Battery control device and battery system

Abstract

To ensure the reliability of a battery system while avoiding the increase of cost and / or operation load of the battery system, ensuring the input-output performance of a battery, and avoiding the deviation of the use range of SOC of all batteries of the battery system.SOLUTION: A battery control device for controlling a battery pack with multiple batteries connected includes: detecting a voltage variation of each of the multiple batteries; calculating a limit coefficient based on the charging rate and voltage variation of the battery pack; and putting a limit on the input-output possible power that is the maximum power enabling input and output of the battery pack based on the limit coefficient.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a battery control device and a battery system. [Background technology]

[0002] Electric vehicle systems installed in vehicles such as electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs) include a battery that supplies power to the drive source and a battery control device. To maximize battery performance, the battery control device detects the battery's voltage, temperature, and current, and uses these data to calculate the battery's state of charge (SOC), state of deterioration (SOH), and available input / output power when charging and discharging the battery.

[0003] The input / output power of a battery is calculated as the maximum power that can be input / output within the range in which the battery voltage does not deviate from the upper or lower limit voltage using the battery's upper or lower limit voltage and the battery's internal resistance. In the case of a multi-series battery system in which multiple batteries are connected in series, the input / output power is limited to be near a preset limit value during charging / discharging so that the battery temperature, SOC, and voltage remain within their respective operating ranges.

[0004] However, if all batteries in a multi-series battery system are treated as a single battery and the input / output available power is limited using only the average SOC of all batteries as an indicator for determining whether to limit the input / output available power, the following disadvantages arise: In a multi-series battery system, if only a specific battery deteriorates and its internal resistance increases, resulting in a decrease in capacity, that specific battery may deviate from its SOC usage range during charging and discharging.

[0005] Therefore, Patent Document 1 discloses a conventional technique in which the variation in internal resistance extracted from the variation in voltage change of each battery when current flows through the battery is reflected in the calculation of the input / output available power. This conventional technique makes it possible to avoid deviations from the upper and lower limit voltages of the batteries that may occur due to the variation in internal resistance of each battery. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3528428 Summary of the Invention [Problem to be solved by the invention]

[0007] However, during charging and discharging, where the voltage change due to internal resistance causes a large change in SOC with a relatively small current, small-capacity batteries may fall outside their SOC operating range. Therefore, it is possible to estimate the SOC of each battery in a multi-series battery system individually and reflect this in the calculation of available input and output power.

[0008] However, a temperature sensor must be installed for each battery to measure the temperature required for SOC estimation, which increases the cost of the battery system and increases the calculation load.

[0009] The present invention has been made in consideration of the above, and aims to ensure the reliability of the battery system by avoiding an increase in the cost and computational load of the battery system, while ensuring the input / output performance of the battery and preventing deviation of the SOC of all batteries in the battery system from the operating range. [Means for solving the problem]

[0010] In order to solve the problems of the prior art described above, a battery control device according to the present invention is a battery control device that controls an assembled battery consisting of multiple connected batteries, and is characterized in that it detects voltage variations among the multiple batteries, calculates a limiting coefficient based on the charging rate of the assembled battery and the voltage variations, and limits the input / output power, which is the maximum power that can be input / output to / from the assembled battery, based on the limiting coefficient. [Effects of the Invention]

[0011] According to the present invention, it is possible to avoid an increase in the cost and computational load of the battery system, ensure the input / output performance of the battery, and prevent the SOC of all batteries in the battery system from deviating from the operating range, thereby ensuring the reliability of the battery system. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of an electric power system of an automobile according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a cell control unit in the first embodiment. [Figure 3] FIG. 2 is a block diagram showing an example of the configuration of a battery pack control unit according to the first embodiment. [Figure 4] FIG. 2 is a diagram showing an example of the configuration of an SOC table showing the relationship between SOC and OCV. [Figure 5] FIG. 2 is a diagram showing an example of a voltage equivalent circuit model that models the behavior of the voltage of a single cell. [Figure 6] FIG. 10 is a diagram showing an example of SOC and voltage waveforms when a battery with reduced capacity is present in a multi-series battery configuration. [Figure 7] 5A and 5B are diagrams for explaining an example of a method for calculating an input limit coefficient in a power limit value calculation unit. [Figure 8] 5 is a diagram for explaining an example of a method for calculating an output limit coefficient in a power limit value calculation unit. FIG. [Figure 9] FIG. 1 is a diagram for explaining a problem with power limit control based on average SOC. [Figure 10] 5A and 5B are diagrams for explaining an example of the timing to start limiting the SOC in accordance with voltage variations in the first embodiment. [Figure 11] 5A and 5B are diagrams for explaining examples of restriction start points and restriction end points according to voltage variations in the first embodiment. [Figure 12] 4A to 4C are diagrams showing examples of waveforms of power, voltage, SOC, input / output limit coefficient, and input / output limit conditions before the first embodiment is applied. [Figure 13] 5A to 5C are diagrams showing examples of waveforms of power, voltage, SOC, input / output limit coefficient, and input / output limit conditions after the first embodiment is applied. [Figure 14] FIG. 10 is a block diagram showing an example of the configuration of a battery pack control unit in the second embodiment. [Figure 15] FIG. 10 is a diagram showing an example of voltage variation detection timing in the second embodiment. [Figure 16] 10A and 10B are diagrams showing examples of waveforms of current, voltage, SOC, and input / output limit coefficient after the second embodiment is applied. [Figure 17] FIG. 10 is a diagram for explaining a problem in detecting voltage variations. [Figure 18] 11A and 11B are diagrams for explaining an example of a method for determining input / output limiting conditions according to voltage variations and SOC in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiment, the present invention will be described as being applied to a battery system that constitutes a power source for a hybrid vehicle. However, the configuration of the embodiment described below is not limited to this, and can also be applied to a plug-in hybrid vehicle, a passenger vehicle such as an electric vehicle, an industrial vehicle such as a hybrid truck, or a power storage device that constitutes a power source for a railroad vehicle, etc.

[0014] In the following embodiments, a case where a lithium ion battery is used will be described as an example, but any rechargeable secondary battery, such as a lead battery, a nickel-metal hydride battery, a polyvalent cation battery, an electric double layer capacitor, or a hybrid capacitor, can also be used. Furthermore, in the following embodiments, a battery pack is formed by connecting a plurality of unit cells in series, but the present invention can also be applied to a system formed by a battery pack in which a plurality of unit cells connected in parallel are connected in series, or a system formed by a battery pack in which a plurality of unit cells connected in series are connected in parallel.

[0015] In the following description, when describing elements of the same type with distinction between them, reference numerals with subscripts added to the main body are used. When describing elements of the same type without distinction between them, reference numerals with only the main body without the subscripts are used. Furthermore, in the description of the embodiments, descriptions of configurations and processes that have already been described will be omitted, or descriptions of configurations and processes that are the same as those of the previously described embodiments will be omitted, and differences will be mainly described.

[0016] Furthermore, the numbers of various components exemplified in the following description are merely examples.

[0017] (Embodiment 1) A first embodiment of the present invention will be described with reference to FIGS.

