JP6491148B2 - Internal resistance calculation device - Google Patents

Description

  The present invention relates to an internal resistance calculation device that calculates an internal resistance value of a battery such as a secondary battery.

  For example, in various vehicles such as an electric vehicle (EV) that travels using an electric motor and a hybrid vehicle (HEV) that travels using both an engine and an electric motor, a lithium ion rechargeable battery is used as a power source for the electric motor. And rechargeable batteries such as nickel metal hydride batteries.

  In secondary batteries used for EVs, HEVs, etc., the degree of deterioration SOH (State Of Health) is determined by the ratio between the initial capacity and the current capacity of the secondary battery. For example, if the current capacity is 80% of the initial capacity, the SOH is 80%. There are various methods for detecting the SOH, and one of them is a method for predicting based on the internal resistance value of the secondary battery.

  As a calculation method of the internal resistance value of the secondary battery, for example, a method described in Patent Document 1 can be given. In Patent Document 1, the current detection circuit 23 connected in series to the power storage unit 25, the first sample hold circuit 27 and the second sample hold circuit 29 connected to the power storage unit 25, and the outputs of both are connected. A differential amplifier circuit 43 is included. Then, with the power storage unit 25 charged or discharged at a constant current value Ic, the voltage hold timing when charging or discharging is interrupted is set to the time when a predetermined time has elapsed after the interruption, and charging or discharging is resumed. It is described that the voltage hold timing at the time is the time when the current value from the current detection circuit 23 becomes equal to the constant current value Ic within the detection error range.

Japanese Patent No. 5228403

  However, in the case of the method described in Patent Document 1, since the charging rate SOC (State Of Charge) is not taken into account when measuring for calculating the internal resistance, the internal resistance value varies depending on the SOC at the time of measurement. There was a problem that occurred.

  In the case of the method described in Patent Document 1, it is necessary to temporarily suspend charging or discharging in order to calculate internal resistance.

  In view of the above problems, an object of the present invention is to provide an internal resistance calculation device that can calculate an internal resistance with a high accuracy and a simple configuration.

The invention according to claim 1, which has been made to solve the above-mentioned problems, is an internal resistance calculation device for calculating an internal resistance value of a secondary battery, charging / discharging means for charging or discharging the secondary battery; A voltage measuring means for measuring a voltage value at both ends of the battery, and a first voltage holding for holding the first voltage value determined in advance by the voltage measuring means after the charging or discharging by the charging / discharging means is started. And when the charging current or discharging operation by the charging / discharging means changes the charging current or discharging current more than a predetermined value within a predetermined time after the voltage value at both ends becomes the first voltage value. Second voltage holding means for holding the voltage value across the battery as a second voltage value, a first current value that is a charge current value or a discharge current value when the first voltage value is reached, and the second voltage value Charging power when Current measuring means for measuring a second current value which is a value or a discharge current value, and the secondary battery based on the first voltage value, the second voltage value, the first current value and the second current value. And an internal resistance calculating unit that calculates an internal resistance value.

  According to a second aspect of the present invention, in the first aspect of the invention, the internal resistance calculating unit is configured to store the first voltage value held by the first voltage holding unit and the second voltage holding unit. A difference amplifier for calculating a difference from the second voltage value is provided.

  According to a third aspect of the present invention, in the second aspect of the present invention, the first voltage holding unit and the second voltage holding unit are each configured by a capacitor, and the capacitor that holds the first voltage value and the It has switching means for switching between a capacitor for holding the second voltage value and connecting it to one terminal of the battery.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the second voltage holding unit is configured to charge the capacitor after the charge current or the discharge current has changed more than the predetermined current value within the predetermined time. The voltage value between both ends of the secondary battery after the lapse of time is held as a second voltage value, and the current measuring means measures the charge current value or the discharge current value after the lapse of the charge time as the second current value. It is a feature.

  As described above, according to the first aspect of the present invention, since the first voltage value is a predetermined value, measurement with a constant SOC is possible. It is known that there is a correlation between the SOC and the battery terminal voltage (both-end voltage), and by measuring with a constant SOC, variation in internal resistance due to the SOC can be eliminated. Further, there is no need to temporarily stop charging or discharging for calculating the internal resistance. For example, if the secondary battery is charged or discharged in EV or HEV, the calculation timing of the internal resistance occurs naturally.

  According to the second aspect of the present invention, the difference between the first voltage value and the second voltage value can be calculated by the differential amplifier, and the difference value can be amplified with a necessary amplification factor. Even if the difference from the voltage value is very small, it can be detected. Therefore, measures against low noise and high resolution AD converters are not required.

  According to the invention of claim 3, since the first voltage value and the second voltage value are held in the two capacitors by being switched by the switching means, the first voltage value and the second voltage value are not affected by the cell voltage. The voltage value can be acquired.

  According to the fourth aspect of the present invention, the second voltage value is held after the capacitor charging time has elapsed, and the charging current value or the discharging current value at that time is set as the second current value. Since it waits until it becomes the same voltage as the both-ends voltage value of a battery, the 2nd voltage value and the 2nd current value can be measured with sufficient accuracy.

