Secondary battery control device

Abstract

Provided is a control device 10 used for a secondary battery 110 and being capable of limiting a power value per unit time of the secondary battery 110 without excessively limiting an allowable power value of the secondary battery 110. The control device 10 for the secondary battery 110 has an allowable power setting unit 421 and an allowable power limiting unit 422. On the basis of predetermined information about the secondary battery 110, the allowable power setting unit 421 sets an allowable power value allowed for the secondary battery 110 in at least one of discharging and charging of the secondary battery 110. Before the power value of the secondary battery 110 reaches the allowable power value, the allowable power limiting unit 422 limits the power value. The allowable power limiting unit 422 limits the power value at stages by two or more different ratios.

Description

Control Device for Secondary Battery

[0001] The present invention relates to a control device for a secondary battery.

[0002] Conventionally, a technique for limiting the power value per unit time of a secondary battery has been known (see, for example, Patent Document 1).

[0003] International Publication No. 2008 / 111594

[0004] There is a demand for a control device for a secondary battery that can limit the power value per unit time of the secondary battery without excessively limiting the allowable power value of the secondary battery.

[0005] The control device for a secondary battery includes an allowable power setting unit that sets an allowable power value allowed for the secondary battery in at least one of discharging and charging of the secondary battery based on predetermined information of the secondary battery, and an allowable power limiting unit that limits the power value before the power value of the secondary battery reaches the allowable power value. The allowable power limiting unit limits the power value stepwise by two or more different ratios.

[0006] According to the present invention, it is possible to obtain a control device for a secondary battery that can limit the power value per unit time of the secondary battery without excessively limiting the allowable power value of the secondary battery.

[0007] Block diagram showing a battery system 1 etc. including the control device 10 of the secondary battery 110 of the first embodiment. Block diagram showing the battery state estimation control unit 400 of the battery system 1. Graph showing the relationship between the discharge allowable power limiting rate [%] etc. of the secondary battery 110 of the first embodiment and the threshold value of the discharge voltage [V] of the secondary battery 110. Graph showing the relationship between the allowable power [kW / sec] per unit time of the secondary battery 110 of the first embodiment and the threshold value of the discharge voltage [V] of the secondary battery 110. Graph showing the hunting phenomenon of a proportional secondary battery. Graph showing the relationship between the charge allowable power limiting rate [%] of the secondary battery 110 of the second embodiment and the threshold value of the charge voltage [V] of the secondary battery 110.

[0008] (First Embodiment) (Configuration of Battery System 1 Including Control Device 10 for Secondary Battery 110) The configuration of the battery system 1 including the control device 10 for secondary battery 110 will be described with reference to Figures 1 to 4.

[0009] Figure 1 is a block diagram showing the battery system 1, including the control device 10 of the secondary battery 110 in the first embodiment. Figure 2 is a block diagram showing the battery state estimation control unit 400 of the battery system 1. Figure 3 is a graph showing the relationship between the limit rate [%] of the discharge allowable power of the secondary battery 110 in the first embodiment and the threshold value of the discharge voltage [V] of the secondary battery 110. Figure 4 is a graph showing the relationship between the allowable power per unit time [kW / sec] of the secondary battery 110 in the first embodiment and the threshold value of the discharge voltage [V] of the secondary battery 110.

[0010] In the first embodiment, the control device 10 for the secondary battery 110 includes, for example, an allowable power setting unit 421 and an allowable power limiting unit 422 of the battery state estimation control unit 400 of the battery system 1, as shown in Figure 2.

[0011] The battery system 1 is a system that supplies power from a secondary battery 110 to an external power source. Examples of power sources include electric vehicles, hybrid vehicles, trains, and industrial equipment. The battery system 1 shown in Figure 1 is a system that supplies power from a secondary battery 110 to a motor generator 1300 (M / G) used for driving a hybrid vehicle.

[0012] The battery system 1 is connected to the inverter 1200 via a pair of relays 1100. The inverter 1200 converts the power from the secondary battery 110 to AC and supplies it to the motor generator 1300 from the battery system 1. In Figure 1, the motor generator 1300 is referred to as M / G. The motor / inverter control unit 1400 controls the inverter 1200 and the motor generator 1300. The vehicle control unit 1500 determines the distribution of power output from the battery pack 100 based on information about the secondary battery 110 input from the battery system 1, information input from the motor / inverter control unit 1400, information input from an engine (not shown), etc.

[0013] As shown in Figure 1, the battery system 1 includes a battery pack 100, a battery control unit 200, a measurement unit 300, a battery state estimation control unit 400, a communication unit 500, and a storage unit 600. The configuration of the battery pack 100 to the storage unit 600 included in the battery system 1 will be described below.

[0014] (Configuration of the battery pack 100) The configuration of the battery pack 100 will be explained with reference to Figure 1.

[0015] The battery pack 100 supplies power to an external power source. The battery pack 100 includes a plurality of secondary batteries 110. In the battery pack 100, the plurality of secondary batteries 110 are divided into two groups: a first battery group 100A and a second battery group 100B. In the battery pack 100, the plurality of secondary batteries 110 may be divided into three or more groups, or into one group. The first battery group 100A and the second battery group 100B are connected in series. The first battery group 100A and the second battery group 100B may be connected in parallel. In the first battery group 100A and the second battery group 100B, the plurality of secondary batteries 110 are connected in series. In the first battery group 100A and the second battery group 100B, the plurality of secondary batteries 110 may be connected in series and in parallel, or in parallel. The secondary batteries 110 are, for example, lithium-ion secondary batteries. The secondary battery 110 may be a nickel-metal hydride battery, a lead-acid battery, an electric double-layer capacitor, or a device equipped with an energy storage function.

[0016] (Configuration of the battery control unit 200) The configuration of the battery control unit 200 will be described with reference to Figure 1.

[0017] The battery control unit 200 controls the secondary batteries 110 included in the battery pack 100. The battery control unit 200 includes a first battery control unit 210 and a second battery control unit 220. The first battery control unit 210 controls the first battery group 100A based on information input from the battery state estimation control unit 400, the measurement unit 300, etc. The first battery control unit 210 measures the voltage of each secondary battery 110 included in the first battery group 100A. The first battery control unit 210 is supplied with driving power from the first battery group 100A. The second battery control unit 220 controls the second battery group 100B based on information input from the battery state estimation control unit 400, the measurement unit 300, etc. The second battery control unit 220 measures the voltage of each secondary battery 110 included in the second battery group 100B. The second battery control unit 220 is supplied with driving power from the second battery group 100B. The battery control unit 200 may be configured integrally with the battery state estimation control unit 400.

[0018] (Configuration of the measuring unit 300) The configuration of the measuring unit 300 will be explained with reference to Figure 1.

[0019] The measuring unit 300 measures the current, voltage, and temperature of the secondary batteries 110 included in the battery pack 100. The measuring unit 300 includes a current measuring unit 310, a voltage measuring unit 320, and a temperature measuring unit 330. The current measuring unit 310 measures the current of the secondary batteries 110 included in the battery pack 100. The current measuring unit 310 is connected in series with the battery pack 100. The voltage measuring unit 320 measures the voltage of the secondary batteries 110 included in the battery pack 100. The voltage measuring unit 320 is connected in parallel with the battery pack 100. The temperature measuring unit 330 measures the temperature of one or more secondary batteries 110 included in the battery pack 100. The temperature measuring unit 330 is attached to the secondary batteries 110. The measuring unit 300 may be configured integrally with the battery state estimation control unit 400.

[0020] (Configuration of the battery state estimation control unit 400) The configuration of the battery state estimation control unit 400 will be described with reference to Figures 1 to 4.

[0021] The battery state estimation control unit 400 estimates and controls the state of the secondary battery 110 included in the battery pack 100. The battery state estimation control unit 400 includes a SOC / SOHR calculation unit 410 and a battery state calculation unit 420.

[0022] (Configuration of the SOC / SOHR calculation unit 410) The configuration of the SOC / SOHR calculation unit 410 will be explained with reference to Figure 2.

