WO2022201915A1

WO2022201915A1 - Battery device

Info

Publication number: WO2022201915A1
Application number: PCT/JP2022/004620
Authority: WO
Inventors: 将且堀口; 正規内山
Original assignee: 株式会社デンソー
Priority date: 2021-03-23
Filing date: 2022-02-07
Publication date: 2022-09-29
Also published as: JP7468420B2; JP2022147801A

Abstract

This battery device comprises: a detection unit; a level shifter; an AD conversion unit; a storage unit; and a calculation unit. The detection unit detects the closed circuit voltage of a plurality of electrically-connected battery cells. The level shifter adjusts a gain and an offset of the detected closed circuit voltage. The AD conversion unit converts the closed circuit voltage, of which the gain and offset were adjusted, to a digital signal. The storage unit stores: battery information including a closed circuit voltage; and conversion unit information related to ideal characteristics and actual characteristics which serve as input/output characteristics of an input voltage and an output voltage of the AD conversion unit. The calculation unit adjusts at least the gain and/or the offset so as to narrow a difference between the closed circuit voltage stored in the storage unit and an input voltage at an intersection of the actual characteristics and the ideal characteristics.

Description

battery device

Cross-reference to related applications

This application is based on Patent Application No. 2021-49207 filed in Japan on March 23, 2021, and the content of the underlying application is incorporated by reference in its entirety.

The disclosure described in this specification relates to a battery device.

Patent Document 1 discloses a capacity adjustment device that equalizes the SOC of a plurality of lithium secondary batteries.

JP 2010-141957 A

The closed-circuit voltage of lithium secondary batteries is used to equalize the SOCs of multiple lithium secondary batteries. Therefore, it is required to improve the detection accuracy of the closed circuit voltage.

An object of the present disclosure is to provide a battery device with improved detection accuracy of the closed circuit voltage.

A battery device according to an aspect of the present disclosure includes a detection unit that detects closed circuit voltages of a plurality of electrically connected battery cells;
a level shifter that adjusts the gain and offset of the closed circuit voltage detected by the detector;
an AD converter that converts the closed-circuit voltage whose gain and offset are adjusted by the level shifter into a digital signal;
a storage unit for storing battery information including closed-circuit voltage and conversion unit information related to actual characteristics and ideal characteristics as input/output characteristics of the input voltage and output voltage of the AD conversion unit;
and an arithmetic unit that narrows the difference between the input voltage at the intersection of the actual characteristic and the ideal characteristic and the closed circuit voltage stored in the storage unit by adjusting at least one of the gain and the offset.

According to this, it is expected that the detection accuracy of the closed circuit voltage will be improved.

It should be noted that the reference numbers in parentheses above merely indicate the correspondence with the configurations described in the embodiments described later, and do not limit the technical scope in any way.

1 is a block diagram showing a battery device and an assembled battery; FIG. It is a graph chart which shows the characteristic of SOC and OCV. FIG. 3 is a graph showing the relationship between actual characteristics and ideal characteristics; FIG. 10 is a graph diagram showing the relationship between the ideal characteristics and the actual characteristics; FIG. 5 is a graph showing offset adjustment; FIG. 5 is a graph diagram showing gain adjustment; 4 is a flowchart for explaining voltage detection; 4 is a timing chart for explaining voltage detection; 4 is a flowchart for explaining voltage detection; 4 is a flowchart for explaining voltage detection;

A plurality of modes for carrying out the present disclosure will be described below with reference to the drawings. In each form, the same reference numerals may be given to the parts corresponding to the matters described in the preceding form, and overlapping explanations may be omitted. When only a part of the configuration is described in each form, the previously described other forms can be applied to other parts of the configuration.

It is possible to combine parts that are specifically stated to be combinable in each embodiment. In addition, if there is no particular problem with the combination, it is possible to partially combine the embodiments, the embodiments and the modified examples, and the modified examples even if it is not explicitly stated that the combination is possible. be.

<First Embodiment>
A first embodiment will be described with reference to FIGS. 1 to 7. FIG.

A battery device 100 and an assembled battery 200 are shown in FIG. The battery device 100 and the assembled battery 200 are mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle. The electric vehicles include passenger cars, buses, construction vehicles, agricultural machinery vehicles, and the like.

The battery device 100 monitors and controls the state of the assembled battery 200 . The assembled battery 200 supplies power to various in-vehicle devices such as an electric motor that provides propulsion to the electric vehicle.

<Battery pack>
The assembled battery 200 has a plurality of battery stacks 210 . Each of the plurality of battery stacks 210 has a plurality of battery cells 220 electrically connected in series. As the battery cell 220, a secondary battery such as a lithium-ion secondary battery, a nickel-hydrogen secondary battery, or an organic radical battery can be employed. The output voltage of the battery cells 220 connected in series is the output voltage of the battery stack 210 . In FIG. 1, a plurality of battery cells 220 included in one battery stack 210 are shown surrounded by dashed lines.

The plurality of battery stacks 210 are electrically connected in series or in parallel. In this embodiment, a plurality of battery stacks 210 are electrically connected in series. The output voltage of the assembled battery 200 is the sum of the output voltages of the plurality of battery stacks 210 connected in series. Power supply power dependent on this output voltage is supplied to various vehicle-mounted devices.

A physical quantity sensor 230 that detects the physical quantity of the battery cell 220 is provided in each of the plurality of battery stacks 210 . Physical quantities detected by the physical quantity sensor 230 include, for example, the temperature and current of the battery cell 220 .

The physical quantity detected by the physical quantity sensor 230 is used for estimating the SOC of each of the battery cells 220, the battery stack 210, and the assembled battery 200. SOC is an abbreviation for state of charge. SOC corresponds to the amount of charge.

