JP4833788B2 - Battery voltage prediction method, program, state monitoring device, and power supply system - Google Patents

Description

  The present invention relates to a battery voltage prediction method, a program for realizing the method, a voltage prediction apparatus, and a power supply system.

  In order for electrical components, etc., required for running an automobile to function properly, the voltage between terminals when a load current is passed from a battery mounted on the vehicle must be maintained at a predetermined voltage value or higher. It becomes. Therefore, there is a strong demand for a technique that can predict a change in the voltage between terminals in an arbitrary charge / discharge state of the battery.

  As a conventional technique for predicting a change in the voltage between terminals of a battery, for example, in Non-Patent Document 1, a battery is simulated as an electrical circuit using an equivalent circuit 101 as shown in FIG. A technique for predicting the voltage between terminals of a battery by calculating the behavior of the voltage between terminals A and B is proposed. The parameters of each circuit element constituting the equivalent circuit are determined so that the impedance frequency characteristic calculated from the equivalent circuit matches the impedance frequency characteristic obtained from voltage fluctuation when an alternating current is passed through an actual battery. Is done.

  Further, a conventional technique in which the calculation method of the voltage between terminals is changed according to the state of the battery is already known. This is because the physical process different from that in the case of normal charge / discharge becomes dominant in the overcharged state. For example, in Non-Patent Document 1, the inter-terminal voltage is usually calculated using the equivalent circuit of FIG. 10, but the above-described equivalent circuit is not used when the battery is overcharged, and a water electrolysis reaction model is used. To calculate the voltage between terminals.

  Based on the same concept, Patent Document 1 proposes a method for predicting state quantities such as OCV (Open Circuit Voltage), state of charge (SOC), and state of health (SOH), A method of selecting a calculation method of the voltage between terminals according to the operating state of the battery is disclosed.

Further, Patent Documents 2 to 4 propose methods for predicting voltage fluctuations in a state where the current after charge / discharge is zero. Specifically, a plurality of inter-terminal voltages are measured within a predetermined time immediately after the end of charging / discharging, and the adjustment parameters are determined by fitting the plurality of measured voltages with a predetermined function including the adjustment parameters. After the adjustment parameter is determined, the OCV is estimated using this function.
JP 2003-217686 A JP-A-7-98367 JP 2002-234408 A JP 2005-43339 A S. Buller, E. Karden, RW De Doncker, (2003), “Impedance-Based Non-Linear Dynamic Battery Modeling for Automotive Applications”, J. Power. Sources, 113, pp. 422-430.

  However, the conventional battery voltage prediction method has the following problems. This will be described below using an example in which the voltage between the terminals of the battery is predicted by the equivalent circuit of FIG. 10 shown in Non-Patent Document 1. A case will be described in which a current 102 having a time waveform as shown in FIG. 11, for example, needs to be supplied from a vehicle-mounted battery to any electrical component. In the current waveform 102 shown in FIG. 11, when the time after the start of power feeding is t, the current flows only for 0 <t ≦ 328.5 sec, and the current is 0 at t> 328.5 sec.

  FIG. 12 shows the amount of change in voltage between terminals when the current shown in FIG. 11 is supplied from the vehicle battery (hereinafter referred to as voltage change). In the figure, a measured value of the voltage change is indicated by 103, and a predicted value of the voltage change predicted by using the equivalent circuit 101 shown in FIG. However, it is assumed that the voltage change immediately before the current shown in FIG. In FIG. 12, in the time range of 0 <t ≦ 328.5 sec where the current is supplied, the measured value 103 of the voltage change and the predicted value 104 show a good match, while the current becomes 0> t> The difference between the two is large in the 328.5 sec time range.

  As a physical phenomenon inside the battery, activation polarization and concentration polarization are generated while a current is flowing, whereas concentration polarization becomes dominant when the current becomes zero. That is, the physical phenomenon that occurs inside the battery differs depending on whether current is flowing or not. In Non-Patent Document 1, it is considered that the equivalent circuit shown in FIG. 10 is optimized including the physical phenomena of both activation polarization and concentration polarization that occur when the current is not zero. The voltage between terminals is predicted using a circuit. Therefore, a large deviation occurs with respect to the voltage change after the current becomes zero.