[0023] The SOC / SOHR calculation unit 410 calculates the State of Charge (SOC) and State of Health based on Resistance (SOHR) of the secondary battery 110 based on the current, voltage, and temperature of the secondary battery 110 input from the measurement unit 300. The SOC / SOHR calculation unit 410 outputs the calculated SOC and SOHR of the secondary battery 110 to the battery state calculation unit 420.

[0024] The voltage information of the secondary battery 110 input to the SOC / SOHR calculation unit 410 includes information such as the maximum voltage, average voltage, minimum voltage, and voltage variation of the secondary battery 110. The current information of the secondary battery 110 includes the instantaneous current acquired at the same timing as the voltage acquisition timing. The current information of the secondary battery 110 includes the interval average current obtained by continuously sampling the current flowing through the battery pack 100 over a predetermined time period and averaging the sampled current values. The temperature information of the secondary battery 110 includes the maximum temperature, average temperature, and minimum temperature obtained by multiple temperature sensors provided on the battery pack 100. The temperature information of the secondary battery 110 includes temperatures that reflect the temperature distribution of the battery pack 100, the first battery group 100A, the second battery group 100B, and the secondary battery 110. The information input to the SOC / SOHR calculation unit 410 includes the results of a diagnosis of whether the secondary battery 110 is overcharged or over-discharged, and abnormal signals output from the communication unit 500 if a communication error occurs in the communication unit 500, etc. The diagnosis of the secondary battery 110 is performed, for example, by the measurement unit 300.

[0025] The SOC / SOHR calculation unit 410 may be replaced with an SOC / SOHC calculation unit. That is, in the first embodiment, the SOHC may be calculated instead of the SOHR. SOHC (State Of Health based on Capacity) is the degradation rate of the capacity of the secondary battery 110. In such a configuration, the configuration is changed from calculating the increase in the resistance value of the secondary battery 110 to calculating the capacity of the secondary battery 110. That is, in such a configuration, the capacity of the secondary battery 110 is calculated based on the SOC of the secondary battery 110 at a predetermined time and a value that takes into account the integrated current value of the secondary battery 110 from the predetermined time onward. Furthermore, in the first embodiment, the SOC / SOHR calculation unit 410 and the SOC / SOHC calculation unit may be used in combination.

[0026] (Configuration of the battery state calculation unit 420) The configuration of the battery state calculation unit 420 will be explained with reference to Figures 2 to 4.

[0027] The battery state calculation unit 420 calculates the state of the secondary battery 110 included in the battery pack 100. The battery state calculation unit 420 receives information regarding the SOC and SOHR of the secondary battery 110 from the SOC / SOHR calculation unit 410. Based on the information regarding the SOC and SOHR of the secondary battery 110, the battery state calculation unit 420 calculates and outputs the charge-to-charge power and discharge-to-charge power of the secondary battery 110. The charge-to-charge power of the secondary battery 110 is the power corresponding to the upper limit voltage at which the secondary battery 110 can be charged, and includes a predetermined margin. The discharge-to-charge power of the secondary battery 110 is the power corresponding to the lower limit voltage at which the secondary battery 110 can be discharged, and includes a predetermined margin.

[0028] The battery state calculation unit 420 includes an allowable power setting unit 421 and an allowable power limiting unit 422.

[0029] (Configuration of the Allowable Power Setting Unit 421) The configuration of the allowable power setting unit 421 included in the battery state calculation unit 420 will be explained with reference to Figure 2.

[0030] The allowable power setting unit 421 is included in the control device 10 of the secondary battery 110.

[0031] The allowable power setting unit 421 sets the allowable power value for the secondary battery 110 during discharge and charging, based on predetermined information of the secondary battery 110. The predetermined information includes the voltage value (OCV), current value, internal resistance value (DCR: Direct Current Resistance), charge state, temperature, and degradation state (SOHR, SOHC) of the secondary battery 110. The allowable power value of the secondary battery 110 is set based on the allowable voltage value of the secondary battery 110.

[0032] The allowable power setting unit 421 sets the allowable power of the secondary battery 110 based on the SOC, SOHR, voltage, current, and temperature of the secondary battery 110. The allowable power setting unit 421 inputs the battery information of the secondary battery 110 (SOC, voltage, temperature, and current, etc.) into the equivalent circuit model of the secondary battery 110 and calculates the allowable power of the secondary battery 110. In other words, the allowable power setting unit 421 sets the allowable power of the secondary battery 110 based on the equivalent circuit model of the secondary battery 110. The equivalent circuit model of the secondary battery 110 is shown in the allowable power setting unit 421 in Figure 2 and corresponds to equation (1) described later.

[0033] (Configuration of the allowable power limiting unit 422) The configuration of the allowable power limiting unit 422 included in the battery state calculation unit 420 will be explained with reference to Figures 2 to 4.

[0034] The permissible power limiting unit 422 is included in the control device 10 of the secondary battery 110.

[0035] The allowable power limiting unit 422 determines whether or not to limit the allowable power of the secondary battery 110 based on information such as the state of charge (SOC), voltage, current, and temperature of the secondary battery 110, in relation to the allowable power of the secondary battery 110 set by the allowable power setting unit 421. If the allowable power limiting unit 422 determines that the allowable power of the secondary battery 110 should be limited, it limits the allowable power of the secondary battery 110.

[0036] The permissible power limiting unit 422 limits the power value of the secondary battery 110 before it reaches the permissible power value, for example, when the secondary battery 110 is being discharged. The permissible power limiting unit 422 limits the power value in stages by two different ratios. When the secondary battery 110 is being discharged, the permissible power limiting unit 422 limits the power value in stages such that the amount of change in the power value per unit time due to the power value limiting implemented relatively earlier is smaller than the amount of change in the power value per unit time due to the power value limiting implemented relatively later. The amount of change in the power value per unit time due to the power value limiting implemented relatively earlier corresponds to the amount of change in the first limiting rate region S1 in Figure 3. The amount of change in the power value corresponds to the limiting rate [%] of the discharge permissible power of the secondary battery 110 and the discharge permissible power [kW] of the secondary battery 110. The amount of change in the power value per unit time due to the power value limiting implemented relatively later corresponds to the amount of change in the second limiting rate region S2 in Figure 3.

[0037] The allowable power limiting unit 422 starts limiting the power value of the secondary battery 110 when the power of the secondary battery 110 decreases and reaches a predetermined threshold related to limiting the power value of the secondary battery 110. The predetermined threshold corresponds to the first threshold Vth1 shown in Figure 3. The predetermined threshold is, for example, 3.0V in OCV. The predetermined threshold includes thresholds measured by sensors, such as the voltage V, temperature T, current I, and container pressure of the secondary battery 110. The predetermined threshold also includes thresholds calculated, such as the SOC of the secondary battery 110.

[0038] The allowable power limiting unit 422 releases the power limit after it has limited the power value. The allowable power limiting unit 422 relaxes the second threshold for releasing the power limit more than the first threshold for limiting the power value. For example, if the allowable power limiting unit 422 starts limiting the allowable power of the secondary battery 110 when the SOC is 90%, it releases the allowable power limit of the secondary battery 110 after the SOC becomes 80%. Also, for example, if the allowable power limiting unit 422 starts limiting the allowable power of the secondary battery 110 when the voltage of the secondary battery 110 is 4.3V, it releases the allowable power limit of the secondary battery 110 after the voltage of the secondary battery 110 becomes 4.2V.

[0039] (Configuration of the change amount limiting unit 422A) The configuration of the change amount limiting unit 422A will be explained with reference to Figure 2.

[0040] The change amount limiting unit 422A includes a charge change amount limiting unit 422A1 and a discharge change amount limiting unit 422A2.

[0041] The charge change limiting unit 422A1 limits the maximum amount of change per unit time in the charge allowable power of the secondary battery 110 during charging in order to suppress abrupt changes in the charge allowable power of the secondary battery 110 during charging. The charge change limiting unit 422A1 receives the set charge allowable power from the allowable power setting unit 421. The set charge allowable power is different from the final allowable power output from the allowable power limiting unit 422. The charge change limiting unit 422A1 receives the charge allowable limit value from the charge allowable power limiting unit 422B1 via the charge multiplication unit 431. The charge change limiting unit 422A1 calculates and outputs the charge allowable power based on the set charge allowable power input from the allowable power setting unit 421 and the charge allowable limit value input from the charge allowable power limiting unit 422B1.

