JP2007170953A - Deterioration determining device of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deterioration determining device of a secondary battery precisely determining the degree of deterioration of a secondary battery while suppressing increase in costs. <P>SOLUTION: When an ignition key is turned off (Yes in S100), an ECU executes a program including a step (S102) for performing counting-up until the lapse of a predetermined waiting time, a step (S106) for executing discharge processing, a step (S108) for counting up a determination time until the variation in voltage settles, a step (S112) for storing the determination time, and a step (S114) for estimating the degree of deterioration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a deterioration determination device that determines the degree of deterioration of a secondary battery, and more particularly, to a deterioration determination device that determines the degree of deterioration with high accuracy.

  Since the secondary battery deteriorates in battery performance, represented by input / output power and full charge capacity (battery capacity after full charge), in the process of use, the performance changes in time series. In particular, when power input / output exceeding the battery performance is performed, the deterioration is rapidly accelerated, and there is a possibility of failure if it is remarkable. In order to solve such a problem, a technique for quantitatively grasping the current degree of deterioration and detecting the limit amount of the performance of the secondary battery is known.

  Japanese Patent Laying-Open No. 5-281309 (Patent Document 1) discloses a deterioration determination device that safely and accurately determines deterioration of a sealed lead-acid battery in a very short time. This deterioration determiner is applied to a switch unit and a load circuit unit for discharging a constant current to a lead storage battery to be tested for a short time, and a voltage detection unit or voltage detection unit and a lead storage battery for detecting the battery voltage of the lead storage battery. A current detection unit for detecting a flowing current, and a difference voltage or a difference voltage between the detected battery voltage after a lapse of 1 msec or less from the start of discharge and the detected battery voltage before the start of discharge is detected. Calculate the internal resistance from the current flowing in the lead-acid battery and substitute the voltage or internal resistance of the difference into the regression equation of the difference voltage and battery capacity or the regression formula of the internal resistance and battery capacity obtained in advance. A storage calculation unit for estimating a battery capacity, a display unit for displaying a differential voltage or internal resistance or an estimated battery capacity, at least a switch unit, a voltage detection unit, Comprising an operation portion for operating orderly the 憶 calculating section.

According to the deterioration determination device disclosed in the above-mentioned publication, the test is completed in a very short time, so that the burden on the maintenance person is extremely reduced and the test time is 1 msec or less. Even if the connection is disconnected due to a mistake by the maintenance person, the discharge is terminated at that time, and there is no fear of occurrence of a spark, so that the safety is extremely high and the deterioration determination can be realized with higher accuracy than before.
Japanese Patent Laid-Open No. 5-281309

  However, when performing deterioration determination based on the voltage polarization characteristics of the secondary battery, such as the deterioration determination device disclosed in the above-mentioned publication, it is possible to make an appropriate deterioration determination because it depends on the accuracy of the measuring instrument. There is sex. The voltage polarization characteristics of the secondary battery depend on the current and temperature and are affected by the charge / discharge history. Therefore, in order to acquire accurate voltage polarization characteristics, it is necessary to acquire not only voltage but also absolute values of current and temperature with high accuracy. If the accuracy of each measuring instrument that detects voltage, current, and temperature is improved, there is a problem that the cost increases.

  In the deterioration determination device disclosed in the above-mentioned publication, since the measurement accuracy at the time of obtaining the voltage polarization characteristic of the secondary battery is not considered at all, the above-described problem cannot be solved.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a secondary battery deterioration determination device that accurately determines the degree of deterioration of a secondary battery while suppressing an increase in cost. Is to provide.

  A secondary battery deterioration determination device according to a first aspect of the present invention determines the degree of deterioration of a secondary battery. This deterioration determination device is detected after the secondary battery is discharged, the detection means for detecting the voltage of the secondary battery, the discharge means for discharging the secondary battery until a predetermined time elapses. Deterioration determining means for determining the degree of deterioration based on the determination time until the change in voltage is converged.

  According to the first invention, the deterioration determination means determines the degree of deterioration based on the determination time until the detected voltage change converges after the secondary battery is discharged. At the time of discharging the secondary battery, the voltage drops, and after the end of discharging, the voltage rises so as to approach the voltage before discharging. After the discharge is completed, the time until the voltage changes below a predetermined change amount and converges is a time depending on the degree of deterioration. The longer it takes to converge, the greater the degree of degradation. Therefore, the degree of deterioration can be determined by measuring the determination time until convergence. In this way, it is sufficient to improve the resolution with respect to changes around the converging voltage, and it is not necessary to accurately measure the absolute values of the voltage, current and temperature of the secondary battery. Therefore, it is possible to provide a secondary battery deterioration determination device that accurately determines the degree of deterioration of the secondary battery while suppressing an increase in cost.

