JP4638175B2 - Remaining capacity display device for power storage device - Google Patents

Description

  The present invention relates to a remaining capacity display device for an electricity storage device that displays the remaining capacity of an electricity storage device such as a secondary battery or an electrochemical capacitor.

  In recent years, energy storage devices such as secondary batteries such as nickel metal hydride batteries and lithium ion batteries, and electrochemical capacitors such as electric double layer capacitors have been reduced in size and weight, and energy density has increased. It is actively used as a power source for automobiles.

  The amount of energy that can be used in such an electricity storage device can be known by calculating and displaying the remaining capacity. In general, as a technique for calculating the remaining capacity, a technique for calculating the remaining capacity by accumulating the charge / discharge current of the storage device and a technique for determining the remaining capacity based on the open circuit voltage are known. Although it is strong against load fluctuations such as the above, there is a drawback that errors tend to accumulate (especially, errors become large when high load is continued), and the latter is highly effective as long as the open-circuit voltage can be estimated accurately, but short. There is a drawback that the calculated value tends to fluctuate when the load fluctuates greatly with time. Therefore, various techniques for obtaining the remaining capacity by combining the two have been proposed.

  For example, in Patent Document 1, the remaining capacity at the time of stoppage is obtained from the open-circuit voltage obtained from the battery voltage at the time of stopping the electric vehicle, and the discharge electric capacity is detected based on the integrated value of the discharge current of the battery. A technique is disclosed in which a full charge capacity is calculated from the electric capacity and the remaining capacity at stop, and the remaining capacity is obtained from the full charge capacity and the discharge electric capacity.

  Further, in Patent Document 2, a battery capacity and a battery voltage, such as a lithium ion battery, having a linear proportional relationship, an accumulated amount of current when discharging or charging for an arbitrary time, and discharging or charging. A technique for obtaining and displaying a remaining capacity from a previous voltage, a voltage after discharge or a charge is disclosed.

Further, Patent Document 3 discloses a method for calculating the remaining capacity based on the rate of change of the difference between the remaining capacity obtained by integrating the charging / discharging current of the battery and the remaining capacity estimated based on the open terminal voltage of the battery. A technique for correcting the above is disclosed.
JP-A-6-242193 JP-A-8-179018 Japanese Patent Laid-Open No. 11-223665

  However, in the technique disclosed in Patent Document 1, the accuracy with respect to the remaining capacity of the battery while the electric vehicle is running is not guaranteed, and the open voltage is obtained from the battery voltage when the vehicle is stopped. Since the current flows through the load such as the inverter even when the motor is stopped, it is not always possible to detect an accurate open-circuit voltage. Therefore, in the technique of Patent Document 1, not only the display accuracy of the remaining capacity is insufficient, but the application range is limited. For example, it is difficult to use as display data in a hybrid vehicle or the like in which charging / discharging continues. It is.

  Similarly, in the technique disclosed in Patent Document 2, the voltage before and after charge / discharge is treated as an open circuit voltage (open voltage). However, if the open circuit voltage can be detected accurately for the reason described above, In addition, since accuracy is mainly improved at the time of discharging, the accuracy at the time of charging is not much considered, and it is difficult to apply to a hybrid vehicle or the like in which charging / discharging continues.

  Furthermore, the technique disclosed in Patent Document 3 updates the remaining capacity calculation value only when the difference between the remaining capacity calculation value based on current integration and the remaining capacity estimation value based on the open circuit voltage is greater than a predetermined value. ing. For this reason, there is a high possibility that the remaining capacity calculation value will change greatly in a step shape at the moment of update. If the remaining capacity is displayed as it is, the display value will change abruptly and it will be difficult to convey information appropriately.

  The present invention has been made in view of the above circumstances, and recognizes the calculated remaining capacity while calculating the remaining capacity with high accuracy by taking advantage of both the remaining capacity based on the current integration and the remaining capacity based on the open circuit voltage. It is an object of the present invention to provide a remaining capacity display device for an electricity storage device that can be easily displayed.