[0042] The discharge change limiting unit 422A2 limits the maximum amount of change per unit time in the discharge allowable power of the secondary battery 110 during discharge in order to suppress abrupt changes in the discharge allowable power of the secondary battery 110 during discharge. The discharge change limiting unit 422A2 receives the set discharge allowable power from the allowable power setting unit 421. The set discharge allowable power is different from the final allowable power output from the allowable power limiting unit 422. The discharge change limiting unit 422A2 receives the discharge allowable limit value from the discharge allowable power limiting unit 422B2 via the discharge multiplication unit 432. The discharge change limiting unit 422A2 calculates and outputs the discharge allowable power based on the set discharge allowable power input from the allowable power setting unit 421 and the discharge allowable limit value input from the discharge allowable power limiting unit 422B2.

[0043] (Configuration of the allowable power limiting unit 422B) The configuration of the allowable power limiting unit 422B will be explained with reference to Figure 2.

[0044] The allowable power limiting section 422B includes a charge allowable power limiting section 422B1 and a discharge allowable power limiting section 422B2.

[0045] The charge allowable power limiting unit 422B1 receives the voltage, current, and temperature of the secondary battery 110 during charging from the measurement unit 300. The charge allowable power limiting unit 422B1 receives the SOC of the secondary battery 110 during charging from the SOC / SOHR calculation unit 410. The charge allowable power limiting unit 422B1 outputs a signal regarding the limitation of the allowable power of the secondary battery 110 during charging to the charge change amount limiting unit 422A1 of the change amount limiting unit 422A via the charge multiplication unit 431. The charge multiplication unit 431 sets a charge limiting rate for limiting the allowable power of the secondary battery 110 during charging from 100% (no limitation) to 0% (fully limited, 0 kW).

[0046] The discharge allowable power limiting unit 422B2 receives the voltage, current, and temperature of the secondary battery 110 during discharging from the measurement unit 300. The discharge allowable power limiting unit 422B2 receives the SOC of the secondary battery 110 during discharging from the SOC / SOHR calculation unit 410. The discharge allowable power limiting unit 422B2 outputs a signal regarding the limitation of the allowable power of the secondary battery 110 during discharging to the discharge change amount limiting unit 422A2 of the change amount limiting unit 422A via the discharge multiplication unit �432. The discharge multiplication unit 432 sets a discharge limiting rate for limiting the allowable power of the secondary battery 110 during discharging from 100% (no limitation) to 0% (fully limited, 0 kW).

[0047] (Voltage V of the secondary battery 110) The voltage V of the secondary battery 110 will be described with reference to Equation (1).

[0048] Equation (1) represents the voltage V of the secondary battery 110.

[0049]

[0050] The voltage V of the secondary battery 110 is represented by the sum of the value of the open circuit voltage (OCV: Open Circuit Voltage), the value obtained by multiplying the current I by the DC resistance Ro, and the value obtained by connecting the capacitor component τ and the polarization voltage Vp in parallel. The polarization voltage Vp occurs when the current I flows through the CR parallel circuit of the polarization resistance Rp and the polarization capacitance component of the secondary battery 110.

[0051] (Chargeable power of secondary battery 110) The chargeable power of secondary battery 110 will be explained with reference to equations (2) to (5).

[0052] Equation (2) represents the rechargeable current Ichg of the secondary battery 110.

[0053]

[0054] The rechargeable current Ichg of the secondary battery 110 is the maximum current that can be input to the secondary battery 110. The rechargeable current Ichg of the secondary battery 110 is the current of the secondary battery 110 when the voltage V of the secondary battery 110 is equal to the upper limit voltage Vmax used in the battery system 1, in the equivalent circuit model of the secondary battery 110 shown in the allowable power setting unit 421 of Figure 2. Equation (2) is derived by substituting the current I as the reference and rearranging the I × Ro part of equation (1). The open-circuit voltage OCV of the secondary battery 110 is calculated based on the current SOC and temperature T of the secondary battery 110, while referring to the OCV-SOC map which shows the correspondence between the SOC of the secondary battery 110 and the battery temperature. The DC resistance Ro of the secondary battery 110 is calculated from the current SOC and temperature T of the secondary battery 110, while referring to the Ro map.

[0055] Equation (3) represents the maximum rechargeable current Imax,chg of the secondary battery 110.

[0056]

[0057] The secondary battery 110 is controlled so that it is not charged beyond the upper limit current Ilimit on the charging side of the battery system 1, even if the rechargeable current Imax,chg is less than the maximum rechargeable current Imax,chg.

[0058] Equation (4) represents the maximum rechargeable voltage Vmax,chg of the secondary battery 110.

[0059]

[0060] Equation (4) is derived by rearranging the I × Ro part of equation (1). The Ro map is composed of the values ​​of a new secondary battery 110. Equation (4) takes into account the case where the secondary battery 110 has deteriorated by multiplying the Ro map by the SOHR of the secondary battery 110.

[0061] Equation (5) represents the charge-permissible power Wchg of the secondary battery 110.

[0062]

[0063] The chargeable power Wchg of the secondary battery 110 is derived by multiplying the chargeable current Imax,chg expressed in equation (3) by the chargeable voltage Vmax,chg expressed in equation (4). The battery pack 100 is constructed by connecting N secondary batteries 110 in series. Therefore, the chargeable power Wchg of the battery pack 100 is expressed by multiplying the chargeable power of the secondary battery 110 by N.

[0064] (Discharge power of secondary battery 110) The discharge power of secondary battery 110 will be explained with reference to equations (6) to (9).

[0065] Equation (6) represents the dischargeable current Idischg of the secondary battery 110.

[0066]

[0067] The dischargeable current Idischg of the secondary battery 110 is the maximum current that can be output from the secondary battery 110. The dischargeable current Idischg of the secondary battery 110 is defined as the current of the secondary battery 110 when the voltage V of the secondary battery 110 is equal to the lower limit voltage Vmin used in the battery system 1, in the equivalent circuit model of the secondary battery 110 shown in the allowable power setting section 421 of Figure 2. Equation (6) is derived by rearranging the part of equation (1) relating to the current I.

[0068] Equation (7) represents the maximum dischargeable current Imax,dischg of the secondary battery 110.

[0069]

[0070] The secondary battery 110 is controlled so that it does not discharge beyond the upper limit current Ilimit on the discharge side of the battery system 1, even if the discharge current Imax,dischg is less than the chargeable current.

[0071] Equation (8) represents the maximum discharge voltage Vmax,dischg of the secondary battery 110.

[0072]

[0073] Equation (8) is derived by rearranging the I × Ro part of equation (1). The Ro map is composed of the values ​​of a new secondary battery 110. Equation (8) considers the case where the secondary battery 110 has deteriorated by multiplying the Ro map by the SOHR of the secondary battery 110.

[0074] Equation (9) represents the discharge power Wdischg of the secondary battery 110.

[0075]

[0076] The dischargeable power Wdischg of the secondary battery 110 is derived by multiplying the dischargeable current Imax,dischg, expressed in equation (7), by the dischargeable voltage Vmax,dischg, expressed in equation (8). The battery pack 100 is constructed by connecting N secondary batteries 110 in series. Therefore, the dischargeable power Wdischg of the battery pack 100 is expressed by multiplying the dischargeable power of the secondary battery 110 by N.

[0077] (Principle of calculating the charge limiting rate Dchg of the secondary battery 110 by the charge allowable power limiting unit 422B1) The principle of calculating the charge limiting rate Dchg of the secondary battery 110 by the charge allowable power limiting unit 422B1 will be explained with reference to equation (10).

[0078] Equation (10) represents the charge limiting rate Dchg of the secondary battery 110.