  In addition, regarding the above problems, Patent Document 1 does not describe a specific method for calculating the inter-terminal voltage after the time when the current becomes 0, and thus realizes accurate prediction of the inter-terminal voltage. It was difficult to do.

  Also, the functions used for fitting in Patent Documents 2 to 4 are not shown to be created based on the physical phenomenon of concentration polarization.

  Therefore, the present invention has been made to solve these problems, a battery voltage prediction method, a program, a state monitoring device, and a power source for predicting the voltage between terminals when the current is 0 based on the concentration polarization. The purpose is to provide a system.

が事前に与えられ、前記バッテリーから放電を開始する前に前記ＯＣＶを測定し、前記バッテリーから放電を開始すると前記測定されたＯＣＶを初期値として前記端子間電圧を所定の電気的等価回路を用いて算出し、前記バッテリーの電流が０または予め設定された一定電流値になると、前記式（３）を用いて前記変動分η(t)を予測し、前記変動分η(t)を前記初期値ＯＣＶに加算することで前記端子間電圧を予測することを特徴とする。 According to a first aspect of the battery voltage prediction method of the present invention, c (t) is a function that represents a change in the concentration of the electrolyte contained in the battery over time, and the OCV of the battery terminal voltage at the elapsed time t. When the variation from (Open Circuit Voltage) is η (t) and the separately defined parameter is α, the function c (t) converges to a predetermined electrolyte concentration c _eq over time t And calculating the variation η (t) including the function c (t)

The OCV is measured before starting discharging from the battery, and when discharging starts from the battery, the voltage between the terminals is set to a predetermined electrical equivalent circuit using the measured OCV as an initial value. When the battery current reaches 0 or a preset constant current value, the variation η (t) is predicted using the equation (3), and the variation η (t) is calculated as the initial value. The terminal voltage is predicted by adding to the value OCV .

Another aspect of the battery voltage prediction method of the present invention is characterized in that the function c (t) is a solution of a predetermined diffusion equation relating to the concentration of the electrolytic solution.

Another aspect of the battery voltage prediction method of the present invention is characterized in that the function c (t) is created by using the concentration of the electrolytic solution obtained by actual measurement.

Another aspect of the battery voltage prediction method of the present invention is characterized in that the function c (t) is created using the concentration of the electrolytic solution calculated by a predetermined electrochemical model.

In another aspect of the battery voltage predicting method of the present invention, the function c (t) is calculated as follows: the current flowing from the battery to the load becomes 0 or a preset constant current value, and the variation η It is characterized in that (t) is monotonously decreased and asymptotically approaches zero.

を用いて予測することを特徴とする。 In another aspect of the battery voltage prediction method of the present invention, the elapsed time when the current flowing from the battery to the load becomes 0 or a preset constant current value is t _0, and A and B are set in advance. When the parameter is determined, the variation η (t) is expressed by the following equation:

It is characterized by predicting using.

を用いて予測し、前記変動分η(t)を前記初期値ＯＣＶに加算することで前記端子間電圧を予測することを特徴とする。 According to another aspect of the battery voltage predicting method of the present invention , the OCV is measured before starting the discharge from the battery, and when the discharge from the battery is started, the voltage between the terminals of the battery is determined using the measured OCV as an initial value. When the current of the battery is 0 or a preset constant current value is calculated using a predetermined electrical equivalent circuit, the elapsed time at that time is set to t _0, and the parameter A based on the charge rate and temperature of the battery , B, and using the parameters A, B, the variation η (t) of the inter-terminal voltage from the OCV is expressed by the following equation:

And the terminal voltage is predicted by adding the variation η (t) to the initial value OCV .