The SOC is reduced by supplying the above-mentioned power supply power to various on-vehicle devices. Also, the battery cell 220 self-discharges. Therefore, the SOC decreases even when the power supply is not supplied.

This reduction in SOC is improved by supplying charging power to the assembled battery 200 from a charging device such as a desk lamp provided outside the vehicle, for example. The supply of charging power from this charging device to the assembled battery 200 is controlled by the battery device 100 . The battery device 100 controls charging of the assembled battery 200 while transmitting/receiving a CPLT signal to/from a charging device via wiring (not shown).

It should be noted that the quality and environment of the plurality of battery cells 220 are not uniform. Therefore, the SOCs of the plurality of battery cells 220 vary. This variation is improved by an equalization process, which will be described later.

<OCV, CCV, SOC>
The battery cell 220 has internal resistance. Therefore, there is a difference between the actual cell voltage corresponding to the SOC of the battery cell 220 and the cell voltage detected by the monitoring unit 10 by this internal resistance and the voltage drop corresponding to the current flowing through the battery cell 220 .

In the following, the actual cell voltage corresponding to the SOC of the battery cell 220 is indicated as open circuit voltage OCV as necessary. A cell voltage detected by the monitoring unit 10 is indicated as a closed circuit voltage CCV. Assume that the internal resistance R is the resistance in the battery cell 220 and the actual current I is the current that actually flows through the battery cell 220 . OCV is an abbreviation for Open Circuit Voltage. CCV stands for Closed Circuit Voltage.

The relationship between the closed circuit voltage CCV and the open circuit voltage OCV is expressed as CCV=OCV±I×R. When the battery cell 220 is discharged, CCV=OCV-I×R. When charging the battery cell 220, CCV=OCV+I×R.

<Characteristics of SOC and OCV>
The battery cell 220 has SOC and OCV characteristics. FIG. 2 shows SOC and OCV characteristic data when the battery cell 220 is a lithium ion secondary battery.

As shown in FIG. 2, in the overdischarge region where the SOC is close to 0%, the rate of change of OCV with respect to SOC is high. In the overcharge region where the SOC is close to 100%, the rate of change of OCV with respect to SOC is high.

On the other hand, in the charge/discharge region between the overdischarge region and the overcharge region, the rate of change of OCV with respect to SOC is low. Battery cell 220 is mainly used in this charge/discharge region. In FIG. 2, as an example, the values of SOC and OCV between the overdischarge region and the charge/discharge region are expressed as SOC1 and OCV1. SOC and OCV values between the charge/discharge region and the overcharge region are denoted as SOC2 and OCV2.

The characteristic data shown in Fig. 2 depend on temperature. Therefore, the rate of change of OCV with respect to SOC changes depending on the temperature. Along with this, the values of SOC1, SOC2, OCV1 and OCV2 also change.

<Battery device>
The battery device 100 has a monitoring section 10 and a control section 30 . The battery device 100 has the same number of monitoring units 10 as the battery stacks 210 . The plurality of monitoring units 10 detect battery information related to the state of each of the plurality of battery stacks 210 .

The control unit 30 acquires battery information detected by the multiple monitoring units 10 . The control unit 30 also acquires vehicle information input from various other ECUs and various sensors (not shown). When a charging device is connected to the electric vehicle, the control unit 30 acquires charging information input from the charging device. The input to the control unit 30 of the vehicle information and charging information, and the output of the processing results of the control unit 30 to various ECUs, charging equipment, etc. are indicated by white arrows in FIG.

The control unit 30 determines the state of the assembled battery 200 based on the acquired information. At the same time, the control unit 30 executes processing for the assembled battery 200 . The processing for the assembled battery 200 includes, for example, charging and discharging of the assembled battery 200, equalization processing for equalizing the SOCs of the plurality of battery cells 220 included in the assembled battery 200, and the like.

<Monitoring part>
Each of the plurality of monitoring units 10 is individually provided for each of the plurality of battery stacks 210 . One monitoring unit 10 detects the inter-terminal voltage (closed-circuit voltage) between the positive and negative electrodes of each of the plurality of battery cells 220 included in one battery stack 210 . Also, the monitoring unit 10 acquires the physical quantity detected by the physical quantity sensor 230 . The monitoring unit 10 executes processing based on instruction signals input from the control unit 30 .

As shown in FIG. 1, the monitoring unit 10 has a multiplexer 11, a level shifter 12, an AD conversion unit 13, a monitoring control unit 14, and a monitoring communication unit 15. In the drawing, the multiplexer 11 is written as MUX. The level shifter 12 is written as LS. The AD converter 13 is written as AD. The monitor control unit 14 is written as MCU. The monitoring communication unit 15 is written as MCS.

The multiplexer 11 is connected to the positive and negative electrodes of each of the plurality of battery cells 220 included in one battery stack 210 . As a result, the multiplexer 11 receives the closed circuit voltages of the plurality of battery cells 220 .

Also, the multiplexer 11 is connected to the physical quantity sensor 230 . Thereby, the physical quantity is input to the multiplexer 11 .

The multiplexer 11 sequentially selects and detects a plurality of input closed circuit voltages. The multiplexer 11 sequentially outputs the detected closed circuit voltages to the level shifter 12 . The multiplexer 11 also sequentially selects and detects a plurality of input physical quantities. The multiplexer 11 also sequentially outputs the detected physical quantities to the level shifter 12 . The multiplexer 11 corresponds to the detection section.

The level shifter 12 has an operational amplifier and a plurality of feedback circuits connected in parallel between the input terminal and the output terminal of the operational amplifier. The feedback circuit includes a series connected switch and capacitor. Capacitances of capacitors included in a plurality of feedback circuits may be the same or different.