[0079]

[0080] Dmax_chg is the maximum value of the charge limiting rate Dchg of the secondary battery 110. Dvol_chg is the limiting rate at which charging of the secondary battery 110 is restricted due to overcharging of the secondary battery 110. Dsoc_chg is the limiting rate at which charging of the secondary battery 110 is restricted due to reaching the upper limit of the State of Charge (SOC) of the secondary battery 110. Dcur is the limiting rate at which charging of the secondary battery 110 is restricted due to an abnormal current in the secondary battery 110. Dtemp is the limiting rate at which charging of the secondary battery 110 is restricted due to an abnormal temperature in the secondary battery 110.

[0081] Each limiting factor is set within the range of 0% to 100%. After each limiting factor is calculated by the charge-permitted power limiting unit 422B1, the charge limiting factor Dchg of the secondary battery 110 is determined based on the minimum limiting factor among the respective limiting factors. If an abnormality occurs in any of the indicators representing the battery state of the secondary battery 110, such as voltage V, current I, temperature T, and SOC, the charge-permitted power limiting unit 422B1 limits the charge-permitted power of the secondary battery 110. In this case, it is preferable to determine the charge limiting factor Dchg of the secondary battery 110 based on the minimum limiting factor, i.e., the strictest limiting factor.

[0082] Dchg is the charge limiting factor. Dchg is set within the range of 0% to Dmax_chg%. When Dmax_chg is set to 100%, Dchg is calculated without constraints according to Dvol_chg, Dsoc_chg, Dcur, and Dtemp. When Dmax_chg is set to less than 100%, the upper limit of Dchg is calculated based on factors other than the voltage, current, temperature, and SOC of the secondary battery 110. In other words, Dmax_chg may be used as a margin means to always set a limiting factor for the allowable power of the secondary battery 110, or it may be used to set an upper limit of the limiting factor due to factors not attributable to the state of the secondary battery 110.

[0083] (Principle of calculating the discharge limiting rate Ddischg of the secondary battery 110 by the discharge power limiting unit 422B2) The principle of calculating the discharge limiting rate Ddischg of the secondary battery 110 by the discharge power limiting unit 422B2 will be explained with reference to equation (11).

[0084] Equation (11) represents the discharge limiting rate Ddischg of the secondary battery 110.

[0085]

[0086] Dmax_dischg is the maximum value of the limiting factor Ddischg of the secondary battery 110. Dvol_dischg is the limiting factor that restricts the charging of the secondary battery 110 due to overcharging of the secondary battery 110. Dsoc_dischg is the limiting factor that restricts the charging of the secondary battery 110 due to reaching the lower limit of the State of Charge (SOC) of the secondary battery 110. The method for calculating the limiting factor Dvol_dischg corresponds to the method for calculating the limiting factor of the discharge voltage of the secondary battery 110 by the discharge allowable power limiting unit 422B2. Dcur is the limiting factor that restricts the charging of the secondary battery 110 due to an abnormal current in the secondary battery 110. Dtemp is the limiting factor that restricts the charging of the secondary battery 110 due to an abnormal temperature in the secondary battery 110.

[0087] Each limiting factor is set within the range of 0% to 100%. After each limiting factor is calculated by the discharge allowable power limiting unit 422B2, the discharge limiting factor Ddischg of the secondary battery 110 is determined based on the minimum limiting factor among the various limiting factors.

[0088] Ddischg is the discharge limiting factor. Ddischg is set within the range of 0% to Dmax_dischg%. If Dmax_dischg is set to 100%, Ddischg is calculated without constraints according to Dvol_dischg, Dsoc_dischg, Dcur, and Dtemp. If Dmax_dischg is set to less than 100%, the upper limit of Ddischg is calculated based on factors other than the voltage, current, temperature, and SOC of the secondary battery 110.

[0089] (An example of calculating the discharge limiting rate Ddischg of the secondary battery 110 by the discharge allowable power limiting unit 422B2) An example of calculating the discharge limiting rate Ddischg of the secondary battery 110 by the discharge allowable power limiting unit 422B2 will be explained with reference to Figure 3 and equation (11).

[0090] The upper limit threshold Vth_sys is a threshold corresponding to the upper limit of the voltage of the secondary battery 110 within the normal operating range of the battery system 1. The upper limit threshold Vth_sys is, for example, the voltage of the secondary battery 110 just before lithium deposition occurs.

[0091] The lower threshold Vth_cell is a threshold value corresponding to the lower limit of the voltage of the secondary battery 110 within the normal operating range of the battery system 1. The lower threshold Vth_cell is, for example, the voltage just before the secondary battery 110 over-discharges.

[0092] The limit rate is set in two separate limit rate areas: a first limit rate area S1 and a second limit rate area S2. The first limit rate area S1 and the second limit rate area S2 are adjacent to each other. The first limit rate area S1 and the second limit rate area S2 are set between the upper threshold Vth_sys and the lower threshold Vth_cell.

[0093] The first limiting rate region S1 is set closer to the upper limit threshold Vth_sys than the second limiting rate region S2. The first threshold Vth1 is set to a value less than or equal to the upper limit threshold Vth_sys. The first limiting rate region S1 is defined as the voltage region from the first threshold Vth1 to the second threshold Vth2. The first threshold Vth1 is the voltage value at the start of the voltage limiting of the secondary battery 110 in the first limiting rate region S1. The second threshold Vth2 is the voltage value at the end of the voltage limiting of the secondary battery 110 in the first limiting rate region S1.

[0094] The second limiting rate region S2 is set closer to the lower threshold Vth_cell than the first limiting rate region S1. The third threshold Vth3 is set to a value greater than or equal to the lower threshold Vth_cell. The second limiting rate region S2 is defined as the voltage region from the second threshold Vth2 to the third threshold Vth3. The second threshold Vth2 is the voltage value at the start of the voltage limiting of the secondary battery 110 in the second limiting rate region S2. The third threshold Vth3 is the voltage value at the end of the voltage limiting of the secondary battery 110 in the second limiting rate region S2.

[0095] The second threshold Vth2 serves as both the termination voltage threshold for the first limiting rate region S1 and the starting voltage threshold for the second limiting rate region. The second threshold Vth2 is set to a value between the first threshold Vth1 and the third threshold Vth3, and is closer to the third threshold Vth3 than to the first threshold Vth1. The second threshold Vth2 is provided to ensure that the system transitions from the first limiting rate region S1 to the second limiting rate region S2 when the voltage of the secondary battery 110 drops to near the over-discharge voltage.

[0096] Equation (12) shows the relative magnitudes of the first threshold Vth1, the third threshold Vth3, and the second threshold Vth2 of the secondary battery 110.

[0097]

[0098] The first limiting rate region S1 is the region where the voltage limiting rate of the secondary battery 110 is within the range of 100% to a_Vth2 (%). The second limiting rate region S2 is the region where the voltage limiting rate of the secondary battery 110 is within the range of a_Vth2 (%) to 0%. The second threshold Vth2 is the limiting rate that forms the boundary between the first limiting rate region S1 and the second limiting rate region S2. The second threshold Vth2 is set as a value where the voltage limiting rate of the secondary battery 110 is greater than 50% and less than or equal to 100%. In other words, the limiting rate range of the first limiting rate region S1 is set to be wider than the limiting rate range of the second limiting rate region S2.

[0099] The first limiting rate region S1 has a wider voltage range and a smaller change in the limiting rate per unit voltage than the second limiting rate region S2. As shown in Figure 3, the slope representing the change in the limiting rate in the first limiting rate region S1 is set to be gentler than the slope of the second limiting rate region S2. The first limiting rate region S1, with its gentle slope of the limiting rate, is set on the side of the upper limit threshold Vth_sys of the battery system 1. The second limiting rate region S2, with its steep slope of the limiting rate, is set on the side of the lower limit threshold Vth_cell of the battery system 1.

[0100] (Normal limitations on the discharge voltage of the secondary battery 110) The normal limitations on the discharge voltage of the secondary battery 110 will be explained with reference to Figure 3.