In order to achieve the above object, a remaining capacity display device for an electricity storage device according to the present invention includes a first remaining capacity based on an integrated value of charge / discharge current of an electricity storage device and a second value based on an estimated value of an open circuit voltage of the electricity storage device. The remaining capacity is weighted and synthesized using a weight set according to the usage status of the power storage device, and the remaining capacity calculation means for calculating the remaining capacity of the power storage device, the change in charge / discharge current of the power storage device and the temperature Data discharge time interval setting means for setting a data discharge time interval for displaying the remaining capacity calculated by the remaining capacity calculation means, and when the power storage device is in a charged state, the remaining capacity calculation means The calculated remaining capacity data is sequentially compared in time series to select only the data that is increasing, and when the power storage device is in a discharged state, the remaining capacity is selected. The data of the remaining capacity calculated by the calculating means chronologically only sorted data in the sequence comparison to decline, and outputs the data by該選 the data release time interval set by the data release time interval setting means And a display output means.

  At that time, the remaining capacity is preferably set based on the moving average value of the charge / discharge current of the electricity storage device, while estimating the open circuit voltage of the electricity storage device based on the electrochemical relationship inside the electricity storage device, It is desirable to set the data release time interval for displaying the remaining capacity based on the moving average value of the charge / discharge current of the power storage device and the temperature.

  The remaining capacity display device for an electricity storage device according to the present invention can easily recognize the calculated remaining capacity while calculating a highly accurate remaining capacity that takes advantage of both the remaining capacity based on current integration and the remaining capacity based on the open circuit voltage. It is possible to display the remaining energy amount that can be actually used.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 12 relate to an embodiment of the present invention, FIG. 1 is a block diagram showing a battery remaining capacity calculation and display system, FIG. 2 is a block diagram showing a battery remaining capacity estimation algorithm, and FIG. 3 is equivalent. 4 is a circuit diagram showing a calculation process of the remaining battery capacity, FIG. 5 is an explanatory diagram of the current capacity table, FIG. 6 is an explanatory diagram of the impedance table, FIG. 7 is an explanatory diagram of the remaining capacity table, FIG. 8 is an explanatory diagram of the weight table, FIG. 9 is an explanatory diagram showing the remaining capacity without current moving average processing, FIG. 10 is an explanatory diagram showing the remaining capacity with current moving average processing, and FIG. 11 is an actual vehicle FIG. 12 is a flow chart showing the battery remaining capacity display process.

  In FIG. 1, reference numeral 1 denotes a power supply device mounted on a hybrid vehicle that travels using both an engine and a motor, an electric vehicle that travels only by a motor, and the like. In this power supply device 1, for example, a battery 2 configured by connecting a plurality of battery packs in which a plurality of cells are sealed in series as an electricity storage device, calculation of the remaining capacity of the battery 2, cooling and charging of the battery 2, etc. An arithmetic unit (arithmetic ECU) 3 that performs energy management such as control, abnormality detection, and protection operation at the time of abnormality detection is packaged in one casing.

  In this embodiment, a lithium ion secondary battery will be described as an example of an electricity storage device. However, the remaining capacity calculation method in the present invention can also be applied to an electrochemical capacitor and other secondary batteries.

  The arithmetic ECU 3 is composed of a microcomputer or the like, and the terminal voltage V of the battery 2 measured by the voltage sensor 4, the charge / discharge current I of the battery 2 measured by the current sensor 5, and the temperature (cell) of the battery 2 measured by the temperature sensor 6. Based on the temperature (T), the state of charge (SOC), that is, the remaining capacity SOC (t) is calculated every set time t. Note that the remaining capacity SOC (t−1) one calculation cycle before is input to the calculation ECU 3 as a base value in a periodic calculation (a base value in a remaining capacity calculation by current integration described later).