The switches of a plurality of feedback circuits of the level shifter 12 are selectively turned on and off by the monitor control unit 14 . This changes the number of capacitors connected between the input and output terminals of the operational amplifier. The capacitance between the input and output terminals of the operational amplifier changes. Also, the resistance between the input terminal and the output terminal of the operational amplifier changes. As a result, the gain and offset of the level shifter 12 are controlled.

The AD conversion unit 13 receives from the level shifter 12 an analog signal of a closed circuit voltage and a physical quantity whose gain and offset have been adjusted. The AD converter 13 has a clamp circuit for limiting the input range. This clamp circuit is controlled by the monitor controller 14 . The input range of the AD converter 13 is thereby controlled.

By limiting the input range of the AD converter 13 and adjusting the gain and offset of the level shifter 12, the voltage range of the analog signal converted from analog to digital by the AD converter 13 is controlled. The voltage range of the closed circuit voltage and the physical quantity that are analog-to-digital converted by the AD converter 13 are controlled. As a result, the acquisition range of the closed circuit voltage and the physical quantity is controlled.

The AD converter 13 intermittently samples continuous analog signals. Then, the AD converter 13 quantizes the sampled values and converts them into discrete digital signals. Due to such conversion, there is an error (quantization error) between the analog signal and the digital signal.

This quantization error becomes smaller as the number of quantization bits of the AD converter 13 increases. However, the number of quantization bits is fixed. Therefore, for example, when the acquisition range of the closed circuit voltage is 0.0 V to 5.0 V, the resolution of the AD converter 13 is the value obtained by dividing this 0.0 V to 5.0 V by the number of quantization bits.

On the other hand, for example, when the acquisition range of the closed circuit voltage is 3.0 V to 3.5 V, which is 1/10, the resolution of the AD conversion unit 13 is 3.0 V to 3.5 V with the number of quantization bits. becomes the divided value. In this case, the resolution of the AD converter 13 is increased by about ten times. By limiting the acquisition range in this way, the detection accuracy of the closed circuit voltage is improved.

The monitoring control unit 14 has a processor and a non-transitional material storage medium that non-temporarily stores a program readable by this processor. A digital signal input from the AD conversion unit 13 and an instruction signal input from the control unit 30 are stored in this non-transitional substantive storage medium. The processor of the monitor controller 14 controls the multiplexer 11, the level shifter 12, and the AD converter 13 based on the instruction signal.

The instruction signal input to the monitoring control unit 14 includes the acquisition range of the closed circuit voltage of the battery cell 220 to be detected. The monitor control unit 14 controls the gain and offset of the level shifter 12 when the multiplexer 11 selects the closed circuit voltage to be detected. The monitor controller 14 limits the input range of the AD converter 13 . This controls the acquisition range of the closed circuit voltage. Note that the monitoring control unit 14 does not need to limit the acquisition range of the closed circuit voltage. Similarly, the monitoring control unit 14 does not have to limit the acquisition range of physical quantities.

The closed-circuit voltage of the digital signal and the physical quantity are input to the monitoring communication unit 15 . The monitor communication unit 15 outputs this digital signal to the control unit 30 .

<Control unit>
As shown in FIG. 1 , the control unit 30 has a control communication unit 31 , a storage unit 32 and a calculation unit 33 . In the drawing, the control communication unit 31 is denoted as CCU. The storage unit 32 is written as MU. The calculation unit 33 is written as OP.

Various information is input to the control communication unit 31 . This information includes the closed circuit voltage and the physical quantity acquired by the monitoring unit 10 . In addition, this information includes vehicle information and charging information. The vehicle information includes the running state of the electric vehicle and the current time. The charging information includes charging power.

Note that vehicle information and charging information may be input to a communication unit (not shown). And when the control part 30 has RTC, the present time does not need to be contained in vehicle information. RTC is an abbreviation for real time clock.

The storage unit 32 is a non-transitional material storage medium that non-temporarily stores programs readable by computers and processors. The storage unit 32 has a volatile memory and a nonvolatile memory. Various information input to the control communication unit 31 and processing results of the calculation unit 33 are stored in the storage unit 32 .

In addition, the storage unit 32 stores in advance programs and reference values for the operation unit 33 to carry out operation processing. The reference values include, for example, the temperature dependence of SOC and OCV characteristic data of various secondary batteries, an equalization determination value for determining execution of equalization processing, manufacturing dates of the plurality of battery cells 220, and deterioration determination. including values. Further, the reference value includes converter information related to the input/output characteristics of the AD converter 13 .

The computing unit 33 includes a processor. The calculation unit 33 stores various information input to the control communication unit 31 in the storage unit 32 . The calculation unit 33 executes various calculation processes based on information stored in the storage unit 32 . An electrical signal including the result of this arithmetic processing is output to the monitoring section 10 via the control communication section 31 . An electrical signal including the result of this arithmetic processing is output to various ECUs via the control communication unit 31 or a communication unit (not shown).

To give a specific example of the arithmetic processing, the arithmetic unit 33 estimates the SOC of the battery cell 220 based on the information stored in the storage unit 32 . The calculation unit 33 generates an instruction signal for instructing the operation of the monitoring unit 10 based on the estimated SOC and the information stored in the storage unit 32 . This instruction signal includes gain and offset adjustments, which will be described later. Note that if the battery information for estimating the SOC is not stored in the storage unit 32, the calculation unit 33 sets the gain and offset of the level shifter 12 to initial values.

In addition to adjusting the gain and offset, the calculation unit 33 may determine the acquisition range of the closed circuit voltage of the battery cell 220 to be detected. The calculation unit 33 outputs an instruction signal including the acquisition range for each of the plurality of battery stacks 210 to the monitoring unit 10 . Note that if the battery information for estimating the SOC is not stored in the storage unit 32 , the calculation unit 33 sets the acquisition range of the closed circuit voltage to a possible range of the closed circuit voltage of the battery cell 220 .

