JP2006343165A - Battery resistance measuring device - Google Patents

Abstract

To accurately measure the internal resistance of a battery.
A discharge unit 2 that discharges a discharge current I having a constant value from a battery 51, a current blocking unit 3 that blocks a discharge current I from the battery 51, and a current detection unit 4 that detects the discharge current I as a detection current. And a voltage detection unit 5 that detects the voltage V between both electrodes of the battery 51 as a detection voltage, and a calculation control unit 8. The calculation control unit 8 has a current value of the discharge current I after being cut off by the current cut-off unit 3. The time point when it becomes zero is detected based on the detected current, the electromotive force Vdc of the battery 51, a constant value, a detection voltage when discharging the discharge current I of a constant value, and the current value of the discharge current I The electrolyte resistance and reaction resistance of the battery 51 are calculated based on the detected voltage at the time when becomes zero.
[Selection] Figure 1

Description

  The present invention relates to a battery resistance measuring apparatus suitable for measuring battery resistance, particularly internal resistance of a fuel cell.

  As this type of battery resistance measuring device, a state determination device for a secondary battery disclosed in Japanese Patent Application Laid-Open No. 2000-299137 is known. In this secondary battery state determination device, the discharge is interrupted in a state where the secondary battery is discharged with a constant current. At this time, the voltage between both electrodes of the secondary battery rapidly increases immediately after the discharge is cut off, and then gradually increases with the elapsed time. This state determination device detects a voltage component corresponding to a sudden rise immediately after the interruption of the discharge and a voltage component that gradually rises thereafter, and detects the voltage value of each detected voltage component and a constant value at the time of discharge. Based on this, the electrolyte resistance and reaction resistance of the secondary battery (which are collectively referred to as internal resistance) are calculated (measured), and the state of the secondary battery is determined based on these calculated resistance values. .

In addition, this type of battery resistance measuring device generally detects a portion where the change in voltage between both ends changes abruptly, that is, a portion where an abrupt increase immediately after the interruption of the discharge ends (inflection point). Thus, a voltage component corresponding to a rapid rise immediately after the discharge is cut off and a voltage component that gradually rises thereafter are detected.
JP 2000-299137 A (page 12, FIG. 7)

  However, the above-described conventional battery resistance measuring apparatus has the following problems to be solved. That is, a lot of ringing occurs in the actual waveform of the voltage between both ends. For this reason, this battery resistance measuring device may not be able to accurately detect the inflection point with respect to the voltage between both ends due to ringing. It cannot be detected. Therefore, this battery resistance measuring device has a problem to be solved in that, when a large amount of ringing occurs in the voltage between both electrodes of the battery, the internal resistance of the battery may not be accurately measured.

  The present invention has been made to solve such a problem, and a main object of the present invention is to provide a battery resistance measuring apparatus capable of accurately measuring the internal resistance of a battery.

  In order to achieve the above object, a battery resistance measuring apparatus according to claim 1, wherein a discharge unit for discharging a discharge current of a constant value from the battery, a current blocking unit for cutting off the discharge current from the battery, and the discharge current are provided. A current detection unit for detecting as a detection current; a voltage detection unit for detecting a voltage between both electrodes of the battery as a detection voltage; and a measurement unit, wherein the measurement unit is configured to detect the discharge current after being cut off by the current cut-off unit. The time when the current value becomes zero is detected based on the detection current, the electromotive force of the battery, the constant value, the detection voltage when discharging the discharge current of the constant value, Based on the detected voltage when the current value of the discharge current becomes zero, the electrolyte resistance and reaction resistance of the battery are calculated.

  The battery resistance measuring device according to claim 2 is the battery resistance measuring device according to claim 1, wherein the current detection unit outputs a first detection signal whose amplitude changes in proportion to the current value of the discharge current. The detection current is generated, and the voltage detection unit generates a second detection signal whose amplitude changes in proportion to the voltage value of the voltage between the two electrodes as the detection voltage, and the first detection signal is the first detection signal. A first A / D conversion unit that converts the second detection signal into second digital data, and the measurement unit includes a first A / D conversion unit that converts the second detection signal into second digital data. Based on the first and second digital data, detection when the current value of the discharge current becomes zero, and the voltage between the electrodes when the discharge current is the constant current value and when the current value becomes zero As well as the electrolyte resistance and Executing a calculation of the reaction resistance.