It is a schematic block diagram of the internal resistance calculation apparatus concerning the 1st Embodiment of this invention. FIG. 2 is an explanatory diagram showing a relationship between a voltage between both ends of the secondary battery shown in FIG. 1, an electromotive force, and an internal resistance. It is a flowchart of operation | movement of the internal resistance calculation apparatus shown by FIG. It is a wave form diagram of operation | movement of the internal resistance calculation apparatus shown by FIG. It is a flowchart of operation | movement of the internal resistance calculation apparatus concerning the 2nd Embodiment of this invention. It is a wave form chart of operation of an internal resistance calculation device concerning a 2nd embodiment of the present invention. It is a schematic block diagram of the internal resistance calculation apparatus concerning the 3rd Embodiment of this invention. It is explanatory drawing which showed the relationship between the both-ends voltage of the secondary battery shown by FIG. 7, an electromotive force, and internal resistance. It is a flowchart of operation | movement of the internal resistance calculation apparatus shown by FIG. FIG. 8 is a waveform diagram of the operation of the internal resistance calculation device shown in FIG. 7. It is a flowchart of operation | movement of the internal resistance calculation apparatus concerning the 4th Embodiment of this invention. It is a wave form diagram of operation | movement of the internal resistance calculation apparatus concerning the 4th Embodiment of this invention. It is a schematic block diagram of the internal resistance calculation apparatus concerning the 5th Embodiment of this invention. It is a flowchart of operation | movement of the internal resistance calculation apparatus shown by FIG. It is a wave form diagram of operation | movement of the internal resistance calculation apparatus shown by FIG. It is the schematic block diagram which showed the structural example of the internal resistance calculation apparatus in the case of multicell connection. It is the schematic block diagram which showed the structural example of the internal resistance calculation apparatus in the case of multicell connection. It is the schematic block diagram which showed the structural example of the internal resistance calculation apparatus in the case of multicell connection. It is the schematic block diagram which showed the structural example of the internal resistance calculation apparatus in the case of multicell connection.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an internal resistance calculation device according to a first embodiment of the present invention.

  The internal resistance calculation device according to the present embodiment is mounted on, for example, an EV, and calculates an internal resistance value of a secondary battery included in the EV. Of course, you may apply to the apparatus, system, etc. which were equipped with secondary batteries other than EV.

  As shown in FIG. 1, the internal resistance calculation device (indicated by reference numeral 1 in the figure) of the present embodiment is connected to a secondary battery B mounted on an EV, HEV or the like (not shown), and the internal of the secondary battery B Calculate the resistance value.

  The secondary battery B has an electromotive force portion e that generates a voltage and an internal resistance r. As shown in FIG. 2, the secondary battery B generates a voltage V between both electrodes (the positive electrode Bp and the negative electrode Bn). When the secondary battery B is charged with the current I, the voltage V is a voltage value (cell voltage) Ve generated by the electromotive force of the electromotive force unit e and a voltage value (voltage drop) generated by the current flowing through the internal resistance r. ) Vr (V = Ve + Vr). Therefore, when the current I changes, the voltage drop Vr also changes (Vr = R × I, where R is an internal resistance value).

  The internal resistance calculation apparatus 1 of the present embodiment includes a charging unit 15, a current measuring unit 21, a voltage measuring unit 22, a differential amplifier 23, a first analog-digital converter 24, and a second analog-digital conversion. And a third analog-digital converter 26, a μCOM 30, a switch SW, and capacitors C1 and C2.

  The charging unit 15 includes, for example, a power supply device that can output a charging current having an arbitrary current value to the secondary battery B by being supplied with power from an external power source connected to an EV or the like. The charging means 15 has a pair of output terminals connected to the positive electrode Bp and the negative electrode Bn of the secondary battery B, respectively. The charging unit 15 outputs a predetermined charging current when charging the secondary battery B by being controlled by the μCOM 30 described later. That is, the charging unit functions as a charging / discharging unit that charges the secondary battery B.

  The current measuring unit 21 is provided in series between one terminal of the charging unit 15 and the positive electrode Bp of the secondary battery B, and measures a current value flowing in the charging direction and the discharging direction with respect to the secondary battery B. And output.

  The voltage measuring means 22 outputs a signal (voltage signal) corresponding to the voltage (both ends voltage) between the positive electrode Bp and the negative electrode Bn of the secondary battery B. In the present embodiment, for example, a plurality of fixed resistors that divide the voltage between both electrodes of the secondary battery B so as to match a voltage range that can be input to the second analog-digital converter 25 described later. It is configured.

  The differential amplifier 23 calculates the difference between the both-end voltage value of the secondary battery B held in the capacitor C1, which will be described later, and the both-end voltage value of the secondary battery B held in the capacitor C2, and uses the amplification factor Av. Amplify and output.

  The first analog-digital converter 24 (hereinafter referred to as “first A / D 24”) quantizes the analog signal output from the current measuring means 21 and outputs a signal indicating the digital value of the analog signal. Similarly, the second analog-digital converter 25 (hereinafter referred to as “second A / D 25”) quantizes the analog signal output from the voltage measuring means 22 and outputs a signal indicating the digital value of the analog signal. To do. Similarly, the third analog-digital converter 26 (hereinafter referred to as “third A / D 26”) quantizes the analog signal output from the differential amplifier 23 and outputs a signal indicating the digital value of the analog signal. To do. In the present embodiment, the first A / D 24, the second A / D 25, and the third A / D 26 are mounted as individual electronic components. However, the present invention is not limited to this, and is, for example, incorporated in the μCOM 30 described later. Each signal may be quantized using an analog-digital converter or the like.

  The μCOM 30 is a microcomputer incorporating a CPU, ROM, RAM, timer, and the like, and controls the entire internal resistance calculation apparatus 1. The ROM stores in advance a control program for causing the CPU to function as an internal resistance calculation unit. The CPU functions as internal resistance calculation means by executing this control program.

  In addition, the μCOM 30 outputs a control signal for causing the charging unit 15 to charge the secondary battery B. Further, the μCOM 30 receives the output signals of the first A / D 24, the second A / D 25, and the third A / D 26. Further, the μCOM 30 outputs a switching signal for the switch SW.

  The switch SW is a switch that can switch the connection from the terminal c on one side to any one of the terminals a and b on the other side. The terminal c of the switch SW is connected to the positive electrode Bp of the secondary battery B, the terminal a is connected to one side of the capacitor C1 and the + input terminal of the differential amplifier 23, and the terminal b is connected to one side of the capacitor C2 and the differential. Connected to the negative input terminal of the amplifier 23. That is, the switch SW functions as a switching unit that switches between the capacitor C1 and the capacitor C2 and connects to the positive electrode Bp of the secondary battery B.

  The capacitor C1 is a small-capacitance capacitor having one side connected to the terminal a of the switch SW and the other side grounded. As will be described later, the capacitor C1 is electrically connected to the positive electrode Bp of the secondary battery B when the switch SW is switched to the terminal a side, and the potential of the capacitor C1 is set to the voltage across the secondary battery Bp. Can be equal.

