JP2013118056A - Power storage system and temperature estimation method of storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a temperature corresponding to internal resistance of a storage element.SOLUTION: A power storage system comprises: a storage element (11) which performs charging/discharging; a temperature sensor (23) which acquires a temperature outside the storage element; and a controller (30) which calculates a temperature at a reference point indicating a temperature corresponding to internal resistance of the storage element by using the temperature outside the storage element and an equation expressing heat transfer. The controller determines whether a temperature variation inside the storage element is resolved or not when resuming the charging/discharging of the storage element. The controller uses a surface temperature on the surface of the storage element as the temperature at the reference point when the temperature variation is resolved, and calculates the temperature at the reference point when the temperature variation is not resolved.

Description

  The present invention relates to a power storage system that estimates a temperature inside a power storage element, and a temperature estimation method for the power storage element.

  When controlling charging / discharging of a single cell, the temperature of the single cell is detected and the detected temperature is used as one of the control parameters. When detecting the temperature of the unit cell, a temperature sensor such as a thermocouple is used, and the temperature sensor is attached to the outer surface of the unit cell.

JP 09-092347 A JP 2008-06496 A

  Within the unit cell, the temperature distribution varies due to heat dissipation and the like. In general, the temperature at the center of the unit cell tends to be higher than the temperature at the outer surface of the unit cell. In the unit cell having such a temperature distribution, the temperature inside the unit cell cannot be acquired only by the output of the temperature sensor attached to the outer surface of the unit cell.

  The power storage system according to the first invention of the present application includes a power storage element that performs charging / discharging, a temperature sensor for acquiring a temperature outside the power storage element, a temperature outside the power storage element, and an expression that represents heat transfer. And a controller for calculating a temperature of a reference point indicating a temperature corresponding to the internal resistance of the power storage element. When resuming charging / discharging of the power storage element, the controller determines whether or not the temperature variation within the power storage element has been eliminated. The controller uses the surface temperature on the surface of the electricity storage element as the reference point temperature when the temperature variation is eliminated, and calculates the reference point temperature when the temperature variation is not eliminated.

  When resuming charging / discharging of the power storage element, temperature variation in the power storage element may be eliminated depending on the state of the power storage element when charging / discharging is stopped. Therefore, in the first invention of the present application, the estimation accuracy of the reference point temperature can be improved by changing the method of calculating the reference point temperature depending on whether or not the temperature variation is eliminated.

  When the temperature variation is eliminated, the surface temperature may be used as the reference point temperature. When the temperature variation is not eliminated, the temperature at the reference point can be calculated by using the temperature outside the power storage element and an expression representing heat transfer. As a result, the temperature corresponding to the internal resistance of the power storage element can be estimated in the power storage element in which temperature variation tends to occur. When calculating the temperature of the reference point, the temperature and heat conduction equation on the outer surface of the power storage element can be used.

  As a first method for determining whether or not the temperature variation has been eliminated, first, an elapsed time during which the storage element is not being charged or discharged is measured. When the elapsed time is longer than the predetermined time, it can be determined that the temperature variation is eliminated. The predetermined time can be set in advance as a time for eliminating the temperature variation.

  As a second method for determining whether or not the temperature variation is eliminated, first, the surface temperature is acquired at a predetermined cycle while the power storage element is not being charged or discharged. And when the variation | change_quantity of the surface temperature in a predetermined period is smaller than a threshold value, it can discriminate | determine that the temperature variation is eliminated. When the temperature variation begins to disappear, the amount of change in surface temperature begins to decrease. Therefore, it is possible to determine whether or not the temperature variation is eliminated by comparing the change amount of the surface temperature with the threshold value. The threshold value can be appropriately set within a range that allows the temperature variation to be eliminated.

  When calculating the temperature of the reference point, it is possible to consider a temperature change from when charging / discharging of the power storage element is stopped to when charging / discharging of the power storage element is restarted. Specifically, the temperature of the reference point can be calculated based on the change over time of the temperature detected by the temperature sensor.

  The temperature of the reference point can be used to estimate the internal state of the power storage element. The internal state includes SOC (State Of Charge) or SOH (State Of Health). The SOC is a value indicating a ratio (Cc / Cf) of the current charge capacity (Cc) to the full charge capacity (Cf) of the power storage element. SOH is a ratio (Cf_c / Cf_ini) between the full charge capacity (Cf_ini) in the initial state and the full charge capacity (Cf_c) after deterioration, and serves as an index indicating the deterioration state of the storage element.