  ADVANTAGE OF THE INVENTION According to this invention, the voltage prediction method of the battery which estimates the voltage between terminals when an electric current is 0 based on concentration polarization, and the program which implement | achieves this with a computer can be provided. Moreover, the voltage prediction apparatus and power supply system using this voltage prediction method can be provided. In the battery voltage prediction method according to the present invention, the calculation method based on the physical phenomenon of concentration polarization that is dominant when the current is 0 is used, so that the voltage between terminals can be predicted with high accuracy. .

A battery voltage prediction method, a program, a voltage prediction apparatus, and a power supply system according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.
The battery voltage prediction method according to the present invention is characterized in that when the battery current is zero, the terminal voltage is predicted based on the concentration polarization.

FIG. 1 is a schematic diagram for explaining a battery voltage prediction method according to an embodiment of the present invention. The battery voltage prediction method of the present embodiment has two types of calculation methods for predicting a voltage change from the OCV: an equivalent circuit calculation method 10 and a concentration polarization calculation method 20. The battery terminal voltage 30 is calculated by adding the voltage change calculated by any of the calculation methods to the OCV 40. The selection of which one of the equivalent circuit calculation method 10 and the concentration polarization calculation method 20 is used is determined based on the battery current 50. When the current 50 is 0, the concentration polarization calculation method 20 is selected. In other cases, the equivalent circuit calculation method 10 is selected.

と表すことができる。ここで、c_eqは、電流が０になってから時間が十分経過して平衡状態になったときの濃度を表わしており、αは初期条件等から定まるパラメータである。 An example of the calculation method of the concentration polarization calculation method 20 will be described below. It is known that the relational expression expressed by the Nernst equation holds between the battery terminal voltage and the electrolyte (sulfuric acid) concentration. The amount of change in voltage between terminals at the time t from the OCV, that is, when the voltage change is η (t) and the electrolyte concentration is c (t), the voltage change η (t) is

It can be expressed as. Here, c _eq represents the concentration when a sufficient time has elapsed since the current became zero and the equilibrium state is reached, and α is a parameter determined from the initial conditions and the like.

ここで、Ｄは拡散係数を示す。上記拡散方程式に対し、例えばバッテリーが充放電を終了する時点（時刻t0とする）の電解液濃度ｃ(x,t0)を初期条件として与えることにより、式（５）の解を求めることができる。初期条件の一例として、下記の値を用いた例を以下に説明する。
c(x, t=t0) = c1 （一定値） at 0≦x≦d
c(x, t=t0) = ceq （一定値） at x＞d The electrolyte concentration c (t) in the battery changes according to the diffusion equation shown in the following equation (5), where x is the distance from the electrode surface.

Here, D indicates a diffusion coefficient. For the above diffusion equation, for example, by giving, as an initial condition, the electrolyte concentration c (x, t0) at the time when the battery finishes charging and discharging (time t0), the solution of equation (5) can be obtained. . As an example of the initial condition, an example using the following values will be described below.
c (x, t = t0) = c1 (constant value) at 0 ≦ x ≦ d
c (x, t = t0) = ceq (constant value) at x> d

式（６）においてｘ＝０とすると、電極面での電解液濃度ｃ(0,t)が与えられ、これは次式のように表わされる。

When equation (5) is solved under the above initial conditions, electrolyte concentration c (t) is given by equation (6) below.

If x = 0 in the equation (6), an electrolyte concentration c (0, t) on the electrode surface is given, which is expressed as the following equation.

ここで、Ａ、Ｂは、初期条件や拡散係数Ｄ等から決まるパラメータである。
Since c (t) included in equation (3) corresponds to c (0, t) in equation (7) above, by substituting this into equation (3) , voltage change η (t) It can be expressed as a function of time t as in the equation.

Here, A and B are parameters determined from the initial conditions, the diffusion coefficient D, and the like.

By using Equation (4), the temporal change in the voltage between the terminals can be calculated from the voltage change η (t). Therefore, it is possible to predict the voltage between the terminals after the battery current becomes zero using Equation (4). The equation (4) is derived using the equation (6) as a solution of the diffusion equation, but the solution of the diffusion equation of the equation (5) is the initial condition, boundary condition, and the nature of the diffusion (normal diffusion or abnormal) Since it differs depending on whether it is diffusion) or the like, the solution of the diffusion equation of equation (5) other than equation (6) may be used.

