the upper-limit voltage;
execute control for raising power storage amounts of the battery cells, when the processor determines that: (1) the voltage difference is equal to or larger than the predetermined value; (2) the open circuit voltage of at least one of the battery cells is equal to or higher than the upper-limit voltage, and (3) the open circuit voltage of at least another one of the battery cells is lower than the upper-limit voltage; and
after performing the first determination and the second determination, execute control for homogenizing the power storage amounts of the battery cells controlled by the controller.
2. The battery control device according to claim 1 , wherein the processor is programmed to:
start a count upon a trip counter being reset; and
when the count reaches a predetermined count value and the processor determines that the voltage difference is smaller than the predetermined value and the open circuit voltages of all of the battery cells are equal to or higher than the lower-limit voltage and lower than the upper-limit voltage, perform the control for raising the power storage amounts of the battery cells.
3. The battery control device according to claim 1 , wherein the processor performs control for keeping the power storage amounts of the battery cells, when the processor determines that the voltage difference is equal to or larger than the predetermined value, and the processor determines that the open circuit voltages of all of the battery cells are lower than the lower-limit voltage or higher than the upper-limit voltage.
4. The battery control device according to claim 1 , wherein the processor performs control for lowering the power storage amounts of the battery cells, when the processor determines that the voltage difference is equal to or larger than the predetermined value, and the processor determines that the open circuit voltage of at least one of the battery cells is equal to or higher than the lower-limit voltage and lower than the upper-limit voltage, and the open circuit voltages of all the plurality of the battery cells other than the at least one of the battery cells are lower than the lower-limit voltage.
5. The battery control device according to claim 4 , wherein the processor is programmed to:
perform a third determination of a power storage amount of a battery to which electric power discharged from the battery cells under the control for lowering the power storage amounts of the battery cells is allowed to be transferred; and
execute the control for lowering the power storage amounts of the battery cells by transferring electric power to the battery, based on the results of the first and second determinations, when the processor determines that the power storage amount of the battery is equal to or smaller than a predetermined value.