  The remaining capacity SOC calculated by the calculation ECU 3 is output to the inverter device 10 and the display device 20 via, for example, CAN (Controller Area Network) communication. The inverter device 10 performs drive control and regenerative control of a motor (not shown) based on the remaining capacity SOC of the battery, and the display device 20 takes in data of the remaining capacity SOC output from the arithmetic ECU 3 and takes in the remaining capacity The SOC data is converted into display data and displayed.

  The display device 20 includes an arithmetic unit (arithmetic ECU) 21 composed of a microcomputer or the like, and a display 22 that displays the remaining capacity SOC. The calculation ECU 21 receives various data and signals representing the state of the battery 2 transmitted from the power supply device 1, that is, the terminal voltage V, the charge / discharge current I, the cell temperature T, the remaining capacity SOC (t), SOC (t-1 ), A power generation signal indicating that the battery 2 is in a charged state by the power generation of the motor is input, and the remaining capacity SOC transmitted from the power supply device 1 is converted into an appropriate data group that can be easily recognized by the driver. 22 for output.

  That is, the remaining capacity SOC calculated at the set time t in the calculation ECU 3 of the power supply device 1 can satisfactorily capture changes in the battery status, and highly accurate data can be obtained. Therefore, the remaining capacity SOC calculated by the calculation ECU 3 is effective for controlling the driving force of the vehicle via the inverter device 10 and the like. However, for a general driver who wants to grasp the approximate remaining capacity of the battery, the data remains unchanged. Even when displayed, the data is too fine and too sensitive to changes in the battery status, and the display fluctuates, making it difficult to see.

For this reason, the calculation ECU 21 of the display device 20 outputs the data of the remaining capacity SOC calculated by the calculation ECU 3 of the power supply device 1 every set time t to the display 22 according to the state of charge / discharge of the battery. By setting the data emission time interval and selecting and outputting the data to the display unit 22, data that is not necessary for general drivers is excluded, and display fluctuation is reduced. Accordingly, the driver can easily determine the travelable distance, the necessity for charging, and the like from the display of the remaining capacity of the display 22.

  Hereinafter, the calculation process of the remaining capacity SOC in the power supply device 1 and the display process in the display device 20 will be described in detail.

  First, the function as the remaining capacity calculation means in the calculation ECU 3 of the power supply apparatus 1 is realized according to the remaining capacity estimation algorithm shown in FIG. In this estimation algorithm, parameters that can be measured by the battery 2, that is, the terminal voltage V, the current I, and the temperature T are used, the remaining capacity SOCc as the first remaining capacity based on the current integration, and the estimated value of the battery open voltage Vo. The remaining capacity SOCv as the second remaining capacity based on the above is calculated in parallel, and the remaining capacity SOC synthesized by weighting each is output as the remaining capacity of the battery 2.

  The remaining capacity SOCc obtained by integrating the current I and the remaining capacity SOCv obtained by estimating the open circuit voltage Vo have their merits and demerits, and the remaining capacity SOCc obtained by integrating the current is likely to accumulate errors. However, it is resistant to load fluctuations such as inrush current. On the other hand, the remaining capacity SOCv based on the open-circuit voltage estimation can be obtained as a substantially accurate value during normal use, but the value may oscillate when the load greatly fluctuates in a short time.

Therefore, in the present SOC estimation algorithm, the remaining capacity SOCc (t) obtained by integrating the current I and the remaining capacity SOCv (t) obtained from the estimated value of the battery open voltage Vo are determined according to the usage state of the battery 2. Thus, the weights (weighting factors) w that are changed as needed are weighted and combined, so that the disadvantages of both the remaining capacities SOCc and SOCv are canceled out and the mutual advantages are maximized. The weight w is changed between w = 0 and 1, and the final remaining capacity SOC (t) after synthesis is given by the following equation (1).
SOC (t) = w.SOCc (t) + (1-w) .SOCv (t) (1)

  The weight w needs to be determined using a parameter that can accurately represent the current battery usage. The parameters include the current change rate per unit time and the deviation between the remaining capacities SOCc and SOCv. Etc. can be used. The current change rate per unit time directly reflects the load fluctuation of the battery, but the mere current change rate is affected by a sudden change in current that occurs in a spike manner.