  The capacitor C2 is a small-capacitance capacitor having one side connected to the terminal b of the switch SW and the other side grounded. As will be described later, the capacitor C2 is electrically connected to the positive electrode Bp of the secondary battery B when the switch SW is switched to the terminal b side, and the potential of the capacitor C2 is set to the voltage across the secondary battery Bp. Can be equal.

  As described above, the voltage V across the secondary battery B is the sum of the cell voltage Ve and the voltage drop Vr. When the current (charge current) changes, the voltage drop Vr also changes. Here, assuming that voltage drops when charging with different charging current values Ic and Id are Vrc and Vrd, respectively, Vrc> Vrd when Ic> Id. When the voltage value across the secondary battery B when the voltage drop Vrc is Vc and the voltage value across the secondary battery B when the voltage drop Vrd is Vd, Vc = Ve + Vrc and Vd = Ve + Vrd, so Vc−Vd. If Vrc−Vrd, and the voltage across the secondary battery B can be input to the differential amplifier 23, Vrc−Vrd can be obtained.

  Next, the internal resistance calculation operation described above will be described with reference to the flowchart of FIG. 3 and the waveform diagram of FIG. The flowchart shown in FIG. 3 is mainly executed by the μCOM 30. Note that the terminal SW and the terminal c are connected to the switch SW before the flowchart is executed.

  First, in step S101, charging of the secondary battery B is started. In this step, a charging start control signal is output to the charging unit 15, and the charging unit 15 starts charging the secondary battery B. At the same time, in step S102, the switch SW is switched so that the terminals a and c are connected (time t1 in FIG. 4). At this time, a charging current flows through the secondary battery B, and the voltage across the secondary battery B extends from the voltage value Ve generated by the electromotive force to the vicinity of the potential obtained by adding the voltage drop Vr generated by the current flowing through the internal resistance r. To rise.

  Next, in step S103, it is determined whether or not the voltage value V across the secondary battery B detected by the voltage measuring means 22 has reached a predetermined threshold voltage Vth as the first voltage value. In the case of (No), the process stands by in this step. When the threshold voltage is reached (in the case of Yes), the charging current value detected by the current measuring means 21 is acquired in Step S104. The threshold voltage Vth is not limited to a specific value, and may be a value having a range of about ± X%. This X% may be arbitrarily determined from the viewpoint of how much the SOC may be shifted depending on the relationship between the internal resistance value to be acquired and the SOC. In general, a large difference does not occur in the detected resistance value if it is about ± 5%. Let the charging current value acquired at this time be Ic. That is, the charging current value Ic becomes the first current value. In step S105, the switch SW is switched so that the terminals b and c are connected (time t2 in FIG. 4).

  Next, in step S106, it is determined whether or not a predetermined time has elapsed since the switch SW was switched in step S105. If it has elapsed (in the case of Yes), the process returns to step S102, and if it has not elapsed (in the case of No). In Step S107, it is determined whether or not the charging current has decreased by a predetermined current value or more. If not (No), the process returns to Step S106, and if it has decreased (Yes), the process proceeds to Step S108 (FIG. 4 at time t3). At this time, since the charging current decreases, the voltage value across the secondary battery B also decreases.

  The predetermined time is determined by the accuracy of the capacitors C1 and C2 and the differential amplifier 23 and the required accuracy of the internal resistance value R finally calculated. Generally, the charge stored in the capacitor is discharged due to the leakage current of the capacitor and the input impedance of the differential amplifier. As a result, the potential of the capacitor changes, the differential amplifier is affected, and the absolute accuracy of the internal resistance value R finally calculated is lowered. Therefore, it is ideal that the predetermined time is such that Vc does not fall below Vd when accuracy is not desired, and is slightly slower than the response speed of the battery when accuracy is important.

  The predetermined current value is also determined by the required accuracy of the internal resistance value R finally calculated in the same manner as the predetermined time. This is because a smaller change cannot be required due to the detection resolution of the current measuring means 21 to be used. Therefore, the predetermined current value is ideal when a change of 1 resolution or more of the current detecting means 21 is obtained when accuracy is not desired, and when the change of current is obtained so that the resolution can be ignored when importance is placed on accuracy. Is. However, if the predetermined current value is increased, the predetermined time becomes longer. Therefore, it is desirable to determine in consideration of the balance between them.

  Next, in step S108, it is determined whether or not the charging time of the capacitor C2 has elapsed since the decrease in charging current was detected in step S107. If not, the process waits in this step. In step S109, the charging current value detected by the current measuring means 21 is acquired. The charging time is a time until the voltage of the capacitor C2 becomes equal to the voltage across the secondary battery B, and is a value determined in advance by the capacity of the capacitor C2 and the like. The charging current value acquired at this time is defined as Id (time t4 in FIG. 4). That is, the charging current value Id becomes the second current value.

  Next, in step S110, the output from the differential amplifier 23 via the third A / D 26 is acquired. That is, the difference value is calculated. At the time when the switch SW is switched in step S105, the capacitor C1 holds Vc (= Vth) which is the voltage value across the secondary battery B at the time of measuring the charging current Ic. At the time of step S109, the capacitor C2 Vd that is the voltage value across the secondary battery B when the charging current Id is measured after the charging time of the capacitor C2 has elapsed is held. That is, the capacitor C1 serves as a first voltage holding unit, the voltage value Vd between both ends serves as a second voltage value, and the capacitor C2 serves as a second voltage holding unit (second voltage acquisition unit). Therefore, by obtaining the output of the differential amplifier 23 in step S110, the difference value (Vm = (Vc−Vd) × Av) of the voltage across the secondary battery B between the charging current Ic measurement and the charging current Id measurement is obtained. Can be calculated.

