JP4918895B2 - Electric vehicle system - Google Patents

Description

  The present invention relates to an electric vehicle system.

Conventionally, when performing offset correction of a voltage sensor that detects the voltage of a battery mounted on a vehicle, the offset correction is performed while the vehicle is traveling in consideration of the offset error caused by the temperature change of the voltage sensor while the vehicle is traveling. What to do is disclosed in US Pat.
JP 2006-170889 A

  However, in the above invention, a switch is provided so that the input voltage to the voltage sensor becomes 0 V, and the offset error is obtained from the measured value of the battery monitoring device at this time, but the assembled battery is used as the battery of the vehicle. In such a case, the offset error in each cell is not obtained, and the voltage detection value cannot be corrected by the offset error for each cell. Therefore, when the offset error is obtained by the battery monitoring device, the offset correction cannot be performed accurately, the actual cell voltage varies, and the assembled battery cannot be used in a wide voltage range. There is a point.

  The present invention was invented in order to solve such problems, and has an object to accurately perform offset correction, accurately calculate a cell voltage, and to be usable in a wide voltage range in an assembled battery. To do.

The present invention includes an assembled battery in which a plurality of cells are connected in series, a vehicle driving motor that inputs and outputs power from the assembled battery, current detection means that measures a current flowing between the assembled battery and the motor, A battery monitoring device having a cell voltage detection circuit for detecting a voltage of each cell, and a cell for detecting a voltage of each cell when the current value is sufficiently small as an estimated open voltage of each cell Based on the correlation between the internal resistance and the SOC from the estimated open-circuit voltage detection means, the internal resistance calculation means for calculating the internal resistance of each cell by dividing the voltage of each cell by the current, and the internal resistance calculated by the internal resistance calculation means Then, based on the SOC calculated by the SOC calculating means for calculating the SOC and the SOC calculated by the SOC calculating means, the cell actual open voltage of each cell is estimated based on the correlation between the SOC and the cell open voltage. It comprises a voltage estimating unit discharge, the cell voltage offset error estimating means for calculating an offset error correction from the deviation between the actual open-circuit voltage and the estimated open-circuit voltage of the voltage of each cell voltage detection circuit.

  According to the present invention, the offset voltage for correcting the voltage detected by each cell voltage detection circuit is calculated based on the correlation between the SOC of the cell and the internal resistance, thereby correcting the cell voltage by the offset error calculated for each cell. Therefore, the offset correction can be performed accurately, the cell voltage can be calculated accurately, the assembled battery can be used in a wider voltage range, the assembled battery can be reduced in size, and the cost can be reduced.

  A drive system for an electric vehicle according to a first embodiment of the present invention will be described with reference to the schematic configuration diagram of FIG.

  The drive system for an electric vehicle according to this embodiment includes an AC motor (hereinafter referred to as a motor) 1, an assembled battery 2 that supplies electric power to the motor 1, and an inverter 3 that is disposed between the motor 1 and the assembled battery 2. And a battery monitoring device 4 that monitors the voltage of the assembled battery 2. Furthermore, a voltage sensor 6 that detects the voltage of the entire assembled battery 2, a temperature sensor (temperature measuring means) 7 that detects the temperature in the vicinity of the assembled battery 2, and a temperature sensor (battery that detects the temperature in the vicinity of the battery monitoring device 4 (Monitoring device temperature measuring means) 8, a current sensor (current detecting means) 9 for detecting a current flowing from the assembled battery 2, and a temperature sensor 10 for detecting a temperature in the vicinity of the current sensor 9. The temperature sensor 8 may detect the temperature inside the battery monitoring device 4.

  The motor 1 is operated by AC power supplied via the inverter 3 and generates torque for driving the vehicle.

  The assembled battery 2 is a battery in which a plurality of cells 11 are connected in series, supplies power to the motor 1, and is charged by the external charger 12. The motor 1 and the assembled battery 2 are electrically connected or disconnected by switching ON / OFF of the high voltage relay 13.

  The inverter 3 converts the DC power supplied from the assembled battery 2 into AC power, and supplies the converted AC power to the motor 1.

  The battery monitoring device 4 will be described with reference to FIG. FIG. 2 is a schematic block diagram of the battery monitoring device 4.