[0101] The battery system 1 normally operates within a voltage range above the lower threshold Vth_cell. The battery system 1 repeatedly charges and discharges the secondary battery 110 depending on the conditions of the electric vehicle equipped with the battery system 1. For example, if an abnormality occurs in the secondary battery 110 or the electric vehicle, and the voltage of the secondary battery 110 drops sharply below the upper threshold Vth_sys and decreases toward the lower threshold Vth_cell, the battery system 1 limits the discharge voltage of the secondary battery 110. That is, if the voltage of the secondary battery 110 drops below a predetermined value, the battery system 1 limits the discharge power of the secondary battery 110 so that the voltage of the secondary battery 110 does not fall below the lower threshold Vth_cell.

[0102] (Restriction of discharge allowable power of secondary battery 110 by discharge allowable power limiting unit 422B2) The restriction of discharge allowable power of secondary battery 110 by discharge allowable power limiting unit 422B2 will be explained with reference to Figure 3.

[0103] The discharge power of the secondary battery 110 shown on the right vertical axis of Figure 3 is correlated with the limiting rate of the discharge power of the secondary battery 110 shown on the left vertical axis of Figure 3. The discharge power W1 of the secondary battery 110 shown on the right vertical axis of Figure 3 corresponds to the power when the discharge voltage limiting rate of the secondary battery 110 shown on the left vertical axis of Figure 3 is 100%. The discharge power W2 of the secondary battery 110 shown on the right vertical axis of Figure 3 corresponds to the power when the discharge voltage of the secondary battery 110 shown on the left vertical axis of Figure 3 is a_Vth2%.

[0104] (Gentle limiting of discharge voltage based on the first limiting rate region S1 of the secondary battery 110) The gentle limiting of discharge voltage based on the first limiting rate region S1 of the secondary battery 110 will be explained with reference to Figures 3 and 4.

[0105] When the voltage of the secondary battery 110 falls below the upper threshold Vth_sys and also below the first threshold Vth1, the voltage of the secondary battery 110 enters the first limiting rate region S1. If the first threshold Vth1 is set to be the same as or near the upper threshold Vth_sys, the probability of the voltage of the secondary battery 110 falling below the upper threshold Vth_sys and then below the first threshold Vth1 becomes relatively high. Even if the voltage of the secondary battery 110 falls below the first threshold Vth1, if it is above the second threshold Vth2, the limiting rate of the voltage of the secondary battery 110 is lenient. That is, because a first limiting rate region S1 with relatively lenient limiting of the discharge voltage is provided near the upper threshold Vth_sys of the secondary battery, the discharge voltage of the secondary battery is not excessively limited. The lenient limiting of the secondary battery 110 based on the first limiting rate region S1 suppresses the occurrence of a hunting phenomenon in the discharge voltage of the secondary battery 110. In other words, the secondary battery 110 of the first embodiment suppresses the occurrence of the hunting phenomenon compared to a proportional secondary battery. Furthermore, since a first limiting rate region S1 with relatively lenient limiting of the discharge voltage is provided near the upper limit threshold Vth_sys of the secondary battery 110, the limiting of the discharge voltage of the secondary battery 110 starts relatively earlier. This safely suppresses the voltage drop of the secondary battery 110. The allowable power W2 per unit time of the secondary battery in the first limiting rate region S1 shown in Figure 4 correlates with the limit value of a_Vth2% of the allowable discharge power of the secondary battery 110 in the first limiting rate region S1 shown in Figure 3.

[0106] (Sharp limitation of discharge voltage based on the second limiting rate region S2 of the secondary battery 110) The sharp limitation of discharge voltage based on the second limiting rate region S2 of the secondary battery 110 will be explained with reference to Figures 3 and 4.

[0107] When the voltage of the secondary battery 110 falls below the second threshold Vth2, the voltage of the secondary battery 110 enters the second limiting region S2. The steep second limiting region S2 limits the discharge voltage, preventing the discharge voltage of the secondary battery 110 from reaching the lower threshold Vth_cell. In other words, if the decrease in the discharge voltage of the secondary battery 110 cannot be suppressed by the gentle limiting region S1, it is suppressed by the steep limiting region S2. The allowable power W1 per unit time of the secondary battery in the second limiting region S2 shown in Figure 4 correlates with the 100% limit value of the allowable discharge power of the secondary battery 110 in the second limiting region S2 shown in Figure 3.

[0108] (Hunting of the discharge voltage of a proportional secondary battery) Hunting of the discharge voltage of a proportional secondary battery will be explained with reference to Figure 5.

[0109] Figure 5 is a graph illustrating the hunting phenomenon of a proportional secondary battery. Figure 5(A) is a graph showing the relationship between the discharge voltage [V] of a proportional secondary battery and time. Figure 5(B) is a graph showing the relationship between the discharge voltage limiting factor [%] of a proportional secondary battery and time. Figure 5(C) is a graph showing the relationship between the discharge power [kW] of a proportional secondary battery and time. Time t1 < Time t2 < Time t3 < Time t4 < Time t5 < Time t6.

[0110] A proportional secondary battery is a secondary battery controlled by a conventional secondary battery control device. The hunting phenomenon of the discharge voltage in a proportional secondary battery is, for example, a phenomenon in which the limit on the discharge voltage of the secondary battery becomes steeper. Alternatively, the hunting phenomenon is a phenomenon in which the limit on the discharge voltage of the secondary battery is frequently released.

[0111] Time t1 is the time before the secondary battery voltage limit is reached. At time t1, the secondary battery voltage is greater than the upper limit threshold Vth_sys. At time t1, the secondary battery limit rate is 100%. At time t1, the secondary battery discharge power limit is not restricted. If the secondary battery voltage drops sharply between times t1, t2, t3, and t4, the following will occur.

[0112] Between time t2 and time t3, the voltage of the secondary battery is less than the upper threshold Vth_sys. Between time t2 and time t3, the voltage of the secondary battery is greater than or equal to the first threshold Vth1. Between time t2 and time t3, the discharge power of the secondary battery is not limited. Therefore, between time t2 and time t3, the secondary battery continues to discharge, and its voltage decreases.

[0113] Beyond time t3, the voltage of the secondary battery falls below the first threshold Vth1. As a result, the discharge limiting rate of the secondary battery decreases, and the dischargeable power of the secondary battery begins to decline. In other words, the discharge of the secondary battery is restricted.

[0114] Beyond time t4, the discharge capacity of the secondary battery decreases further, resulting in a further reduction in its discharge capacity. In other words, the discharge of the secondary battery is further restricted. Therefore, the voltage of the secondary battery recovers from time t4 to time t5.

[0115] At time t5, the discharge limit rate of the secondary battery recovers to 100%. At time 5t, the discharge of the secondary battery increases.

[0116] At time t6, the voltage of the secondary battery begins to decrease again. From this point onward, the proportional secondary battery repeats the behavior from time t1 to time t6. In other words, the proportional secondary battery experiences repeated decreases and increases in discharge capacity within relatively short periods, which may lead to instability in the operation of the battery system.

[0117] (Configuration of the communication unit 500) The configuration of the communication unit 500 will be explained with reference to Figure 1.

[0118] The communication unit 500 communicates information regarding the secondary battery 110, etc., between multiple components included in the battery system 1. The communication unit 500 communicates between the first battery control unit 210 and the second battery control unit 220. The communication unit 500 connects the first battery control unit 210 to the battery state estimation control unit 400, and the second battery control unit 220 to the battery state estimation control unit 400 in a loop. Such connections are called daisy-chain connections, bead-chain connections, or domino-chain connections.

[0119] The communication unit 500 communicates between the first battery control unit 210 and the battery state estimation control unit 400 via an insulating element. The communication unit 500 also communicates between the second battery control unit 220 and the battery state estimation control unit 400 via an insulating element. The insulating element is, for example, a photocoupler. The insulating element cancels out the difference between the reference potential of the battery control unit 200 and the reference potential of the battery state estimation control unit 400. The battery state estimation control unit 400 is powered by a battery for onboard auxiliary equipment (reference potential is, for example, 12V). The battery control unit 200 is powered by a battery pack 100 (reference potential is, for example, 48V or higher).

[0120] (Configuration of the memory unit 600) The configuration of the memory unit 600 will be explained with reference to Figure 1.