  In the deterioration determination device for a secondary battery according to the second invention, in addition to the configuration of the first invention, the deterioration determination means determines that the degree of deterioration of the secondary battery is larger as the determination time is longer. Including means.

  According to the second invention, the deterioration determining means determines that the degree of deterioration of the secondary battery is larger as the determination time is longer. As the secondary battery deteriorates, the voltage drop increases so that the time from the end of discharge to the convergence of voltage tends to be longer. Therefore, it can be determined that the degree of deterioration of the secondary battery is greater as the determination time is longer.

  In the secondary battery deterioration determination device according to the third aspect of the invention, in addition to the configuration of the first or second aspect of the invention, the deterioration determination means determines in advance the amount of change in the detected voltage after the secondary battery is discharged. Convergence determining means for determining that the change in voltage has converged when the amount of change is less than or equal to the change amount.

  According to the third invention, the deterioration determining means determines that the change in voltage has converged when the detected change in voltage is equal to or less than a predetermined change after discharging the secondary battery. This makes it possible to accurately measure the determination time until the voltage converges to a substantially constant state from the end of discharge.

  A secondary battery deterioration determination device according to a fourth aspect of the invention is mounted on a vehicle in addition to any one of the first to third aspects of the invention.

  According to the fourth invention, by mounting the deterioration determination device on the vehicle, it is possible to accurately determine the degree of deterioration of the secondary battery mounted on the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, a vehicle equipped with the secondary battery deterioration determination device according to the present embodiment includes an ECU (Electronic Control Unit) 100, a battery 200, a load 300, and a discharging resistance device 400. A current sensor 500 and a voltage sensor 600 are provided. The secondary battery deterioration determination device according to the present embodiment is implemented by ECU 100. The vehicle on which the secondary battery deterioration determination device according to the present embodiment is mounted is, for example, an electric vehicle using a rotating electrical machine as a drive source, but is particularly limited as long as the vehicle is mounted with a battery. Instead, for example, it may be a hybrid vehicle that uses an engine and a rotating electric machine as drive sources, or a vehicle that uses an engine equipped with an auxiliary battery as a drive source.

  Load 300 is, for example, a rotating electrical machine connected via a converter and an inverter. In the present embodiment, battery 200 is not particularly limited as long as it is a secondary battery, and is, for example, a nickel metal hydride battery or a lithium ion battery.

  The discharging resistance device 400 is configured, for example, by connecting a relay switch (hereinafter simply referred to as a relay) and a resistor. The discharging resistance device 400 is connected to a power line 202 connected to the + terminal of the battery 200 and a power line 204 connected to the − terminal. The discharge resistance device 400 switches the relay in accordance with a discharge control signal received from the ECU 100 to electrically connect the power supply line 202 and the power supply line 204 via a resistor, To do. At this time, since the circuit including the power supply lines 202 and 204, the discharging resistance device 400, and the battery 200 is closed, a current flows and the battery 200 is discharged. It should be noted that discharge resistance device 400 is particularly a device that can electrically connect power supply line 202 and power supply line 204 via a resistor, or can be cut off in response to a control signal from ECU 100. It is not limited to the structure which connects a relay switch and a resistor in series.

  Current sensor 500 is connected in series with battery 200. The current sensor 500 detects the current value of the current flowing through the power supply line 204. Current sensor 500 transmits a signal representing the detected current value to ECU 100.

  Voltage sensor 600 is connected in parallel to battery 200. The voltage sensor 600 detects the voltage value of the battery 200. Voltage sensor 600 transmits a signal representing the detected voltage value to ECU 100.

  The ECU 100 includes a CPU and a memory. The ECU 100 is provided with a counter unit 102. The counter unit 102 measures time by increasing the count value every calculation cycle. The counter unit 102 may be realized by hardware, or may be realized by a program (software) executed by the ECU 100.

  In the present embodiment, ECU 100 controls discharge resistance device 400 by executing a program stored in a memory based on the count value in counter unit 102 and signals received from current sensor 500 and voltage sensor 600. .