  The battery monitoring device 4 includes a cell voltage detection circuit 20 having an amplification circuit 20a that amplifies each cell voltage, and a capacity adjustment circuit unit 21 that adjusts the SOC (state of charge) of each cell 11 and aligns the voltage of each cell 11. A CPU (cell voltage offset error estimating means) 22 for calculating an offset error of each cell 11; an interface circuit 23 for inputting an output of the voltage sensor 6 or the like to the A / D port of the CPU 22; EEPROM (storage device) 24. In this embodiment, the amplification factor by the amplifier circuit is 1.

  The cell voltage detection circuit 20 generates an error in the voltage to be detected depending on the element to be used. In this embodiment, the cell voltage detection circuit 20 corrects the voltage to be detected using an offset error described later to accurately detect the cell voltage. The error in the cell voltage detection circuit 20 includes an offset error and a gain error. By making the amplification factor in the amplifier circuit 20a 1 time, the offset error becomes dominant and the gain error can be ignored. it can.

  The capacity adjustment circuit unit 21 controls ON / OFF of a switch provided inside, thereby controlling a current flowing through a resistor provided therein, adjusting the SOC of each cell 11, and adjusting the voltage of each cell 11. Align.

  As shown in FIG. 3, the CPU 22 includes a capacity adjustment unit 30, an SOC calculation unit 31, a cell voltage detection circuit unit error calculation unit 32, and a cell voltage detection error correction calculation unit 33.

  Here, the capacity adjustment control in which the capacity adjustment unit 30 adjusts the voltage variation in each cell 11 of the assembled battery 2 will be described with reference to the flowchart of FIG.

In step S100, the current is detected by the current sensor 9, and the cell voltage of each cell 11 is detected by the battery monitoring device 4. Then, the internal resistance R1 of each cell 11 is estimated from the map shown in FIG. FIG. 5 shows the cell 11 created by detecting and plotting the voltage and current values of each cell 11 after performing capacity adjustment control, which is the main control, and drawing an approximate line based on the plotted points. It is a map which calculates | requires the estimated value of internal resistance. The slope of the approximate line in FIG. 5 is the internal resistance R1 of the cell 11. The map in FIG. 5 is created for each cell 11. And using the detected current, cell voltage, and cell internal resistance R1,
Cell open-circuit voltage = cell voltage− (current × cell internal resistance) (1)
Thus, the cell open voltage V1 is calculated.

  In step S101, it is determined whether an offset error, which will be described in detail later, is stored. If the offset error is stored, the offset error is read. If the offset error is not stored, the offset error is read. Is zero.

In step S102, the cell open voltage V1 detected in step S100 by the cell voltage detection error correction calculation unit 33 and the offset error read out in step S101 are used.
Cell open voltage correction value = cell open voltage + offset error (2)
Thus, a cell open voltage correction value is calculated.

  In step S103, the lowest cell open voltage correction value having the smallest voltage among the cell open voltage correction values calculated in step S102 is detected, and each cell open voltage correction value and the minimum cell open voltage correction value are In the cell 11 where the deviation is calculated and the cell open voltage correction value is larger than the minimum cell open voltage, by passing a current through the bypass circuit in the capacity adjustment circuit unit 21, power corresponding to the calculated deviation is consumed, Adjust the open circuit voltage of each cell.

  In step S104, it is determined whether or not the deviations of the cells 11 calculated in step S103 are all zero. When the deviations of all the cells 11 are all zero, that is, when the cell open voltages of all the cells 11 become the minimum cell open voltage correction value, this control is finished. When even one cell 11 has no deviation, the capacity adjustment circuit unit 21 adjusts the open voltage of each cell 11.

  By performing the above capacity adjustment control while traveling, the open voltage of each cell 11 can be adjusted, the assembled battery 2 can be used in a wider voltage range, the assembled battery 2 can be reduced in size, The cost of the vehicle can be reduced.

  In step S100, the internal resistance R1 of the cell 11 is estimated from the map shown in FIG. 5. However, the internal resistance of the assembled battery 2 is estimated from the voltage and current values of the assembled battery 2, and the internal resistance is calculated as the number of cells in series. The internal resistance of the cell 11 may be estimated by dividing by.

  Next, an offset error calculation method will be described with reference to the flowchart of FIG.