[0121] The memory unit 600 stores information about the secondary battery 110, etc. This information includes, for example, the internal resistance characteristics, polarization resistance characteristics, degradation characteristics, capacity at full charge, and individual differences of the secondary battery 110. The memory unit 600 also stores a map related to the secondary battery 110. This map is, for example, an OCV-SOC map that shows the correspondence between the open-circuit voltage (OCV) and state of charge (SOC) of the secondary battery 110. The memory unit 600 may be configured integrally with the battery state estimation control unit 400 and the battery control unit 200.

[0122] (Confirmation of the effectiveness of the implementation of the first embodiment) The confirmation of the effectiveness of the implementation of the first embodiment will be explained with reference to the discharge allowable power of the secondary battery 110 in Figure 3.

[0123] If the implementation of the first embodiment is effective, the plot of the discharge allowable power [kW] obtained by actual measurement of the secondary battery 110 shown on the right vertical axis of Figure 3 will be similar to the plot of the discharge limiting rate [%] of the secondary battery 110 shown on the left vertical axis of Figure 3. That is, if the implementation of the first embodiment is effective, the waveform of the measured discharge voltage of the secondary battery 110 will be a waveform that includes regions with multiple slopes. The waveform that includes regions with multiple slopes corresponds to the waveform in the first limiting rate region S1 and the waveform in the second limiting rate region S2.

[0124] The effectiveness of the first embodiment is confirmed by measuring the discharge voltage of the secondary battery 110 while decreasing it from the upper threshold Vth_sys to the lower threshold Vth_cell. The voltage of the secondary battery 110 is measured at regular intervals, for example, 0.1V intervals. The measurement of the secondary battery 110 is performed after a sufficiently long predetermined time has elapsed, for example, 1 minute, after each discharge voltage has been set. The reason for setting a predetermined time is that the discharge voltage of the secondary battery 110 is generally subject to a limit on the amount of change. For this reason, the stable discharge voltage of the secondary battery 110 is measured after a predetermined time has elapsed for the change in the allowable power of the secondary battery 110 to stop.

[0125] The effectiveness of implementing the first embodiment is confirmed using the same method for Dvol_chg and Dsoc_chg in formula (10), Dsoc_dischg in formula (11), or Dcur and Dtemp common to formulas (10) and (11). For Dvol_chg and Dsoc_chg, the change in the charge-permissible power of the secondary battery 110 is the subject of confirmation. For Dsoc_dischg, the change in the discharge-permissible power is the subject of confirmation. For Dcur and Dtemp, the changes in charge-permissible power and discharge-permissible power are the subject of confirmation.

[0126] (Effects of the control device 10 for the secondary battery 110 in the first embodiment) The effects of the control device 10 for the secondary battery 110 in the first embodiment will be described.

[0127] (1) The control device 10 for the secondary battery 110 has an allowable power setting unit 421 and an allowable power limiting unit 422. The allowable power setting unit 421 sets an allowable power value that is permitted for the secondary battery 110 during discharge, based on predetermined information of the secondary battery 110. The allowable power limiting unit 422 limits the power value of the secondary battery 110 before it reaches the allowable power value. The allowable power limiting unit 422 limits the power value in stages by two or more different percentages.

[0128] With a control device 10 for a secondary battery 110 configured in this way, the allowable power limiting unit 422 limits the power value in stages by two or more different ratios. Therefore, even if the fluctuation in the power value of the secondary battery 110 becomes relatively large, the control device 10 for the secondary battery 110 can prevent the power value of the secondary battery 110 from exceeding the allowable power value, as long as the allowable power value of the secondary battery 110 is not excessively limited. As a result, the control device 10 for the secondary battery 110 can limit the power value of the secondary battery 110 per unit time without excessively limiting the allowable power value of the secondary battery 110.

[0129] In the first embodiment, a state in which the allowable power value of the secondary battery 110 is not excessively restricted corresponds, for example, to a state in which there is no margin in the threshold value of the allowable power value of the secondary battery 110. In the first embodiment, a power value of the secondary battery 110 exceeding the allowable power value corresponds, for example, to falling below the allowable voltage value when the secondary battery 110 is discharged. Also, in the first embodiment, a power value of the secondary battery 110 exceeding the allowable power value corresponds, for example, to exceeding the allowable voltage value when the secondary battery 110 is charged.

[0130] In the first embodiment, the control device 10 of the secondary battery 110 limits the power value in stages by two or more different ratios during both discharge and charge. The control device 10 of the secondary battery 110 may also be configured to limit the power value in stages by two or more different ratios during either discharge or charge.

[0131] In the first embodiment, the control device 10 of the secondary battery 110 limits the power value in stages by two different ratios. The control device 10 of the secondary battery 110 may also be configured to limit the power value in stages by three or more different ratios. The control device 10 of the secondary battery 110 may also be configured to limit the power value in stages by three different ratios during discharge and by two different ratios during charging.

[0132] In the first embodiment, the power value is defined for two or more different ratios by the gradient of the power value of the secondary battery 110 in the first limiting rate region S1 and the gradient of the power value of the secondary battery 110 in the second limiting rate region S2 in Figure 3. The gradient of the power value of the secondary battery 110 is, for example, linear. The gradient of the power value of the secondary battery 110 may also be curved.

[0133] (2) In the control device 10 for the secondary battery 110, the allowable power value is set based on one or more of the allowable voltage value and allowable current value of the secondary battery 110.

[0134] With a control device 10 for a secondary battery 110 having such a configuration, the power value per unit time of the secondary battery 110 can be limited without excessively restricting the allowable power value of the secondary battery 110, based on the allowable voltage value or allowable current value of the secondary battery 110, which have relatively high versatility in controlling the secondary battery 110.

[0135] In the first embodiment, the control device 10 of the secondary battery 110 limits the power value in stages by two or more different ratios based on the allowable voltage value. The control device 10 of the secondary battery 110 may also be configured to limit the power value in stages by two or more different ratios based on the allowable current value.

[0136] (3) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 limits the power value in stages during the discharge of the secondary battery 110 such that the amount of change in the power value per unit time due to the power value limiting that is performed relatively earlier is smaller than the amount of change in the power value per unit time due to the power value limiting that is performed relatively later.

[0137] With a control device 10 for a secondary battery 110 configured in this way, during the discharge of the secondary battery 110, the limit on the power value of the secondary battery 110 can be relatively reduced until the power value of the secondary battery 110 approaches the allowable power value. As a result, the control device 10 for the secondary battery 110 can limit the power value of the secondary battery 110 per unit time while reducing the limit on the allowable power value of the secondary battery 110 during the discharge of the secondary battery 110.

[0138] In the first embodiment, the control device 10 for the secondary battery 110 limits the power value in stages by two different ratios when the secondary battery 110 is discharged. That is, "relatively earlier" refers to the first of the two different ratios, and "relatively later" refers to the second of the two different ratios. When the control device 10 for the secondary battery 110 is configured to limit the power value in stages by three or more different ratios, it is as follows: That is, "relatively earlier" refers to, for example, the second of four different ratios, and relatively later refers to, for example, the fourth of four different ratios.

[0139] (4) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 limits the power value of the secondary battery 110 when the secondary battery 110 is being discharged, before the power value of the secondary battery 110 reaches the lower limit of the allowable power value.

[0140] With a control device 10 for a secondary battery 110 configured in this way, the power value per unit time of the secondary battery 110 can be limited without excessively restricting the allowable power value on the discharge side of the secondary battery 110, before the power value of the secondary battery 110 reaches the lower limit of the allowable power value.

[0141] (5) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 starts limiting the power value of the secondary battery 110 when it reaches a predetermined threshold for limiting the power value.

[0142] With a control device 10 for a secondary battery 110 configured in this way, it is possible to stably start limiting the power value of the secondary battery 110 based on a predetermined threshold.

[0143] (6) In the control device 10 for the secondary battery 110, the predetermined information includes one or more of the following: voltage value, current value, internal resistance value, charge state, temperature, and degradation state of the secondary battery 110.