  Therefore, in this embodiment, in order to prevent the influence of a change in current that instantaneously stops, a current change rate that has been processed by a simple average, a moving average, a weighted average, or the like of a predetermined sampling number is used. In particular, when considering a delay in current, the weight w is determined using a moving average that can appropriately reflect the past history without excessively changing the charge / discharge state of the battery. I have to.

  By determining the weight w based on the moving average value of the current I, when the moving average value of the current I is large, the weight of the current integration is increased to lower the weight of the open circuit voltage estimation, and the influence of the load fluctuation is While accurately reflecting by integration, vibration during open circuit voltage estimation can be prevented. Conversely, when the moving average value of current I is small, the effect of error accumulation during current integration is avoided by reducing the current integration weight and increasing the open-circuit voltage estimation weight. The remaining capacity can be calculated.

  That is, the moving average of the current I becomes a low-pass filter with respect to the high frequency component of the current, and the moving average filtering can remove the spike component of the current generated by the load fluctuation during traveling without promoting the delay component. it can. As a result, the battery state can be grasped more accurately, the disadvantages of both the remaining capacities SOCc and SOCv can be canceled, the mutual advantages can be maximized, and the estimation accuracy of the remaining capacities can be greatly improved.

  Further, as a feature of the present SOC estimation algorithm, the internal state of the battery is electrochemically grasped based on the battery theory, and the calculation accuracy of the remaining capacity SOCv based on the battery open voltage Vo is improved. Next, the calculation of the remaining capacities SOCc and SOCv by this estimation algorithm will be described in detail.

First, as shown in the following equation (2), the remaining capacity SOCc by current integration is obtained by integrating the current I every predetermined time with the remaining capacity SOC synthesized using the weight w as a base value.
SOCc (t) = SOC (t−1) −∫ [(100ηI / Ah) + SD] dt / 3600 (2)
Where η: current efficiency
Ah: Current capacity (variable depending on temperature)
SD: Self-discharge rate

  Although the current efficiency η and the self-discharge rate SD in the equation (2) can be regarded as constants (for example, η = 1, SD = 0), the current capacity Ah varies depending on the temperature. Therefore, when calculating the remaining capacity SOCc by this current integration, the current capacity Ah calculated by functionalizing the variation of the cell capacity with temperature is used.

Further, the calculation of the remaining capacity SOCc (t) by the equation (2) is specifically executed by discrete time processing in the calculation ECU 3, and the combined remaining capacity SOC (t−1) one calculation cycle before is calculated as the current integration. It is input as a base value (delay operator Z ⁻¹ in the block diagram of FIG. 2). Therefore, errors do not accumulate or diverge, and even if the initial value is significantly different from the true value, it should converge to the true value after a predetermined time (for example, after several minutes). Can do.

  On the other hand, in order to obtain the remaining capacity SOCv based on the estimation of the open circuit voltage Vo, first, the internal impedance Z of the battery is obtained using the equivalent circuit model shown in FIG. This equivalent circuit is an equivalent circuit model in which parameters of resistance components R1 to R3 and capacitance components C1, CPE1, and CPE2 (where CPE1 and CPE2 are double layer capacitance components) are combined in series and in parallel. Each parameter is determined by curve fitting a well-known Cole-Cole plot in the method.

The impedance Z obtained from these parameters varies greatly depending on the temperature of the battery, the electrochemical reaction rate, and the frequency component of the charge / discharge current. Accordingly, the moving average value of the current I per unit time described above is used as a frequency component replacement as a parameter for determining the impedance Z, and impedance measurement is performed on the condition of the moving average value of the current I and the temperature T. After accumulating data, an impedance Z table (an impedance table in FIG. 6 described later) is created based on the temperature T and the moving average value of the current I per unit time. Then, the impedance Z is obtained using this table, and the estimated value of the open circuit voltage Vo is obtained from the impedance Z, the measured terminal voltage V, and the current I using the following equation (3).
V = Vo-I · Z (3)

  As described above, the moving average value of the current I is also used as a parameter for determining the weight w, and the calculation of the weight w and the impedance Z is facilitated. Since the internal impedance increases and the current change rate decreases, as will be described later, the weight w and the impedance Z are directly set to the corrected current change rate KΔI / Δt obtained by temperature-correcting the moving average value of the current I. Use to determine.