  In step S200, the voltage of each cell 11 is detected, and the current is detected by the current sensor 9.

In step S201, the SOC calculation unit 31 uses the voltage and current values detected in step S200 to set the internal resistance R2 of each cell 11 to
Internal resistance = voltage / current ... Formula (3)
(Step S201 constitutes an internal resistance calculating means).

  In step S202, the SOC calculation unit 31 calculates the SOC from the internal resistance R2 calculated in step S201 using a map showing the correlation between the internal resistance and the SOC shown in FIG. The internal resistance of the cell 11 varies depending on the SOC, and as shown in FIG. 7, the internal resistance of the cell increases as the SOC increases. By preparing such a map in advance, the SOC of each cell 11 can be calculated from the internal resistance R2 calculated in step S201 (step S202 constitutes an SOC calculation unit).

  In step S203, the cell voltage detection circuit unit error calculation unit 32 calculates the cell open voltage (actual open voltage) V2 of each cell 11 using the map showing the correlation between the SOC and the cell open voltage shown in FIG. . The cell open voltage V2 varies depending on the SOC. As shown in FIG. 8, the cell open voltage V2 increases as the SOC increases. By preparing such a map in advance, the cell open voltage V2 can be calculated from the SOC calculated in step 202 (step S203 constitutes the cell actual open voltage estimation means).

  In this embodiment, the internal resistance R2 of the cell 11 is calculated, the SOC is calculated based on the calculated internal resistance R2 of the cell 11, and the cell open circuit voltage V2 is calculated based on the calculated SOC.

  In step S204, the cell open circuit voltage (estimated open circuit voltage) V1 is calculated by the cell voltage detection circuit unit error calculation unit 32. In this embodiment, the cell open voltage V1 is detected based on the formula (1). For example, at the time of idling or the like, the voltage of the cell 11 is settled and the current value becomes sufficiently small, so that the second term of the equation (1) can be regarded as zero, and the cell open voltage V1 is detected by the battery monitoring device 4 (Step S204 constitutes a cell estimated open circuit voltage detection means).

In step S205, the offset error of the cell voltage detection circuit 20 is obtained by calculating the deviation between the cell open voltage V2 and the cell open voltage V1 in each cell 11 by the cell voltage detection circuit unit error calculation unit 32.
Offset error = battery open voltage V2−battery open voltage V1 Equation (4)
Calculated by

  In step S206, the cell voltage detection error correction calculation unit 33 stores the offset error of each cell 11 in the EEPROM 24.

  By the above control, the offset error in each cell 11 is calculated during traveling, and the value is stored in the EEPROM 24, so that the equipment adjustment time at the time of vehicle production and shipment can be shortened and the work efficiency can be improved. it can. Moreover, the voltage of each cell 11 can be detected with high accuracy by correcting the voltage value of each cell 11 detected by the battery monitoring device 4 using the offset error calculated and stored during traveling.

  In order to calculate the offset error with high accuracy, the calculation of the offset error may be limited when the following conditions are satisfied.

(1) When the degradation coefficient of the cell is equal to or greater than a threshold value The degradation coefficient of the cell 11 is calculated, and when the degradation coefficient is equal to or greater than a preset threshold value, an offset error is calculated. Here, the internal resistance R1 is estimated from the map of FIG. 5, and this internal resistance R1 and the initial internal resistance set at the time of manufacture (new time) and stored in the EEPROM 24 are used.
Deterioration coefficient = initial internal resistance / internal resistance × 100 (5)
To calculate the degradation coefficient. The cell 11 is deteriorated by use, and the internal resistance increases as the deterioration progresses. However, when the deterioration coefficient is equal to or higher than a preset threshold (first threshold, for example, 90%), that is, when the deterioration has not progressed so much. Only, the offset error is calculated. Thereby, when the deterioration of the cell 11 progresses, it is possible to suppress the deterioration of the accuracy of the cell voltage detection value due to the deterioration of the cell 11 without calculating the offset error.