[0018] (Configuration of Electric System 1 of Embodiment 1) 1 is a block diagram showing an example configuration of an electric motor system 1 of an automobile in embodiment 1. The electric motor system 1 in this embodiment has a battery system 100, an inverter 400 connected to the battery system 100 via relays 300 and 310, and a motor 410 driven by the inverter 400. A vehicle control unit 200 determines the distribution of driving force and the like based on information about the battery system 100 such as the SOC, information from the inverter 400 and the motor 410, information about the engine (not shown), and the like.

[0019] The battery system 100 includes a battery pack 110, a cell management unit 120, a current detection unit 130, a voltage detection unit 140 that detects the total voltage of the battery pack 110, a battery pack control unit 150, and a memory unit 180. The battery pack 110 includes a plurality of cells 111. The cells 111 are also called cells.

[0020] The cell management unit 120 monitors the state of the cells 111. The current detection unit 130 detects the current flowing through the battery system 100. The battery pack control unit 150 controls the battery pack 110. The memory unit 180 stores information related to the battery characteristics of the battery pack 110, the cells 111, and the cell group 112.

[0021] The battery pack control unit 150 receives inputs such as the battery voltage and temperature of the battery cell 111, the current value flowing through the battery, the total voltage value of the battery pack 110, the diagnosis result of whether the battery cell 111 is overcharged or overdischarged, and an abnormality signal that is output when a communication error occurs in the battery cell management unit 120, etc.

[0022] The battery voltage and temperature of the battery 111 are output from the battery management unit 120. The value of the current flowing through the battery is output from the current detection unit 130. The total voltage value of the battery pack 110 is output from the voltage detection unit 140. The diagnosis result of whether the battery 111 is overcharged or overdischarged, and an abnormality signal that is output when a communication error occurs in the battery management unit 120, are output from the battery management unit 120. The battery pack control unit 150 detects the state of the battery pack 110 based on the input information. In addition, the results of the processing performed by the battery pack control unit 150 are transmitted to the battery management unit 120 and the vehicle control unit 200.

[0023] The battery pack 110 is configured by electrically connecting in series a plurality of cells 111 capable of storing and discharging electrical energy (charging and discharging DC power). Each cell 111 has an output voltage of 3.0 to 4.2 V (average output voltage: 3.6 V). The OCV (Open Circuit Voltage) and SOC (State Of Charge) of the cells 111 are assumed to have the correlation shown in FIG. 4. However, this is not limiting and other voltage specifications may also be used.

[0024] The cells 111 that make up the battery pack 110 are grouped into a predetermined number of units for managing and controlling the state of the cells 111. The grouped cells 111 are electrically connected in series to form a cell group 112. The predetermined number of units may be equal, for example, 1, 4, 6, etc., or may be a composite number, such as a combination of 4 and 6.

[0025] The cell management unit 120 monitors the state of the cells 111 that make up the battery pack 110. The cell management unit 120 is made up of a plurality of cell control units 121, and one cell control unit 121 is assigned to each of the cell groups 112 that are grouped as described above. The cell control unit 121 operates by receiving power from the assigned cell group 112, and monitors the battery voltage and temperature of the cells 111 that make up the cell group 112.

[0026] 1, the cell control units 121a and 121b are provided corresponding to the cell groups 112a and 112b. In this embodiment, for ease of explanation, the cell group 112 is configured such that four cells 111 are electrically connected in series, and further, one cell control unit 121 monitors the four cells 111, but this is not limiting.

[0027] (Configuration of the cell control unit 121 of the first embodiment) 2 is a block diagram showing an example of the configuration of the cell control unit 121 in embodiment 1. The cell control unit 121 has a voltage detection circuit 122, a control circuit 123, a signal input / output circuit 124, and a temperature detection unit 125.

[0028] The voltage detection circuit 122 measures the voltage across the terminals of each cell 111. The temperature detection unit 125 measures the temperature of the cell group 112. The control circuit 123 transmits the measurement results received from the voltage detection circuit 122 and the temperature detection unit 125 to the battery pack control unit 150 via the signal input / output circuit 124. Note that in the explanation of the cell control unit 121, the circuit configuration for equalizing the variations in voltage and SOC between the cells 111 that occur due to self-discharge, variations in current consumption, etc. has been omitted as it is well known.

[0029] The temperature detection unit 125 has a function of measuring the temperature of the cell group 112. The temperature detection unit 125 measures one temperature for the cell group 112 as a whole, and treats the measured temperature as a representative temperature value for the cells 111 that make up the cell group 112. The temperature measured by the temperature detection unit 125 is used for various calculations to detect the state of the cell 111, the cell group 112, or the assembled battery 110. Based on this premise, FIG. 2 shows an example in which one temperature detection unit 125 is provided in the cell control unit 121. It is also possible to provide a temperature detection unit 125 for each cell 111 to measure the temperature and perform various calculations based on the temperature of each cell 111, but this would require a large number of temperature detection units 125, making the configuration of the cell control unit 121 complex.

[0030] FIG. 2 shows a simplified temperature detection unit 125. In reality, a temperature sensor is installed on the object to be measured, and the temperature sensor outputs temperature information as a voltage. The voltage measurement result output from the temperature sensor is transmitted to the signal input / output circuit 124 via the control circuit 123. The signal input / output circuit 124 outputs the measurement result to the outside of the cell control unit 121. A function for realizing this series of processes is implemented in the cell control unit 121 as the temperature detection unit 125. Temperature information (voltage) can also be measured using the voltage detection circuit 122.

[0031] The assembled battery control unit 150 and the cell management unit 120 transmit and receive signals via the signal communication unit 160 via an insulating element 170 such as a photocoupler. The insulating element 170 is provided because the assembled battery control unit 150 and the cell management unit 120 use different operating power sources. That is, the cell management unit 120 operates by receiving power from the assembled battery 110, whereas the assembled battery control unit 150 uses a battery for on-board accessories (e.g., a 12V battery) as its power source. The insulating element 170 may be mounted on a circuit board that constitutes the cell management unit 120, or may be mounted on a circuit board that constitutes the assembled battery control unit 150. Depending on the system configuration, the insulating element 170 may be omitted.

[0032] Next, a description will be given of the communication unit between the battery pack control unit 150 and the cell control units 121a and 121b in this embodiment. The cell control units 121a and 121b are connected in series in descending order of potential of the cell groups 112a and 112b that they monitor.

[0033] The signal output from the battery pack control unit 150 is input to the cell control unit 121a by the signal communication unit 160 via the insulating element 170. Similarly, the output of the cell control unit 121a and the input of the cell control unit 121b are connected by the signal communication unit 160 to transmit signals. The output of the cell control unit 121b is input to the battery pack control unit 150 by the signal communication unit 160 via the insulating element 170.

[0034] In this way, the battery pack control unit 150 and the cell control units 121a and 121b are connected in a loop by the signal communication unit 160. This loop connection is also called a daisy chain connection, a daisy chain connection, or a root-and-root connection.

[0035] In this embodiment, the insulating element 170 is not interposed between the cell control unit 121a and the cell control unit 121b, but the insulating element 170 may be interposed therebetween.