In addition to adjusting the gain and offset and determining the acquisition range of the closed circuit voltage, the computing unit 33 may determine execution of an equalization process to reduce variations in the SOCs of the plurality of battery cells 220 . The calculation unit 33 outputs an instruction signal including equalization processing for each of the plurality of battery stacks 210 to the monitoring unit 10 .

The computing unit 33 computes the difference between the maximum value and the minimum value of the closed circuit voltage input from the monitoring unit 10 . If this difference exceeds the equalization determination value, the calculation unit 33 decides to execute the equalization process. This equalization process may be performed, for example, only in the battery stack 210 in which at least one of the maximum value and the minimum value of the closed circuit voltage is detected. The equalization process may be performed on all battery stacks 210 .

Although not clearly shown in the drawing, the monitoring unit 10 has a plurality of switches that bridge a plurality of wires connecting the multiplexer 11 and the positive and negative electrodes of the plurality of battery cells 220, respectively. The monitoring control unit 14 selectively controls the plurality of switches to the energized state and the cut-off state based on the instruction signal input from the arithmetic unit 33 . As a result, the battery cell 220 with a relatively high SOC among the plurality of electrically connected battery cells 220 is discharged. Conversely, battery cells 220 with relatively low SOC are charged. As a result, the SOCs of the plurality of battery cells 220 are equalized.

<Integral nonlinearity error>
As described above, the AD converter 13 converts continuous analog signals into discrete digital signals. Therefore, there is a quantization error between the analog signal and the digital signal. Further, the AD converter 13 has an integral nonlinear error.

Ideally, the input/output characteristics of the AD conversion unit 13 with respect to the analog signal input to the AD conversion unit 13 and the digital signal output from the AD conversion unit 13 are expected to exhibit linear behavior. . However, the input/output characteristics of the AD converter 13 actually exhibit nonlinear behavior.

The integral non-linearity error corresponds to the difference between the digital signal output from the AD converter 13 having ideal input/output characteristics and the digital signal output from the AD converter 13 having actual input/output characteristics. . The integral nonlinearity error increases or decreases depending on the value of the analog signal input to the AD converter 13 .

3 to 6 show the relationship between the analog signal input to the AD converter 13 and the digital signal output from the AD converter 13. FIG. The horizontal axis represents the voltage value of the analog signal input to the AD converter 13, which is indicated by AV. The vertical axis represents the voltage value of the digital signal output from the AD converter 13, which is indicated by DV. The units of the horizontal and vertical axes are volts. In the following description, the voltage of the analog signal input to the AD converter 13 will be referred to as an input voltage for the sake of simplicity. The voltage of the digital signal output from the AD converter 13 is indicated as output voltage.

In the drawing, the ideal input/output characteristics are indicated by a dashed line. The solid line indicates the actual input/output characteristics. The integral nonlinearity error is indicated by a two-dot chain line. In the following description, ideal input/output characteristics are referred to as ideal characteristics for the sake of simplicity. Actual input/output characteristics are indicated as actual characteristics.

　The ideal characteristics and the actual characteristics have temperature dependence. The conversion unit information of this embodiment includes the temperature dependence of the ideal characteristics and the actual characteristics. Note that the conversion unit information may include the temperature dependence of the integral nonlinearity error.

For example, as schematically shown in FIG. 3, the ideal characteristic of the AD converter 13 exhibits linear behavior. Real characteristics show nonlinear behavior. However, in order to simplify the explanation below, as shown in FIGS. 4 to 6, ideal characteristics and actual characteristics are shown linearly.

As shown in Fig. 4, the ideal characteristics and the actual characteristics intersect. The input voltage at the intersection of these two characteristics is LST. In the case of the relationship shown in FIG. 4, when the input voltage of LST is input to the AD converter 13, it is expected that the difference between the ideal characteristics and the actual characteristics will be the smallest. Minimal integral nonlinearity error is expected. The input voltage at the intersection of the two characteristics is hereinafter referred to as the minimum error point.

However, when the input voltage that is actually input is IV, the output voltage that is actually output from the AD converter 13 is OV1. The output voltage expected to be ideally output from the AD converter 13 is OV0. The integral nonlinearity error is the absolute value of the difference between OV1 and OV0.

　In order to reduce the integral non-linearity error, the calculation unit 33 adjusts the gain and offset of the level shifter 12 . Adjusting the gain and offset changes the actual characteristics. The minimum error point changes.

The calculation unit 33 adjusts the offset of the level shifter 12 . By doing so, for example, as simply shown in FIG. 5, the calculation unit 33 changes the offset of the actual characteristic. The calculation unit 33 sets the minimum error point LST to the input voltage IV. As a result, it is expected that the actual output voltage OV1 becomes the ideal output voltage OV0. As a result, less integral nonlinearity error is expected.

The calculation unit 33 adjusts the gain of the level shifter 12 . By doing so, the calculation unit 33 changes the slope of the actual characteristic, as simply shown in FIG. 6, for example. The calculation unit 33 sets the minimum error point LST to the input voltage IV. As a result, the output voltage OV1 is expected to become the output voltage OV0. Less integral nonlinearity error is expected.

It should be noted that, as shown in FIG. 3, the original real characteristics exhibit nonlinearity. Therefore, as shown in FIGS. 5 and 6, it is difficult to set the minimum error point LST to the input voltage IV by changing only one of the gain and the offset. The calculation unit 33 narrows the difference between the minimum error point LST and the input voltage IV by changing at least one of the gain and the offset.

In addition, since the original real characteristics show nonlinearity as described above, it is assumed that there will be multiple intersections between the ideal characteristics and the real characteristics. In the example shown in FIG. 3, there are two intersections. The voltage values of the analog signals at the two intersections are the first error minimum point LST1 and the second error minimum point LST2.