(2) When the current increases to a threshold value The vehicle accelerates from the state where the vehicle is stopped or idled and the internal resistance of the cell 11 is settled, and the current value exceeds a certain threshold value (second threshold value). In this case, an offset error is calculated. For example, the current value corresponding to the power consumption in the auxiliary machine is stored when the vehicle is stopped and the current value is offset when the current value exceeds the threshold from the stored current value corresponding to the vehicle stopped. Calculate the error. The relationship between the input / output current value to the cell 11 and the SOC is as shown in FIG. 9, and the output current extracted from the cell 11 increases when the SOC is large, and decreases when the SOC is small. In addition, the input current when the cell 11 is charged increases when the SOC is small, and decreases when the SOC is large. The current value in FIG. 9 is the maximum input / output current with respect to the SOC, and the threshold is calculated according to the SOC based on the map showing the relationship between the SOC and the current shown in FIG. The frequency of calculating the offset error may be increased as a value lower than the maximum input / output current. Thus, since the offset error is calculated when the internal resistance of the cell 11 is settled, it is possible to suppress deterioration in accuracy of the cell voltage detection value due to fluctuation of the internal resistance.

(3) When the voltage fluctuation is in the SOC range When the voltage fluctuation is in the SOC range, the offset error is calculated. Here, in the map (control means) showing the correlation between the SOC and the voltage fluctuation shown in FIG. 10, the offset error is calculated in the SOC range where the voltage fluctuation is relatively large. The map of FIG. 10 shows the voltage fluctuation that is the product of the internal resistance and the current based on the map that shows the correlation between the SOC and the input / output current shown in FIG. 9 and the correlation between the SOC and the internal resistance shown in FIG. It is a map which shows the correlation with SOC. In the SOC region where the voltage fluctuation is relatively large, the influence of the detection value noise and the calculation error due to the number of bits is relatively small with respect to the voltage to be detected, and the accuracy of the cell voltage detection value can be improved.

  Only when the above conditions are satisfied, an offset error can be calculated, an accurate offset error can be set, and the voltage of the cell 11 can be detected with high accuracy.

  The effect of 1st Embodiment of this invention is demonstrated.

  Even if the open-circuit voltages are apparently uniform in the cell voltage detection circuit for detecting the voltage of each cell (FIG. 11 (a)), when current flows, voltage variation occurs between the cells 11 ( FIG. 11B).

  In order to correct the variation, a switch 41 and a resistor 44 are provided in a cell voltage detection circuit that detects the voltage of each cell 11 in the battery monitoring device 40 as shown in FIG. The voltage can be adjusted by the capacity adjustment circuit unit 21 based on the value. In FIG. 12, the same reference numerals as those in FIG. 2 are assigned to the same functions as those of the battery monitoring device 4 in FIG. 2.

  However, in the battery monitoring device 40 as shown in FIG. 12, it is necessary to provide elements such as the switch 41 and the resistor 44, which increases the cost.

  In this embodiment, the cell open voltage of each cell 11 is detected by using the offset error estimated using the correlation between the internal resistance R2 of the cell 11 and the SOC, so that the cell open voltage is converted into a cell voltage detection circuit. It is possible to detect accurately without providing an element such as a switch in 20. Therefore, the assembled battery 2 can be reduced in size and cost can be suppressed. In addition, since the offset error is detected and updated when the vehicle is traveling, the adjustment time at the time of production and shipment of the vehicle can be shortened, and the working efficiency can be improved.

  The offset error detects the voltage and current value of the cell 11 after the vehicle is started, calculates the internal resistance R2 based on the voltage and current value, and calculates the cell open voltage V2 from the internal resistance R2. Then, the deviation between the cell open voltage V2 and the cell open voltage V1 is stored in the EEPROM 24 as an offset error, and when the voltage of the cell 11 is detected, the voltage of the cell 11 is corrected by correcting the stored offset error. It can be calculated accurately.

  The degradation coefficient of the cell 11 is calculated. When the degradation coefficient is larger than the threshold value and the degradation of the cell 11 has not progressed much, the offset error is calculated. When the degradation of the cell 11 has progressed, the offset error is calculated. By avoiding this, it is possible to prevent the offset error whose accuracy has deteriorated due to the deterioration of the cell 11 from being calculated, and to prevent the accuracy of the cell voltage detection value from being deteriorated.

  Further, an offset error is calculated when the current value exceeds the threshold value from a state where the internal resistance of the cell 11 is calm, for example, when the vehicle is stopped or idling. By calculating the offset error when the variation of the internal resistance of the cell 11 is small, it is possible to prevent the accuracy of the cell voltage detection value from deteriorating due to the variation of the internal resistance.