[0036] (Configuration of battery pack control unit 150 of embodiment 1) 3 is a block diagram showing an example of the configuration of the battery pack control unit 150 in embodiment 1. In this embodiment, a description will be omitted of the processing content based on the diagnosis results regarding the cells 111 and the abnormality signal output when a communication error or the like occurs in the cell management unit 120. The battery pack control unit 150 has a SOC / SOH calculation unit 151, an input / output allowable power calculation unit 152, a voltage variation detection unit 153, and a power limit value calculation unit 154.

[0037] The SOC / SOH calculation unit 151 receives as input the average voltage of the cells 111 constituting the battery pack 110, the current flowing through the battery pack 110, and the average temperature of the cells 111 detected by the temperature detection unit 125, and calculates and outputs the SOC and SOH. In this embodiment, the SOH (deterioration rate) is SOHR (State Of Health based on Resistance), but may also be SOHC (State Of Health based on Capacity).

[0038] The input / output available power calculation unit 152 uses the SOC and SOHR calculated by the SOC / SOH calculation unit 151, the current of the battery pack 110, and the lowest temperature in the battery system 100 as inputs, and calculates and outputs the maximum power that can be input / output to / from the battery (input / output available power (input available power Wmax_c, output available power Wmax_d)).

[0039] The voltage variation detection unit 153 receives the voltage and average voltage of each battery 111 as input, calculates voltage variation information for each cell, for example, the difference between the highest cell voltage and the average voltage and the difference between the lowest cell voltage and the average voltage, and outputs voltage variations based on these.

[0040] The power limit value calculation unit 154 receives as input the inputtable power Wmax_c and outputtable power Wmax_d output by the input / output power calculation unit 152, the SOC output by the SOC / SOH calculation unit 151, the minimum and maximum temperatures of each cell, each cell voltage, and the voltage variation output by the voltage variation detection unit 153, and outputs power limit values ​​(inputtable power Pmax_c, outputtable power Pmax_d).

[0041] The memory unit 180 stores information such as the internal resistance characteristics, fully charged capacity, polarization resistance characteristics, degradation characteristics, individual difference information, and the correspondence between SOC and OCV of the battery pack 110, the cell 111, and the cell group 112. Note that, in this embodiment, the memory unit 180 is configured to be installed outside the battery pack control unit 150 or the cell management unit 120, but the battery pack control unit 150 or the cell management unit 120 may be configured to include a memory unit.

[0042] (Configuration of SOC table 181) Fig. 4 is a diagram showing an example of the configuration of an SOC table 181 showing the relationship between SOC and OCV. The SOC table 181 is a data table that describes the relationship between OCV and SOC in the cell 111 for each temperature. Fig. 4 shows the relationship between OCV and SOC at a certain temperature, and does not show the relationship between OCV and SOC at other temperatures. The values ​​shown in Fig. 4 are an example, and illustrate that the smaller the SOC, the smaller the OCV of the battery.

[0043] Similar to the SOC table 181, the storage unit 180 also stores a data table describing the correspondence between various battery characteristic information such as internal resistance characteristics and polarization resistance characteristics and various parameters such as SOC, temperature, etc. In this embodiment, the SOC table 181 indicates the correspondence between SOC and OCV, but the correspondence is not limited to a data table and may be expressed by a mathematical formula or the like.

[0044] Returning to Fig. 3, the input / output power calculation unit 152 receives the battery parameters, SOC, SOHR, current, and minimum temperature within the battery system 100 stored in the storage unit 180 as inputs, calculates the maximum current that can be input / output to / from the battery (input / output current (inputable current Imax_c, outputable current Imax_d)), and multiplies the calculated values ​​by the respective battery voltages when the inputable currents are flowing, thereby outputting the inputable power Wmax_c and the outputable power Wmax_d.

[0045] A method for calculating the input / output available current Imax_c and the output available current Imax_d by the input / output available power calculation unit 152 will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of an equivalent circuit model that models the behavior of the voltage of the cell 111. The equivalent circuit in Fig. 5 is configured by connecting in series an electromotive force component indicating the OCV of the cell 111, a time-independent DC resistance component Ro, and a parallel circuit of a time-dependent polarization resistance component Rp and capacitance C.

[0046] The parameters (OCV, Ro, Rp, C) of the equivalent circuit shown in Fig. 5 are extracted from test results using an actual battery. In this embodiment, these parameters are extracted for a brand new battery. Then, the DC resistance component Ro_new, which is an internal resistance component that does not depend on time when the battery is new, the polarization resistance component Rp_new, which is an internal resistance component that depends on time, and the polarization time constant τ (the product of Rp and C) are each stored in advance in the storage unit 180 as a map corresponding to the SOC or temperature.

[0047] As shown in equation (1), the DC resistance component Ro is calculated by reflecting the SOH estimated by the SOC / SOH calculation unit 151 on the DC resistance component Ro_new stored in the storage unit 180. Similarly, as shown in equation (2), the polarization resistance component Rp is calculated by reflecting the SOH estimated by the SOC / SOH calculation unit 151 on the polarization resistance component Rp_new stored in the storage unit 180.

[0048]

number

[0049] Furthermore, the voltage change Vp due to the polarization resistance component Rp is calculated as shown in equation (3) using the polarization resistance component Rp and the polarization time constant τ, with the charge / discharge time being ts. As shown in equation (3), the voltage change V due to the polarization resistance component Rp is calculated as the weighted average of the voltage (I × Rp) and the voltage Vp_z of the capacitance C.

[0050]

number

[0051] Based on the DC resistance component Ro, the polarization resistance component Rp, the voltage change Vp due to the polarization resistance component Rp calculated using equations (1) to (3), and the τ stored in memory unit 180, the inputtable current Imax_c and the outputtable current Imax_d are calculated as shown in equations (4) and (5).

[0052]

number

[0053] In equations (4) and (5), tcont represents the number of seconds (sec) of continuous current flow, Ilimit represents the upper limit current value determined in consideration of the resistance of components such as relays and fuses of the battery system 100, Vmax represents the upper limit voltage, and Vmin represents the lower limit voltage. The number of seconds of continuous current flow, tcont, is the number of seconds set when specifying the current and power that can be continuously passed; for example, when calculating the current or power that can be continuously passed for 5 seconds, tcont=5.

[0054] Next, a method for calculating the input / output allowable power using the calculated input / output allowable current Imax_c and outputtable current Imax_d by the input / output allowable power calculation unit 152 will be described. The input / output allowable power calculation unit 152 receives the inputtable current Imax_c and the outputtable current Imax_d as inputs and calculates the maximum inputtable power (inputtable power Wmax_c) and the maximum outputtable power (outputtable power Wmax_d) using equations (6) and (7). N in equations (6) and (7) represents the number of cells constituting the battery system 100.

[0055]

number

[0056] (Regarding the voltage variation detection unit 153) Next, voltage variation detection unit 153 will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of SOC and voltage waveforms when a battery with reduced capacity is present in a multi-series battery. In Fig. 6, as shown on the left side of the figure, it is assumed that a single cell #1 with reduced capacity is present in a multi-series battery in which multiple cells 111 are connected in series. The SOC waveform when the current shown in the upper part of Fig. 6 is passed through this multi-series battery is shown in the middle part of Fig. 6, and the voltage waveform is shown in the lower part of Fig. 6.