In this case, the computing section 33 changes at least one of the gain and the offset so that either one of the first minimum error point LST1 and the second minimum error point LST2 becomes the input voltage IV. The calculation unit 33 selects, for example, the first minimum error point LST1 or the second minimum error point LST2, whichever has the smaller difference from the input voltage IV. Alternatively, when the difference between the input voltage IV and the first minimum error point LST1 or the second minimum error point LST2 is narrowed as much as possible, the calculation unit 33 reduces the integral nonlinearity in the vicinity of the minimum error point. Choose the one with the least error. Then, the calculation unit 33 changes at least one of the gain and the offset so that the selected minimum error point becomes the input voltage IV.

It should be noted that the neighborhood corresponds to the width centered on the minimum error point. The neighboring values correspond to the difference between the minimum error point and the upper and lower limits of the width. The value in the neighborhood can be determined, for example, based on the amount of voltage change that the closed circuit voltage is expected to change during the time of the acquisition period described later.

<Voltage detection processing>
Next, the voltage detection processing of the computing section 33 will be described with reference to FIG. The calculation unit 33 executes this voltage detection process as a cycle task.

　The voltage detection process is executed at the acquisition cycle. The acquisition period is a time interval at which the SOC of the battery cell 220 is expected not to change suddenly unless the charge/discharge state of the battery cell 220 changes suddenly due to rapid charging or the like.

In step S10, the calculation unit 33 determines whether or not the closed circuit voltage is stored in the storage unit 32. When the closed circuit voltage is stored in the storage unit 32, the calculation unit 33 proceeds to step S20. If the closed circuit voltage is not stored in the storage unit 32, the calculation unit 33 proceeds to step S60.

When proceeding to step S20, the calculation unit 33 acquires the temperature detected by the physical quantity sensor 230. Then, the calculation unit 33 reads from the storage unit 32 the temperature dependence of the ideal characteristics and the actual characteristics corresponding to the temperature. The calculation unit 33 calculates the minimum error point based on these ideal characteristics and actual characteristics. If the storage unit 32 stores the temperature dependence of the integral nonlinearity error, the calculation unit 33 reads the minimum error point corresponding to the temperature detected by the physical quantity sensor 230 in step S20. After that, the calculation unit 33 proceeds to step S30.

When proceeding to step S<b>30 , the calculation unit 33 calculates the difference value between the calculated minimum error point and the closed circuit voltage stored in the storage unit 32 . After that, the calculation unit 33 proceeds to step S40.

When proceeding to step S40, the calculation unit 33 calculates a gain and an offset for bringing the difference value calculated in step S40 closer to zero. After this, the calculation unit 33 proceeds to step S50.

When proceeding to step S50, the calculation unit 33 transmits an instruction signal including the gain and offset calculated in step S40 to the monitoring unit 10 as an adjustment signal. After this, the calculation unit 33 proceeds to step S60.

When proceeding to step S60, the calculation unit 33 acquires the closed circuit voltage detected by the monitoring unit 10. After that, the calculation unit 33 proceeds to step S70.

When proceeding to step S70, the calculation unit 33 stores the acquired closed circuit voltage in the storage unit 32. Then, the calculation unit 33 terminates the voltage detection process.

<Effect>
As described above, the calculation unit 33 adjusts at least one of the gain and offset of the level shifter 12 to narrow the difference between the past closed circuit voltage stored in the storage unit 32 and the minimum error point. . Then, the calculation unit 33 acquires a new closed circuit voltage.

According to this, it is expected that the difference between the newly acquired closed-circuit voltage and the minimum error point will become smaller. It is expected that the integral nonlinearity error of the AD converter 13 will be reduced. As a result, an improvement in detection accuracy of the closed circuit voltage is expected.

(Second embodiment)
Next, a second embodiment will be described with reference to FIGS. 8 to 10. FIG.

In the first embodiment, an example was shown in which the calculation unit 33 adjusts at least one of the gain and offset of the level shifter 12 so that the difference between the past closed circuit voltage stored in the storage unit 32 and the minimum error point is narrowed.

On the other hand, in the present embodiment, the calculation unit 33 estimates the new closed circuit voltage based on the past closed circuit voltage stored in the storage unit 32 and the information stored in the storage unit 32 . Then, the calculation unit 33 adjusts at least one of the gain and offset of the level shifter 12 so that the difference between the estimated closed circuit voltage (estimated voltage) and the minimum error point is narrowed. After this, the calculation unit 33 newly acquires the closed circuit voltage.

As a result, it is expected that the integral nonlinearity error of the AD converter 13 will be effectively reduced. It is expected that the detection accuracy of the closed circuit voltage will be effectively improved.

<Time change of closed circuit voltage>
Due to the SOC and OCV characteristics of the battery cell 220 shown in FIG. 2, when the SOC drops due to discharge, the OCV also drops. Accordingly, the closed circuit voltage CCV of the battery cell 220 also decreases. Conversely, when the SOC increases due to the supply of charging power from the charging equipment, the closed circuit voltage CCV also increases. Thus, the closing voltage CCV changes with time.

Fig. 8 shows the time change of the closed circuit voltage. The vertical axis is in arbitrary units. The horizontal axis is time. Arbitrary units are a.d. u. is indicated. Time is denoted by T.

In addition to the closed circuit voltage, FIG. 8 shows the driving state of the battery device 100, the actual current flowing through the assembled battery 200, and the closed circuit voltage of one battery cell 220. FIG. The drive state of the battery device 100 is denoted as DS. For simplicity of explanation, the behavior of the closed circuit voltage of the battery cell 220 and the behavior of the closed circuit voltage of the assembled battery 200 shown in the drawings are assumed to be the same. In order to clarify the behavior, the drawing shows that the closed circuit voltage of the battery cell 220 changes greatly in a short period of time.