  Further, by detecting the offset error in the SOC range where the internal resistance of the cell 11 is large, it is possible to reduce the influence of the detection error on the voltage of the detected cell 11 and the calculation error due to the number of bits. The voltage can be calculated with high accuracy.

  Next, a second embodiment of the present invention will be described.

  Since the configuration of the drive system for the electric vehicle in this embodiment is the same as that in the first embodiment, description thereof is omitted here.

  A method for calculating the offset error will be described with reference to the flowchart of FIG.

  In step S300, the voltage of each cell 11 is detected, and the current is detected by the current sensor 9.

In step S301, the SOC calculation unit 31 sets the internal resistance R2 of each cell 11 according to the detected voltage and current.
Internal resistance = voltage / current ... Formula (3)
Calculated by

  In step S <b> 302, the temperature sensor 7 detects the temperature of the assembled battery 2. Then, the temperature coefficient is calculated from the detected temperature from a map showing the correlation between the temperature of the assembled battery and the temperature coefficient in FIG. The temperature of the assembled battery 2 affects the correlation between the SOC and the internal resistance of the cell 11, and as shown in FIG. 15, the internal resistance of the cell increases with respect to a certain SOC as the temperature decreases.

In step S303, the internal resistance R2 calculated in step S301 is determined based on the temperature and temperature coefficient of the assembled battery calculated in step S302.
Corrected internal resistance = Internal resistance × Temperature coefficient × Battery temperature ... Equation (6)
Thus, the corrected internal resistance is calculated. As a result, the offset error can be accurately calculated in consideration of the change in the internal resistance R2 of the cell 11 due to the temperature of the assembled battery 2.

  Since the control from step S304 to step S308 is the same as the control from step S202 to step S206 of the first embodiment, description thereof is omitted here. In this embodiment, the corrected internal resistance is used instead of the internal resistance R2 of the first embodiment in step S304.

  Note that the correction of this embodiment may be performed only in a temperature range in which the internal resistance is greater than a predetermined value.

  With the above control, the voltage of the cell 11 can be calculated more accurately.

  The effect of 2nd Embodiment of this invention is demonstrated.

  The temperature in the vicinity of the assembled battery 2 is detected by the temperature sensor 7, and the internal resistance R <b> 2 is corrected by the temperature of the assembled battery 2. Although the internal resistance of the cell 11 varies depending on the temperature of the assembled battery 2, in this embodiment, the internal resistance R2 of the cell 11 is corrected based on the temperature of the assembled battery 2. Can be detected more accurately.

  Next, a third embodiment will be described.

  In this embodiment, the CPU 22 further includes a cell voltage detection temperature error correction calculation unit 34 shown in FIG.

  Next, an offset error calculation method according to this embodiment will be described with reference to the flowchart of FIG.

  Since the control from step S400 to step S405 is the same as the control from step S200 to step 205 of the first embodiment, a description thereof is omitted here.

  In step 406, the offset error of each cell 11 is stored in the EEPROM 24 by the cell voltage detection error correction calculation unit 33. Further, the temperature of the battery monitoring device 4 is detected by the temperature sensor 8 and stored in the EEPROM 24.

  Next, cell voltage correction control performed by the cell voltage detection temperature error correction calculation unit 34 will be described with reference to the flowchart of FIG.

  In step S500, the temperature of the battery monitoring device 4 is detected by the temperature sensor 8.

  In step S501, the offset error stored in the EEPROM 24 and the temperature of the battery monitoring device 4 when the offset error is stored are read.

  In step S502, the temperature difference between the stored temperature of the battery monitoring device 4 and the current temperature of the battery monitoring device 4 is calculated.

  In step S503, the temperature coefficient of the offset error is calculated from the map showing the correlation between the temperature of the battery monitoring device 4 and the temperature coefficient of the offset error shown in FIG. The map in FIG. 19 is obtained in advance by experiments or the like.