[0057] As shown in the middle of Figure 6, over time, the SOC of cell #1 drops below the average SOC of all cells in the multi-series battery, and the voltage of cell #1 also drops below the average voltage. This is because cell #1's internal resistance increases as well as its capacity as it ages, resulting in a large change in voltage when current is passed through it. Furthermore, as shown in Figure 4, the lower the SOC, the lower the OCV of the battery. This is because the OCV of cell #1, whose SOC is lower than the other cells, is decreasing.

[0058] In this way, when low-capacity cells are mixed in a multi-series battery, variations in battery voltage may occur. Therefore, by detecting battery voltage variations, it is possible to detect the presence of a low-capacity cell that has deteriorated among the cells that make up the multi-series battery. In this embodiment, for example, an index shown in Equation (8) is used as the battery voltage variation.

[0059] According to equation (8), the larger of the absolute value of the difference between the average voltage of all cells constituting the multi-series battery and the highest cell voltage of all cells, or the absolute value of the difference between the average voltage and the lowest cell voltage of all cells, is output as the battery voltage variation. If the voltage variation is equal to or greater than a predetermined value, it is detected that there is a cell with a low capacity among all cells constituting the multi-series battery. Note that the voltage variation may be determined by using either the absolute value of the difference between the average voltage of all cells constituting the multi-series battery and the highest cell voltage of all cells, or the absolute value of the difference between the average voltage and the lowest cell voltage of all cells.

[0060]

number

[0061] (Regarding the power limit value calculation unit 154) Next, the power limit value calculation unit 154 will be described with reference to Figures 7 to 11. The power limit value calculation unit 154 receives as input the allowable input power Wmax_c and allowable output power Wmax_d output by the allowable input / output power calculation unit 152, the maximum and minimum temperatures of the cells 111 constituting the battery system 100, the voltage of each cell 111, the voltage variation detected by the voltage variation detection unit 153, and the SOC. The power limit value calculation unit 154 then limits the allowable input / output power by multiplying the allowable input power Wmax_c by an input limit coefficient kchg (kchg ≦ 1) and multiplying the allowable output power Wmax_d by an output limit coefficient kdis (kdis ≦ 1) according to each input value. As a result, all of the cells 111 are controlled so as not to deviate from the SOC usage range.

[0062] Fig. 7 is a diagram for explaining an example of a method for calculating the input limit coefficient kchg in the power limit value calculation unit 154. Fig. 7 shows an example of the input limit coefficient according to each input value for the inputtable power Wmax_c during charging.

[0063] Figure 7(a) shows the input limiting coefficient (first input limiting coefficient) according to the average SOC, where the input limiting coefficient is 1 when the average SOC is below threshold Th11, decreases from 1 at threshold Th11, and becomes 0 when the average SOC is above threshold Th12.

[0064] Figure 7(b) shows the input limiting coefficient (second input limiting coefficient) according to the highest cell voltage among the cells of the multi-series battery, and the input limiting coefficient is 1 when the highest cell voltage is below threshold Th21, decreases from 1 at threshold Th21, and becomes 0 when the highest cell voltage is above threshold Th22.

[0065] Figure 7(c) shows the input limiting coefficient (third input limiting coefficient) according to the lowest cell temperature among the cells of the multi-series battery, where the input limiting coefficient is 0 when the lowest cell temperature is below threshold Th31, increases from 0 at threshold Th31, and becomes 1 when the lowest cell temperature is above threshold Th32.

[0066] Figure 7(d) shows the input limiting coefficient (fourth input limiting coefficient) according to the highest cell temperature among the cells of the multi-series battery, and the input limiting coefficient is 1 when the highest cell temperature is below threshold Th41, decreases from 1 at threshold Th41, and becomes 0 when the highest cell temperature is above threshold Th42.

[0067] 7(a) to 7(d), and sets the minimum value of all the input limiting coefficients as the final input limiting coefficient kchg. The power limiting value calculating unit 154 multiplies the input limiting coefficient kchg by the input limiting coefficient Wmax_c to calculate and output the final input limiting power Pmax_c, as shown in equation (9).

[0068]

number

[0069] It is also possible to calculate only the input limiting coefficient corresponding to the average SOC and use this as the final input limiting coefficient kchg, without calculating all of the input limiting coefficients shown in FIGS. 7(a) to 7(d).

[0070] Fig. 8 is a diagram for explaining an example of a method for calculating the output limit coefficient kdis in the power limit value calculation unit 154. Fig. 8 shows an example of the output limit coefficient according to each input value for the permissible output power Wmax_d during discharge.

[0071] Figure 8(a) shows the output limiting coefficient (first output limiting coefficient) according to the average SOC, where the output limiting coefficient is 1 when the average SOC is equal to or greater than a threshold Th51, decreases from 1 at the threshold Th51, and becomes 0 when the average SOC is equal to or less than a threshold Th52.

[0072] Figure 8(b) shows the output limiting coefficient (second output limiting coefficient) according to the lowest cell voltage among the cells of the multi-series battery, and the output limiting coefficient is 1 when the lowest cell voltage is equal to or greater than threshold Th61, decreases from 1 at threshold Th61, and becomes 0 when the lowest cell voltage is equal to or less than threshold Th62.

[0073] Figure 8 (c) shows the output limiting coefficient (third output limiting coefficient) according to the lowest cell temperature among the cells of the multi-series battery, where the output limiting coefficient is 1 when the lowest cell temperature is equal to or higher than threshold Th71, decreases from 1 at threshold Th71, and becomes 0 when the lowest cell temperature is equal to or lower than threshold Th72.

[0074] Figure 8(d) shows the output limiting coefficient (fourth output limiting coefficient) according to the highest cell temperature among the cells of the multi-series battery, and the output limiting coefficient is 0 when the highest cell temperature is equal to or higher than threshold Th81, increases from 0 at threshold Th81, and becomes 1 when the highest cell temperature is equal to or lower than threshold Th82.

[0075] The power limit value calculation unit 154 calculates all of the output limit coefficients corresponding to the input values ​​shown in Figures 8(a) to 8(d), and sets the smallest value of all of the output limit coefficients as the final output limit coefficient kdis. The power limit value calculation unit 154 multiplies the output limit coefficient kdis by the output limit coefficient Wmax_d as in equation (10), to calculate and output the final output limit power Pmax_d.

[0076]

number

[0077] It is also possible to calculate only the output limiting coefficient corresponding to the SOC without calculating all the output limiting coefficients shown in FIGS. 8(a) to 8(d), and use this as the final output limiting coefficient kdis.

[0078] (Calculation method of input / output limit coefficient according to SOC) Next, a method for calculating the input / output limit coefficient according to the SOC in this embodiment will be described with reference to FIGS.