  In addition, it is good also as calculating | requiring based on the measured value of electrolyte solution concentration instead of calculating | requiring c (t) in Formula (3) using a diffusion equation. The c (t) may be obtained by another calculation method. For example, there is a method for performing precise calculation based on an electrochemical model.

  As described above, for example, equation (4) can be used as the calculation method of the concentration polarization calculation method 20. In the battery voltage prediction method of the present embodiment, the equivalent circuit calculation method 10 or the concentration polarization calculation method 20 is selected according to the state of the current 50 to predict a voltage change, and the predicted voltage change is added to the OCV. The voltage between the terminals of the battery is predicted. As described above, when the current 50 in which the concentration polarization is dominant is 0, the concentration polarization calculation method 20 capable of accurately predicting the temporal change of the concentration polarization is selected. The voltage change can be predicted with high accuracy.

  The parameters A and B used in the equation (4) can be determined and used in advance based on data obtained by measuring the battery under predetermined conditions. For example, a voltage curve can be obtained by measuring a change in voltage after the end of charging / discharging, and parameters A and B can be determined based on this. Also, a plurality of parameters A and B may be set in correspondence with the charging rate and temperature of the battery at the time of measurement, and the parameters A and B may be determined and used from the charging rate and temperature of the battery at the time of prediction. .

  Furthermore, when the charging rate, temperature, or the like exceeds a predetermined range, it may be preferable to determine the parameters A and B depending on the charge / discharge conditions until the current becomes zero. In this case, it is preferable to determine the parameters A and B in correspondence with physical property values (for example, η (t0)) depending on the charging / discharging conditions in addition to the charging rate and temperature.

  The battery voltage prediction method of this embodiment will be described in more detail with reference to the flowchart shown in FIG. Prior to starting the prediction of the voltage between the terminals of the battery, the initial state quantity of the battery is first input in step S1. The initial state quantity includes, for example, a charging rate before being discharged from the battery to the load, a battery temperature, and an OCV. Subsequently, in step S2, calculation conditions for performing prediction calculation of the inter-terminal voltage are input. As calculation conditions, there are a time length T of a prediction period, a prediction time interval Δt, and the like.

Next, in step S3, the load current pattern I (ti) in the prediction period is input. The load current pattern I (ti) can be generated in advance for each load, for example, and stored in the storage unit, and input from the storage unit in step S3. Here, the time ti is a discrete time given by the following equation from the predicted time interval Δt.
ti = (i-1) * Δt i = 1,2,3, ..., N
tN = (N-1) * Δt = T

  In step S4, i = 1 is set as an initial setting for starting the prediction calculation. From step 5 onward, the time variation of the inter-terminal voltage with respect to the load current pattern I (ti) input in step S3 is sequentially predicted every prediction time interval Δt until the end of the prediction period T.

  In step S5, it is first determined whether or not the current value I (ti) of the load current pattern is 0, and a prediction calculation method for the voltage between terminals is selected. That is, when the current value I (ti) is 0, the concentration polarization calculation method of step S6a is selected, while when the current value I (ti) is not 0, the equivalent circuit calculation method of step S6b is selected. . When the concentration polarization calculation method is selected by the determination in step S5, for example, equation (4) is read from the storage unit in step S6a. If the equivalent circuit calculation method is selected by the determination in step S5, a calculation formula based on the equivalent circuit is read from the storage unit in step S6b.

  Subsequently, when the process proceeds to step S7a, parameters used in the concentration polarization calculation formula, for example, parameters A and B in formula (4) are determined based on the battery charge rate, temperature, and the like. When the process proceeds to step 7b, the circuit constant used in the equivalent circuit is determined.

  When the parameter used in the formula for calculating the inter-terminal voltage is determined in step S7a or S7b, the inter-terminal voltage V (ti) at time ti is calculated in step S8a or S8b. In step S9, the inter-terminal voltage V (ti) calculated in step S8a or S8b is stored in a predetermined storage unit.