In the initial state at time 0, the battery device 100 is in a non-driving state. The storage unit 32 does not store battery information such as closed circuit voltage and physical quantity. A system main relay that controls electrical continuity between the assembled battery 200 and various vehicle-mounted devices is in a disconnected state. Therefore, substantially no current flows through the assembled battery 200 . The closed circuit voltage of the battery cell 220 has a value in the charge/discharge region.

The SOC of the battery cell 220 decreases due to self-discharge even if the current does not substantially flow through the battery cell 220 . Therefore, in the initial state at time 0, the closed circuit voltage of the battery cell 220 tends to decrease, albeit slightly.

At time t0, the battery device 100 changes from the non-driving state to the driving state. The system main relay changes from the cut-off state to the energized state. As a result, supply of power supply power from the assembled battery 200 to various vehicle-mounted devices is started. An actual current begins to flow in the assembled battery 200 . The rate of decrease of the SOC of battery cell 220 increases. Along with this, the reduction rate of the closed circuit voltage of the battery cell 220 also increases.

At time t1, the calculation unit 33 acquires the closed circuit voltage of the battery cell 220. At this time, the battery information is not stored in the storage unit 32 . Therefore, the calculation unit 33 sets the gain and offset of the level shifter 12 at time t1 to initial values. The calculation unit 33 acquires the closed circuit voltage detected by the monitoring unit 10 at this time t1. Note that there is practically no time difference between time t1 and time t0. When the battery device 100 shifts from the non-driving state to the driving state, the process of detecting the closed circuit voltage is substantially started.

At time t2 after the acquisition cycle has elapsed from time t1, the calculation unit 33 acquires the closed circuit voltage of the battery cell 220 again. The SOC of battery cell 220 changes while time elapses from time t1 to time t2. In the example shown in FIG. 8, the amount of power indicated by hatching is discharged. It is assumed that the closed circuit voltage at time t1 and the closed circuit voltage at time t2 are different due to this discharge.

Therefore, the calculation unit 33 estimates the closed circuit voltage at time t2 based on the closed circuit voltage obtained at time t1 and the amount of change in the closed circuit voltage from time t1 to time t2. Then, the calculation unit 33 calculates a gain and an offset for zeroing the difference between the estimated voltage and the minimum error point. The calculation unit 33 outputs an instruction signal including changes to the calculated gain and offset to the monitoring unit 10 . The calculation unit 33 acquires the closed circuit voltage detected by the monitoring unit 10 whose gain and offset have been adjusted at this time t2. When time t1 corresponds to the first detection timing, time t2 corresponds to the second detection timing. The estimated voltage corresponds to the estimated value.

Strictly speaking, since there is arithmetic processing in the battery device 100, the gain and offset adjustment timing and the closed circuit voltage acquisition timing at time t2 are not the same. The adjustment timing is before the acquisition timing. However, the difference between these two timings is minute. Therefore, these two timings are considered to be the same and described.

At time t3 after the acquisition cycle has elapsed from time t2, the calculation unit 33 calculates the estimated voltage based on the closed circuit voltage at time t2 and the amount of change in the closed circuit voltage from time t2 to time t3. Then, the calculation unit 33 calculates gain and offset based on the estimated voltage and the minimum error point. The calculation unit 33 acquires the closed circuit voltage detected by the monitoring unit 10 whose gain and offset have been adjusted at this time t3. When time t2 corresponds to the first detection timing, time t3 corresponds to the second detection timing.

From time t3 to time tc1, the actual current decreases. Along with this, the reduction rate of the closed circuit voltage is also reduced.

When the acquisition cycle has passed from time t3 to time t4, the calculation unit 33 calculates the estimated voltage based on the closed circuit voltage at time t3 and the amount of change in the closed circuit voltage from time t3 to time t4. Then, the calculation unit 33 calculates gain and offset based on the estimated voltage and the minimum error point. The calculation unit 33 acquires the closed-circuit voltage detected by the monitoring unit 10 whose gain and offset have been adjusted at this time t4.

Since the amount of change in closed circuit voltage between time t3 and time t4 is taken into account in this way, even if the rate of decrease in closed circuit voltage begins to decrease at time tc1 between time t3 and time t4, This prevents the integral nonlinearity error from being effectively reduced at time t4.

From time t4 to time tc2, the charging equipment is connected to the electric vehicle. The battery pack 200 is rapidly charged by the charging equipment. This causes the actual current to rise sharply. The calculation unit 33 acquires such information from vehicle information or charging information.

At time t5 after the acquisition cycle has elapsed from time t4, the calculation unit 33 calculates the estimated voltage based on the closed circuit voltage at time t4 and the amount of change in the closed circuit voltage from time t4 to time t5. The calculation unit 33 calculates gain and offset based on the estimated voltage and the minimum error point. The calculation unit 33 acquires the closed circuit voltage detected by the monitoring unit 10 with the gain and offset adjusted at this time t5.

Since the amount of change in the closed-circuit voltage between time t4 and time t5 is taken into account in this way, even if the closed-circuit voltage begins to rise sharply at time tc2 between time t4 and time t5, the integration at time t5 It is suppressed that the non-linearity error is no longer effectively reduced.

From time t5 to time tc3, the output voltage of the assembled battery 200 reaches the target voltage. When detecting this, the calculation unit 33 terminates the rapid charging by the charging equipment. The calculation unit 33 causes the charging equipment to perform full charging.

The amount of supplied current differs between the above-mentioned rapid charging and full charging. The amount of supplied current is larger in quick charge than in full charge.

As described above, there is a difference of the voltage drop I×R between the closed circuit voltage CCV and the open circuit voltage OCV. During charging, CCV=OCV+I×R. Therefore, even if the maximum output voltage of the assembled battery 200 is detected as the closed circuit voltage CCV, the open circuit voltage OCV does not reach the maximum output voltage. This means that the SOC of the assembled battery 200 has not reached the full charge amount.