After the open circuit voltage Vo is estimated, the remaining capacity SOCv is calculated based on the electrochemical relationship in the battery. Specifically, a well-known Nernst equation describing the relationship between the electrode potential and the ion activity in an equilibrium state is applied, and the relationship between the open-circuit voltage Vo and the remaining capacity SOCv is expressed as the following (4). The formula can be obtained.
Vo = E + [(Rg · T / Ne · F) × lnSOCv / (100−SOCv)] + Y (4)
However, E: Standard electrode potential (E = 3.745 in the lithium ion battery of this embodiment)
Rg: Gas constant (8.314 J / mol-K)
T: temperature (absolute temperature K)
Ne: Ion valence (Ne = 1 in the lithium ion battery of this embodiment)
F: Faraday constant (96485 C / mol)

Note that Y in the equation (4) is a correction term and expresses the voltage-SOC characteristic at normal temperature as a function of SOC. If SOCv = X, it can be expressed by a cubic function of SOC as shown in the following equation (5).
Y = −10 ⁻⁶ X ³ + 9 · 10 ⁻⁵ X ² + 0.013X−0.7311 (5)

  From the above equation (4), it can be seen that the remaining capacity SOCv has a strong correlation not only with the open circuit voltage Vo but also with the temperature T. In this case, the remaining capacity SOCv can be calculated directly using the equation (4) using the open-circuit voltage Vo and the temperature T as parameters. Consideration of conditions is necessary.

  Therefore, when grasping the actual state of the battery from the relationship of the above equation (4), a charge / discharge test or simulation in each temperature range is performed based on the SOC-Vo characteristics at room temperature, and the measured data is obtained. accumulate. Then, a table of remaining capacity SOCv (remaining capacity table in FIG. 7 described later) that parameters open circuit voltage Vo and temperature T is created from the accumulated measured data, and the remaining capacity SOCv is obtained using this table.

Then, as shown in the above equation (1), the remaining capacity SOCc based on the current integration and the remaining capacity SOCv based on the estimated value of the open circuit voltage Vo are weighted and synthesized using the weight w, and the combined remaining capacity SOC is obtained. Is output to the display device 20. In the display device 20, the data discharge time interval for displaying the remaining capacity SOC on the display 22 is set as the moving average value of the current I and the temperature T by the function as the data discharge time interval setting means and the display output means in the arithmetic ECU 21. The remaining capacity SOC data is sorted according to the charge / discharge state of the battery and output as display data.

  Specifically, the remaining capacity SOC calculation process and the remaining capacity SOC display process based on the above SOC estimation algorithm are executed as software processes shown in the flowcharts of FIGS. Next, these software processes will be described.

  The flowchart shown in FIG. 4 shows a basic process of battery remaining capacity estimation that is executed at predetermined time intervals (for example, every 0.1 sec) in the arithmetic ECU 3 of the power supply device 1. In FIG. Therefore, the remaining capacity SOCv is calculated by estimating the open circuit voltage Vo following the calculation of the remaining capacity SOCc by current integration. However, actually, the remaining capacity SOCc and SOCv are calculated in parallel. Executed.

  When the process of FIG. 4 starts, first, in step S1, whether or not there is data input of the terminal voltage V, current I, temperature T of the battery 2 and the remaining capacity SOC (t−1) synthesized during the previous calculation process. Investigate. The terminal voltage V is the average value of the plurality of battery packs, and the current I is the sum of the currents of the plurality of battery packs. For example, data is acquired every 0.1 sec. The temperature T is acquired every 10 seconds, for example.