[0079] Fig. 9 is a diagram illustrating the issues with power limit control based on the average SOC. Fig. 9 shows the waveforms of voltage (middle graph) and SOC (lower graph) when a current (upper graph) is input so that the average SOC of the multi-series battery fluctuates within an SOC usage range of, for example, 30% (lower limit) and 80% (upper limit) when a small-capacity cell 111 (cell #1) is included in the multiple batteries constituting the multi-series battery, as shown in the lower graph.

[0080] 9, the voltage waveform in the middle of the figure shows that the voltage of cell #1 fluctuates more widely than the average voltage of the multi-series battery. Therefore, when the average SOC fluctuates within the SOC usage range of 30% (lower limit) and 80% (upper limit), the SOC of cell #1 deviates from the SOC usage range.

[0081] To control the SOC of all batteries, including small-capacity batteries, so that they do not deviate from the SOC usage range, it is possible to calculate the SOC of each battery that makes up the multi-series battery and then use an input limiting coefficient (Figure 7(a)) and an output limiting coefficient (Figure 8(a)) that correspond to the maximum calculated SOC.

[0082] However, when calculating the SOC of each battery, it is necessary to install a temperature sensor for each battery to measure the battery temperature, which increases costs. Therefore, below we describe a limitation method that controls the SOC of all batteries so that they do not deviate from the SOC usage range using only the average SOC, without calculating the SOC of each battery.

[0083] Fig. 10 is a diagram for explaining an example of the timing to start SOC limitation according to voltage variation in embodiment 1. In Fig. 10, the horizontal axis represents SOC, and the vertical axis represents the limitation coefficient. Fig. 10(a) shows the charging side, i.e., the input limitation coefficient according to SOC, and corresponds to Fig. 7(a). Fig. 10(b) shows the discharging side, i.e., the output limitation coefficient according to SOC, and corresponds to Fig. 8(a).

[0084] As shown in Figure 10(a), as the voltage variation increases during charging, the limit start point (the point at which the limit coefficient starts to decrease) and the limit end point (the point at which the limit coefficient decreases to 0) are shifted overall to the left of the figure, in other words, in the direction of decreasing SOC. This means that as the voltage variation between each battery in a multi-series battery increases during charging, the start of limiting according to SOC is advanced.

[0085] Specifically, when the voltage variation is small, the input limit coefficient (first input limit coefficient) according to the SOC is set to 1 when the SOC is SOC_chg_start1 or less, is gradually decreased from 1 at SOC_chg_start1, and is set to 0 when the SOC is SOC_chg_end1 or more. Also, when the voltage variation is medium, the input limit coefficient according to the SOC is set to 1 when the SOC is SOC_chg_start2 or less, is gradually decreased from 1 at SOC_chg_start2, and is set to 0 when the SOC is SOC_chg_end2 or more. Also, when the voltage variation is large, the input limit coefficient according to the SOC is set to 1 when the SOC is SOC_chg_start3 or less, is gradually decreased from 1 at SOC_chg_start3, and is set to 0 when the SOC is SOC_chg_end3 or more.

[0086] Furthermore, as shown in Figure 10(b), as the voltage variation increases during discharge, the limit start point (the point at which the limit coefficient starts to decrease) and the limit end point (the point at which the limit coefficient decreases to 1) are shifted overall to the right of the figure, in other words, in the direction of increasing SOC. This means that as the voltage variation between cells in a multi-series battery increases during discharge, the start of limiting according to the SOC is advanced.

[0087] Specifically, when the voltage variation is small, the output limit coefficient (first output limit coefficient) according to the SOC is set to 1 when the SOC is equal to or greater than SOC_dis_start1, is gradually decreased from 1 at SOC_dis_start1, and is set to 0 when the SOC is equal to or less than SOC_dis_end1. Also, when the voltage variation is medium, the output limit coefficient according to the SOC is set to 1 when the SOC is equal to or greater than SOC_dis_start2, is gradually decreased from 1 at SOC_dis_start2, and is set to 0 when the SOC is equal to or less than SOC_dis_end2. Also, when the voltage variation is large, the output limit coefficient according to the SOC is set to 1 when the SOC is equal to or greater than SOC_dis_start3, is gradually decreased from 1 at SOC_dis_start3, and is set to 0 when the SOC is equal to or less than SOC_dis_end3.

[0088] As shown in Figures 10(a) and (b), the greater the voltage variation, the earlier the input / output power restriction according to the SOC can be started, thereby controlling the input / output power Wmax_c and the output power Wmax_d so that the SOC of a small-capacity battery does not deviate from the SOC usage range.

[0089] Figure 11 shows the limit start point (SOC_chg_start, SOC_dis_start) and limit end point (SOC_chg_end, SOC_dis_end) according to voltage variation on the charge side (Figure 11(a)) and the discharge side (Figure 11(b)). In Figure 11, the horizontal axis represents voltage variation and the vertical axis represents SOC.

[0090] As shown in FIG. 11(a), on the charging side, the greater the voltage variation, the lower the values ​​set for SOC_chg_start and SOC_chg_end. Also, as shown in FIG. 11(b), on the discharging side, the greater the voltage variation, the higher the values ​​set for SOC_dis_start and SOC_dis_end. The relationship shown in FIG. 11 is stored in the storage unit 180 as an SOC limit map for each voltage variation. The power limit value calculation unit 154 references the SOC limit map corresponding to the voltage variation detected by the voltage variation detection unit 153, acquires input limit conditions (SOC_chg_start, SOC_chg_end) and output limit conditions (SOC_dis_start, SOC_dis_end) according to the SOC, and uses them to calculate input / output limit coefficients according to the SOC.

[0091] (Effects of the First Embodiment) The effects of this embodiment will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a diagram showing examples of waveforms of power, voltage, SOC, input / output limit coefficient, and input / output limit conditions before the application of embodiment 1. Fig. 13 is a diagram showing examples of waveforms of power, voltage, SOC, input / output limit coefficient, and input / output limit conditions after the application of embodiment 1.

[0092] 12 and 13 show the time series changes of each value when a certain load pattern is input to a multi-series battery that includes a battery (cell #1) that has a smaller capacity due to degradation compared to the other batteries among the multiple batteries that make up the multi-series battery.

[0093] The values ​​showing time-series changes in Figures 12 and 13 are battery power, voltage, SOC, input limit coefficient kchg, output limit coefficient kdis, input limit conditions (SOC_chg_start and SOC_chg_end), and output limit conditions (SOC_dis_start and SOC_dis_end).

[0094] 12 and 13, a certain load pattern is a pattern in which discharge power is input to the multi-series battery for a predetermined time from time t11 to t13, followed by a rest period from time t13 to t14, and then charge power is input to the multi-series battery for a predetermined time from time t14 to t16. The power waveform input to the multi-series battery is limited to be within the range of the allowable input power Pmax_c and the allowable output power Pmax_d.

[0095] Before this embodiment is applied, when discharge power is input at time t11 as shown in Figure 12(a), the battery voltage decreases as the discharge time passes as shown in Figure 12(b), and the SOC also decreases as shown in Figure 12(c). When the average SOC falls below the threshold SOC_dis_start (Figure 12(f)) at time t12, the output limit coefficient kdis decreases from "1" to "0" as shown in Figure 12(d).