  The battery resistance measuring device according to claim 3 is the battery resistance measuring device according to claim 2, further comprising a display unit and a control unit, wherein the measuring unit is provided every predetermined time after being interrupted by the current interrupting unit. The voltage change amount calculated based on the second digital data is sequentially divided by the current change amount calculated based on the first digital data every predetermined time to obtain the resistance value characteristic of the battery, The control unit displays the resistance value characteristic on the display unit.

  In the battery resistance measuring device according to the first aspect, the measuring unit detects the time when the current value of the discharge current becomes zero and detects the voltage between both electrodes based on the detected voltage. Therefore, according to this battery resistance measuring apparatus, even if a lot of ringing has occurred in the actual waveform of the voltage between the two electrodes, the voltage value at the inflection point of the voltage between the two electrodes can be accurately detected. The internal resistance (electrolyte resistance and reaction resistance) of the battery can be accurately measured based on the voltage value and the like.

  3. The battery resistance measuring apparatus according to claim 2, wherein the measuring unit is configured to determine the current value of the discharge current and the voltage between both electrodes based on the first and second digital data output from the first and second A / D converters. And the time point when the current value of the discharge current becomes zero is detected based on the calculated current value of the discharge current. Therefore, according to this battery resistance measuring apparatus, it is possible to accurately measure the change in the discharge current that becomes zero within a very short time after the stop of the discharge, based on the current value of the discharge current converted into digital data. . For this reason, as a result of being able to accurately detect the time point when the discharge current becomes zero, it is possible to more accurately detect the voltage value at the inflection point of the voltage between both electrodes. Therefore, according to this battery resistance measuring apparatus, the internal resistance (electrolyte resistance and reaction resistance) of the battery can be measured more accurately based on this voltage value and the like.

  In the battery resistance measuring apparatus according to claim 3, the voltage change amount calculated by the measuring unit based on the second digital data every predetermined time after the interruption by the current interruption unit is calculated at the same first digital time. The resistance value characteristic of the battery is obtained by sequentially dividing by the amount of current change calculated based on the data, and the control unit displays the resistance value characteristic on the display unit, thereby visually recognizing the electrolyte resistance and the reaction resistance. be able to.

  Hereinafter, the best mode of a battery resistance measuring apparatus according to the present invention will be described with reference to the accompanying drawings.

  First, an equivalent circuit of a battery 51 (specifically, a fuel cell) that is a measurement object of the battery resistance measuring apparatus 1 will be described with reference to FIG. The battery 51 includes a pair of electrodes 52 and 53, and the inside thereof is equivalently constituted by an electromotive force Vdc, an electrolyte resistance Rsol, a reaction resistance Rct, and an electric double layer capacitance Cdl. In the battery 51, the reaction resistance Rct and the electric double layer capacity Cdl are equivalently connected in parallel, and the parallel circuit, the electrolyte resistance Rsol, and the electromotive force Vdc are connected in series between the pair of electrodes 52 and 53. Yes.

  Next, the configuration of the battery resistance measuring apparatus 1 will be described. As shown in FIG. 1, the battery resistance measuring apparatus 1 includes a discharge unit 2, a current interrupt unit 3, a current detection unit 4, a voltage detection unit 5, two A / D conversion units 6 and 7, an arithmetic control unit 8 and a display. The unit 9 is provided. In this case, the discharge part 2 is connected between the electrodes 52 and 53 of the battery 51 via the current interrupting part 3. The discharge unit includes an electronic load (not shown) and is configured to discharge a discharge current I having a constant current value I1 from the battery 51. The current interrupting unit 3 is composed of, for example, a semiconductor switch such as a transistor or FET, or a mechanical switch such as a relay, and shifts to one of an on state and an off state under the control of the arithmetic control unit 8. The discharge part 2 is disconnected from the battery 51.

  The current detection unit 4 detects the discharge current I from the battery 51 as a detection current and generates a detection signal (first detection signal) S1 whose amplitude changes in proportion to the detected current value of the discharge current I. Output. The voltage detection unit 5 detects a voltage (voltage between both electrodes) V generated between both electrodes 52 and 53 of the battery 51 as a detection voltage, and the amplitude changes in proportion to the voltage value of the detected voltage V between both electrodes. A detection signal (second detection signal) S2 is generated and output. The A / D conversion unit 6 corresponds to the first A / D conversion unit in the present invention, converts the detection signal S1 into digital data (first digital data) D1 by sampling, and the arithmetic control unit 8 Output to. The A / D conversion unit 7 corresponds to the second A / D conversion unit in the present invention, converts the detection signal S2 into digital data (second digital data) D2 by sampling, and the arithmetic control unit 8 Output to. In this case, each of the A / D converters 6 and 7 performs a sampling operation at a predetermined sampling period in synchronization with a common sampling clock.