The above target voltage is a value based on the maximum output voltage of the assembled battery 200. When the calculation unit 33 determines that the closed circuit voltage of the assembled battery 200 has reached the target voltage, it causes the charging device to perform full charging. In full charging, charging power is supplied to the assembled battery 200 while maintaining the closed circuit voltage detected by the assembled battery 200 at the target voltage in order to avoid overcharging and bring the SOC of the assembled battery 200 closer to the full charge amount. is done. The target voltage and the maximum output voltage are pre-stored in the storage section 32 .

At time t6 after the acquisition cycle has elapsed from time t5, the estimated voltage is calculated based on the target voltage and the amount of change in the closed circuit voltage from time t5 to time t6. The calculator 33 calculates gain and offset based on the estimated voltage and the minimum error point. The calculation unit 33 acquires the closed-circuit voltage detected by the monitoring unit 10 with the gain and offset adjusted at time t6.

After time t6, it is expected that the target voltage will be obtained as long as full charging continues. In this case, the calculator 33 calculates the gain and offset based on the target voltage and the minimum error point. The calculation unit 33 continues to acquire the closed-circuit voltage detected by the monitoring unit 10 whose gain and offset have been adjusted. Alternatively, the calculation unit 33 stops acquiring the closed circuit voltage.

Although not shown, when the SOC of the assembled battery 200 is excessively reduced or the electric motor of the electric vehicle malfunctions, the electric vehicle performs constant voltage drive with limited driving. At this time, the voltage of the power supply power output from the assembled battery 200 is limited. The voltage of the power supply is kept at a constant value, for example. Therefore, it is expected that the closed circuit voltage of the battery cell 220 is maintained at a predetermined voltage.

In this case, the calculation unit 33 calculates the gain and offset based on the predetermined voltage and the minimum error point. The calculation unit 33 continues to acquire the closed-circuit voltage detected by the monitoring unit 10 whose gain and offset have been adjusted. Alternatively, the calculation unit 33 stops acquiring the closed circuit voltage.

<Estimation of closed circuit voltage>
As described above, the calculation unit 33 estimates the closed circuit voltage to be newly acquired when calculating the gain and the offset. For example, at time t2 shown in FIG. 8, the calculation unit 33 estimates the closed circuit voltage at time t2 based on the closed circuit voltage acquired at time t1 and the amount of change in the closed circuit voltage from time t1 to time t2.

The amount of change in closed circuit voltage from time t1 to time t2 depends on the charge/discharge history between time t1 and time t2, the temperature between time t1 and time t2, and the temperature dependence of the SOC and OCV characteristic data. calculated based on gender. The charge/discharge history corresponds to the charge/discharge amount.

The charge/discharge history between time t1 and time t2 is calculated, for example, based on the time between time t1 and time t2 and the current between time t1 and time t2. A charge/discharge history between time t1 and time t2 is calculated as an integrated value of current between time t1 and time t2. Note that the current between time t1 and time t2 is estimated by, for example, the addition average value of the current at time t1 and the current at time t2.

The temperature between time t1 and time t2 is estimated, for example, by adding and averaging the temperature at time t1 and the temperature at time t2. The calculation unit 33 reads the SOC and OCV characteristic data of this temperature from the storage unit 32 . Then, the calculation unit 33 calculates the amount of change in closed circuit voltage from time t1 to time t2 based on the read SOC and OCV characteristic data and the calculated charge/discharge history between time t1 and time t2. .

Of course, the calculation unit 33 reads the SOC and OCV characteristic data of the battery cell 220 from the storage unit 32 among the SOC and OCV characteristic data of various secondary batteries. When the battery cell 220 is a lithium ion secondary battery, the calculation unit 33 reads the SOC and OCV characteristic data of the lithium ion secondary battery from the storage unit 32 .

The calculation unit 33 estimates the aged deterioration of the battery cell 220 at the time t2, for example, based on the difference between the date of manufacture of the battery cell 220 and the time t2 stored in the storage unit 32 and the deterioration determination value. good. The calculation unit 33 may estimate the internal resistance of the battery cell 220 at time t2 based on aging deterioration of the battery cell 220 and the temperature at time t2. The calculation unit 33 may calculate the voltage drop occurring in the battery cell 220 at the time t2 based on the internal resistance and the current at the time t2. The calculation unit 33 may also take this voltage drop into account to estimate the closed circuit voltage at time t2.

Further, the calculation unit 33 may estimate the amount of change in the closed circuit voltage from time t1 to time t2 based on the equivalent circuit model or chemical reaction model of the battery cell 220 and the current and temperature of the battery cell 220.

As a further example, the storage unit 32 may store a discharge value and a charge value for estimating the amount of change in the closed circuit voltage described above. The amount of change in closed circuit voltage may be determined by multiplying the predetermined discharge value by the time between time t1 and time t2. The amount of change in closed circuit voltage may be determined by multiplying the predetermined charge value by the time between time t1 and time t2.

<Voltage detection processing>
In the case of this embodiment, the calculation unit 33 executes the voltage detection process shown in FIG. The voltage detection process shown in FIG. 9 has steps S110 and S120 added to the voltage detection process shown in FIG. 7 described in the first embodiment.

When it is determined in step S10 that the closed circuit voltage is stored in the storage unit 32, the calculation unit 33 proceeds to step S110.

When proceeding to step S110, the calculation unit 33 acquires various information for calculating the estimated voltage. This information includes closed-circuit voltage, acquisition cycle, current, temperature, SOC and OCV characteristic data, and the like stored in the storage unit 32 . After that, the calculation unit 33 proceeds to step S120.

When proceeding to step S120, the calculation unit 33 calculates the estimated voltage based on the various information acquired in step S110. After that, the calculation unit 33 proceeds to step S20.