[0096] Then, as shown in Figure 12(c), when the average SOC reaches 30% of the threshold SOC_dis_end (Figure 12(f)) at time t13, the output limit coefficient kdis becomes "0" as shown in Figure 12(d). The available output power Pmax_d is limited by the output limit coefficient kdis in Figure 12(d) and decreases from time t12 as shown in Figure 12(a), and becomes "0" at time t13 when the average SOC reaches 30% (Figure 12(c)), thereby ending discharge.

[0097] At this time, referring to Figure 12(c), it can be seen that the average SOC does not fall below the lower limit of 30% and the output power can be limited, but the SOC of cell #1 changes significantly because its capacity is smaller than the other cells, and it is discharged below the lower limit of 30%.

[0098] Similarly, as shown in Figure 12(a), when charging power is input at time t14, the voltage and SOC increase as charging progresses, as shown in Figures 12(b) and 12(c). When the average SOC exceeds the threshold SOC_chg_start (Figure 12(e)) at time t15, the input limit coefficient kchg decreases from 1 to 0, as shown in Figure 12(d).

[0099] Then, as shown in Figure 12(c), when the average SOC reaches 80% of the threshold SOC_chg_end (Figure 12(e)) at time t16, the input limit coefficient kchg becomes "0" as shown in Figure 12(d). The inputtable power Pmax_c is limited by the input limit coefficient kchg in Figure 12(d) and decreases from time t15 as shown in Figure 12(a), and becomes "0" at time t16 when the average SOC reaches 80% (Figure 12(c)), and charging ends.

[0100] At this time, referring to Figure 12(c), it can be seen that charging is possible without the average SOC exceeding the upper limit of 80%, but because cell #1 has a smaller capacity than the other cells, the SOC fluctuates significantly, and so it is charged above 80%.

[0101] On the other hand, after application of this embodiment, the input limiting conditions (SOC_chg_start and SOC_chg_end) and the output limiting conditions (SOC_dis_start and SOC_dis_end) change as shown in Figures 13(e) and 13(f) based on the relationship between the voltage variation and the input / output limiting conditions according to the SOC shown in Figure 11. The input limiting coefficient kchg is determined based on the input limiting conditions (SOC_chg_start and SOC_chg_end), and the output limiting coefficient kdis is determined based on the output limiting conditions (SOC_dis_start and SOC_dis_end).

[0102] As can be seen from a comparison between FIG. 12(d) and FIG. 13(d), in this embodiment, the limit coefficients are set to be smaller than "1" at an earlier timing than before the application of this embodiment. That is, during charging, the input limit coefficient kchg is set to be smaller than "1" from the time when the average SOC is lower, and during discharging, the output limit coefficient kdis is set to be smaller than "1" from the time when the average SOC is higher. Accordingly, the input allowable power Pmax_c and the output allowable power Pmax_d also become smaller.

[0103] 13(c) and 13(d), on the discharge side, the output limit coefficient kdis calculated based on the average SOC is reduced from "1" at time t22 when the SOC is higher than the lower limit of 30% and set to "0" at time t13, thereby controlling the allowable output power Pmax_d so that the SOC of the small-capacity battery (cell #1) does not fall below the lower limit. Similarly, on the charge side, the input limit coefficient kchg calculated based on the average SOC is reduced from "1" at time t25 when the SOC is lower than the upper limit of 80% and set to "0" at time t16, thereby controlling the allowable input power Pmax_c so that the SOC of the small-capacity battery (cell #1) does not exceed the upper limit.

[0104] In this embodiment, the input limit coefficient kchg and output limit coefficient kdis based on the average SOC are determined according to the larger of the absolute values ​​of the differences between the average voltage and the maximum or minimum voltage of each cell. This makes it possible to calculate the input allowable power Pmax_c and output allowable power Pmax_d that will keep the SOC of the battery with the smallest capacity within the SOC usage range, without having to calculate the SOC for each cell in the multi-series battery configuration.

[0105] In this embodiment, an example has been shown in which the allowable input power Pmax_c and the allowable output power Pmax_d are multiplied by the input limit coefficient kchg and the output limit coefficient kdis, respectively, but the present invention is not limited to this. For example, as shown in equations (11) and (12), the allowable input current Imax_c and the allowable output current Imax_d may be multiplied by the input limit coefficient kchg and the output limit coefficient kdis, respectively, and the results may be output instead of the allowable input power Pmax_c and the allowable output power Pmax_d.

[0106]

number

[0107] In the above-described embodiment, a battery control device that controls a battery pack consisting of multiple connected batteries detects voltage variations among the multiple batteries and limits the input / output power of the battery pack based on a limiting coefficient calculated based on the battery pack's charging rate (average SOC) and voltage variations. Therefore, based on voltage variations, the battery with the lowest capacity among the multiple batteries can be detected, and a limiting coefficient corresponding to the average SOC, which defines different limiting start and end points depending on the voltage variations, can be calculated under a light load. Furthermore, when charging or discharging the battery pack, control can be performed to prevent the battery with the smallest capacity in the battery pack from exceeding the SOC usage range.

[0108] In this embodiment, the voltage variation is an index based on the difference between the average voltage and the maximum voltage of multiple batteries, or the difference between the average voltage and the minimum voltage. Therefore, it is possible to estimate by simple calculation whether there are batteries among multiple batteries whose capacity has decreased and whose internal resistance has increased due to degradation, causing the SOC to deviate from the usable range during charging and discharging.

[0109] In addition, in this embodiment, the limit coefficient for input / output power is calculated based on voltage variation and average SOC, and the available input / output power is limited by multiplying the available input / output power by the limit coefficient, so the available input / output power can be limited by calculating a light load.

[0110] In this embodiment, the limit coefficient of the allowable input power according to the average SOC is 1 when the average SOC is equal to or less than a first threshold, starts to decrease from 1 at the first threshold, becomes 0 at a second threshold greater than a third threshold, and remains 0 when the average SOC is equal to or greater than the second threshold, and the first and second thresholds are smaller as the voltage variation increases. Therefore, the greater the voltage variation, the earlier the limit can be implemented, whereby the allowable input power is reduced from a certain point in time as the average SOC increases, and further reduced to 0 after a certain point in time.

[0111] In this embodiment, the minimum of the input limiting coefficient according to the average SOC, the input limiting coefficient according to the maximum battery voltage, the input limiting coefficient according to the minimum temperature, and the input limiting coefficient according to the maximum temperature is set as the final input limiting coefficient. Therefore, the input / output power can be limited to maximize the safety of the battery in terms of the four indexes of average SOC, maximum voltage, minimum temperature, and maximum temperature.

[0112] In this embodiment, the limit coefficient of the output power capacity according to the average SOC is 1 when the average SOC is equal to or greater than the third threshold, starts to decrease from 1 at the third threshold and becomes 0 at a fourth threshold that is smaller than the third threshold, and is 0 when the average SOC is equal to or less than the fourth threshold, and the third and fourth thresholds are larger as the voltage variation increases. Therefore, the larger the voltage variation, the earlier the control can be implemented to reduce the output power capacity from a certain point in time as the average SOC decreases, and further reduce it to 0 after a certain point in time.

