JP6729312B2 - Battery evaluation method and battery evaluation apparatus - Google Patents

Description

The present invention relates to a battery evaluation method and a battery evaluation device for obtaining at least a DC resistance and a reaction resistance of a battery.

There are three types of battery resistance: pure resistance due to the structure of the battery itself, reaction resistance due to chemical reaction, and polarization resistance due to concentration polarization. The pure resistance corresponds to "DC resistance" described later. In order to estimate the degree of deterioration of the battery, it is desirable to determine the pure resistance and the reaction resistance separately. It is generally known that the pure resistance is obtained using high-frequency alternating current, but it has been difficult for a vehicle-mounted battery to perform sampling in a very short period.

BACKGROUND ART Conventionally, for example, in Patent Document 1 below, a technique relating to a vehicle-mounted battery pure resistance measuring method for the purpose of measuring a pure resistance of a battery even when a vehicle is in use is disclosed. This in-vehicle battery pure resistance measuring method is based on a first approximation formula consisting of a quadratic formula of the current-voltage characteristic for a monotonous increase period of the inrush current showing a correlation between the discharge current and the terminal voltage, and a monotonous decrease period of the inrush current A second approximate expression, which is a quadratic expression of the current-voltage characteristic, is obtained. Then, the unit current at the point corresponding to the peak value of the first and second approximate expressions obtained by removing the voltage drop due to the concentration polarization component caused by the chemical reaction from the voltage drop caused by the flow of the discharge current. An intermediate value between the two terminal voltage change values per change is obtained, and the obtained intermediate value is measured as the pure resistance value of the battery.

Japanese Patent No. 4383020

However, in the technique described in Patent Document 1, it is necessary to perform the measurement a plurality of times during the inrush current period in which the current monotonically increases and to approximate it by a quadratic equation. For example, when a DC motor is used as the starter motor, the inrush current period is 4 [msec] or less. A sensor that measures a normal current or voltage cannot perform practical measurement because the sampling interval is longer than the inrush current period. On the other hand, although there are sensors with short sampling intervals, they are expensive and therefore costly.

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a battery evaluation method and a battery evaluation device that can measure at least a DC resistance and a reaction resistance regardless of the length of a sampling interval.

1st invention made in order to solve the said subject is a battery evaluation method which calculates|requires the direct current resistance (Rd) and reaction resistance (Rr) of the battery (12), and an inrush current is maximum from initial current value (Io). During the initial period (Ts) in which the current value (Imax) is increased and then the maximum current value is decreased to the steady current value (Ist), the discharge current (I) of the battery and the battery corresponding to the discharge current The voltage between terminals (Vb) was repeatedly measured a plurality of times, and was measured in a large current region (Bc) equal to or higher than the threshold current (Ith) during the period (Td) in which the inrush current decreases in the initial period. The DC resistance is obtained by a linear function (L2) indicating the relationship between the discharge current and the terminal voltage, and the intercept voltage (Vs) applied to the linear function and the voltage (Vnow) before the start of the initial period The reaction resistance is obtained by dividing the voltage difference (Vd) of 1 by the maximum current value.

A second aspect of the present invention is a battery evaluation device for determining a direct current resistance (Rd) and a reaction resistance (Rr) of a battery (12), after an inrush current increases from an initial current value (Io) to a maximum current value (Imax). , The discharge current (I) of the battery and the terminal voltage (Vb) of the battery corresponding to the discharge current are repeated a plurality of times during the initial period in which the maximum current value decreases to the steady current value (Ist). In the measurement unit (13d) for measurement and the period (Td) in which the inrush current decreases in the initial period, the discharge current and the inter-terminal voltage in the large current region (Bc) equal to or higher than the threshold current (Ith). Of a direct-current resistance calculating unit (13c) that obtains the direct-current resistance by a linear function (L2) indicating the relationship between the linear function, an intercept voltage (Vs) applied to the linear function, and a voltage (Vnow) before the start of the initial period. And a reaction resistance calculation unit (13f) that obtains the reaction resistance by dividing the voltage difference (Vd) by the maximum current value.

According to the configurations of the above-described inventions, regression analysis is performed on the basis of sample data including a plurality of measured discharge currents and a plurality of terminal voltages, and a linear function is obtained, and a DC resistance is obtained from the slope of the linear function. The reaction resistance is obtained by dividing the difference between the voltage applied to the intercept of the linear function and the voltage measured before the beginning of the initial period by the maximum current value. In addition, regardless of the length of the sampling interval, it can be obtained in simple steps.

The “battery” is a secondary battery or a capacitor that can be charged and discharged. “DC resistance” is an electrical resistance against movement of electrons between electrodes and corresponds to pure resistance. “Reaction resistance” is an electrical resistance against a chemical reaction that occurs during charging or discharging. Both the DC resistance and the reaction resistance are included in the internal resistance of the battery. “Before the start of the initial period” is the start of the initial period (that is, the time point when the inrush current in the discharge current is the initial current value) or the timing before the start regardless of the magnitude of the discharge current. The “sampling interval” is a time interval for acquiring sample data and is also called a sampling cycle. The “load device” is a device through which an inrush current flows due to electrical connection with the battery, and includes a starting device, a starting device, and the like.