  In step S10, it is determined whether the calculation step i has reached the last calculation step N (i = N). If the calculation step i has not reached the final calculation step N, the calculation step is advanced in step S11, and the processing from step S5 is advanced again. On the other hand, if it is determined in step S10 that the calculation step i has reached the last calculation step N, all prediction calculations are terminated. At this time, the prediction up to the time length T of the prediction period is completed, and the predicted inter-terminal voltage V (ti) (i = 1 to N) is stored in a predetermined storage unit.

  An example in which the voltage between terminals is predicted using the battery voltage prediction method of this embodiment will be described below. As a first embodiment, a case will be described in which the current value 102 shown in FIG. 11 is used for the load current pattern I (ti) and the equation (4) is used for the voltage change calculation formula in the concentration polarization calculation method 20. In the load current pattern 102 shown in FIG. 11, the time t0 at which discharge is started is 0, the current is discharged for 328.5 seconds after the start of discharge, and the current is 0 after 328.5 seconds.

  If the time when the discharge ends and the current becomes 0 is t0 = tk (1 <k <N), the equivalent circuit calculation method 10 is used during 0 ≦ ti ≦ tk (1 ≦ i ≦ k), and tk < The concentration polarization calculation method 20 is used during ti ≦ tN (k ≦ i ≦ N). In this embodiment, the formula (4) is used for the prediction by the concentration polarization calculation method 20. Of the terms included in Equation (4), η (t0) is calculated from the terminal voltage V (tk) calculated last by the equivalent circuit calculation method 10 and used. In this embodiment, η (t0) = − 0.330V.

Of the parameters included in Equation (4), A and B are determined as follows. The parameter A is assumed to use a preset value corresponding to the charging rate and the temperature. Here, it is assumed that the battery is kept constant at a charging rate of 98% and a temperature of 25 ° C. The value is 6.71. The parameter B uses a value calculated from the following equation determined depending on η (t0). In this embodiment, B = 0.643.

  The parameter B can be determined depending on the voltage change η (t0) when the current becomes 0 as shown in the equation (8). In this example, when setting the parameter B in advance, the current was set to 0 after discharging with a plurality of different current waveforms under the conditions of a charging rate of 98% and a temperature of 25 ° C. Each subsequent voltage curve is measured. The parameter B is calculated by fitting the measured voltage curve with the equation (4).

  FIG. 3 shows an example in which the parameter B calculated as described above is plotted against the voltage change η (t0) when the current becomes zero. From the figure, it can be seen that the parameter B changes depending on the voltage change η (t0). Expression (8) is a relational expression obtained by linearly approximating the parameter B shown in FIG. 3 with −1 / η (t0). In this embodiment, the parameter B is calculated from the equation (8). For example, the parameter B shown in FIG. 3 is averaged, and this average value is set as the value of the parameter B independent of η (t0). Is also possible.

  FIG. 4 shows the result of predicting the voltage change η (t) of the battery in this example. As shown in the figure, the predicted value 61 of the voltage change in this example shows a very good match with the measured value 103. In the predicted value 104 calculated only with the conventional equivalent circuit, the deviation from the measured value 103 was large between tk <ti ≦ tN (k ≦ i ≦ N) where the current becomes 0, but this implementation In the prediction result 61 of the example, the measured value 103 agrees very well even during tk <ti ≦ tN (k ≦ i ≦ N).

Another embodiment of the battery voltage prediction method of the present invention will be described below. In the first embodiment, the change from the OCV of the inter-terminal voltage is calculated using the voltage change η (t) in the equation (4) derived from the Nernst equation in the equation (3) and the diffusion equation in the equation (5). It was calculated. Instead, in this embodiment, another function having the same characteristic as the change characteristic of Expression (4) is used. That is, a function having the following change characteristics is used.
(1) Monotonic change at t> t0 (2) Convergence to 0 at t → ∞

ここで、パラメータＡ、Ｂは、事前に設定して用いるようにすることができる。 The characteristic of (1) is monotonously increased when a discharge current is flowing at t ≦ t0, and is monotonously decreased when a charging current is flowing. As an example of such a function, the following function can be used.