[0113] In this embodiment, the final output limiting coefficient is the minimum of the output limiting coefficient according to the average SOC, the output limiting coefficient according to the battery's minimum voltage, the output limiting coefficient according to the minimum temperature, and the output limiting coefficient according to the maximum temperature. Therefore, the output power can be limited to maximize the safety of the battery in terms of the four indexes of average SOC, maximum voltage, minimum temperature, and maximum temperature.

[0114] (Embodiment 2) A second embodiment of the present invention will be described with reference to FIGS.

[0115] In the first embodiment, the voltage variation is determined as the larger absolute value of the deviation between the maximum and average voltages of the individual batteries constituting the multi-series battery and the deviation between the minimum and average voltages of the individual batteries, and the limit coefficient for the input / output allowable power based on the average SOC is determined according to the voltage variation. Here, in the first embodiment, the conditions for detecting the voltage variation are not specified.

[0116] The purpose of the present invention is to detect the SOC variation among the batteries constituting the multi-series battery configuration and to prevent the SOC of each battery from deviating from the SOC usage range. Therefore, it is desirable to detect the voltage variation under conditions suitable for detecting the SOC variation and determine the limit coefficient for the input / output allowable power.

[0117] However, because the voltage when current is applied includes voltage changes due to internal resistance, the voltage variation including this does not necessarily coincide with the SOC variation. Therefore, in this embodiment, we will describe the conditions for detecting voltage variation so that the voltage variation among the batteries constituting the multi-series battery connection can be more accurately treated as SOC variation.

[0118] In this embodiment, the battery system 100 is different from the first embodiment in that it has an assembled battery control unit 150B instead of the assembled battery control unit 150. The assembled battery control unit 150B has a voltage variation detection unit 153B instead of the voltage variation detection unit 153.

[0119] (Configuration of battery pack control unit 150B in embodiment 2) First, the battery pack control unit 150B will be described with reference to Fig. 14. Fig. 14 is a block diagram showing an example of the configuration of the battery pack control unit 150B in embodiment 2. Compared to the voltage variation detection unit 153 in embodiment 1, the voltage variation detection unit 153B additionally receives as input the value of the current flowing through the battery pack 110.

[0120] In the present invention, since the purpose is to prevent the SOC of each battery constituting the multi-series battery configuration from deviating from the SOC usage range, it is preferable to detect the voltage variation of each battery under conditions that allow for highly accurate detection of the SOC variation of each battery. Therefore, in this embodiment, the voltage variation detection unit 153B detects voltage variation under the condition that the current value added as input is equal to or less than a predetermined value, and determines the input limiting coefficient kchg and the output limiting coefficient kdis.

[0121] FIG. 15 is a diagram showing an example of the timing of detecting voltage variations in embodiment 2. Assume that one battery (cell #1) among multiple batteries constituting a multi-series battery has a smaller capacity than the others. In the multi-series battery, cell #1 exhibits a greater change in SOC than the other batteries. When discharging is performed for a predetermined period of time from a state in which all battery voltages (=OCV) are the same at time 0 when no current is flowing, the SOC of cell #1 decreases compared to the other batteries. When discharging is then stopped, the voltage approaches the OCV.

[0122] As shown in FIG. 4, there is a correlation between OCV and SOC. Furthermore, voltage variations detected when the current value is equal to or less than a predetermined value are substantially the same as OCV variations. Therefore, voltage variations detected when the current value is equal to or less than a predetermined value can be considered as SOC variations. In this embodiment, voltage variations are detected based on equation (8) at the voltage variation detection timing when the voltage variation detection condition, that is, the current value is a small value equal to or less than a predetermined value, is satisfied. Then, as shown in FIGS. 10 and 11, input / output limit conditions are determined according to the SOC.

[0123] (Effects of the second embodiment) The effect of this embodiment will be described with reference to Fig. 16. Fig. 16 is a diagram showing example waveforms of current, voltage, SOC, and input / output limit coefficient after applying embodiment 2. As with the explanatory diagram of the effect of embodiment 1 (Fig. 13), the diagram shows waveforms when a load pattern of repeatedly discharging and charging is input to a multi-series battery connection including one small-capacity battery (cell #1).

[0124] In this embodiment, the input limiting coefficient kchg and the output limiting coefficient kdis are determined according to the voltage variation detected during the pause period between discharging and charging, which is a no-load state in which no current flows, as shown in Figure 16(a). Then, as in the first embodiment, the input allowable power Pmax_c and the output allowable power Pmax_d are limited to be small. As a result, as shown in Figure 16(c), charging and discharging can be performed so that the SOC of all batteries, including the small-capacity cell #1, does not deviate from the SOC usage range.

[0125] According to this embodiment, by detecting voltage variations when the condition that the current value is equal to or less than a predetermined value is satisfied, voltage variations and SOC variations can be evaluated more accurately. Furthermore, the input / output limit coefficient according to the SOC is determined based on the accurate voltage variations, so that the allowable input power Pmax_c and the allowable output power Pmax_d can be calculated more accurately so that the SOC of the battery with the smallest capacity does not deviate from the SOC usage range.

[0126] (Embodiment 3) A third embodiment of the present invention will be described with reference to FIGS.

[0127] In the second embodiment, the voltage variation, which is the deviation between the maximum and minimum voltages of the multiple batteries constituting the multi-series battery and the average voltage, is detected only when the condition that the current value flowing through the batteries is equal to or less than a predetermined value is satisfied. Then, based on the detected voltage variation, a limit coefficient for the input / output power according to the average SOC is determined.

[0128] However, the voltage and SOC of each battery do not always vary. The reason for this will be explained with reference to Figure 17. Figure 17 is a diagram for explaining the problem in detecting voltage variations.

[0129] Figure 17(a) shows the current waveform input to the multi-series battery, Figure 17(b) shows the voltage when the current of Figure 17(a) is input, and Figure 17(c) shows the SOC waveform when the current of Figure 17(a) is input. If discharge begins immediately after time 0 when the voltage (=OCV) and SOC of all batteries are uniform, the SOC of the small-capacity battery will change more significantly than the other batteries, resulting in greater variation in voltage (=OCV). If the battery is charged from that state to the SOC at the start of discharge, the power balance between charging and discharging will be zero, based on the state when the voltage and SOC of all batteries were uniform at the start of discharge, and the SOC will return to a uniform state.

[0130] In this way, the greater the SOC variation, the easier it is to identify batteries with low capacity, based on the point when all batteries have a uniform SOC. However, in the range where the SOC variation is small, the SOC may appear uniform. As a result, when detecting voltage variations, it may be erroneously determined that no SOC variation has occurred, i.e., that no low-capacity batteries exist, and the input / output limit conditions according to the SOC may be relaxed.

[0131] Therefore, in this embodiment, an example is described in which the above-mentioned erroneous detection is prevented by continuing to maintain input / output limiting conditions according to the SOC determined by the maximum voltage variation among the voltage variations detected after the battery has started operating.