  As a result, if there is no new data input in step S1, this process is left as it is, and if there is new data input, the process proceeds from step S1 to step S2 to change the battery current capacity to the current capacity shown in FIG. Operate with reference to the table. This current capacity table stores a capacity ratio Ah ′ with respect to a rated capacity (for example, a rated current capacity when a predetermined number of cells in one battery pack is used as a reference unit) with the temperature T as a parameter. However, the current capacity decreases as the temperature becomes lower than the capacity ratio Ah ′ (= 1.00) at room temperature (25 ° C.), and therefore the value of the capacity ratio Ah ′ increases. Using the capacity ratio Ah ′ referred to from the current capacity table, the current capacity Ah at the temperature T for each measurement target is calculated.

  Next, the process proceeds to step S3, where the current capacity Ah obtained from the current capacity table, the input value of the current I, and the composite remaining capacity SOC (t-1) before one calculation cycle are used, and the current is The remaining capacity SOCc (t) is calculated by integration. Furthermore, in step S4, the current I is subjected to a moving average to obtain a current change rate ΔI / Δt per unit time. For example, when the current I is sampled every 0.1 sec and the current integration calculation cycle is every 0.5 sec, the moving average is a moving average of five pieces of data.

  In the subsequent step S5, the impedance Z of the battery equivalent circuit is calculated with reference to the impedance table shown in FIG. 6, and the open circuit voltage Vo of the battery 2 is estimated from the obtained impedance Z. This impedance table stores the impedance Z of the equivalent circuit with the corrected current change rate KΔI / Δt obtained by correcting the temperature of the current change rate ΔI / Δt (moving average value of the current I per unit time) and the temperature T as parameters. In general, when the corrected current change rate KΔI / Δt is the same, the impedance Z increases as the temperature T decreases. At the same temperature, the corrected current change rate KΔI / Δt is The impedance Z tends to increase as it decreases.

  Thereafter, the process proceeds to step S6, the voltage-SOC characteristic is calculated, and the remaining capacity SOCv is calculated. That is, the remaining capacity SOCv is calculated with reference to the remaining capacity table shown in FIG. 7 using the temperature T and the estimated open circuit voltage Vo as parameters. As described above, this remaining capacity table is a table created by grasping the electrochemical state in the battery based on the Nernst equation. In general, the lower the temperature T and the open circuit voltage Vo, the lower the capacity T. The remaining capacity SOCv tends to increase as the temperature T and the open circuit voltage Vo increase.

  6 and 7 show data in a range that is used under normal conditions, and data in other ranges is omitted.

  Thereafter, the process proceeds to step S7, and the weight w is calculated with reference to the weight table shown in FIG. The weight table is a one-dimensional table using the corrected current change rate KΔI / Δt as a parameter. In general, the smaller the corrected current change rate KΔI / Δt, that is, the smaller the battery load fluctuation, There is a tendency that the value of w is decreased to reduce the weight of the remaining capacity SOCc by current integration. In step S8, the remaining capacity SOCc obtained by current integration and the remaining capacity SOCv estimated by the open circuit voltage Vo are weighted and synthesized using a weight w in accordance with the above-described equation (1), and the remaining capacity SOC (t) is obtained. calculate.

  Here, when the influence of the presence / absence of the current moving average process in the calculation of the remaining capacity is compared, when the remaining capacity SOCv is calculated without performing the current moving average process, as shown in FIG. Under the influence of the components, a rapid change in the local remaining capacity SOCv occurs, which causes a decrease in the accuracy of the final combined remaining capacity SOC. On the other hand, when the remaining capacity SOCv is calculated by performing the current moving average process, as shown in FIG. 10, the influence of the spike component of the current is removed from the remaining capacity SOCv, and the load fluctuation is relatively small. It is possible to accurately grasp the remaining capacity below.