Here, the parameters A and B can be set and used in advance.

  As an example of the battery voltage prediction method of the present embodiment, a second example using Equation (1) will be described below. As the voltage change η (t0) at time t0 when the current becomes 0, the voltage change η (t0) at time t0 calculated by the equivalent circuit calculation method 10 can be used as in the first embodiment. In this embodiment, the value of η (t0) is −0.330V.

  The parameter A in the equation (1) can be determined depending on the charging rate and temperature, and assuming that these are maintained at predetermined values, in this embodiment, the value of the parameter A is set to −5.30. It is said. The parameter B is set based on voltage curves measured with a plurality of different current waveforms, as in the first embodiment. As an example, under the conditions of a charging rate of 98% and a temperature of 25 ° C., the discharge is performed with a plurality of different current waveforms, the current is set to 0, and the voltage curve after the current becomes 0 is measured.

  FIG. 5 shows the result of calculating the parameter B by fitting the measured voltage curve with the equation (1). In this embodiment, the average value of the data surrounded by the ellipse range 62 among the calculated parameters B is used as the value of the parameter B, and B = 0.0928. The result of predicting the voltage change η (t) using such parameter values is indicated by a predicted value 63 in FIG. Again, the load current pattern shown in FIG. 11 is used. Similar to the first embodiment, this embodiment also greatly improves the prediction accuracy compared to the prediction result obtained only by the conventional equivalent circuit calculation method.

この場合には、B=0.0988となる。 In the above embodiment, the parameter B is a constant value that does not depend on η (t0), but may be determined depending on η (t0) as in the first embodiment. That is, as shown in FIG. 7, the parameter B can be approximated by a linear expression of η (t0) and can be expressed as the following expression.

In this case, B = 0.0988.

  A result of prediction using the value of the parameter B calculated based on the equation (9) is indicated by a predicted value 64 in FIG. Again, the load current pattern shown in FIG. 11 is used. Similar to the above embodiments, in this embodiment, the prediction accuracy is greatly improved as compared with the prediction result obtained by using only the conventional equivalent circuit calculation method.

  The voltage prediction method according to the present invention can be a computer-executable program. As an embodiment of the voltage prediction program of the present invention, a program is created so that each step of the flowchart shown in FIG. 2 is executed on a computer. In this case, the initial battery state quantity input in step S1, the calculation conditions input in step S2, and the load current pattern input in step S3 are stored in advance in a storage device connected to the computer, for example. be able to. Or you may make it input from the outside of a computer. For example, it is input from a GUI (Graphical User Interface) on the computer.

In addition, in steps S7a and S7b, data used to determine parameters of each calculation formula can also be stored in the storage device in advance.
Furthermore, in step S9, the predicted inter-terminal voltage V (ti) can also be stored in the storage device.

The power supply system and state monitoring apparatus of the present invention that monitors the discharge capability of the battery using any one of the voltage prediction methods of the present invention described above will be described below.
FIG. 9 is a block diagram showing the configuration of the power supply system and state monitoring apparatus according to the embodiment of the present invention. The power supply system 70 includes a battery 1 and a state monitoring device 71, and the state monitoring device 71 includes a voltage between terminals, a current, And a control unit 72 for inputting temperature, a storage unit 73 connected to the control unit 72, and a display 74 and a buzzer 75 for providing information to users and the like. The battery 1 is connected to an electrical component 5 serving as a load.

  Examples of the battery 1 include secondary batteries such as a lead storage battery, a lithium ion battery, and a nickel metal hydride battery. The control unit 72 predicts a voltage change of the battery 1 based on measurement data input from each sensor, and monitors whether a voltage necessary for the load to operate normally is secured. For this purpose, the control unit 72 predicts the inter-terminal voltage using any one of the voltage prediction methods described above.