[0132] The difference between this embodiment and the first embodiment is that the battery system 100 has a battery pack control unit 150C instead of the battery pack control unit 150, and the battery pack control unit 150C has a power limit value calculation unit 154C instead of the power limit value calculation unit 154 (FIG. 3). In the battery system 100, only the processing content of the power limit value calculation unit 154C differs from that of the power limit value calculation unit 154, and the other configurations are the same.

[0133] When determining the limiting conditions based on the average SOC corresponding to the voltage variation based on Figures 10 and 11, the power limit value calculation unit 154C uses the currently detected voltage variation only if the currently detected voltage variation is greater than the previously detected voltage variation. If the currently detected voltage variation is smaller than the previously detected voltage variation, the largest voltage variation among the previously detected voltage variations is used. The previously detected voltage variations are stored in a memory area such as the memory unit 180. This prevents the voltage difference detected under conditions that make it difficult to identify a battery with a small capacity during charging or discharging, as described above, from being used in the voltage variation calculation, thereby preventing erroneous detection that no SOC variation is occurring.

[0134] Fig. 18 is a diagram for explaining an example of a method for determining input / output limiting conditions according to voltage variations and SOC in embodiment 3. Fig. 18(a) shows the current waveform input to the multi-series battery, Fig. 18(b) shows the voltage when a current is input, Fig. 18(c) shows the input limiting conditions according to the SOC when a current is input, and Fig. 18(d) shows the output limiting conditions according to the SOC.

[0135] 28(a), a current is input to the battery system 100, starting from before the start of discharge at time 0 when the voltage and SOC are uniform, followed by discharge, pause, discharge, pause, charge, pause, and charge. When applying the method of detecting a voltage difference under the condition that the current value of the second embodiment is equal to or less than a predetermined value and adopting a method of determining input / output limiting conditions according to the SOC from voltage variations immediately before current is input after pause, the input / output limiting conditions according to the SOC are determined from voltage variations detected during the pause period immediately after the first discharge.

[0136] During the pause immediately after the first discharge, the voltage variation increases compared to time 0. Therefore, as shown in FIG. 18(c), the input limiting conditions (SOC_chg_start, SOC_chg_end) become smaller, and as shown in FIG. 18(d), the output limiting conditions (SOC_dis_start, SOC_dis_end) become larger. After the second discharge, the SOC variation and voltage variation increase further, so the input / output limiting conditions according to the voltage variation become stricter.

[0137] On the other hand, after the rest period immediately after the second discharge, as charging progresses, the power balance between charging and discharging decreases with respect to the SOC when there is no voltage variation at time 0. This reduces the SOC variation and voltage variation. If the previously detected voltage variation is greater than the newly detected voltage variation, the newly detected voltage variation is not adopted, but the largest previous voltage variation is adopted, and input / output limit conditions are set according to this voltage variation.

[0138] (Effects of the third embodiment) According to this embodiment, the input / output limiting conditions determined based on the maximum voltage variation in the time series of detected voltage variations are maintained, thereby preventing erroneous detection of voltage variations that do not exist when they do, and enabling small-capacity batteries to be charged and discharged without deviating from the SOC range.

[0139] The above description is merely an example, and the present invention is not limited to the configuration of the above-described embodiment, but includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to having all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace other configurations with respect to the configuration of each embodiment. [Explanation of symbols]

[0140] 100: battery system, 110: assembled battery, 111: cell, 112: cell group, 120: cell management unit, 121: cell control unit, 122: voltage detection circuit, 123: control circuit, 124: signal input / output circuit, 125: temperature detection unit, 130: current detection unit, 140: voltage detection unit, 150, 150B, 150C: assembled battery control unit, 151: SOC / SOH calculation unit, 152: input / output available power calculation unit, 153, 153B: voltage variation detection unit, 154, 154C: power limit value calculation unit, 180: memory unit, 200: vehicle control unit

Claims

1. A battery control device that controls a battery pack in which a plurality of batteries are connected, Detecting voltage variations among the plurality of batteries; calculating a limiting coefficient based on the charging rate of the battery pack and the voltage variation; The input / output available power, which is the maximum power that can be input / output to / from the battery pack, is limited based on the limit coefficient. A battery control device characterized by:

2. The battery control device according to claim 1, The voltage variation is a difference between an average voltage and a maximum voltage of the plurality of batteries, or a difference between the average voltage and a minimum voltage of the plurality of batteries. A battery control device characterized by:

3. The battery control device according to claim 1, an input / output available power calculation unit that calculates the input / output available power based on the charging rate, the deterioration rate and current of the battery pack, and the lowest temperature of the plurality of batteries; a power limit value calculation unit that calculates the limit coefficient based on the voltage variation and the charging rate and limits the input / output allowable power by multiplying the limit coefficient by the input / output allowable power; A battery control device comprising:

4. The battery control device according to claim 3, The power limit value calculation unit calculating, as the limiting coefficient, a first input limiting coefficient that limits the inputtable power of the input / outputtable power in accordance with the charging rate; the first input limiting coefficient is 1 when the charging rate is equal to or less than a first threshold, starts decreasing from 1 at the first threshold and becomes 0 when the charging rate is equal to or greater than a second threshold, and is 0 when the charging rate is equal to or greater than the second threshold; The first threshold value and the second threshold value are smaller as the voltage variation is larger. A battery control device characterized by:

5. The battery control device according to claim 4, The power limit value calculation unit further calculating a second input limiting coefficient that limits the allowable input power in accordance with the maximum voltage of the plurality of batteries, a third input limiting coefficient that limits the allowable input power in accordance with the minimum temperature of the plurality of batteries, and a fourth input limiting coefficient that limits the allowable input power in accordance with the maximum temperature of the plurality of batteries; The minimum value of the first to fourth input limiting coefficients is set as the limiting coefficient. A battery control device characterized by:

6. The battery control device according to claim 3, The power limit value calculation unit calculating, as the limiting coefficient, a first output limiting coefficient that limits the outputtable power of the input / outputtable power in accordance with the charging rate; the first output limiting coefficient is 1 when the charging rate is equal to or greater than a third threshold, starts decreasing from 1 at the third threshold and becomes 0 at a fourth threshold that is smaller than the third threshold, and is 0 when the charging rate is equal to or less than the fourth threshold, The third threshold value and the fourth threshold value are set to be larger values ​​as the voltage variation is larger. A battery control device characterized by:

7. The battery control device according to claim 6, The power limit value calculation unit further calculating a second output limiting coefficient that limits the allowable output power in accordance with a minimum voltage of the plurality of batteries, a third output limiting coefficient that limits the allowable output power in accordance with a minimum temperature of the plurality of batteries, and a fourth output limiting coefficient that limits the allowable output power in accordance with a maximum temperature of the plurality of batteries; The minimum value of the first to fourth output limiting coefficients is set as the limiting coefficient. A battery control device characterized by:

8. The battery control device according to claim 1, The voltage variation is detected when the absolute value of the current of the battery pack is equal to or less than a predetermined value. A battery control device characterized by:

9. The battery control device according to claim 1, The limiting coefficient is calculated based on the maximum value of the voltage variation detected after a certain point in time when the voltages of the plurality of batteries become uniform. A battery control device characterized by:

10. the assembled battery; A battery control device according to any one of claims 1 to 9; A battery system comprising:

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