It is a schematic diagram which shows the structural example of a power supply system. It is a schematic diagram which shows the structural example of an evaluation apparatus. It is a flowchart figure which shows the procedure example of a battery evaluation process. It is a flowchart figure which shows the procedure example of a start determination process. It is a flowchart figure which shows the procedure example of a deterioration degree estimation process. It is a time chart figure which shows the time-dependent example of a change of discharge current. FIG. 6 is a graph showing an example of the relationship between the discharge current and the terminal voltage when the sampling interval is long. It is a graph which shows the example of a relation of discharge current and voltage between terminals when a sampling interval is short. It is a graph which shows the example of a relationship between reaction resistance and a deterioration degree.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Unless otherwise specified, "connecting" means electrically connecting. Each drawing illustrates the elements necessary for describing the present invention, and not all the actual elements. When referring to directions such as up, down, left and right, the description in the drawings is used as a reference. In this embodiment, the power supply system for a vehicle is applied to an evaluation device and an evaluation method for evaluating a battery. Unless otherwise specified, "before the start of the initial period" includes before energization and before starting, and "calculation" includes estimation and identification.

(Evaluation device)
The power supply system 10 shown in FIG. 1 is provided in a vehicle and has an engine 11, a battery 12, an evaluation device 13, a control device 14, a starting device 15, and the like. The power supply system 10 starts the engine 11 with a starting device 15. The vehicle includes, for example, a vehicle that uses only the engine 11 as a power source, a hybrid vehicle that uses the engine 11 and an electric motor as a power source, and an electric vehicle that uses an electric motor that is operated by electric power supplied from the battery 12 as a power source. The electric motor includes a rotating electric machine that has both an electric function and a power generation function.

The engine 11 may be a prime mover that burns fuel in a cylinder and uses combustion gas directly as a working fluid to perform work by its thermal energy. For example, a gasoline engine, a diesel engine, etc. correspond to the fuel classification, and a reciprocating engine, a rotary engine, etc. correspond to the structure classification.

The battery 12 is a secondary battery or a capacitor that can be charged and discharged by supplying power to devices and parts that require power, including a starter 15 described later. The secondary battery corresponds to, for example, a lithium ion battery, a lithium ion polymer battery, a nickel hydrogen battery, a lead storage battery, or the like. The capacitor corresponds to, for example, an electric double layer capacitor or a lithium ion capacitor. Further, the battery 12 may be configured by connecting a plurality of unit batteries. The battery 12 of this embodiment is a lithium-ion battery.

The evaluation device 13 corresponds to a “battery evaluation device” and may be arbitrarily configured as long as it can realize the functions described below. The evaluation device 13 of this embodiment is an ECU. The ECU is an abbreviated processing device that is an acronym for Electronic Control Unit.

The control device 14 is a higher-level device of the evaluation device 13 connected to be capable of transmitting and receiving via a communication line, and controls the entire power supply system 10. The evaluation device 13 communicates with the control device 14 via the communication unit 13a. The control device 14 of this embodiment is an ECU.

The starting device 15 corresponds to a “load device” in that a rush current flows in connection with the battery 12, and has a function of starting the engine 11 based on a starting signal transmitted from the control device 14. The starting device 15 has a starter motor 15a and a control unit 15b. The starter motor 15a is a motor that starts the engine 11. The "starting" in the present embodiment includes a normal starting performed when the engine is stopped due to parking or the like, and a restart performed when the engine is temporarily stopped including the idling stop. The control unit 15b controls the drive of the starter motor 15a according to the signal transmitted from the evaluation device 13 or the control device 14. The starter motor 15a may be an electric motor or a rotating electric machine. The control unit 15b of this embodiment is an ECU.

The evaluation device 13 shown in FIG. 2 includes a communication unit 13a, a start determination unit 13b, a DC resistance calculation unit 13c, a measurement unit 13d, a power calculation unit 13e, a reaction resistance calculation unit 13f, a deterioration degree estimation unit 13g, a recording medium 13h, and the like. Have. The evaluation device 13 of this embodiment has a software configuration. The software configuration is a configuration in which the function of each element is realized by the CPU executing a program.

The measurement unit 13d includes a current sensor Si, a voltage sensor Sv, and a temperature sensor St, and has a function of measuring a discharge current I, a terminal voltage Vb, and a battery temperature T related to the battery 12. The current sensor Si measures a discharge current I flowing from the battery 12 to the starting device 15 at the time of discharging. The voltage sensor Sv measures the voltage Vb between the terminals of the battery 12. The terminal voltage Vb is the potential difference between the positive pole terminal and the negative pole terminal of the battery 12. The measurement of the current sensor Si and the voltage sensor Sv is performed a plurality of times at sampling intervals during the initial period Ts. Each of the current sensor Si, the voltage sensor Sv, and the temperature sensor St of this embodiment is composed of a sensor IC. The initial period Ts will be described later. The sampling interval may be arbitrarily set regardless of length, although it depends on the type of sensor.

The DC resistance calculation unit 13c has a function of calculating the DC resistance Rd by a linear function obtained based on sample data composed of the plurality of discharge currents I and the plurality of terminal voltages Vb measured by the measurement unit 13d. The sample data is limited to a decrease period Td in which the inrush current decreases in the initial period Ts and a large current region in which the discharge current I becomes a current equal to or higher than the threshold current. A specific method of calculating the DC resistance Rd will be described later.