  In step S111, an internal resistance value is calculated based on the charging currents Ic and Id acquired in steps S104 and S109 and the difference value Vm calculated (acquired) in step S110. That is, the internal resistance value R = (Vc−Vd) / (Ic−Id) = Vm / (Ic−Id). Of course, the amplification factor Av of the differential amplifier 23 is taken into account in this calculation.

  According to the internal resistance calculation device 1 described above, since the voltage value Vc at the time of the first charge current Ic measurement is set to the predetermined threshold voltage value Vth, measurement at a constant SOC is possible. It is known that there is a correlation between the SOC and the battery terminal voltage (both-end voltage), and by measuring with a constant SOC, variation in internal resistance due to the SOC can be eliminated. Further, it is not necessary to temporarily stop charging for calculating the internal resistance. For example, if the secondary battery B is charged in EV or HEV, the calculation timing of the internal resistance occurs naturally.

  Further, the difference between the voltage value Vc and the voltage value Vd can be calculated by the differential amplifier 23, and the difference value can be amplified with the necessary amplification factor Av. Therefore, the difference between the voltage value Vc and the voltage value Vd is very small. Can also be detected. Therefore, measures against low noise and high resolution AD converters are not required.

  In addition, since the voltage value Vc and the voltage value Vd are held in the two capacitors C1 and C2 by switching with the switch SW, the voltage value Vc and the voltage value Vd are not affected by the cell voltage of the secondary battery B. Can be acquired.

  In addition, since the voltage value Vd is held after the charging time of the capacitor C2 has elapsed and the charging current value Id at that time is measured, it waits until the potential of the capacitor C2 becomes equal to the voltage value across the secondary battery B. Therefore, the voltage value Vd and the charging current value Id can be measured with high accuracy.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  This embodiment has the same general configuration as that of FIG. 1, but the calculation method of the internal resistance is different from that of the first embodiment. In the present embodiment, assuming that voltage drops when charging with different charging current values Ic and Id are Vrc and Vrd, respectively, Vrc <Vrd when Ic <Id. Here, assuming that the voltage value across the secondary battery B when the voltage drop Vrc is Vc and the voltage value across the secondary battery B when the voltage drop Vrd is Vd, Vd = Ve + Vrc and Vd = Ve + Vrd, so Vd− If Vc = Vrd−Vrc and the voltage across the secondary battery B can be input to the differential amplifier 23, Vrd−Vrc can be obtained.

  Next, the internal resistance calculation operation described above will be described with reference to the flowchart of FIG. 5 and the waveform diagram of FIG. The flowchart shown in FIG. 5 is mainly executed by the μCOM 30. Before the flowchart is executed, the switch SW is assumed to be connected to the terminal a and the terminal c.

  First, in step S201, charging of the secondary battery B is started. In this step, a charging start control signal is output to the charging unit 15, and the charging unit 15 starts charging the secondary battery B. At the same time, in step S202, the switch SW is switched so that the terminals b and c are connected (time t1 in FIG. 6). At this time, a charging current flows through the secondary battery B, and the voltage across the secondary battery B extends from the voltage value Ve generated by the electromotive force to the vicinity of the potential obtained by adding the voltage drop Vr generated by the current flowing through the internal resistance r. To rise.

  Next, in step S203, it is determined whether or not the voltage value V across the secondary battery B detected by the voltage measuring means 22 has reached a predetermined threshold voltage Vth. In this step, when the threshold voltage is reached (Yes), the charging current value detected by the current measuring means 21 is acquired in step S204. The threshold voltage Vth is not limited to a specific value, and may be a value having a range of about ± X%. Let the charging current value acquired at this time be Ic. In step S205, the switch SW is switched so that the terminals a and c are connected (time t2 in FIG. 6).

  Next, in step S206, it is determined whether or not a predetermined time has elapsed since the switch SW was switched in step S205. If it has elapsed (in the case of Yes), the process returns to step S202, and if it has not elapsed (in the case of No). In step S207, it is determined whether or not the charging current has increased by a predetermined current value or more. If not increased (in the case of No), the process returns to step S206, and if increased (in the case of Yes), the process proceeds to step S208 (FIG. 6 at time t3). At this time, since the charging current increases, the voltage across the secondary battery B also increases.

  Next, in step S208, it is determined whether or not the charging time of the capacitor C1 has elapsed since the increase in the charging current was detected in step S207. If not, the process waits in this step. In step S209, the charging current value detected by the current measuring means 21 is acquired. The charging time is the time until the voltage of the capacitor C1 becomes equal to the voltage across the secondary battery B, and is a value determined in advance by the capacity of the capacitor C1 and the like. Let the charging current value acquired at this time be Id (time t4 in FIG. 6).

  Next, in step S210, the output from the differential amplifier 23 via the third A / D 26 is acquired. That is, the difference value is calculated. At the time of switching the switch SW in step S205, the capacitor C2 holds Vc (= Vth) that is the voltage value across the secondary battery B at the time of measuring the charging current Ic. At the time of step S209, the capacitor C1 Vd, which is the voltage value across the secondary battery B when the charging current Id is measured, is held. Therefore, by acquiring the output of the differential amplifier 23 in step S210, the difference value (Vm = (Vd−Vc) × Av) of the voltage across the secondary battery B between the charging current Ic measurement and the charging current Id measurement is obtained. Can be calculated.

  In step S211, the internal resistance value is calculated based on the charging currents Ic and Id acquired in steps S204 and S209 and the difference value Vm calculated (acquired) in step S210. That is, the internal resistance value R = (Vd−Vc) / (Id−Ic) = Vm / (Id−Ic). Of course, the amplification factor Av of the differential amplifier 23 is taken into account in this calculation.

  According to the present embodiment, since the voltage value Vc at the time of the first charge current Ic measurement is set to the predetermined threshold voltage value Vth, measurement with a constant SOC is possible. Further, it is not necessary to temporarily stop charging for calculating the internal resistance. For example, if the secondary battery B is charged in EV or HEV, the calculation timing of the internal resistance occurs naturally.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first and second embodiments described above are denoted by the same reference numerals and description thereof is omitted.