  The map in FIG. 19 is created as follows. First, an accurate voltage is applied to the cell voltage detection circuit 20 of the battery monitoring device 4. The difference between the detected value at this time and the applied voltage value is an offset error. Change the temperature to find the temperature at several points and the offset error at that temperature. Then, when the average value of the offset error in the cell voltage detection circuit 20 for each temperature is obtained and a curve is drawn, a curve shown in FIG. 20 is obtained. And the map of FIG. 19 is created by calculating | requiring the inclination of the curve in each temperature. For each cell 11, the cell voltage detection circuit 20 has a different offset error in a range of about ± 50 mV. If the cell voltage detection circuit 20 is the same, the characteristics are almost the same as shown in FIG. It becomes.

In step S504, from the stored offset error, temperature difference, and temperature coefficient,
Cell voltage correction value = offset error + temperature difference × temperature coefficient (7)
To calculate the cell voltage correction value of each cell.

  By correcting the offset error based on the temperature of the battery monitoring device 4 by the above control, the voltage of the cell 11 can be accurately calculated.

  The cell voltage correction value is not stored for temperature correction during use.

  The effect of the third embodiment of the present invention will be described.

  Although the voltage detected by the battery monitoring device 4 is affected by the temperature of the battery monitoring device 4, in this embodiment, the offset error is corrected based on the temperature of the battery monitoring device 4, so that the voltage of the cell 11 is more accurately determined. Can be calculated.

  Next, a fourth embodiment of this embodiment will be described with reference to FIG.

  In this embodiment, the CPU 22 further includes a vehicle state determination unit 35 and a charge pattern control unit 36.

  A method for calculating the offset error of this embodiment will be described with reference to the flowchart of FIG.

  In step S <b> 600, the vehicle state determination unit 35 determines whether the vehicle is stopped and whether the assembled battery 2 is charged by the external charger 12. And when a vehicle stops and the assembled battery 2 is charged, it progresses to step S601.

  In step S <b> 601, the voltage adjustment of each cell 11 is performed by the capacity adjustment unit 30. This voltage adjustment is performed by executing the control from step 100 to step 104 of the first embodiment.

  In step S602, the charging pattern control unit 36 temporarily stops charging from the external charger 12 until a predetermined time has elapsed. The predetermined time is a time (about several minutes) until the internal resistance of the assembled battery 2 settles, and is a preset time.

  In step S603, a charging current pattern is set. In this embodiment, a charging current pattern having a predetermined pulse waveform shown in FIG. 23 is set. This charging current pattern is performed at a predetermined cell voltage sampling period and with a predetermined charging current value, a predetermined pulse time, and the number of pulses.

The charging current value of this pulse waveform is determined by the chargeable power of the external charger 12 and the voltage of the assembled battery 2,
Charging current value = Chargeable power of external charger / Battery voltage ... Equation (8)
Is calculated by

  The cell voltage sampling period is a period determined in advance by experiments or the like so as not to overlap with the period of vehicle noise. In this embodiment, since the cycle of the vehicle noise is the cycle of the external charger 12 because the vehicle is stopped, the cell voltage sampling cycle is set so as not to overlap the cycle of the external charger 12. The Note that the cell voltage sampling period is preferably shortened in order to reduce the influence of discretization.

  The pulse time is a charge time per pulse, and when this pulse time becomes long, the internal resistance changes due to the bias of ions inside each cell 11 when a charge current is passed. If the number of pulses increases, the influence of noise can be reduced when the cell voltage values are averaged. However, if the number is too large, the SOC changes and the internal resistance of the cell 11 changes. Therefore, the pulse time and the pulse number are set so that the product of the charging current, the pulse time, and the pulse number is sufficiently smaller than the cell capacity. As a result, the influence of the current flowing by this control on the SOC and internal resistance of the cell 11 can be reduced.

  Since the control from step S604 to step S610 is the same control as the control from step S200 to step S206 of the first embodiment, description thereof is omitted here.

  The effect of 4th Embodiment of this invention is demonstrated.

  In this embodiment, when charging is performed by the external charger 12, a charging pattern that has a small effect on the SOC and internal resistance of the assembled battery 2 is set, and the offset error is calculated at that time, so that the offset error can be accurately determined. The voltage of the cell 11 can be accurately detected.

  It goes without saying that the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea.