  The arithmetic control unit 8 corresponds to the measurement unit and the control unit in the present invention, and includes a CPU and an internal memory (both not shown). In this case, the current value I1 when the battery 51 is discharged by the discharge unit 2 is stored in the internal memory in advance. The arithmetic control unit 8 controls the on / off state of the current interrupting unit 3 by outputting a control signal S3. Further, the arithmetic control unit 8 executes an internal resistance measurement process based on the digital data D1 (current value of the discharge current I) and the digital data D2 (voltage value of the voltage V between both electrodes). Further, the arithmetic control unit 8 causes the display unit 9 to display the internal resistance (electrolyte resistance Rsol and reaction resistance Rct) of the battery 51 calculated by the internal resistance measurement process. The display unit 9 is configured by a display using, for example, a liquid crystal or a CRT.

  Next, the measurement operation of the internal resistance of the battery 51 by the battery resistance measuring device 1 will be described.

  First, the arithmetic control unit 8 outputs the control signal S3 to the current interrupting unit 3 to shift the current interrupting unit 3 from the off state to the on state. Thereby, since the discharge part 2 is connected to the battery 51, the discharge part 2 starts to discharge the discharge current I of the current value I1 to the battery 51. In this state, the current detection unit 4 detects the discharge current I and outputs a detection signal S1, and the A / D conversion unit 6 converts the detection signal S1 into digital data D1 and outputs it to the arithmetic control unit 8. The voltage detection unit 5 detects the voltage V between both electrodes of the battery 51 and outputs a detection signal S2, and the A / D conversion unit 7 converts the detection signal S2 into digital data D2 and outputs it to the arithmetic control unit 8. To do. The arithmetic control unit 8 detects the discharge current I and the interpolar voltage V through the A / D conversion units 6 and 7. Specifically, the control unit 8 calculates the current value of the discharge current I based on the digital data D1 each time new digital data D1 and D2 are input from the A / D conversion units 6 and 7, and the digital data Based on the data D2, the voltage value between the electrodes V is calculated and stored in the internal memory sequentially. Further, each time the calculation control unit 8 calculates the voltage value of the voltage between both electrodes V, for example, by obtaining a difference from the voltage value of the voltage between both electrodes V calculated previously, the rate of change of the voltage between the electrodes V ( Rate of increase).

  Next, the arithmetic control unit 8 outputs the control signal S3 to the current interrupting unit 3 after a predetermined time has elapsed from the start of the discharge by the discharging unit 2 (time t1), thereby changing the current interrupting unit 3 from the on state to the off state. To migrate. Thereby, since the battery 51 and the discharge part 2 are cut away, the discharge of the discharge current I from the battery 51 is stopped. At this time, as shown in FIG. 2, the discharge current I decreases substantially linearly (at a substantially constant rate of change) starting from the current value I1 at time t1, and becomes zero at time t2. (0A) is reached. Therefore, the arithmetic control unit 8 detects a time point (time t2) when the current value of the discharge current I reaches zero based on the digital data D1. In this case, since the circuit impedance at the time of current interruption is very high and ringing does not easily occur in the current waveform, the time t2 when the current value of the discharge current I reaches zero can be detected reliably and accurately. Therefore, it is possible to accurately calculate the voltage value V2 (voltage value at an inflection point described later) of the interpolar voltage V at time t2. On the other hand, as shown in FIG. 3, the voltage V between both electrodes of the battery 51 is maintained at a substantially constant voltage value V1 during the period in which the battery is discharged by the discharge unit 2 (period until time t1). Further, the voltage V between the two electrodes rises substantially linearly (at a substantially constant rate of increase) and suddenly from the stop of discharge (time t1) to time t2. Further, the voltage V between the two electrodes continues to rise gradually after the time t2 while the rate of increase gradually decreases, the rate of increase becomes substantially zero at time t3, and reaches the voltage value of the electromotive force Vdc of the battery 51. . Thus, since the rate of increase of the voltage between both electrodes V changes abruptly at time t2, the portion corresponding to time t2 becomes the inflection point of the voltage between both electrodes V. The arithmetic control unit 8 determines whether or not the voltage V between the electrodes has reached the electromotive force Vdc of the battery 51, whether or not the rate of increase of the voltage V between the electrodes is within a preset range (the rate of increase is approximately When the rate of increase of the voltage V between the two electrodes is within this range, the input of each digital data D1, D2, the calculation of the current value of the discharge current I, the distance between the two electrodes The calculation of the voltage value of the voltage V and the storage process of the calculated current value and voltage value in the internal memory are terminated.