  The calculation result of the remaining capacity during actual driving is shown in FIG. 11, and the remaining capacity SOCc obtained by current integration and the remaining capacity SOC after synthesis are calculated in a state where the cell temperature is approximately 45 ° C. under relatively up-and-down driving conditions. Changes are shown. As shown in FIG. 11, in the state where the battery is repeatedly charged and discharged until the elapsed time of about 1500 seconds, the calculation result of the remaining capacity SOCc by current integration is reflected well in the combined remaining capacity SOC. Further, after the elapsed time of 1500 seconds, in a state where the charge amount of the battery tends to increase, the increase in the remaining capacity SOCc due to current integration tends to slow down and the error tends to increase, but the remaining capacity SOCv ( (Not shown) is reflected on the combined remaining capacity SOC with an increased weight, and the combined remaining capacity SOC rises as the amount of charge increases, and the change in the remaining capacity is accurately captured.

Next, processing for displaying the above remaining capacity SOC will be described with reference to the flowchart of FIG. The flowchart shown in FIG. 12 shows the remaining capacity display process executed at predetermined time intervals in the arithmetic ECU 21 of the display device 20, and is a post-combination operation that is calculated at the set time t by the arithmetic ECU 3 of the power supply device 1. The remaining capacity SOC (t) is input, the data output time interval adjustment and selection processing are performed according to the battery state, and then output to the display 22.

  In the remaining capacity display process shown in FIG. 12, first, in step S11, based on the moving average value of the current I and the cell temperature T, the discharge time interval of the combined remaining capacity SOC (t) (output to the display 22). Time interval). This is because data in the display 22 is displayed in a state where charging / discharging in a short time ascertained from the moving average value of the current I is repeated or when the battery at low temperatures ascertained from the cell temperature T is not stable. This is because by adjusting the discharge time interval, transient elements are eliminated and display fluctuation is reduced.

  The data release time interval to the display 22 is obtained by, for example, performing an experiment or simulation based on human vision using the moving average value of the current I and the cell temperature T as parameters, and obtaining an optimal display interval that is easy to visually recognize. Create a map and refer to this map to find it. In general, as the moving average value of the current I increases and charging / discharging becomes more intense, the display time interval is widened, and as the temperature T decreases and the battery stability decreases, the display time interval decreases. Set to the spreading characteristics. For example, when the calculation period of the remaining capacity SOC is every 0.1 sec, when the charge / discharge is intense and the temperature is extremely low, the data display interval is expanded to about 1 to several sec.

  Next, it progresses to step S12 and it is judged whether it is at the time of the power sudden change when the power amount shown by the maximum electric power which the battery 2 can input / output changes suddenly. During this sudden power change, for example, although the battery should be in a charged state and the remaining capacity should originally show an upward trend, the discharge current increases rapidly due to a sudden change in the load, and the battery temporarily Since this is a transitional state in which the amount of power decreases, and the display of the remaining capacity in such a state is meaningless, the process exits step S12 and the previous display value is updated without updating the display value. Hold.

  On the other hand, if the power is not suddenly changed in step S12, the process proceeds from step S12 to step S13, and it is checked whether the battery is in a power generation state for charging the battery. When the power generation state is set, the process proceeds from step S13 to step S14, and the latest remaining capacity SOC (t) and 1 in the time series data string of the remaining capacity SOC input from the arithmetic ECU 3 of the power supply unit 1 are set. It is checked whether the condition of SOC (t)> SOC (t-1) is satisfied by comparing with the remaining capacity SOC (t-1) before the calculation cycle. If the power generation state is not established, the process proceeds from step S13 to step S15, and the SOC (t) is compared by comparing the latest remaining capacity SOC (t) with the remaining capacity SOC (t-1) one calculation cycle before. <Check whether the condition of SOC (t-1) is satisfied.