  The internal resistance calculation device 1A of the present embodiment shown in FIG. 7 is different from the internal resistance calculation device 1 shown in FIG. 1 in that the charging means 15 is the discharging means 15A. The discharging means 15A has a pair of output terminals connected to the positive electrode Bp and the negative electrode Bn of the secondary battery B, respectively. The discharge unit 15A is controlled by the μCOM 30 described later, and discharges the secondary battery B with a predetermined discharge current. That is, the discharging means functions as charging / discharging means for discharging the secondary battery B.

  As shown in FIG. 8, the secondary battery B generates a voltage V between both electrodes (positive electrode Bp and negative electrode Bn). When the secondary battery B is discharged with the current I, the voltage V is a voltage value (cell voltage) Ve generated by the electromotive force of the electromotive force unit e and a voltage value (voltage drop) generated by the current flowing through the internal resistance r. ) Vr (V = Ve−Vr). Therefore, when the current I changes, the voltage drop Vr also changes (Vr = R × I, where R is an internal resistance value).

  Assuming that the voltage drops when discharging at different discharge current values Ic and Id are Vrc and Vrd, respectively, Vrc> Vrd when Ic> Id. Here, assuming that the voltage value across the secondary battery B when the voltage drop Vrc is Vc and the voltage value across the secondary battery B when the voltage drop Vrd is Vd, Vc = Ve−Vrc, Vd = Ve−Vrd Therefore, if Vd−Vc = Vrc−Vrd and the voltage across the secondary battery B can be input to the differential amplifier 23, Vrc−Vrd can be obtained.

  Next, the above-described internal resistance calculation operation will be described with reference to the flowchart of FIG. 9 and the waveform diagram of FIG. The flowchart shown in FIG. 9 is mainly executed by the μCOM 30. Before the flowchart is executed, the switch SW is assumed to be connected to the terminal a and the terminal c.

  First, in step S301, discharging of the secondary battery B is started. In this step, a discharge start control signal is output to the discharge means 15A, and the discharge means 15A starts discharging the secondary battery B. At the same time, in step S302, the switch SW is switched so that the terminals b and c are connected (time t1 in FIG. 10). At this time, a discharge current flows through the secondary battery B, and the voltage across the secondary battery B reaches the vicinity of the potential obtained by subtracting the voltage drop Vr generated by the current flowing through the internal resistance r from the voltage value Ve generated by the electromotive force. Descend.

  Next, in step S303, it is determined whether or not the voltage value V between both ends of the secondary battery B detected by the voltage measuring unit 22 has reached a predetermined threshold voltage Vth, and when it is not the threshold voltage Vth (in the case of No). In this step, when the threshold voltage is reached (Yes), the discharge current value detected by the current measuring means 21 is acquired in step S304. The threshold voltage Vth is not limited to a specific value, and may be a value having a range of about ± X%. Let the discharge current value acquired at this time be Ic. In step S305, the switch SW is switched so that the terminals a and c are connected (time t2 in FIG. 10).

  Next, in step S306, it is determined whether or not a predetermined time has elapsed since the switch SW was switched in step S305. If it has elapsed (in the case of Yes), the process returns to step S302, and if it has not elapsed (in the case of No). In Step S307, it is determined whether or not the discharge current has decreased by a predetermined current value or more. If not (No), the process returns to Step S306, and if it has decreased (Yes), the process proceeds to Step S308 (FIG. 10 time t3). At this time, since the discharge current decreases, the voltage value across the secondary battery B increases.

  Next, in step S308, it is determined whether or not the charging time of the capacitor C1 has elapsed since the decrease in the discharge current was detected in step S307. If not, the process waits in this step. In step S309, the discharge current value detected by the current measuring means 21 is acquired. The charging time is the time until the voltage of the capacitor C1 becomes equal to the voltage across the secondary battery B, and is a value determined in advance by the capacity of the capacitor C1 and the like. Let the discharge current value acquired at this time be Id (time t4 in FIG. 10).

  Next, in step S310, the output from the differential amplifier 23 via the third A / D 26 is acquired. That is, the difference value is calculated. At the time of switching the switch SW in step S305, the capacitor C2 holds Vc (= Vth) that is the voltage value across the secondary battery B at the time of measuring the discharge current Ic. At the time of step S309, the capacitor C1 Vd, which is the voltage value across the secondary battery B at the time of measuring the discharge current Id, is held. Therefore, by acquiring the output of the differential amplifier 23 in step S310, the difference value (Vm = (Vd−Vc) × Av) of the voltage across the secondary battery B between the discharge current Ic measurement and the discharge current Id measurement is obtained. Can be calculated.

  In step S311, the internal resistance value is calculated based on the discharge currents Ic and Id acquired in steps S304 and S309 and the difference value Vm calculated (acquired) in step S310. That is, the internal resistance value R = (Vd−Vc) / (Id−Ic) = Vm / (Id−Ic). Of course, the amplification factor Av of the differential amplifier 23 is taken into account in this calculation.

  According to this embodiment, since the voltage value Vc at the time of the first discharge current Ic measurement is set to the predetermined threshold voltage value Vth, measurement at a constant SOC is possible. Further, there is no need to temporarily stop the discharge for calculating the internal resistance. For example, if the secondary battery B is discharged in the EV or HEV, the calculation timing of the internal resistance naturally occurs.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same part as the 1st-3rd embodiment mentioned above, and description is abbreviate | omitted.

  This embodiment has the same general configuration as that of FIG. 7, but the calculation method of the internal resistance is different from that of the third embodiment. In this embodiment, assuming that the voltage drops when discharging with different discharge current values Ic and Id are Vrc and Vrd, respectively, Vrc <Vrd when Ic <Id. Here, assuming that the voltage value across the secondary battery B when the voltage drop Vrc is Vc and the voltage value across the secondary battery B when the voltage drop Vrd is Vd, Vc = Ve−Vrc, Vd = Ve−Vrd Therefore, if Vc−Vd = Vrd−Vrc and the voltage across the secondary battery B can be input to the differential amplifier 23, Vrd−Vrc can be obtained.