  The energy output from the power storage element can be used for running the vehicle. When the power storage element is mounted on the vehicle, a plurality of power storage elements can be connected in series.

  The temperature estimation method for a power storage element according to the second invention of the present application is the step of acquiring the temperature outside the power storage element that performs charging and discharging, and the temperature variation inside the power storage element is resolved when the charge and discharge of the power storage element is resumed And determining whether or not. When the temperature variation is eliminated, the surface temperature on the surface of the power storage element is used as the reference point temperature indicating the temperature corresponding to the internal resistance of the power storage element. When the temperature variation is not eliminated, the temperature at the reference point is calculated using the temperature outside the power storage element and the equation representing the heat transfer. Also in the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

It is a figure which shows the structure of a battery system. It is the schematic which shows the structure of a cell. It is the schematic which shows the structure of an electric power generation element. It is sectional drawing which shows the structure of an electric power generation element. It is a figure which shows the temperature distribution in the inside of a cell. It is a figure explaining the some lattice point from which the position in the thickness direction of a cell differs from each other. It is a figure explaining a plurality of lattice points. It is a flowchart explaining the method of specifying the lattice point which shows performance temperature. It is a figure which shows the resistance and temperature relationship of a cell. It is a figure which shows the charging / discharging pattern in a heat_generation | fever period. It is a figure which shows the charging / discharging pattern in a temperature relaxation period. It is a figure which shows resistance in a heat_generation | fever period and a temperature relaxation period. It is a figure which shows the performance temperature and detection temperature in a heat_generation | fever period and a temperature relaxation period. It is a flowchart explaining the process which sets the upper limit of charging / discharging control. It is a map which shows the output upper limit according to temperature and SOC. It is a figure when three lattice points are provided in the unit cell. It is a figure explaining the calculation method of correction coefficient k1, k2. It is a flowchart explaining the process which specifies performance temperature. It is a figure which shows the change of detected temperature while an ignition switch is OFF.

  Examples of the present invention will be described below.

  A battery system (corresponding to a power storage system) that is Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a battery system. The battery system of the present embodiment can be mounted on a vehicle.

  Vehicles include hybrid cars and electric cars. The hybrid vehicle includes an engine or a fuel cell as a power source for running the vehicle in addition to the assembled battery described later. The electric vehicle includes only an assembled battery described later as a power source for running the vehicle.

  The battery system of this embodiment includes an assembled battery 10. The assembled battery 10 includes a plurality of unit cells 11 connected in series. As the single battery (corresponding to a storage element) 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery. The number of the single cells 11 can be appropriately set based on the required output of the assembled battery 10 or the like. In this embodiment, all the unit cells 11 constituting the assembled battery 10 are connected in series, but a plurality of unit cells 11 connected in parallel may be included in the assembled battery 10.

  The voltage sensor 21 detects the inter-terminal voltage (total voltage) of the assembled battery 10 and outputs the detection result to the controller 30. Here, the voltage sensor 21 can be used to detect the voltage of each unit cell 11 or the voltage of the battery block including at least two unit cells 11. The current sensor 22 detects the current value flowing through the assembled battery 10 and outputs the detection result to the controller 30.

  The temperature sensor 23 detects the temperature of the assembled battery 10 (unit cell 11) and outputs the detection result to the controller 30. The number of temperature sensors 23 can be set as appropriate. When a plurality of temperature sensors 23 are used, the temperature sensors 23 can be arranged with respect to the cells 11 arranged at different positions.

  The controller 30 has a memory 30a, and the memory 30a stores various information for the controller 30 to perform predetermined processing. In the present embodiment, the memory 30 a is built in the controller 30, but the memory 30 a may be provided outside the controller 30.

  A system main relay SMR-B is provided on the positive electrode line PL of the assembled battery 10. System main relay SMR-B is switched between on and off by receiving a control signal from controller 30. A system main relay SMR-G is provided on the negative electrode line NL of the assembled battery 10. System main relay SMR-G is switched between on and off by receiving a control signal from controller 30.