The reaction resistance calculation unit 13f has a function of calculating the reaction resistance Rr of the battery 12. Specifically, the reaction resistance Rr is calculated by dividing the voltage difference between the intercept voltage applied to the linear function calculated by the DC resistance calculator 13c and the voltage before the start of the initial period Ts by the maximum current value Imax. .. A specific method of calculating the reaction resistance Rr will be described later. The reaction resistance calculator 13f records the reaction resistance Rr in the recording medium 13h every time it is calculated.

The recording medium 13h may be any medium that can record information necessary for a required process. The information necessary for the required processing includes, for example, the reaction resistance Rr, the direct current resistance Rd, and relationship information indicating the relationship between the battery temperature T and the coefficient K. The relationship information may be recorded as, for example, a map, a table, a database, or the like, or information defined by a mathematical expression including a functional expression of a linear expression or more may be recorded. The recording medium 13h is, for example, one or more of a flash memory including an SSD, a hard disk, an optical disk including a magneto-optical disk, a RAM, and the like. Since the reaction resistance Rr is calculated each time the engine 11 is started, the power may be shut off before parking the vehicle equipped with the power supply system 10 or the like. Therefore, it is desirable that the recording medium 13h includes a non-volatile memory that can retain the recorded contents even after the power is cut off.

The power calculator 13e has a function of calculating the dischargeable power Pd of the battery 12. Specifically, the dischargeable power Pd is calculated using the DC resistance Rd calculated by the DC resistance calculation unit 13c and the reaction resistance Rr calculated by the reaction resistance calculation unit 13f. A specific method of calculating the dischargeable power Pd will be described later.

The start determination unit 13b has a function of determining whether or not the engine 11 can be started. Specifically, the determination is made based on whether the dischargeable power Pd calculated by the power calculation unit 13e is equal to or greater than the threshold power Pth. The threshold power Pth may be set to the minimum power required for the starter motor 15a that is driven when the engine 11 is started. The start determination unit 13b transmits the start determination result Js that determines whether or not the engine 11 can be started to the control device 14.

The deterioration degree estimation unit 13g estimates the deterioration degree SOH of the battery 12 based on the one or more reaction resistances Rr recorded in the recording medium 13h. The deterioration degree is a value indicating the deterioration state of the battery 12, and an abbreviation made of the initials of State Of Health is used as a code. A specific method of estimating the deterioration degree SOH will be described later.

(Evaluation method)
The process repeatedly executed when the evaluation device 13 described above is operated will be described with reference to FIGS. 3 to 5. In the battery evaluation process shown in FIG. 3, steps S18 and S19 correspond to the DC resistance calculation unit 13c and the reaction resistance calculation unit 13f. In the start determination process shown in FIG. 4, steps S22 and S23 correspond to the power calculation unit 13e, and steps S24 to S26 correspond to the start determination unit 13b. The deterioration degree estimating process shown in FIG. 5 corresponds to the deterioration degree estimating unit 13g. The termination of the battery evaluation process and the deterioration degree estimation process includes the case of returning. The current is defined as a positive direction in which the battery 12 is charged and a negative direction in which the battery 12 is discharged.

In step S10 of FIG. 3, it is determined based on the operation signal Ci whether or not the operation for starting the engine 11 has been performed. If the operation of starting the engine 11 is performed, the determination result is YES, and the process proceeds to step S11. On the other hand, when the operation for starting the engine 11 is not performed, the determination is NO, and the battery evaluation process ends.

The operation signal Ci in step S10 is a signal input from the external device shown in FIG. 2 to the evaluation device 13 via the control device 14. The external device (not shown) is a device similar to the evaluation device 13, and detects the operation of the starting operation member provided in the power supply system 10 or the vehicle and outputs the operation signal Ci. The starting operation member corresponds to, for example, an ignition key, a start button, an accelerator pedal, a brake pedal, or the like.

The control device 14 shown in FIG. 2 receives the operation signal Ci, transmits the operation signal Ci to the evaluation device 13, and also transmits the starting signal Cs to the starting device 15 to start the engine 11. Upon receiving the start signal Cs, the starter 15 drives the starter motor 15a with the electric power supplied from the battery 12 to start the engine 11. A discharge current I flows from the battery 12 to the starter motor 15a as the starter motor 15a is driven.

Returning to FIG. 3, in step S11, the terminal voltage Vb of the battery 12 is measured by the voltage sensor Sv, and the measured terminal voltage Vb is recorded as the voltage Vnow before the beginning of the initial period Ts (that is, before energization or before starting). Record on medium 13h. After recording, the battery 12 and the starter motor 15a are connected and energized. Along with this energization, a rush current flows from the battery 12 to the starter motor 15a. This inrush current is a part of the discharge current I described later.

In step S12, the discharge current I of the battery 12, the inter-terminal voltage Vb, and the battery temperature T are measured. The measurement is performed at every sampling interval. The discharge current I is measured by the current sensor Si. The terminal voltage Vb is measured by the voltage sensor Sv as in step S11. The battery temperature T is measured by the temperature sensor St. The measured discharge current I and inter-terminal voltage Vb are recorded on the recording medium 13h as sample data in order to detect a maximum current value Imax described later and to obtain a linear function.

In step S13, it is determined whether or not the maximum current value Imax is detected for the discharge current I measured in step S12. If the maximum current value Imax is detected, the result is YES and the process proceeds to step S14. On the other hand, when the maximum current value Imax is not detected, the result is NO, and the process returns to step S12 to collect the sample data.