Subsequently, the arithmetic control unit 8 executes an internal resistance measurement process based on the current value of the discharge current I and the voltage value of the voltage between both electrodes V stored in the internal memory, and performs an internal resistance (electrolyte) of the battery 51. Resistance Rsol and reaction resistance Rct) are measured. In this internal resistance measurement process, first, the arithmetic control unit 8 determines the voltage value V2 of the interpolar voltage V at time t2 (voltage value at the inflection point) and the voltage value V1 of the interpolar voltage V up to time t1. Is calculated, and the differential voltage Vsol is divided by the current value I1 of the discharge current I until time t1, thereby calculating the electrolyte resistance Rsol of the battery 51 and storing it in the internal memory. Next, the arithmetic control unit 8 calculates a differential voltage Vct between the voltage value (electromotive force Vdc) of the interpolar voltage V at time t3 and the voltage value V2 of the interpolar voltage V at time t2, and also calculates the differential voltage Vct. Is divided by the current value I1, the reaction resistance Rct of the battery 51 is calculated and stored in the internal memory. Subsequently, the arithmetic control unit 8 stops the discharge of the current value of the discharge current I and the voltage value of the voltage V between the electrodes stored in the internal memory (after interruption by the current interruption unit in the present invention: time t1). When the mth (m is an integer of 1 or more) acquired current value and voltage value are Im and Vm, respectively, the voltage value V1 is subtracted from the mth voltage value every predetermined time. By dividing the calculated voltage change amount (Vm−V1) by the current change amount (I1−Im) calculated by subtracting the current value I1 from the m-th current value every predetermined time, the following equation (1) Is sequentially calculated for the period from time t1 to time t3 and stored in the internal memory, and the internal resistance measurement process is terminated. The arithmetic control unit 8 calculates a time tm when the m-th current value and voltage value are sampled based on the sampling period of each of the A / D conversion units 6 and 7, and uses the time tm as the resistance Rm. And stored in the internal memory.
Resistance Rm = Voltage change (Vm−V1) / Current change (I1−Im) (1)

  Finally, the arithmetic control unit 8 reads the electrolyte resistance Rsol, reaction resistance Rct, resistance Rm, and time tm from the internal memory, and displays the electrolyte resistance Rsol and reaction resistance Rct on the display unit 9 as numerical values. Further, as shown in FIG. 4, the control unit 8 causes the display unit 9 to display each resistance Rm measured every predetermined time from time t1 to time t3 as the resistance value characteristic of the battery. In this case, the resistance value of the resistor Rm at time t2 corresponds to the electrolyte resistance Rsol of the battery 51, and the resistance value obtained by subtracting the resistance value of the electrolyte resistance Rsol from the resistance Rm at time t3 corresponds to the reaction resistance Rct. . Thereby, the time series data of the resistance Rm is displayed in a wave shape, and the electrolyte resistance Rsol and the reaction resistance Rct can be visually recognized. Further, the control unit 8 causes the display unit 9 to display a current response waveform based on the current value of the discharge current I stored in the internal memory as shown in FIG. Thereby, the information of the current interruption performance by the current interruption part 3 is acquirable. Moreover, the control part 8 displays the voltage response waveform based on the voltage value of the voltage V between both electrodes on the display part 9 as shown in FIG. As a result, measurement error information such as ringing and noise component superposition can be acquired from the voltage response waveform. Thus, the measurement of the internal resistance of the battery 51 by the battery resistance measuring device 1 is completed.