  For example, the flow of processing by the control unit 72 will be described below when the state of the battery 1 is monitored using the voltage prediction method shown in FIG. First, in the input of the battery initial state quantity in step S1, the voltage between terminals, current, and temperature are input from each sensor. Based on these measurement data, the OCV and the charging rate necessary for predicting the voltage between terminals are calculated. As the charging rate, a value before discharging from the battery 1 to the load is obtained.

  In the input of the calculation conditions in step S2 shown in FIG. 2, calculation conditions such as the time length T of the prediction period and the prediction time interval Δt used for the voltage prediction calculation are input from the storage unit 73. Further, in the input of the load current pattern in step S3, the current pattern for each load is stored in the storage unit 73 in advance, and the current pattern of the starting load is selected and input from this.

  In the prediction calculation after step S4, in the parameter determination of the calculation formula of step S7a or S7b, for example, the values of parameters A and B of formula (5) are determined from the battery temperature, charge rate, etc. input or calculated in step S1. . The values of the parameters A and B can be calculated using a function depending on the battery temperature, the charging rate, etc., or a function stored in advance in the storage unit 73 in the form of a table.

  In the storage of the inter-terminal voltage V (t) in step S9, the calculated inter-terminal voltage V (t) is stored in a predetermined position in the storage unit 73 in time series. In this manner, the predicted inter-terminal voltage V (t) is stored in the storage unit 73 in a lump so that the predicted inter-terminal voltage V (t) is calculated after all the prediction calculations are completed. The data can be read from the storage unit 73 in a lump and displayed on the display 74 for monitoring.

  As monitoring by the state monitoring device 70 of the present embodiment, it is checked whether the voltage necessary for operating the load is secured by using the prediction result of the inter-terminal voltage V (t), and the terminal is below the necessary voltage. When the inter-voltage is lowered, for example, an alarm can be displayed on the display 74 or a buzzer 75 can be sounded. Further, even when the necessary voltage is maintained, a graph of the predicted voltage V (t) between terminals may be displayed on the display 74.

  The state monitoring device 70 of the present embodiment can be applied to various batteries used for various purposes. As an example, the present invention can be applied to a battery mounted on an automobile, a battery for a computer power supply, a battery for a mobile phone, a power source used in a UPS (Uninterruptible Power Supply System), a battery for an information communication system, and the like. .

  In the voltage prediction method and the state monitoring apparatus of the present invention described above, the parameters of the calculation formula (for example, the formula (4) and the formula (1)) used for the prediction of the inter-terminal voltage are used as the relational expressions or tables created in advance. I was going to decide from. On the other hand, as another embodiment of the voltage predicting method or the state monitoring apparatus of the present invention, it is possible to determine the parameter from the measurement data.

  For example, by measuring the voltage between terminals a plurality of times within a predetermined time after the end of charging / discharging, and fitting the measured voltage with Equation (4) or Equation (1), the parameters of Equation (4) or Equation (1) The values of A and B are determined. By using the parameter value determined in this way, the subsequent voltage change can be predicted by the equation (4) or the equation (1).

  In the above, the concentration polarization calculation method 20 shown in FIG. 1 has been applied only to the prediction of the voltage between the terminals when the current is 0, but as still another embodiment of the voltage prediction method and the state monitoring device of the present invention, It is also possible to make it applicable even when a current flows under a predetermined condition. That is, when the current is held at a constant value and a predetermined time or more elapses, the activation polarization reaches a substantially steady state, so that the subsequent voltage change can be evaluated only by the concentration polarization.

  In an embodiment applied to the case where the concentration polarization calculation method 20 is applied even when a current is flowing, in the voltage prediction method shown in FIG. 1, it is determined whether or not the current 50 holds a constant value for a predetermined time or more. . As a result, if it is determined that the current 50 has held a constant value for a predetermined time or more, the concentration polarization calculation method 20 is selected, and otherwise, the equivalent circuit calculation method 10 is selected. Thus, when the current 50 is 0 or a constant value for a predetermined time or more, it is possible to accurately predict the change in the voltage between the terminals using the concentration polarization calculation method 20.