[0144] With a control device 10 for a secondary battery 110 configured in this way, the allowable power setting unit 421 can set the allowable power value of the secondary battery 110 based on various information that gives the secondary battery 110 relatively high versatility.

[0145] (7) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 limits the power value and then releases the limit on the power value of the secondary battery 110.

[0146] With a control device 10 for a secondary battery 110 configured in this way, it is possible to control the secondary battery 110 so that its power can be used again after the power value of the secondary battery 110 has deviated from the allowable power value of the secondary battery 110.

[0147] (8) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 relaxes the second threshold value for releasing the power limit of the secondary battery 110 compared to the first threshold value for limiting the power value of the secondary battery 110.

[0148] With a control device 10 for a secondary battery 110 configured in this way, the allowable power limiting unit 422 can suppress the repeated limiting and release of the power value of the secondary battery 110 at a relatively short frequency. In other words, with a control device 10 for a secondary battery 110 configured in this way, the allowable power limiting unit 422 can suppress the occurrence of hunting.

[0149] (Configuration of the control device 10 for the secondary battery 110 in the second embodiment) The configuration of the control device 10 for the secondary battery 110 in the second embodiment will be described with reference to Figure 6.

[0150] Figure 6 is a graph showing the relationship between the limit rate [%] of the charge-permissible power of the secondary battery 110 in the second embodiment and the threshold value of the charge voltage [V] of the secondary battery 110.

[0151] In the control device 10 for the secondary battery 110 of the second embodiment, the allowable power setting unit 421 sets an allowable power value that is permitted for the secondary battery 110 during charging, based on predetermined information of the secondary battery 110.

[0152] The allowable power limiting unit 422 limits the power value of the secondary battery 110 before it reaches the allowable power value. The allowable power limiting unit 422 limits the power value in stages by two or more different percentages.

[0153] The first limiting rate region S1 is set closer to the lower threshold Vth_cell than the second limiting rate region S2. The first threshold Vth1 is set to a value greater than or equal to the lower threshold Vth_cell. The first limiting rate region S1 is defined as the voltage region from the first threshold Vth1 to the second threshold Vth2. The first threshold Vth1 is the voltage value at the start of the voltage limiting of the secondary battery 110 in the first limiting rate region S1. The second threshold Vth2 is the voltage value at the end of the voltage limiting of the secondary battery 110 in the first limiting rate region S1.

[0154] The second limiting rate region S2 is set closer to the upper limit threshold Vth_sys than the first limiting rate region S1. The third threshold Vth3 is set to a value less than or equal to the upper limit threshold Vth_cell. The second limiting rate region S2 is defined as the voltage region from the second threshold Vth2 to the third threshold Vth3. The second threshold Vth2 is the voltage value at the start of the voltage limiting of the secondary battery 110 in the second limiting rate region S2. The third threshold Vth3 is the voltage value at the end of the voltage limiting of the secondary battery 110 in the second limiting rate region S2.

[0155] The second threshold Vth2 serves as both the termination voltage threshold for the first limiting rate region S1 and the starting voltage threshold for the second limiting rate region. The second threshold Vth2 is set to a value between the first threshold Vth1 and the third threshold Vth3, and is closer to the third threshold Vth3 than to the first threshold Vth1. The second threshold Vth2 is provided to ensure that the voltage of the secondary battery 110 transitions from the first limiting rate region S1 to the second limiting rate region S2 when the voltage rises to near the overcharge voltage.

[0156] The first limiting rate region S1 is the region where the voltage limiting rate of the secondary battery 110 is within the range of 100% to b_Vth2 (%). The second limiting rate region S2 is the region where the voltage limiting rate of the secondary battery 110 is within the range of b_Vth2 (%) to 0%. The second threshold Vth2 is the limiting rate that forms the boundary between the first limiting rate region S1 and the second limiting rate region S2. The second threshold Vth2 is set as a value where the voltage limiting rate of the secondary battery 110 is greater than 50% and less than or equal to 100%. In other words, the limiting rate range of the first limiting rate region S1 is set to be wider than the limiting rate range of the second limiting rate region S2.

[0157] The first limiting rate region S1 has a wider voltage range and a smaller change in the limiting rate per unit voltage than the second limiting rate region S2. As shown in Figure 6, the slope representing the change in the limiting rate in the first limiting rate region S1 is set to be gentler than the slope of the second limiting rate region S2. The first limiting rate region S1, with its gentle slope of the limiting rate, is set on the side of the lower threshold Vth_cell of the battery system 1. The second limiting rate region S2, with its steep slope of the limiting rate, is set on the side of the upper threshold Vth_sys of the battery system 1.

[0158] (Normal limitations on the charging voltage of the secondary battery 110) The normal limitations on the charging voltage of the secondary battery 110 will be explained with reference to Figure 6.

[0159] The battery system 1 normally operates within a voltage range below the upper threshold Vth_sys. The battery system 1 repeatedly charges and discharges the secondary battery 110 depending on the conditions of the electric vehicle equipped with the battery system 1. For example, if an abnormality occurs in the secondary battery 110 or the electric vehicle, and the voltage of the secondary battery 110 rises rapidly, exceeding the lower threshold Vth_cell and rising towards the upper threshold Vth_sys, the battery system 1 limits the charging voltage of the secondary battery 110. That is, if the voltage of the secondary battery 110 rises above a predetermined value, the battery system 1 limits the allowable charging power of the secondary battery 110 so that the voltage of the secondary battery 110 does not exceed the upper threshold Vth_sys.

[0160] (Gentle restriction of the charging voltage based on the first limiting rate region S1 of the secondary battery 110) The gentle restriction of the charging voltage based on the first limiting rate region S1 of the secondary battery 110 will be explained with reference to Figure 6.

[0161] When the voltage of the secondary battery 110 becomes equal to or greater than the lower threshold Vth_cell and also equal to or greater than the first threshold Vth1, the voltage of the secondary battery 110 enters the first limiting rate region S1. If the first threshold Vth1 is set to be the same as or near the lower threshold Vth_cell, the probability of the voltage of the secondary battery 110 becoming equal to or greater than the first threshold Vth1 becomes relatively high when the voltage of the secondary battery 110 becomes equal to or greater than the lower threshold Vth_cell. Even if the voltage of the secondary battery 110 becomes equal to or greater than the first threshold Vth1, if it is less than or equal to the second threshold Vth2, the limiting rate of the voltage of the secondary battery 110 is lenient. That is, because a first limiting rate region S1 with a relatively lenient limit on the charging voltage is provided near the lower threshold Vth_cell of the secondary battery, the charging voltage of the secondary battery is not excessively limited. The lenient limiting of the secondary battery 110 based on the first limiting rate region S1 suppresses the occurrence of hunting phenomena in the charging voltage of the secondary battery 110. Furthermore, since a first limiting rate region S1 with relatively lenient limitations on the charging voltage is provided near the lower threshold Vth_cell of the secondary battery 110, the limiting of the charging voltage of the secondary battery 110 begins relatively early. This safely suppresses the voltage rise of the secondary battery 110.

[0162] (Sharp limiting of the charging voltage based on the second limiting rate region S2 of the secondary battery 110) The sharp limiting control of the charging voltage based on the second limiting rate region S2 of the secondary battery 110 will be explained with reference to Figure 6.

[0163] When the voltage of the secondary battery 110 exceeds the second threshold Vth2, the voltage of the secondary battery 110 enters the second limiting rate region S2. The steep second limiting rate region S2 limits the charging voltage, preventing the charging voltage of the secondary battery 110 from reaching the upper threshold Vth_sys. In other words, if the rise in the charging voltage of the secondary battery 110 cannot be suppressed by the gentle limiting rate of the first limiting rate region S1, it is suppressed by the steep limiting rate of the second limiting rate region S2.

[0164] (Confirmation of the effectiveness of the implementation of the second embodiment) The confirmation of the effectiveness of the implementation of the second embodiment will be explained.

[0165] If the implementation of the second embodiment is effective, the measured waveform of the charging voltage of the secondary battery 110 will be a waveform that includes multiple slope regions. The waveform that includes multiple slope regions corresponds to the waveform in the first limiting rate region S1 and the waveform in the second limiting rate region S2.