  When the ignition key of the vehicle is turned off, ECU 100 transmits a discharge control signal to discharge resistance device 400 when a predetermined standby time has elapsed since the vehicle is turned off, and starts a deterioration determination process. The deterioration determination process is performed after the discharge of the battery 200 is finished by switching the relays of the discharging resistance device 400 to the power supply lines 202 and 204 until a predetermined time elapses. This is a process for determining the degree of deterioration of the battery 200 based on the voltage change.

  FIG. 2A shows a change in discharge current when the horizontal axis is time and the vertical axis is discharge current. When the ignition key is turned off at time T (0), the counter unit 102 measures the time. At time T (1) when a predetermined standby time elapses from time T (0), the power supply lines 202 and 204 are electrically connected based on a discharge control signal received from the ECU 100 by the discharging resistance device 400. As a result, the discharge current A (0) flows, and the discharge of the battery 200 is started. At this time, the counter unit 102 is reset, and the elapsed time after the time T (1) is measured.

  FIG. 2B shows a change in the voltage of the battery 200 when the horizontal axis is time and the vertical axis is voltage. After time T (1), the voltage value detected by voltage sensor 600 drops from V (0) when discharge is started. When the measured time reaches time T (2) when a predetermined discharge time elapses from time T (1), power supply lines 202 and 204 are electrically cut off based on a discharge control signal received from ECU 100. To be in a state. At this time, the discharge current detected by the current sensor 500 becomes zero.

  The voltage that has dropped to V (1) at time T (2) increases from time T (2) so as to approach voltage V (0) before discharge. As shown in FIG. 3, the voltage drop tends to increase as it degrades. Therefore, the time until the voltage converges after the end of discharge tends to be longer as it deteriorates.

  Therefore, the present invention is characterized in that the ECU 100 which is a secondary battery deterioration determination device determines the degree of deterioration of the battery 200 based on the voltage change waveform after the battery 200 is discharged. That is, information about a voltage change corresponding to the degree of deterioration is stored in advance in the memory of the ECU 100, and the degree of deterioration of the battery 200 is determined by comparison with the voltage change after discharge detected by the voltage sensor 600. . More specifically, ECU 100 determines the degree of deterioration of battery 200 based on the determination time until the detected voltage change converges after battery 200 is discharged.

  Hereinafter, with reference to FIG. 4, a control structure of a program executed by ECU 100 that is the secondary battery deterioration determination device according to the present embodiment will be described.

  In step (hereinafter, step is referred to as S) 100, ECU 100 determines whether or not the ignition key is turned off. If the ignition key is turned off (YES in S100), the process proceeds to S102. If not (NO in S100), the process returns to S100.

  In S102, ECU 100 starts counting up the standby time by counter unit 102. “Count-up” is performed by adding a predetermined count value for each calculation cycle to a predetermined initial value.

  In S104, ECU 100 determines whether or not a predetermined standby time has elapsed since the ignition key was turned off. ECU 100 determines whether or not the count value is equal to or greater than a count value corresponding to a predetermined standby time. Note that the “predetermined standby time” is a standby time until an environment with little temperature change, and is not particularly limited, and is adapted by an experiment or the like. When a predetermined standby time has elapsed (YES in S104), the process proceeds to S106. If not (NO in S104), the process returns to S102.

  In S106, ECU 100 executes a discharge process. In the present embodiment, the “discharge process” refers to electrically connecting the power lines 202 and 204 by switching the relay of the discharge resistance device 400 until a predetermined discharge time elapses after the standby time elapses. This is the process to make a state. Specifically, ECU 100 controls discharge resistance device 400 to electrically connect power supply lines 202 and 204 and starts counting up discharge time in counter unit 102. At this time, the counter unit 102 resets the count value to a predetermined initial value, adds a predetermined count value every calculation cycle, and counts up. Then, ECU 100 determines that the predetermined discharge time has elapsed when the count value reaches the count value corresponding to the predetermined discharge time. ECU 100 switches the relay of discharging resistance device 400 to electrically cut off power supply lines 202 and 204. Note that the predetermined discharge time is a time that is adapted from experiments or the like and is not particularly limited. However, it is preferable that the discharge time is short enough that the determination accuracy does not deteriorate.

  In S108, ECU 100 starts counting time determination by counter unit 102. Specifically, the ECU 100 resets the count value to the initial value in the counter unit 102 and adds a predetermined count value for each calculation cycle.

  In S110, ECU 100 determines whether or not the voltage of battery 200 has settled. In the present embodiment, ECU 100 determines whether or not the voltage change has converged based on the voltage change amount input from voltage sensor 600. ECU 100 determines that the voltage has settled when the time variation of the voltage input from voltage sensor 600 is equal to or less than a predetermined variation. The “predetermined amount of change” is a value with which it can be determined that the voltage change is in a substantially constant state, and is not particularly limited, and is adapted by an experiment or the like. If it is determined that the voltage of battery 200 has settled (YES in S110), the process proceeds to S112. If not (NO in S100), the process returns to S108.