In step S14, the maximum current value Imax detected in step S13 is recorded on the recording medium 13h in order to obtain a DC resistance Rd described later.

In step S15, it is determined whether or not the discharge current I measured in step S12 is smaller than the threshold current Ith in order to determine whether or not to collect the sample data. The threshold current Ith is set to a value smaller than the steady current value Ist. If the discharge current I is smaller than the threshold current Ith, the determination is YES and the process proceeds to step S16. On the other hand, if the discharge current I is larger than the threshold current Ith, the determination is NO, and the process returns to step S12 to continue the collection of the sample data.

In step S16, a linear function is obtained by performing regression analysis based on the sample data of the plurality of discharge currents I and the plurality of terminal voltages Vb recorded in the recording medium 13h. The sample data used when obtaining the linear function is measured during the period when the inrush current decreases (hereinafter referred to as “decrease period Td”). The decrease period Td is a period from when the maximum current value Imax of the discharge current I is detected in step S12 to when it is determined in step S15 that the discharge current I is smaller than the threshold current Ith. The regression analysis of this embodiment is the least squares method.

In step S17, it is determined whether or not the test of the correlation coefficient R ² value is significant for the linear function obtained in step S16. In other words, it is determined whether there is a correlation between the expression represented by the linear function and the sample data. Whether or not it is significant may be determined by whether or not Rth≦R ² ≦1 is satisfied, where Rth is a threshold value. If the test of the correlation coefficient R ² value is significant, the determination result is YES, and the process proceeds to step S18. On the other hand, when the test of the correlation coefficient R ² value is not significant, the result is NO, the estimated resistance value is not adopted, and the process returns to step S10 to recollect the sample data.

In step S18, the DC resistance Rd and the reaction resistance Rr are calculated based on the linear function (eg, the characteristic line L2 shown in FIGS. 7 and 8) obtained in step S16. The DC resistance Rd can be calculated from the slope of the linear function. The reaction resistance Rr can be calculated by dividing the difference (that is, the voltage difference Vd) between the intercept voltage applied to the linear function and the voltage Vnow before the start of the initial period Ts by the maximum current value Imax. Of the DC resistance Rd and the reaction resistance Rr, at least the reaction resistance Rr is recorded in the recording medium 13h.

In step S19 indicated by a chain double-dashed line, the DC resistance Rd and the reaction resistance Rr obtained in step S18 are corrected based on the temperature of the battery 12. Specifically, the coefficient K corresponding to the battery temperature T measured in step S12 is first obtained by referring to the relationship information recorded in the recording medium 13h. Then, the DC resistance Rd and the reaction resistance Rr are respectively corrected by the coefficient K. That is, Rd=Rd×K and Rr=Rr×K are calculated. After the calculated DC resistance Rd and reaction resistance Rr are recorded as sample data in the recording medium 13h, the battery evaluation process is terminated. Note that step S19 may be executed when the temperature correction of the resistance value is necessary, and may not be executed when the temperature correction is not necessary.

In the start determination process shown in FIG. 4, it is determined whether the engine 11 can be started. In step S20, it is determined whether or not the start determination condition is satisfied. The start determination condition may be arbitrarily set as long as it is a condition for determining whether or not the engine 11 is started. For example, the same conditions as step S10 in FIG. 3 may be used, conditions relating to the state of the battery 12 (for example, terminal voltage Vb, charging capacity, etc.) may be used, and other conditions may be used. If the start determination condition is satisfied, the determination is YES and the process proceeds to step S21. On the other hand, if the start determination condition is not satisfied, the determination result is NO, and the start determination process ends.

In step S21, step S18 of FIG. 3 is executed to determine whether or not the DC resistance Rd and the reaction resistance Rr are recorded in the recording medium 13h. If the DC resistance Rd and the reaction resistance Rr are recorded, the determination result is YES and the process proceeds to step S22. On the other hand, when the DC resistance Rd and the reaction resistance Rr are not recorded, the determination result is NO, and the start determination process ends. In other words, even if the battery evaluation process is executed at the first start, the DC resistance Rd and the reaction resistance Rr have not been recorded yet, so that the step S22 and the subsequent steps of the start determination process are not executed. Therefore, step S22 and the subsequent steps are executed after the second start (especially restart).

In step S22, the dischargeable electric power of the battery 12 is calculated. Here, the dischargeable power is Pd, the voltage of the battery 12 measured in step S11 of FIG. 3 before the start of the initial period Ts (that is, before energization or before starting) is Vnow, and the lower limit voltage of use of the battery 12 is Vmin. And Along with these, when expressed by an equation using the DC resistance Rd and the reaction resistance Rr, the relationship of Pd=(Vnow−Vmin)/(Rd+Rr)×Vmin is established.

In step S23 indicated by a chain double-dashed line, the dischargeable power obtained in step S22 is corrected by the coefficient K in the same manner as step S19 in FIG. That is, the calculation of Pd=Pd×K is performed and the corrected dischargeable power Pd is recorded in the recording medium 13h. Similar to step S19 of FIG. 3, step S23 may be executed when the resistance value temperature correction is necessary, and may not be executed when the temperature correction is unnecessary.