It is a schematic block diagram of the drive system of the electric vehicle system of 1st Embodiment of this invention. It is a schematic block diagram of the battery monitoring apparatus of 1st Embodiment of this invention. It is a schematic block diagram of CPU of 1st Embodiment of this invention. It is a flowchart which shows the capacity | capacitance adjustment control of 1st Embodiment of this invention. It is a map which calculates the internal resistance of a cell. It is a flowchart for calculating the offset error of the first embodiment of the present invention. It is a map which shows the correlation of internal resistance and SOC. It is a map which shows the correlation with SOC and a cell open circuit voltage. It is a map which shows correlation with SOC and the maximum input / output current of a cell. It is a map which shows the correlation with SOC and a voltage fluctuation. (A) It is a schematic diagram which shows the state in which the voltage of a cell is seemingly equal. (B) It is a schematic diagram which shows the state at the time of taking out an electric current from the state of (a). It is a schematic block diagram of the battery monitoring apparatus when not using this invention. It is a flowchart for calculating the offset error of the second embodiment of the present invention. It is a map which shows the correlation with an assembled battery and a temperature coefficient. It is a map which shows the correlation of SOC and internal resistance which changes with the temperature of a cell. It is a one part schematic block diagram of CPU of 3rd Embodiment of this invention. It is a flowchart for calculating the offset error of the third embodiment of the present invention. It is a flowchart which shows the cell voltage correction control of 3rd Embodiment of this invention. It is a map which shows the correlation with the temperature of a battery monitoring apparatus, and the temperature coefficient of offset error. It is a map which shows the correlation with the temperature of a battery monitoring apparatus, and an offset error. It is a schematic block diagram of CPU of 4th Embodiment of this invention. It is a flowchart for calculating the offset error of the fourth embodiment of the present invention. It is a map which shows the charging current pattern of 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Assembly battery 4 Battery monitoring apparatus 7 Temperature sensor (temperature measurement means)
8 Temperature sensor (battery monitoring device)
9 Current sensor (current detection means)
11 cell 22 CPU (cell voltage offset error estimating means)
24 EEPROM (storage device)

Claims (8)

An assembled battery in which a plurality of cells are connected in series;
A vehicle driving motor that inputs and outputs power from the assembled battery;
Current detection means for measuring a current flowing between the assembled battery and the motor;
A battery monitoring device having a cell voltage detection circuit for detecting the voltage of each cell, and an electric vehicle system comprising:
Cell estimated open-circuit voltage detecting means for detecting the voltage of each cell when the current value is sufficiently small as the estimated open-circuit voltage of each cell;
Internal resistance calculation means for calculating the internal resistance of each cell by dividing the voltage of each cell by the current;
SOC calculating means for calculating SOC based on the correlation between the internal resistance and SOC from the internal resistance calculated by the internal resistance calculating means;
Cell actual open-circuit voltage estimating means for estimating the actual open-circuit voltage of each cell based on the correlation between the SOC and the cell open-circuit voltage from the SOC calculated by the SOC calculating means;
An electric vehicle system comprising cell voltage offset error estimation means for calculating an offset error for correcting a voltage for each cell voltage detection circuit from a deviation between the actual open voltage and the estimated open voltage . Temperature measuring means for measuring the temperature of the assembled battery,
  The electric vehicle system according to claim 1, wherein the cell voltage offset error estimation unit corrects the offset error according to a temperature of the assembled battery. Battery monitoring device temperature measuring means for measuring the temperature around or in the battery monitoring device;
  A storage device provided in the battery monitoring device,
  A temperature characteristic of a temperature of a cell voltage detection circuit provided in the battery monitoring device and a temperature coefficient of an offset error is stored in advance, and the estimated offset error is corrected from a temperature characteristic map. Item 4. The electric vehicle system according to Item 1. 4. The electric vehicle system according to claim 1, wherein the cell voltage offset error estimation unit includes a limiting unit that limits input / output by SOC and provides an SOC range in which error estimation is performed. 5. . Sampling multiple points of current and voltage during travel, performing linear regression, calculating internal resistance from the slope, and estimating the error when the ratio of the internal resistance calculated from the slope to the internal resistance at the time of a new product is greater than or equal to the first threshold The electric vehicle system according to any one of claims 1 to 4, wherein: The electric vehicle system according to claim 1, wherein the electric vehicle system has a charging function and estimates an offset error at the time of charging. The electric vehicle system according to claim 6, wherein an offset error is estimated at a specific charging pattern. The electric vehicle system according to claim 1, wherein the offset error is estimated when the vehicle is traveling.

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