  In step S112, the ECU 100 stores the count value corresponding to the measured determination time in the memory, assuming that the acquisition of the voltage polarization characteristics of the battery 200 has been completed. The ECU 100 may store the measured determination time in a memory.

  In S114, ECU 100 estimates the degree of deterioration (deterioration degree) of battery 200 based on the stored count value. For example, ECU 100 may store a map indicating the relationship between the count value and the degree of deterioration in advance in the memory, and estimate the degree of deterioration from the stored count value and the map. It is also possible to store a table or a function expression indicating the relationship between the value and the deterioration level in advance and estimate the deterioration level from the stored count value and the table or expression. ECU 100 may estimate the degree of deterioration from the determination time measured instead of the count value and a map, table, or function expression.

  The operation of ECU 100, which is the secondary battery deterioration determination apparatus according to the present embodiment based on the structure and flowchart as described above, will be described with reference to FIG.

  As shown in FIG. 5A, when the ignition key is turned off at time T (3) (YES in S100), count-up is executed (S102). When time T (4) at which count value Ca corresponding to predetermined standby time Ta is reached (YES in S104), discharging is performed (S106). At this time, as shown in FIG. 5C, the voltage decreases from V (0) as the discharge starts. After the count value is reset to the initial value at time T (4), the count up is executed. When the time T (5) at which the count value Cb corresponding to the predetermined discharge time Tb is reached, the discharge resistance device 400 is controlled so that the power supply lines 202 and 204 are cut off, and the discharge process ends. To do. At time T (5), after the count value is reset to the initial value again, the count up is executed.

  At time T (5), as shown in FIG. 5C, when the time change amount of the voltage value detected by the voltage sensor 600 is equal to or less than a predetermined change amount, it is determined that the voltage change has settled. (YES in S110), Cc is stored in the memory as the count value at the time T (5). Then, based on the stored count value Cc or the determination time Tc corresponding to the count value Cc, the degree of deterioration of the battery 200 is estimated from a map or the like (S114).

  As described above, according to the secondary battery deterioration determination device according to the present embodiment, the time until the voltage change is equal to or less than the predetermined change amount after the discharge is completed is the battery deterioration. The time depends on the degree. The longer it takes to converge, the greater the degree of degradation. Therefore, the degree of deterioration can be determined by measuring the determination time. In this way, it is sufficient to improve the resolution with respect to changes around the converging voltage, and it is not necessary to accurately measure the absolute values of the voltage, current and temperature of the secondary battery. Therefore, it is possible to provide a secondary battery deterioration determination device that accurately determines the degree of deterioration of the secondary battery while suppressing an increase in cost.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the deterioration determination apparatus of the secondary battery which concerns on this Embodiment. It is a timing chart which shows the change of the voltage at the time of discharge. It is a timing chart which shows the change of the voltage according to the degree of degradation. It is a flowchart which shows the control structure of the program performed by ECU which is a deterioration determination apparatus of the secondary battery which concerns on this Embodiment. It is a timing chart which shows operation | movement of ECU which is a deterioration determination apparatus of the secondary battery which concerns on this Embodiment.

Explanation of symbols

100 ECU, 102 counter unit, 200 battery, 300 load, 400
Discharge resistance device, 500 current sensor, 600 voltage sensor.

Claims (4)

A deterioration determination device that determines the degree of deterioration of a secondary battery,
Detection means for detecting the voltage of the secondary battery;
Discharging means for discharging the secondary battery until a predetermined time elapses;
A deterioration determination device for a secondary battery, comprising: deterioration determination means for determining the degree of deterioration based on a determination time until the detected voltage change converges after the secondary battery is discharged.   The deterioration determination device for a secondary battery according to claim 1, wherein the deterioration determination unit includes a unit for determining that the degree of deterioration of the secondary battery is larger as the determination time is longer.   The deterioration determination means includes a convergence determination means for determining that the change in the voltage has converged when the detected change in the voltage is equal to or less than a predetermined change after the secondary battery is discharged. The degradation determination apparatus of the secondary battery of Claim 1 or 2 containing.   The deterioration determination device for a secondary battery according to any one of claims 1 to 3, wherein the deterioration determination device is mounted on a vehicle.

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