In step S24, it is determined whether or not the dischargeable power Pd is equal to or higher than the threshold power Pth at which the discharge is possible. That is, it is determined whether or not Pd≧Pth is satisfied. If the dischargeable power Pd is greater than or equal to the threshold power Pth, the determination is YES and the process proceeds to step S25. On the other hand, if the dischargeable power Pd is less than the threshold power Pth, the determination result is NO, and the process proceeds to step S26.

In step S25, "startable" is transmitted to the control device 14 as the start determination result Js, and in step S26, "start impossible" is transmitted to the control device 14 as the start determination result Js. In either case, after the start determination result Js is transmitted, the start determination process is returned.

In FIG. 2, the control device 14, which has received the start determination result Js from the evaluation device 13, transmits the start signal Cs to the start device 15 only when “startable”. The starter 15, which receives the start signal Cs from the controller 14, starts driving the starter motor 15a to start the engine 11. On the other hand, when the starting device 15 does not receive the starting signal Cs from the control device 14, the driving of the starter motor 15a is not started.

Next, a deterioration degree estimation process for estimating the deterioration degree of the battery 12 will be described with reference to FIG. This deterioration degree estimation processing is executed when the reaction resistance Rr is recorded in the recording medium 13h, and is executed independently of the battery evaluation processing shown in FIG.

In step S30 of FIG. 5, the deterioration degree SOH of the battery 12 is estimated based on the reaction resistance Rr recorded on the recording medium 13h. In the present embodiment, the relationship between the deterioration degree SOH and the reaction resistance Rr is recorded in the recording medium 13h as a characteristic line, and the deterioration degree SOH corresponding to the reaction resistance Rr is specified and estimated.

In step S31, it is determined whether the deterioration degree SOH estimated in step S30 exceeds the threshold deterioration degree SOHth. If the deterioration degree SOH exceeds the threshold deterioration degree SOHth, the determination result is YES, and the process proceeds to step S32. On the other hand, if the deterioration degree SOH is equal to or lower than the threshold deterioration degree SOHth, the determination result is NO, and the process proceeds to step S33.

In step S32, the deterioration degree estimation result Jd is set to "abnormal" and is transmitted to the control device 14 via the communication unit 13a. After the deterioration degree estimation result Jd is transmitted, the deterioration degree estimation process ends.

In step S33, the deterioration degree estimation result Jd is set to "normal" and is transmitted to the control device 14 via the communication unit 13a. After the deterioration degree estimation result Jd is transmitted, the deterioration degree estimation process ends.

An evaluation example performed by the evaluation device 13 described above will be described with reference to FIGS. 6 to 9. However, in FIGS. 6 to 9, the current flowing from the outside into the battery 12 is positive, and the current flowing out from the battery 12 to the outside is negative. The discharge current I has a negative value because it becomes a current flowing out from the battery 12. Therefore, the discharge current I increases as the negative value increases.

FIG. 6 shows an example of the discharge current I that changes with the passage of time t. The starter 15 is operated by the operation of the starting operation member at time t1, and the discharge current I starts to flow. This time t1 corresponds to the beginning of the initial period Ts. The initial current value Io of the discharge current I at time t1 shown in FIG. 6 is 0 [A]. The initial current value Io may be a value other than 0 [A] in idling stop or the like. The value other than 0 [A] may be, for example, a current value at a predetermined time point, or an average value of current values measured at a plurality of time points (including a simple average value, a weighted average value, and a moving average value). That is, the initial current value Io may be 0 [A] or a value other than 0 [A]. The discharge current I rapidly increases, the maximum current value -Imax is detected at time t2, and the steady current value -Ist is reached at time t3. This time t3 corresponds to the end of the initial period Ts. Therefore, the period from time t1 to time t3 corresponds to the initial period Ts, and the period from time t2 to time t3 corresponds to the decreasing period Td. The negative discharge current I that is equal to or less than the threshold current −Ith corresponds to the large current region Bc.

FIG. 7 shows a measurement example in which the sampling interval is 8 [msec]. When the discharge current I is 0 [A], the inter-terminal voltage Vb is equal to the voltage Vnow before the start of the initial period Ts. A characteristic line L2 shown by a solid line is a linear function obtained by performing a regression analysis from the discharge current I in the decreasing period Td. When the discharge current I is 0 [A], the intercept voltage Vs is obtained by the characteristic line L2. The characteristic line L1 indicated by the chain double-dashed line is a linear function having the same slope as the characteristic line L2, and passes through the voltage Vnow. As shown, the maximum value of the discharge current I related to the characteristic line L2 is the current −I1, and the maximum value of the discharge current I related to the characteristic line L1 is the current −I2. That is, the maximum current −I1 when the discharge current I increases on the negative side and the maximum current −I2 when the discharge current I attenuates on the negative side have different current values.

FIG. 8 shows a measurement example in which the sampling interval is 0.1 [msec]. Although the number of measurable samplings is significantly larger than that in FIG. 7, the voltage Vnow before the start of the initial period Ts and the voltage Vs of the intercept of the linear function are obtained in the same manner as in FIG. 7. Further, the current value is different between the maximum current −I1 when the discharge current I increases on the negative side and the maximum current −I2 when the discharge current I attenuates on the negative side.