When proceeding to step S20, the calculation unit 33 calculates the minimum error point. Alternatively, the calculation unit 33 reads the minimum error point from the storage unit 32 . After that, the calculation unit 33 proceeds to step S30.

When proceeding to step S30, the calculation unit 33 calculates the difference value between the minimum error point and the estimated closed circuit voltage (estimated voltage). After that, the calculation unit 33 proceeds to step S40. Henceforth, the calculating part 33 performs the process equivalent to having demonstrated in 1st Embodiment.

<Acquisition range>
As described in the first embodiment, the calculation unit 33 may determine the acquisition range of the closed circuit voltage of the battery cell 220 to be detected. For example, the center value of the acquisition range at time t2 can be determined based on the closed circuit voltage at time t1. The center value of the acquisition range at time t2 can also be determined based on the closed circuit voltage at time t1 and the amount of change in the closed circuit voltage from time t1 to time t2.

Then, the width of the acquisition range can be set to a value larger than the detection error of the closed circuit voltage. The width of the acquisition range at time t2 can also be determined based on the temperature and current of the battery cell 220 at time t2. The width of the acquisition range at time t3 can also be determined based on the difference (estimation error) between the center value of the acquisition range at time t2 and the closed circuit voltage acquired at time t2. Note that the difference between the center value and the upper limit value of the acquisition range and the difference between the center value and the lower limit value may be the same or different.

When executing the process of determining the acquisition range of the closed circuit voltage, the calculation unit 33 executes the voltage detection process shown in FIG. The voltage detection process shown in FIG. 10 has steps S210 and S220 added to the voltage detection process shown in FIG.

After step S50, the calculation unit 33 proceeds to step S210. When proceeding to step S210, the calculation unit 33 calculates the acquisition range based on the estimated voltage and the like. Then, the calculation unit 33 transmits an instruction signal including the acquisition range to the monitoring unit 10 as a limited range signal.

When the closed circuit voltage is not stored in the storage unit 32, the calculation unit 33 proceeds from step S10 to step S220. When proceeding to step S220, the calculation unit 33 sets the entire range of possible closed-circuit voltages as the acquisition range. Then, the calculation unit 33 transmits an instruction signal including the acquisition range to the monitoring unit 10 as a full range signal.

(Other modifications)
In this embodiment, an example is shown in which one control unit 30 is provided for a plurality of monitoring units 10 . However, a configuration in which a plurality of controllers 30 are provided individually for a plurality of monitoring units 10 can also be adopted.

In the present embodiment, an example is shown in which the computing unit 33 adjusts the gain and offset of the level shifter 12 when detecting the closed circuit voltage of each of the plurality of battery cells 220 . However, it is also possible to employ a configuration in which the calculation unit 33 adjusts the gain and offset of the level shifter 12 when detecting the closed circuit voltage of each of the plurality of battery stacks 210 . It is also possible to employ a configuration in which the calculation unit 33 adjusts the level shifter 12 to a common gain and offset when detecting the closed circuit voltages of the plurality of battery cells 220 included in one battery stack 210 . In such a modification, the assembled battery 200 has at least two battery stacks 210 .

In this embodiment, an example is shown in which each of the plurality of battery cells 220 is the same type of secondary battery. However, a secondary battery in which some of the plurality of battery cells 220 are different may be used. For example, some battery stacks 210 among the plurality of battery stacks 210 include first type battery cells 220, and the remaining battery stacks 210 include second type battery cells 220 different from the first type. may As the battery cells 220 of different types, for example, battery cells 220 having the same internal configuration and external configuration but different composition materials for the positive and negative electrodes can be employed.

In the case of such a modification, when estimating the amount of change in the closed circuit voltage, the calculation unit 33 uses the SOC and OCV characteristic data of the first type battery cell 220 and the SOC and OCV characteristic data of the second type battery cell 220 Data is read from the storage unit 32 .

Although the present disclosure has been described with reference to examples, it is understood that the present disclosure is not limited to those examples or structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, while various combinations and configurations are shown in this disclosure, other combinations and configurations, including single elements, more, or less, are within the scope and spirit of this disclosure. is to enter.

Claims

a detection unit (11) for detecting closed circuit voltages of a plurality of electrically connected battery cells (220);
a level shifter (12) that adjusts the gain and offset of the closed circuit voltage detected by the detector;
an AD converter (13) that converts the closed-circuit voltage, the gain and the offset of which are adjusted by the level shifter, into a digital signal;
A storage unit (32) for storing battery information including the closed circuit voltage and conversion unit information related to actual characteristics and ideal characteristics as input/output characteristics of the input voltage and the output voltage of the AD conversion unit. When,
a computing unit (33) for narrowing the difference between the input voltage at the intersection of the actual characteristic and the ideal characteristic and the closed circuit voltage stored in the storage unit by adjusting at least one of the gain and the offset; A battery device comprising:
The battery information includes an amount of change in the closed circuit voltage in addition to the closed circuit voltage,
The amount of change includes a period from a first detection timing at which the closed-circuit voltage stored in the storage unit is detected by the detection unit to just before a second detection timing at which the closed-circuit voltage is newly detected by the detection unit. 2. The battery device according to claim 1, wherein the charge/discharge amount of the battery cell during the period is included.
The calculation unit is
estimating the closed circuit voltage at the second detection timing based on the battery information and storing it in the storage unit;
Adjusting at least one of the gain and the offset narrows a difference between the input voltage at the intersection and the estimated value of the closed circuit voltage at the second detection timing stored in the storage unit. The battery device according to .
The calculation unit sets an acquisition range of the closed circuit voltage based on the battery information,
The battery device according to any one of claims 1 to 3, wherein the AD conversion unit converts the closed circuit voltage detected by the detection unit into the digital signal within the acquisition range set by the calculation unit. .