  Next, the internal resistance calculation operation described above will be described with reference to the flowchart of FIG. 11 and the waveform diagram of FIG. The flowchart shown in FIG. 11 is mainly executed by the μCOM 30. Before the flowchart is executed, it is assumed that the switch SW is connected to the terminal b and the terminal c.

  First, in step S401, the secondary battery B starts to be discharged. In this step, a discharge start control signal is output to the discharge means 15A, and the discharge means 15A starts discharging the secondary battery B. At the same time, in step S402, the switch SW is switched so that the terminals a and c are connected (time t1 in FIG. 12). At this time, a discharge current flows through the secondary battery B, and the voltage across the secondary battery B reaches the vicinity of the potential obtained by subtracting the voltage drop Vr generated by the current flowing through the internal resistance r from the voltage value Ve generated by the electromotive force. Descend.

  Next, in step S403, it is determined whether or not the voltage value V across the secondary battery B detected by the voltage measuring unit 22 has reached a predetermined threshold voltage Vth. In this step, when the threshold voltage is reached (Yes), the discharge current value detected by the current measuring means 21 is acquired in step S404. The threshold voltage Vth is not limited to a specific value, and may be a value having a range of about ± X%. Let the discharge current value acquired at this time be Ic. In step S405, the switch SW is switched so that the terminals b and c are connected (time t2 in FIG. 12).

  Next, in step S406, it is determined whether or not a predetermined time has elapsed since the switch SW was switched in step S405. If it has elapsed (in the case of Yes), the process returns to step S402, and if it has not elapsed (in the case of No). In step S407, it is determined whether or not the discharge current has increased by a predetermined current value or more. If not increased (in the case of No), the process returns to step S406, and if increased (in the case of Yes), the process proceeds to step S408 (see FIG. 12 time t3). At this time, since the discharge current increases, the voltage value across the secondary battery B decreases.

  Next, in step S408, it is determined whether or not the charging time of the capacitor C2 has elapsed since the increase in discharge current was detected in step S407. If not, the process waits in this step. In step S409, the discharge current value detected by the current measuring means 21 is acquired. The charging time is a time until the voltage of the capacitor C2 becomes equal to the voltage across the secondary battery B, and is a value determined in advance by the capacity of the capacitor C2 and the like. Let the discharge current value acquired at this time be Id (time t4 in FIG. 12).

  Next, in step S410, the output from the differential amplifier 23 via the third A / D 26 is acquired. That is, the difference value is calculated. At the time of switching the switch SW in step S405, the capacitor C1 holds Vc (= Vth) that is the voltage value across the secondary battery B at the time of measuring the discharge current Ic, and at the time of step S409, the capacitor C2 Vd, which is the voltage value across the secondary battery B at the time of measuring the discharge current Id, is held. Therefore, by obtaining the output of the differential amplifier 23 in step S410, the difference value (Vm = (Vc−Vd) × Av) of the voltage across the secondary battery B between the discharge current Ic measurement and the discharge current Id measurement is obtained. Can be calculated.

  In step S411, the internal resistance value is calculated based on the discharge currents Ic and Id acquired in steps S404 and S409 and the difference value Vm calculated (acquired) in step S410. That is, the internal resistance value R = (Vc−Vd) / (Id−Ic) = Vm / (Id−Ic). Of course, the amplification factor Av of the differential amplifier 23 is taken into account in this calculation.

  According to this embodiment, since the voltage value Vc at the time of the first discharge current Ic measurement is set to the predetermined threshold voltage value Vth, measurement at a constant SOC is possible. Moreover, there is no need to temporarily stop the discharge for calculating the internal resistance, and if the secondary battery B is discharged in the EV or HEV, the internal resistance calculation timing naturally occurs.

  In the first to fourth embodiments described above, the both-end voltage value Vc of the secondary battery B when measuring the charging (discharging) current Ic and the both-end voltage value of the secondary battery B when measuring the charging (discharging) current Id. Although Vd is held in the capacitor C1 or C2, a capacitor that holds Vd is not necessarily provided. If a capacitor for holding Vd is not provided, the switch SW is switched so that the voltage value across the secondary battery B is input to the input terminal of the differential amplifier 23 not provided with the capacitor after a certain time has elapsed, What is necessary is just to calculate the difference value Vm by making the both-ends voltage value of the secondary battery B at the time of fixed time passage into Vd.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same part as the 1st-4th embodiment mentioned above, and description is abbreviate | omitted.

  This embodiment is a combination of the first to fourth embodiments, and calculates the internal resistance in either case of charging or discharging, or in the case of increasing or decreasing current. It is something that can be done.

  FIG. 13 shows a schematic configuration of the internal resistance calculation device 1B according to the present embodiment. The internal resistance calculation device 1B includes a charging / discharging unit 15B, a current measuring unit 21, a voltage measuring unit 22, differential amplifiers 23a and 23b, a first analog-digital converter 24, and a second analog-digital converter. 25, a third analog-digital converter 26a, a fourth analog-digital converter 26b, a μCOM 30, a switch SW, and capacitors C1, C2.

  In the configuration shown in FIG. 13, the current measuring means 21, the voltage measuring means 22, the first analog-digital converter 24, the second analog-digital converter 25, the μCOM 30, the switch SW, and the capacitor C1. , C2 are the same as in FIG. 1 and FIG.

  The charging / discharging unit 15B has both the function of the charging unit 15 and the function of the discharging unit 15A. That is, the charging / discharging unit 15B charges or discharges the secondary battery.

  In the present embodiment, two differential amplifiers (23a, 23b) are provided as functions, as in the above-described embodiment, and both end voltage values of the secondary battery B held in the capacitor C1 and the capacitor C2 The difference between the voltage values of both ends of the secondary battery B held in the battery is calculated, amplified by the amplification factor Av, and output.

  In the differential amplifier 23a, the + input terminal, the a terminal of the switch SW, and one side of the capacitor C1 are connected, and the − input terminal, the b terminal of the switch SW, and one side of the capacitor C2 are connected. In the differential amplifier 23b, the + input terminal, the b terminal of the switch SW, and one side of the capacitor C2 are connected, and the − input terminal, the a terminal of the switch SW, and one side of the capacitor C1 are connected.