FIG. 9 shows a change in the deterioration degree SOH with respect to the reaction resistance Rr by a characteristic line L3. In the characteristic line L3, as the reaction resistance Rr increases, the deterioration rate SOH also increases at an increasing rate. When the deterioration degree SOH is SOH1, the reaction resistance Rr is R1. When the deterioration degree SOH is SOH2, the reaction resistance Rr is R2. The criterion for determining whether or not the battery 12 is abnormal is the threshold deterioration degree SOHth, and a specific numerical value may be determined by experiments, field data, or the like. When the deterioration degree SOH is SOHth, the reaction resistance Rr is Rth. According to the example of FIG. 9, R1<Rth<R2 and SOH1<SOHth<SOH2. For example, if the reaction resistance Rr is R1, the deterioration degree SOH is SOH1<SOHth, and therefore the battery 12 can be determined to be normal. On the other hand, if the reaction resistance Rr is R2, the deterioration degree SOH is SOH2>SOHth, and therefore it can be determined that the battery 12 is abnormal.

According to the embodiment described above, the following operational effects can be obtained.

The battery evaluation process corresponding to the battery evaluation method is performed by discharging the battery 12 during the initial period Ts in which the inrush current increases from the initial current value Io to the maximum current value Imax and then decreases from the maximum current value Imax to the steady current value Ist. The current I and the inter-terminal voltage Vb of the battery 12 corresponding to the discharge current I are repeatedly measured a plurality of times, and in the decreasing period Td in which the inrush current decreases in the initial period Ts, the large current region Bc equal to or more than the threshold current Ith. The direct current resistance Rd is calculated by a linear function (that is, the characteristic line L2 shown in FIGS. 7 and 8) showing the relationship between the discharge current I and the terminal voltage Vb measured in step S1, and the intercept voltage Vs applied to the linear function, The reaction resistance Rr is obtained by dividing the voltage difference Vd from the voltage Vnow before the start of the initial period Ts by the maximum current value Imax. According to this structure, a linear function is obtained by performing regression analysis based on the sampled data composed of the plurality of measured discharge currents I and the plurality of inter-terminal voltages Vb, and the DC resistance Rd is obtained from the slope of the linear function. The reaction resistance Rr is obtained by dividing the difference (that is, the voltage difference Vd) between the voltage Vs of the intercept related to the linear function and the voltage Vnow before the start of the initial period Ts by the maximum current value Imax. In addition, regardless of the length of the sampling interval, it can be obtained in simple steps.

Whether the dischargeable electric power Pd of the battery 12 is calculated using the DC resistance Rd and the reaction resistance Rr, and whether the dischargeable electric power Pd is equal to or more than the threshold electric power Pth can start the engine 11 by the starter 15. Whether or not. According to this configuration, it is possible to accurately determine whether or not the engine 11 can be started based on the required dischargeable power Pd.

The reaction resistance Rr was recorded, and the deterioration degree SOH of the battery 12 was estimated based on the recorded reaction resistance Rr. According to this configuration, the deterioration degree SOH of the battery 12 can be accurately estimated by the change in the reaction resistance R.

The evaluation device 13 corresponding to the battery evaluation device is configured to increase the initial current value Io to the maximum current value Imax and then decrease the maximum current value Imax to the steady-state current value Ist during the initial period Ts in which the inrush current flows. A discharge current I of 12 and a measurement unit 13d that repeatedly measures a voltage Vb between terminals of the battery 12 corresponding to the discharge current I a plurality of times, and a threshold current in a decrease period Td in which the inrush current decreases in the initial period Ts. A direct current resistance calculating unit 13c for calculating a direct current resistance Rd by a linear function showing a relationship between the discharge current I measured in the large current region Bc equal to or more than Ith and the terminal voltage Vb; and an intercept voltage Vs applied to the linear function. The reaction resistance calculator 13f calculates the reaction resistance Rr by dividing the voltage difference Vd from the voltage Vnow before the start of the initial period Ts by the maximum current value Imax. According to this structure, a linear function is obtained by performing regression analysis based on the sampled data composed of the plurality of measured discharge currents I and the plurality of inter-terminal voltages Vb, and the DC resistance Rd is obtained from the slope of the linear function. The reaction resistance Rr is obtained by dividing the difference (that is, the voltage difference Vd) between the voltage Vs of the intercept related to the linear function and the voltage Vnow before the start of the initial period Ts by the maximum current value Imax. In addition, regardless of the length of the sampling interval, it can be obtained in simple steps.

The evaluation device 13 uses the DC resistance Rd and the reaction resistance Rr to calculate the dischargeable power Pd of the battery 12, and the starter based on whether the dischargeable power Pd is equal to or greater than the threshold power Pth. And a start determination unit 13b that determines whether or not the engine 11 can be started by 15. According to this configuration, it can be accurately determined whether the engine 11 can be started based on the calculated dischargeable power Pd.

The evaluation device 13 includes a recording medium 13h that records the reaction resistance Rr by the reaction resistance calculation unit 13f, and a deterioration degree estimation unit 13g that estimates the deterioration degree SOH of the battery 12 based on the reaction resistance Rr recorded in the recording medium 13h. Have and. According to this configuration, the deterioration degree SOH of the battery 12 can be accurately estimated by the change in the reaction resistance R.

[Other Embodiments]
Although the embodiment for carrying out the present invention has been described above, the present invention is not limited to the embodiment. In other words, various forms can be implemented without departing from the scope of the present invention. For example, each of the following forms may be realized.