Note that the description in the present embodiment shows an example of a battery voltage prediction method, a program, a state monitoring device, and a power supply system according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the battery voltage prediction method, the program, the state monitoring device, and the power supply system in the present embodiment can be appropriately changed without departing from the spirit of the present invention.
Furthermore, the battery voltage prediction method and program according to the present invention can be applied to battery design, manufacture, maintenance, and the like.

It is a schematic diagram for demonstrating the voltage prediction method of the battery which concerns on embodiment of this invention. 3 is a flowchart of a battery voltage prediction method according to an embodiment of the present invention. It is a graph which shows the change of the parameter B with respect to voltage change (eta) (t0). It is a graph which shows the Example which estimated the voltage change of the battery. It is a graph which shows another change of parameter B to voltage change eta (t0). It is a graph which shows another Example which estimated the voltage change of the battery. It is the graph which approximated another change of parameter B to voltage change eta (t0) with a straight line. It is a graph which shows another Example which estimated the voltage change of the battery. 1 is a block diagram of a power supply system and a state monitoring device according to an embodiment of the present invention. It is a figure which shows the equivalent circuit of a battery. It is a graph which shows a load current waveform. It is a graph which shows the change of the voltage between terminals when a load current is supplied.

Explanation of symbols

1 battery 2 voltmeter 3 ammeter 4 temperature sensor 5 electrical equipment

10 Equivalent circuit calculation method 20 Concentration polarization calculation method 30 Terminal voltage 40 OCV
50 Current 61, 63, 64 Voltage change predicted value 62 Data range 70 Power supply system 71 Status monitoring device 72 Control unit 73 Storage unit 74 Display 75 Buzzer 101 Equivalent circuit 102 Current waveform 103 Voltage change measured value 104 Voltage change predicted value

Claims (7)

The function representing the time variation of the concentration of the electrolyte incorporated in the battery as c (t), the variation from the OCV (Open Circuit Voltage) of the terminal voltage of the battery at the elapsed time t and eta (t) When the separately defined parameter is α, the function c (t) converges to a predetermined electrolyte concentration c _eq over time t, and includes the function c (t). The following formula to calculate η (t)

Is given in advance,
Measure the OCV before starting to discharge from the battery,
When discharging from the battery is started, the measured OCV is used as an initial value to calculate the inter-terminal voltage using a predetermined electrical equivalent circuit,
When the current of the battery reaches 0 or a preset constant current value, the variation η (t) is predicted using the equation (3),
A battery voltage prediction method , wherein the terminal voltage is predicted by adding the variation η (t) to the initial value OCV . 2. The battery voltage prediction method according to claim 1 , wherein the function c (t) is a solution of a predetermined diffusion equation related to the concentration of the electrolytic solution. The battery voltage prediction method according to claim 1 , wherein the function c (t) is created using a concentration of the electrolytic solution obtained by actual measurement. The battery voltage prediction method according to claim 1 , wherein the function c (t) is created using a concentration of the electrolytic solution calculated by a predetermined electrochemical model. The function c (t) is such that the variation η (t) monotonously decreases and gradually approaches 0 after the time when the current flowing from the battery to the load becomes 0 or a preset constant current value. The battery voltage prediction method according to claim 1 , wherein When the elapsed time when the current flowing from the battery to the load becomes 0 or a preset constant current value is t ₀ and A and B are predetermined parameters, the variation η (t) The following formula

The battery voltage prediction method according to claim 1 , wherein the battery voltage prediction method is used. Measure OCV before starting to discharge from the battery,
When discharging from the battery is started, the measured OCV is used as an initial value to calculate the terminal voltage of the battery using a predetermined electrical equivalent circuit,
When the current of the battery reaches 0 or a preset constant current value, the elapsed time at that time is set to t ₀ , parameters A and B are determined based on the charging rate and temperature of the battery, and the parameters A and B are The variation η (t) of the inter-terminal voltage from the OCV is expressed by the following equation:

Predict using
A battery voltage prediction method , wherein the terminal voltage is predicted by adding the variation η (t) to the initial value OCV .

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