Processing in steps S14, S15 monitors the rise and fall of the remaining capacity SOC in accordance with the status of the charging and discharging of the battery, a treatment that limits the uptake of finely changing the data, in this embodiment, the remaining capacity Data selection is performed by sequentially comparing SOC data in time series. That is, when the condition of SOC (t)> SOC (t−1) is not satisfied in step S14 even though the battery is in the power generation state and the remaining capacity SOC is increasing, or the battery is in the power generation state. If the condition of SOC (t) <SOC (t-1) is not satisfied in step S15 even though the remaining capacity SOC is decreasing, the acquisition of the latest data SOC (t) is stopped. The process exits and the current display data is retained.

  If the condition of SOC (t)> SOC (t−1) is satisfied in step S14, or if the condition of SOC (t) <SOC (t−1) is satisfied in step S15, step S14 is performed. Or it progresses to step S16 from step S15, the newest synthetic | combination residual capacity SOC (t) is output, a display value is updated, and a process is exited. The display output of the remaining capacity SOC (t) is performed at the time interval set in step S11, and when the battery is in the charged state, fine data that partially falls in a short time is ignored and data in the upward direction is ignored. Only when the display value is updated and the battery is in a discharged state, fine data that partially rises in a short time is ignored, and the display value is updated only with the data in the downward direction.

As described above, in the present embodiment, the remaining capacity SOCc based on the current integration and the remaining capacity SOCv based on the estimated value of the open circuit voltage are weighted and combined using the weight w set according to the battery usage state. Then, while obtaining a high-accuracy remaining capacity that takes advantage of both advantages, the fine remaining capacity data is selected and output to the display 22 at time intervals set according to the state of charge / discharge of the battery. As a result, it is possible to reduce the display wobbling by excluding too small data unnecessary for a general driver, and to easily recognize the remaining energy amount that can actually be used.

Configuration diagram showing battery remaining capacity calculation and display system Block diagram showing the remaining battery capacity estimation algorithm Circuit diagram showing equivalent circuit model Flow chart showing battery remaining capacity calculation processing Illustration of current capacity table Illustration of impedance table Explanation of remaining capacity table Illustration of weight table Explanatory diagram showing the remaining capacity without the current moving average process Explanatory diagram showing the remaining capacity with current moving average processing Explanatory drawing showing the remaining capacity calculation result during actual vehicle running Flowchart showing battery remaining capacity display processing

Explanation of symbols

1 Power unit 2 Battery 3 Calculation unit (remaining capacity calculation means)
21 arithmetic unit (data release time interval setting means, display output means)
I charge / discharge current SOC remaining capacity SOCc remaining capacity (first remaining capacity)
SOCv remaining capacity (second remaining capacity)
Vo open circuit voltage Z impedance w weight
Agent Patent Attorney Susumu Ito

Claims (3)

Using a weight that is set according to the usage status of the power storage device, the first remaining capacity based on the integrated value of the charge / discharge current of the power storage device and the second remaining capacity based on the estimated open circuit voltage of the power storage device A remaining capacity calculating means for calculating the remaining capacity of the power storage device,
Data discharge time interval setting means for setting a data discharge time interval for displaying the remaining capacity calculated by the remaining capacity calculation means based on the change and temperature of the charge / discharge current of the power storage device;
When the power storage device is in a charged state, the remaining capacity data calculated by the remaining capacity calculating means is sequentially compared in time series to select only data that tends to increase, and when the power storage device is in a discharged state, The remaining capacity data calculated by the remaining capacity calculating means is sequentially compared in time series to select only the data that tends to decrease, and the selected data is selected at the data release time interval set by the data release time interval setting means. A remaining capacity display device for an electricity storage device, comprising: a display output means for outputting. The data release time interval setting means includes:
2. The remaining capacity display device for an electricity storage device according to claim 1, wherein the data release time interval is set based on a moving average value and a temperature of a charge / discharge current of the electricity storage device. The remaining capacity calculating means is
The open circuit voltage of the power storage device is estimated based on an electrochemical relationship inside the power storage device, and the weight is set based on a moving average value of charge / discharge current of the power storage device. 3. A remaining capacity display device for an electricity storage device according to 1 or 2 .

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