  The third analog-digital converter 26a (hereinafter referred to as “third A / D 26a”) quantizes the differential signal output from the differential amplifier 23a and outputs a signal indicating a digital value corresponding to the differential signal. .

  The fourth analog-digital converter 26b (hereinafter referred to as “third A / D 26b”) quantizes the differential signal output from the differential amplifier 23b and outputs a signal indicating a digital value corresponding to the differential signal. .

  Next, the internal resistance calculation operation of the internal resistance calculation apparatus 1B having the above-described configuration will be described with reference to the flowchart of FIG. 14 and the waveform diagram of FIG. The flowchart shown in FIG. 14 is mainly executed by the μCOM 30. FIG. 14 is a flowchart showing the operation during charging. Note that the terminal SW and the terminal c are connected to the switch SW before the flowchart is executed.

  First, in step S501, charging of the secondary battery B is started. In this step, a charging start control signal is output to the charging / discharging unit 15B, and the charging / discharging unit 15B starts charging the secondary battery B. At the same time, in step S502, the switch SW is switched so that the terminals a and c are connected (time t1 in FIGS. 15A and 15B). At this time, a charging current flows through the secondary battery B, and the voltage across the secondary battery B extends from the voltage value Ve generated by the electromotive force to the vicinity of the potential obtained by adding the voltage drop Vr generated by the current flowing through the internal resistance r. To rise.

  Next, in step S503, it is determined whether or not the voltage value V between both ends of the secondary battery B detected by the voltage measuring unit 22 has reached a predetermined threshold voltage Vth, and if it is not the threshold voltage Vth (in the case of No). In this step, when the threshold voltage is reached (Yes), the charging current value detected by the current measuring means 21 is acquired in step S504. The threshold voltage Vth is not limited to a specific value, and may be a value having a range of about ± X%. Let the charging current value acquired at this time be Ic. In step S505, the switch SW is switched so that the terminals b and c are connected (time t2 in FIGS. 15A and 15B).

  Next, in step S506, it is determined whether or not a predetermined time has elapsed since the switch SW was switched in step S505. If it has elapsed (in the case of Yes), the process returns to step S502, and if it has not elapsed (in the case of No). In step S507, it is determined whether or not the charging current has changed by a predetermined current value or more. If not changed (in the case of No), the process returns to step S506, and if changed (in the case of Yes), the process proceeds to step S108. At this time, when the charging current changes so as to decrease, the voltage value across the secondary battery B decreases (time t3 in FIG. 15A), and when the charging current changes so as to increase, the secondary battery B decreases. The voltage value across the battery B rises (time t3 in FIG. 15B).

  Next, in step S508, it is determined whether or not the charging time of the capacitor C2 has elapsed since the change in the charging current was detected in step S507. If not, the process waits in this step. In step S509, the charging current value detected by the current measuring means 21 is acquired. The charging time is a time until the voltage of the capacitor C2 becomes equal to the voltage across the secondary battery B, and is a value determined in advance by the capacity of the capacitor C2 and the like. The charging current value acquired at this time is set as Id (time t4 in FIGS. 15A and 15B).

  Next, in step S510, it is determined whether or not charging current Ic> charging current Id. If Yes, the process proceeds to step S511, and if NO, the process proceeds to step S513. That is, this step determines whether the change in the charging current is increased or decreased.

  Next, in step S511, an output through the third A / D 26a is obtained from the differential amplifier 23a. That is, the difference value is calculated. At the time of switching the switch SW in step S505, the capacitor C1 holds Vc (= Vth) that is the voltage value across the secondary battery B at the time of measuring the charging current Ic, and at the time of step S509, the capacitor C2 Vd, which is the voltage value across the secondary battery B when the charging current Id is measured, is held. In the differential amplifier 23a, the capacitor C1 is connected to the + input terminal and the capacitor C2 is connected to the − input terminal. Therefore, by acquiring the output of the differential amplifier 23a, the charging current Ic is measured and the charging current Id is measured. The difference value (Vm = (Vc−Vd) × Av) of the voltage across the secondary battery B at the time can be calculated.

  In step S512, the internal resistance value is calculated based on the charging currents Ic and Id acquired in steps S504 and S509 and the difference value Vm calculated (acquired) in step S511. That is, the internal resistance value R = (Vc−Vd) / (Ic−Id) = Vm / (Ic−Id). Of course, the amplification factor Av of the differential amplifier 23 is taken into account in this calculation.

  On the other hand, in step S513, an output through the third A / D 26b is acquired from the differential amplifier 23b. That is, the difference value is calculated. In the differential amplifier 23b, the capacitor C2 is connected to the + input terminal and the capacitor C1 is connected to the − input terminal. Therefore, by acquiring the output of the differential amplifier 23b, the charge current Ic is measured and the charge current Id is measured. The difference value (Vm = (Vd−Vc) × Av) of the voltage across the secondary battery B at the time can be calculated.

  In step S514, the internal resistance value is calculated based on the charging currents Ic and Id acquired in steps S504 and S509 and the difference value Vm calculated (acquired) in step S513. That is, the internal resistance value R = (Vd−Vc) / (Id−Ic) = Vm / (Id−Ic). Of course, the amplification factor Av of the differential amplifier 23 is taken into account in this calculation.

  Note that the flowchart of FIG. 14 and the waveform diagram of FIG. 15 show the operation at the time of charging, but the internal resistance value of the secondary battery B can be similarly measured in the case of discharging. That is, when the discharge current Ic> the discharge current Id, the voltage value Vc at both ends is less than the voltage value Vd at both ends, so that the value of the differential amplifier 23b is obtained, and when the discharge current Ic <the discharge current Id, the voltage value Vc at both ends> Since the voltage value is Vd, the value of the differential amplifier 23a may be acquired.