In the above-described embodiment, the power supply system 10 is applied to the vehicle. Instead of this form, the power supply system 10 may be applied to a device other than the vehicle. The other device corresponds to, for example, a generator used in the field without a commercial power source, a transportation device including a railway vehicle, a ship, and an aircraft. The evaluation device 13 may be applied to a general electric device that uses the battery 12 as a power source, such as a mobile phone or a storage battery. Besides, it may be applied to home electric appliances, audio equipment, mobile equipment other than mobile phones, communication equipment, power equipment, and the like. Since the objects to which the power supply system 10 and the evaluation device 13 are applied are only different, it is possible to obtain the same effect as that of the embodiment.

In the embodiment described above, the lithium ion battery that is the battery 12 was evaluated. Instead of this form, secondary batteries other than lithium ion batteries may be evaluated. Secondary batteries other than lithium-ion batteries include general type, liquid circulation type, mechanical charge type, high temperature operation type, and electron trap type secondary batteries. The general type secondary battery includes, for example, a lead storage battery, a lithium ion polymer battery, a nickel/hydrogen storage battery, a nickel/cadmium storage battery, a nickel/iron storage battery, a nickel/zinc storage battery, a silver oxide/zinc storage battery, and the like. The liquid circulation type secondary battery corresponds to, for example, a redox flow battery, a zinc/chlorine battery, a zinc/bromine battery, a mechanical charge type, an aluminum/air battery, an air zinc battery, an air/iron battery, or the like. The mechanical charge type secondary battery corresponds to, for example, a lithium/air battery, a zinc air battery, an air/iron battery, or the like. The high temperature operation type secondary battery corresponds to, for example, a sodium/sulfur battery or a lithium/iron sulfide battery. The electron trap type secondary battery corresponds to, for example, a semiconductor secondary battery. Since the type of the battery 12 is different, the same effect as that of the embodiment can be obtained.

In the above-described embodiment, the load device through which the inrush current flows due to the connection with the battery 12 is the starting device 15 including the starter motor 15a. Instead of this form, another load device may be used. The other load device may be arbitrarily applied as long as it is a device that receives electric power supplied from the battery 12 to operate, and that a rush current flows in connection with the battery 12. For example, a starter, a generator, an electric motor, a rotary electric machine, an electrical component, a commercial power source, and the like are applicable, and are devices mainly including an inductive element. The electric motor and the rotating electric machine include a motor used when operating transportation equipment including a vehicle. Since only the types of load devices are different, the same effects as those of the embodiment can be obtained.

In the above-described embodiment, the evaluation device 13 and the control device 14 are software-configured ECUs. Instead of this form, it may be a hardware configuration or a control device other than the ECU. The hardware configuration is a configuration in which the function of each element is realized by hardware logic including electronic circuits and logic circuits. The control device other than the ECU corresponds to a computer, a microcomputer including a one-chip microcomputer, or the like. Since only the configurations of the evaluation device 13 and the control device 14 are different, it is possible to obtain the same effect as that of the embodiment.

In the above-described embodiment, the linear function representing the relationship between the discharge current I and the terminal voltage Vb is obtained by the least square method. Instead of this form, it may be obtained by regression analysis other than the least squares method. Multiple regression analysis may be included in the regression analysis other than the least squares method, regardless of the model. For example, linear regression, ridge regression, Lasso regression, elastic net, etc. are applicable. The model corresponds to, for example, a general linear model, a generalized linear model, a mixed model, or a generalized linear mixed model. Since only the method of obtaining the linear function is different, it is possible to obtain the same effect as that of the embodiment.

In the above-described embodiment, in step S12 of FIG. 3, the discharge current I and the terminal voltage Vb of the battery 12 are measured at each sampling interval. The sampling interval in FIG. 8 is 8 [msec], and the sampling interval in FIG. 9 is 0.1 [msec]. Instead of this form, the discharge current I and the terminal voltage Vb of the battery 12 may be measured at every other sampling interval. That is, the sampling interval may be determined according to the types of the current sensor Si and the voltage sensor Sv. It is only necessary that the characteristic line L2, which is a linear function, can be obtained only by the difference in the length of the sampling interval, and therefore the same effect as that of the embodiment can be obtained.

In the above-described embodiment, in step S30 of FIG. 5 and FIG. 9, it is estimated by specifying the deterioration degree SOH corresponding to the reaction resistance Rr based on the characteristic line L3 recorded on the recording medium 13h. Instead of this form, the deterioration degree SOH may be estimated by another estimation method. In another estimation method, for example, the relationship between the deterioration degree SOH and the reaction resistance Rr is recorded in the recording medium 13h by a functional expression, the reaction resistance Rr is used as a variable, and the functional expression is calculated to obtain the deterioration degree SOH. It may be estimated. Further, similarly to step S16 of FIG. 3, even if the regression analysis is performed based on the plurality of reaction resistances Rr to obtain a linear function, and the deterioration degree SOH is estimated from the reaction resistance Rr at the present time in accordance with the linear function, it is estimated. Good. Since only the method of estimating the deterioration degree SOH is different, the same effect as that of the embodiment can be obtained.