[0166] The effectiveness of the second embodiment is confirmed by measuring the charging voltage of the secondary battery 110 while increasing it from a lower threshold Vth_cell to an upper threshold Vth_sys. The voltage of the secondary battery 110 is measured at regular intervals, for example, 0.1V intervals. The measurement of the secondary battery 110 is performed after a sufficiently long predetermined time has elapsed, for example, 1 minute, after each charging voltage has been set.

[0167] (Effects of the control device 10 for the secondary battery 110 in the second embodiment) The effects of the control device 10 for the secondary battery 110 in the second embodiment will be described.

[0168] (9) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 limits the power value in stages during charging of the secondary battery 110 such that the amount of change in the power value per unit time due to the power value limiting that is performed relatively earlier is smaller than the amount of change in the power value per unit time due to the power value limiting that is performed relatively later.

[0169] With a control device 10 for a secondary battery 110 configured in this way, during charging of the secondary battery 110, the limit on the power value of the secondary battery 110 can be relatively reduced until the power value of the secondary battery 110 approaches the allowable power value. As a result, the control device 10 for the secondary battery 110 can limit the power value of the secondary battery 110 per unit time while reducing the limit on the allowable power value of the secondary battery 110 during charging.

[0170] In the second embodiment, the control device 10 for the secondary battery 110 limits the power value in stages by two different ratios when charging the secondary battery 110. That is, "relatively earlier" refers to the first of the two different ratios, and "relatively later" refers to the second of the two different ratios. When the control device 10 for the secondary battery 110 is configured to limit the power value in stages by three or more different ratios, it is as follows: That is, "relatively earlier" refers to, for example, the second of four different ratios, and "relatively later" refers to, for example, the fourth of four different ratios.

[0171] Furthermore, with a control device 10 for a secondary battery 110 having such a configuration, constant voltage (CV) control becomes unnecessary when controlling a secondary battery 110 such as a deteriorated BEV.

[0172] (10) In the control device 10 for the secondary battery 110, the allowable power limiting unit 422 limits the power value of the secondary battery 110 when charging the secondary battery 110 before the power value of the secondary battery 110 reaches the upper limit of the allowable power value.

[0173] With a control device 10 for a secondary battery 110 configured in this way, it is possible to limit the power value per unit time of the secondary battery 110 without excessively restricting the allowable power value on the charging side of the secondary battery 110, before the power value of the secondary battery 110 reaches the upper limit of the allowable power value.

[0174] (Control devices for secondary batteries in other embodiments) The control device for secondary batteries of the present invention is not limited to the configuration of the control device for secondary batteries described in the first and second embodiments, but can be configured as appropriate based on the contents described in the claims.

[0175] The first and second embodiments are described in detail or in a simplified manner for the purpose of clearly illustrating the present invention, and it is not necessary to have all the configurations described, or to have configurations that are not shown.

[0176] In other embodiments, the maximum amount of change in the change limit can be made variable in response to changes in the input limiting rate. That is, the maximum amount of change in the change limit can be switched in stages between the first limiting rate region S1 and the second limiting rate region S2 and beyond. The maximum amount of change in the second limiting rate region S2 is set to be larger than the maximum amount of change in the first limiting rate region S1. That is, the maximum amount of change in the first limiting rate region S1 is set to remain unchanged from the voltage range used by the system (upper limit threshold Vth_sys or higher). This is because the first limiting rate region S1 is a voltage range close to the system usage range, so there is a margin up to the over-discharge voltage where battery protection is required. On the other hand, the second limiting rate region S2 is a region where the discharge allowable power is to be sharply limited near the over-discharge voltage, and battery use is to be prohibited. Therefore, by increasing the maximum amount of change, the ability to follow the limit of allowable power is improved. In other embodiments, the maximum amount of change in the system usage voltage range and the maximum amount of change in the first limiting rate region S1 are the same value, but this is not limited to this, and any value smaller than the maximum amount of change in the second limiting rate region S2 is acceptable. Furthermore, the maximum change in the second limiting rate region S2 may be set to a large value that effectively renders the change limit ineffective. A method for limiting the change in the discharge change limiting unit 422A2 in accordance with the first limiting rate region S1 and the second limiting rate region S2 of the over-discharge voltage has been described. This is because, in terms of battery safety, preventing abnormal voltages is a serious issue when there is a sharp change or increase in allowable power, and therefore, the maximum change in the voltage-based change limit is being considered. Although not explained here, the charge change limiting unit 422A1 employs the same configuration using the voltage-based overcharge voltage. This is expected to improve safety in the charging direction when the voltage rises sharply, even in terms of allowable charging power. In other embodiments, a method for limiting the maximum change in the voltage-based change limiting unit has been described, but the input target for varying the maximum change in the change limit is not limited to voltage. That is, battery state values ​​such as SOC, current, and temperature may be used. Even in that case, safety is improved during sharp increases or decreases in input.

[0177] 1 Battery System 10 Control Device 100 Battery Pack 100A First Battery Group 100B Second Battery Group 110 Secondary Battery 200 Battery Control Unit 210 First Battery Control Unit 220 Second Battery Control Unit 300 Measurement Unit 310 Current Measurement Unit 320 Voltage Measurement Unit 330 Temperature Measurement Unit 400 Battery State Estimation Control Unit 410 SOC / SOHR Calculation Unit 420 Battery State Calculation Unit 421 Allowable Power Setting Unit (Control Device 10) 422 Allowable Power Limiting Unit (Control Device 10) 422A Change Amount Limiting Unit 422A1 Charge Change Amount Limiting Unit 422A2 Discharge Change Amount Limiting Unit 422B Allowable Power Limiting Unit 422B1 Charge Allowable Power Limiting Unit 422B2 Discharge Allowable Power Limiting Unit 431 Charge Multiplication Unit 432 Discharge Multiplication Unit 500 Communication Unit 600 Memory Unit 1100 Relay 1200 Inverter 1300 Motor Generator 1400 Motor / Inverter Control Unit 1500 Vehicle Control Unit

Claims

A power allowance setting unit sets an allowable power value that is permissible for the secondary battery in at least one of the discharge and charge of the secondary battery, based on predetermined information of the secondary battery. A power limiting unit that limits the power value of the secondary battery before it reaches the allowable power value, It has, The aforementioned power limiting unit limits the power value in stages by two or more different ratios. A control device for secondary batteries. 　 The aforementioned allowable power value is set based on one or more of the allowable voltage value and allowable current value of the secondary battery. A control device for a secondary battery according to claim 1. 　 The allowable power limiting unit limits the power value in stages during the discharge of the secondary battery such that the amount of change in the power value per unit time due to the power value limiting performed relatively earlier is smaller than the amount of change in the power value per unit time due to the power value limiting performed relatively later. A control device for a secondary battery according to claim 1. 　 The allowable power limiting unit limits the power value in stages during charging of the secondary battery such that the amount of change in the power value per unit time due to the power value limiting performed relatively earlier is smaller than the amount of change in the power value per unit time due to the power value limiting performed relatively later. A control device for a secondary battery according to claim 1. 　 The power limiting unit limits the power value of the secondary battery before it reaches the lower limit of the allowable power value during discharge of the secondary battery. A control device for a secondary battery according to claim 1. 　 The power limiting unit limits the power value of the secondary battery before it reaches the upper limit of the allowable power value when the secondary battery is being charged. A control device for a secondary battery according to claim 1. 　 The allowable power limiting unit starts limiting the power value when it reaches a predetermined threshold related to limiting the power value. A control device for a secondary battery according to claim 1. 　 The predetermined information includes one or more of the following: voltage value, current value, internal resistance value, charge state, temperature, and degradation state of the secondary battery. A control device for a secondary battery according to claim 1. 　 The aforementioned power limiting unit, after limiting the power value, then releases the limit on the power value. A control device for a secondary battery according to claim 1. 　 The allowable power limiting unit relaxes the second threshold for releasing the power limit compared to the first threshold for limiting the power value. A control device for a secondary battery according to claim 9.

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