  According to the present embodiment, since the voltage value Vc at the time of the first charge (discharge) current Ic measurement is set to the predetermined threshold voltage value Vth, measurement at a constant SOC is possible. Further, it is not necessary to temporarily stop charging / discharging for calculating the internal resistance. For example, if the secondary battery B is charged / discharged in EV or HEV, the calculation timing of the internal resistance occurs naturally.

  Further, since the differential amplifiers 23a and 23b are provided, the internal resistance value can be calculated in any state of charging or discharging, or in any state where the current increases or decreases.

  In addition, in vehicles such as EVs on which the above-described internal resistance calculation device 1 is mounted, the current increases during acceleration. Therefore, if it is desired to measure the internal resistance value at this time, it should be measured when the current value increases by a predetermined value within a predetermined time. Further, the current decreases during deceleration. Therefore, if it is desired to measure the internal resistance value at this time, it should be measured when the current value decreases by a predetermined value within a predetermined time. In addition, since the regenerative current can be controlled during deceleration, the current value (both increase and decrease) to be measured can be generated arbitrarily if the total deceleration amount does not change by coordinating the hydraulic brake so that the driver does not feel it. It is also possible.

  Further, the present invention can be applied even in the case of multi-cell series connection (a plurality of secondary batteries are connected in series). In that case, the charging means and discharging means need only have one system.

  Further, in the case of multi-cell serial connection, the analog-digital converter provided in the subsequent stage of the differential amplifier may be provided at a rate of, for example, every 8 cells. In this case, the switch SW, the capacitors C1 and C2, and the differential amplifier may be provided for each cell, and one cell may be selected by a multiplexer (MUX). 16 and 17 show an example in the case of three cells. In the configuration of FIG. 16, the other side of the capacitors C11, C12, C21, and C22 corresponding to the first cell B1 and the second cell B2 is grounded similarly to the other side of the capacitors C31 and C32 corresponding to the third cell B3. . In this case, since the differential amplifier output selected other than the third cell B3 other than the third cell B3 having the negative electrode Bn grounded includes the voltage drop of the other cell, the μCOM 30 needs to subtract the voltage drop of the other cell. In the configuration of FIG. 17, since the capacitor corresponding to each cell is connected to the negative electrode Bn side of the cell, subtraction for the voltage drop of other cells is not necessary.

  Alternatively, a switch for connecting the positive side potential of each cell to the differential amplifier may be provided, and only one set of capacitors C1 and C2, a differential amplifier, and an analog-to-digital converter may be provided after the switch (FIG. 18). , See FIG. In the configuration of FIG. 18, a switch SW4 for selecting the positive potential of each cell is provided, and the switch SW shown in FIG. The other side of the capacitors C1 and C2 is grounded as in FIG. In this case, since the differential amplifier output other than the third cell B3 whose negative electrode Bn is grounded includes the voltage drop of the other cell, the μCOM 30 needs to subtract the voltage drop of the other cell. In the configuration of FIG. 19, in addition to the switch SW4 described above, a switch SW5 for selecting the negative side potential of each cell is provided. In this case, since the switch SW5 switches the other side of the capacitor so as to be connected to the negative electrode side of the measurement target cell, subtraction for the voltage drop of the other cells is unnecessary.

  16 to 19 are configurations in which the configuration of FIG. 1 is made compatible with multi-cell connection. Of course, the configurations of FIGS. 7 and 13 are also connected to other cells based on the same purpose as in FIGS. It can be made to correspond.

  The present invention is not limited to the above embodiment. That is, those skilled in the art can implement various modifications in accordance with conventionally known knowledge without departing from the scope of the present invention. Of course, such modifications are included in the scope of the present invention as long as the configuration of the internal resistance calculation apparatus of the present invention is provided.

1, 1A, 1B Internal resistance calculation device 15 Charging means (charging / discharging means)
15A Discharge means (charge / discharge means)
15B Charging / discharging means 21 Current measuring means 22 Voltage measuring means 23, 23a, 23b Differential amplifier (internal resistance calculating means)
30 μCOM (Internal resistance calculation means)
B secondary battery C1 capacitor (second voltage acquisition means, first voltage holding means, second voltage holding means)
C2 capacitor (second voltage acquisition means, first voltage holding means, second voltage holding means)
SW switch (switching means)
R Internal resistance value

Claims (4)

In the internal resistance calculation device for calculating the internal resistance value of the secondary battery,
Charging / discharging means for charging or discharging the secondary battery;
Voltage measuring means for measuring a voltage value across the secondary battery;
A first voltage holding means for holding the first voltage value determined in advance by the voltage value measured by the voltage measuring means after the start of charging or discharging by the charging / discharging means;
After the voltage value at both ends becomes the first voltage value, both ends of the secondary battery when the charging current or discharging current changes by a predetermined value or more within a predetermined time by the charging operation or discharging operation by the charging / discharging means. Second voltage holding means for holding the voltage value as the second voltage value;
A first current value that is a charging current value or a discharging current value when the first voltage value is reached, and a second current value that is a charging current value or a discharging current value when the second voltage value is reached. Current measuring means for
Internal resistance calculation means for calculating an internal resistance value of the secondary battery based on the first voltage value, the second voltage value, the first current value, and the second current value;
An internal resistance calculation device comprising:   The internal resistance calculating means includes a differential amplifier that calculates a difference between the first voltage value held by the first voltage holding means and the second voltage value held by the second voltage holding means. The internal resistance calculation device according to claim 1. The first voltage holding means and the second voltage holding means are each composed of a capacitor,
3. The internal structure according to claim 2, further comprising a switching unit that switches between a capacitor that holds the first voltage value and a capacitor that holds the second voltage value and connects the capacitor to one terminal of the secondary battery. Resistance calculation device. The second voltage holding means holds, as a second voltage value, a voltage value across the secondary battery after the charging time of the capacitor has elapsed after the charging current or discharging current has changed within the predetermined time by the predetermined current value or more. And
The current measuring means measures a charging current value or a discharging current value after the charging time has elapsed as a second current value;
The internal resistance calculation device according to claim 3.

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