In the above-described embodiment, in step S15 of FIG. 5, it is determined whether or not the discharge current I is smaller than the threshold current Ith as the determination as to whether or not the collection of the sample data is completed. Instead of this form, it may be determined whether or not other conditions are satisfied. Other conditions may be arbitrarily set as long as they are conditions for ending the collection of sample data. For example, the fact that the number of sample data necessary for obtaining the characteristic line L2 has been collected, that a predetermined period has elapsed from the time t1 in FIG. 6 when the start operation member is operated, and the like are applicable. The predetermined period is a time interval in which the number of sample data required to obtain the characteristic line L2 can be collected. Since only the condition of whether or not the collection of the sample data is finished is different, it is possible to obtain the same effect as that of the embodiment.

In the above-described embodiment, the voltage Vnow before the start of the initial period Ts is the voltage measured at the time when the operation of starting the engine 11 is performed in step S11 of FIG. 3 (time t1 in FIG. 6). Instead of this form, a voltage measured at another timing before the start of the initial period Ts may be used as the voltage Vnow. The other timing corresponds to, for example, the time when the engine 11 is stopped, the time when the state of the battery 12 (for example, the terminal voltage Vb, the charge capacity, etc.) reaches a required state, or the like. Alternatively, it may be an average value of voltage values measured at a plurality of time points (including a simple average value, a weighted average value, and a moving average value). Since only the timing of measuring the voltage Vnow before the start of the initial period Ts is different, the same effect as that of the embodiment can be obtained.

10... Vehicle, 11... Engine, 12... Battery, 13... Evaluation device, 14... Control device, 13a... Communication part, 13b... Start determination part, 13c... DC resistance calculation part, 13d... Measuring part, 13e... Electric power calculation part , 13f... Reaction resistance calculation unit, 13g... Degradation estimation unit, 13h... Recording medium, 15... Starter device, 15a... Starter motor, 15b... Control unit, Sv... Voltage sensor, Si... Current sensor, Rd... DC resistance, Rr... Reaction resistance, Pd... Dischargeable power, Pth... Threshold power, I... Discharge current, I1, I2... Current, Io... Initial current value, Imax... Maximum current value, Ist... Steady current value, Ith... Threshold current, Vb... inter-terminal voltage, V1, V2, V3... voltage, Vd... voltage difference, Ts... initial period, Td... decreasing period, Bc... large current region, Vnow... voltage before start of initial period, Vs... intercept voltage , Vd... voltage difference, L1, L2, L3... characteristic line, SOH... deterioration degree, SOHth... threshold deterioration degree, Jd... deterioration degree estimation result, Js... start determination result, Ci... operation signal, Cs... start signal

Claims (6)

In the battery evaluation method for obtaining the direct current resistance (Rd) and the reaction resistance (Rr) of the battery (12),
During the initial period (Ts) in which the inrush current increases from the initial current value (Io) to the maximum current value (Imax) and then decreases from the maximum current value to the steady current value (Ist), the discharge current (I ) And the terminal voltage (Vb) of the battery corresponding to the discharge current are repeatedly measured a plurality of times,
A linear function showing the relationship between the discharge current and the terminal voltage measured in a large current region (Bc) equal to or higher than the threshold current (Ith) in the period (Td) in which the inrush current decreases in the initial period. Calculate the DC resistance from (L2),
A battery evaluation method for obtaining the reaction resistance by dividing the voltage difference (Vd) between the intercept voltage (Vs) applied to the linear function and the voltage (Vnow) before the start of the initial period by the maximum current value. .. The dischargeable power (Pd) of the battery is obtained using the DC resistance and the reaction resistance,
The battery evaluation method according to claim 1, wherein it is determined whether or not the load device (15) can be operated based on whether or not the dischargeable power is equal to or higher than a threshold power (Pth). Recording the reaction resistance,
The battery evaluation method according to claim 1, wherein the deterioration degree (SOH) of the battery is estimated based on the recorded reaction resistance. In a battery evaluation device for obtaining a direct current resistance (Rd) and a reaction resistance (Rr) of a battery (12),
During the initial period in which the inrush current increases from the initial current value (Io) to the maximum current value (Imax) and then decreases from the maximum current value to the steady current value (Ist), the discharge current (I) of the battery, A measuring unit (13d) that repeatedly measures a voltage (Vb) between terminals of the battery corresponding to the discharge current, a plurality of times;
In the period (Td) in which the inrush current decreases in the initial period, a linear function (L2) indicating the relationship between the discharge current and the terminal voltage in a large current region (Bc) equal to or higher than the threshold current (Ith). A DC resistance calculation unit (13c) for obtaining the DC resistance according to
Reaction resistance calculation to obtain the reaction resistance by dividing the voltage difference (Vd) between the intercept voltage (Vs) applied to the linear function and the voltage (Vnow) before the start of the initial period by the maximum current value. Part (13f),
Battery evaluation device having a. An electric power calculation unit (13e) for obtaining a dischargeable electric power (Pd) of the battery using the DC resistance and the reaction resistance;
A start determination unit (13b) that determines whether or not the load device (15) can be operated depending on whether or not the dischargeable power is equal to or greater than a threshold power (Pth);
The battery evaluation device according to claim 4, further comprising: A recording medium (13h) for recording the reaction resistance obtained by the reaction resistance calculation unit;
A deterioration degree estimating unit (13g) for estimating a deterioration degree (SOH) of the battery based on the reaction resistance recorded in the recording medium,
The battery evaluation device according to claim 4 or 5, further comprising:

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