  A system main relay SMR-P and a current limiting resistor R are connected in parallel to the system main relay SMR-G. System main relay SMR-P and current limiting resistor R are connected in series. System main relay SMR-P is switched between on and off by receiving a control signal from controller 30. The current limiting resistor R is used to suppress an inrush current from flowing when the assembled battery 10 is connected to a load (an inverter 31 described later).

  When the ignition switch is switched from OFF to ON, the assembled battery 10 is connected to a load. When connecting the assembled battery 10 to a load, the controller 30 switches the system main relays SMR-B and SMR-P from off to on. As a result, a current flows through the current limiting resistor R. Next, the controller 30 switches the system main relay SMR-P from on to off after switching the system main relay SMR-G from off to on.

  Thereby, connection of the assembled battery 10 and load is completed. On the other hand, when the ignition switch is switched from on to off, the connection between the assembled battery 10 and the load is cut off. When cutting off the connection between the assembled battery 10 and the load, the controller 30 switches the system main relays SMR-B and SMR-G from on to off.

  The inverter 31 converts the DC power from the assembled battery 10 into AC power, and outputs the AC power to the motor / generator 32. As the motor generator 32, for example, a three-phase AC motor can be used. The motor / generator 32 receives AC power from the inverter 31 and generates kinetic energy for driving the vehicle. The kinetic energy generated by the motor generator 32 is transmitted to the wheels.

  When the vehicle is decelerated or stopped, the motor / generator 32 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The inverter 31 converts the AC power generated by the motor / generator 32 into DC power and outputs the DC power to the assembled battery 10. Thereby, the assembled battery 10 can store regenerative electric power.

  In the present embodiment, the assembled battery 10 is connected to the inverter 31, but this is not a limitation. Specifically, a booster circuit can be arranged in the current path between the assembled battery 10 and the inverter 31. By using the booster circuit, the output voltage of the assembled battery 10 can be boosted. Further, the booster circuit can step down the output voltage from the inverter 31 to the assembled battery 10.

  Next, the structure of the unit cell 11 will be described with reference to FIG. FIG. 2 is a schematic view showing the structure of the unit cell 11. In FIG. 1, an X axis, a Y axis, and a Z axis are orthogonal to each other, and the relationship between the X axis, the Y axis, and the Z axis is the same in other drawings.

  The unit cell 11 includes a power generation element 111 and a battery case 112 that houses the power generation element 111. As shown in FIG. 3, the power generation element 111 includes a positive electrode plate 111a, a negative electrode plate 111b, and a separator 111c disposed between the positive electrode plate 111a and the negative electrode plate 111b. The separator 111c contains an electrolytic solution. The power generating element 111 is configured by rolling a laminated body (configuration shown in FIG. 3) in which a positive electrode plate 111a, a separator 111c, and a negative electrode plate 111b are stacked around the Y axis (see FIG. 2).

  In the present embodiment, the power generation element 111 is configured by rolling a laminated body in which the positive electrode plate 111a, the separator 111c, and the negative electrode plate 111b are stacked. However, the present invention is not limited to this. For example, the power generation element 111 can be configured by simply stacking the positive electrode plate 111a, the separator 111c, and the negative electrode plate 111b.

  In the present embodiment, the separator 111c containing an electrolytic solution is used, but a solid electrolyte can be used instead of the separator 111c. As the solid electrolyte, a polymer solid electrolyte or an inorganic solid electrolyte can be used.

  As shown in FIG. 4, the positive electrode plate 111a is obtained by forming a positive electrode active material layer 111a2 on the surface of the current collector plate 111a1, and the positive electrode active material layer 111a2 contains a positive electrode active material, a conductive agent, and the like. The negative electrode plate 111b is obtained by forming a negative electrode active material layer 111b2 on the surface of the current collector plate 111b1, and the negative electrode active material layer 111b2 includes a negative electrode active material, a conductive agent, and the like.

When a lithium ion secondary battery is used as the unit cell 11, for example, the current collecting plate 111a1 of the positive electrode plate 111a can be formed of aluminum, and the current collecting plate 111b1 of the negative electrode plate 111b can be formed of copper. Also, as the positive electrode active material, using _{Li (Li a Ni x Mn y} Co z) O 2, as a negative electrode active material, carbon can be used.

  The positive electrode plate 111a and the negative electrode plate 111b are not limited to the configuration shown in FIG. For example, an electrode plate (so-called bipolar electrode) in which a positive electrode active material layer is formed on one surface of a current collector plate and a negative electrode active material layer is formed on the other surface of the current collector plate can be used.