  As described above, in the battery resistance measuring apparatus 1, the arithmetic control unit 8 detects the time point when the current value of the discharge current I becomes zero based on the digital data D1, and the voltage V between the electrodes at this time point. The voltage value V2 is detected. Therefore, according to the battery resistance measuring apparatus 1, even if a lot of ringing occurs in the actual waveform of the voltage V between the electrodes, the voltage value V2 at the inflection point of the voltage V between the electrodes is accurately detected. As a result, the internal resistance (electrolyte resistance Rsol and reaction resistance Rct) of the battery 51 can be accurately measured based on the voltage value V2 and the like.

  Further, in this battery resistance measuring apparatus 1, the calculation control unit 8 determines the current value of the discharge current I and the voltage V between both electrodes V based on the digital data D1 and D2 output from the A / D conversion units 6 and 7. A voltage value is calculated, and a point in time when the current value of the discharge current I becomes zero is detected based on the calculated current value of the discharge current I. Therefore, according to the battery resistance measuring apparatus 1, the change in the discharge current I which becomes zero within a very short time from the stop of the discharge (time t1) based on the current value of the discharge current I converted into digital data. It can be measured accurately. For this reason, as a result of being able to accurately detect when the discharge current I becomes zero, it is possible to more accurately detect the voltage value V2 at the inflection point of the voltage V between both electrodes. Therefore, according to the battery resistance measuring apparatus 1, the internal resistance (electrolyte resistance Rsol and reaction resistance Rct) of the battery 51 can be measured more accurately based on the voltage value V2 and the like.

  Further, according to the battery resistance measuring apparatus 1, the calculation control unit 8 calculates the voltage change amount calculated based on the digital data D2 every predetermined time after the interruption by the current interruption unit 3 at the same predetermined time. By displaying the resistance value characteristic of the battery 51 sequentially obtained by dividing by the amount of current change calculated based on the above on the display unit 9, the electrolyte resistance Rsol and the reaction resistance Rct can be visually recognized.

  In addition, this invention is not limited to said structure. For example, two A / D converters 6 and 7 are used to convert the discharge current I and the interpolar voltage V, but the A / D conversion is performed by switching the discharge current I and the interpolar voltage V with a scanner. It is also possible to adopt a configuration in which the discharge current I and the voltage V between the two electrodes are converted into digital data D1 and D2 by outputting to the unit. Further, a printer or a plotter can be used as the display unit 9.

1 is a block diagram showing a configuration of a battery resistance measuring device 1. FIG. 2 is a waveform diagram of a discharge current I. FIG. It is a wave form diagram of the voltage V between both electrodes. 4 is a waveform diagram of resistance value characteristics of a battery 51. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery resistance measuring apparatus 2 Discharge part 3 Current interruption part 4 Current detection part 5 Voltage detection part 8 Calculation control part I Discharge current Rct Reaction resistance Rsol Electrolyte resistance V Voltage between both poles Vdc Battery electromotive force 51 Battery

Claims (3)

A discharge unit that discharges a discharge current of a constant value from the battery; a current blocking unit that blocks the discharge current from the battery; a current detection unit that detects the discharge current as a detection current; and a voltage between both electrodes of the battery. A voltage detection unit that detects the detection voltage, and a measurement unit;
The measuring unit detects a time point when the current value of the discharge current becomes zero after being interrupted by the current interrupting unit based on the detected current, and the electromotive force of the battery, the constant value, and the constant A battery resistance for calculating an electrolyte resistance and a reaction resistance of the battery based on the detection voltage when discharging a discharge current of the value and the detection voltage when the current value of the discharge current becomes zero measuring device. The current detection unit generates, as the detection current, a first detection signal whose amplitude changes in proportion to the current value of the discharge current,
The voltage detection unit generates, as the detection voltage, a second detection signal whose amplitude changes in proportion to the voltage value of the voltage between both electrodes,
A first A / D converter for converting the first detection signal into first digital data;
A second A / D converter that converts the second detection signal into second digital data;
The measurement unit detects when the current value of the discharge current becomes zero based on the first and second digital data, and when the discharge current becomes the constant current value and when the current value becomes zero. The battery resistance measuring device according to claim 1, wherein the calculation of the voltage between the electrodes and the calculation of the electrolyte resistance and the reaction resistance are performed. A display unit and a control unit;
The measuring unit calculates a voltage change amount calculated based on the second digital data every predetermined time after being interrupted by the current interrupting unit, based on the first digital data every predetermined time. Sequentially dividing by the amount to obtain the resistance characteristic of the battery,
The battery resistance measuring apparatus according to claim 2, wherein the control unit displays the resistance value characteristic on the display unit.

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