  The battery case 112 can be made of metal, for example. As shown in FIG. 2, a positive electrode terminal 113 and a negative electrode terminal 114 are provided on the upper surface of the battery case 112. The positive electrode terminal 113 is electrically connected to the positive electrode plate 111 a of the power generation element 111, and the negative electrode terminal 114 is electrically connected to the negative electrode plate 111 b of the power generation element 111.

  In the configuration shown in FIG. 2, the temperature sensor 23 is provided on the upper surface of the battery case 112. Since the temperature sensor 23 is attached to the outer surface of the unit cell 11 (battery case 112), the temperature detected by the temperature sensor 23 is the temperature on the outer surface of the unit cell 11. As the temperature sensor 23, for example, a thermocouple can be used. Moreover, the attachment position of the temperature sensor 23 with respect to the battery case 112 can be set suitably. Here, when the plurality of single cells 11 are arranged in the X direction, the temperature sensor 23 can be arranged on the upper surface of the battery case 112.

  Next, temperature characteristics inside the unit cell 11 will be described with reference to FIG. In FIG. 5, a coordinate system in which the vertical axis is the temperature and the horizontal axis is the thickness of the unit cell 11 and the internal structure of the unit cell 11 are overlapped. The thickness of the cell 11 is the length of the cell 11 in the X direction. The direction of the horizontal axis shown in FIG. 5 is the direction in which the positive electrode plate 111a, the separator 111c, and the negative electrode plate 111b overlap. FIG. 5 shows a temperature distribution (one example) inside the unit cell 11. A center point O shown in FIG. 5 indicates a position corresponding to the center of the power generation element 111 in the thickness direction of the unit cell 11.

  The unit cell 11 (power generation element 111) generates heat by charging and discharging, but the temperature distribution shown in FIG. The outer surface of the power generation element 111 has the easiest heat release and the lowest temperature. The outer surface of the power generation element 111 is adjacent to the inner wall surface of the battery case 112. On the other hand, as it approaches the center point O, it becomes difficult for heat to escape and the temperature tends to increase.

  As shown in FIG. 5, the temperature inside the unit cell 11 varies depending on the position of the unit cell 11 in the thickness direction. In the present embodiment, the temperature corresponding to the internal resistance of the power generation element 111 is used as the temperature of the unit cell 11 (hereinafter referred to as performance temperature), and the performance temperature of the unit cell 11 is estimated as described below. .

  In this embodiment, in order to estimate the performance temperature of the battery cell 11, the heat conduction equation shown in the following formula (1) is used.

  In Equation (1), T is temperature, t is time, λ is thermal conductivity, ρ is density, c is specific heat, x is a thermal diffusion distance, and q is a calorific value per unit volume. On the right side of Equation (1), the first term indicates the thermal diffusion term, and the second term indicates the heat generation term.

  In this embodiment, a one-dimensional heat conduction equation is used, but a two-dimensional or three-dimensional heat conduction equation can also be used. If a one-dimensional heat conduction equation is used, the arithmetic processing for estimating the performance temperature of the unit cell 11 can be simplified.

  Equation (1) can be differentiated as in Equation (2) below.

  In Expression (2), i represents a lattice point in the thickness direction of the unit cell 11. As shown in FIGS. 6 and 7, the lattice points indicate points in each region when the region between the center point O and the point S is divided into a plurality in the thickness direction of the unit cell 11. The point S is located farthest from the center point O in the thickness direction of the unit cell 11 and is located on the outer surface of the battery case 112.

  The number of grid points can be set as appropriate. If the number of lattice points is increased, the temperature estimation accuracy according to the position of the unit cell 11 in the thickness direction can be improved. Moreover, if the number of lattice points is reduced, the arithmetic processing when estimating the temperature according to the position of the unit cell 11 in the thickness direction can be simplified.

  As shown in Expression (2), the temperature of the lattice point i is affected by the temperature at two lattice points (i−1) and (i + 1) adjacent to the lattice point i. The temperature at the point S is regarded as the temperature detected by the temperature sensor 23. That is, the temperature of the point S and the temperature of the part to which the temperature sensor 23 is attached are considered to be substantially equal. When the battery case 112 is formed of a metal having excellent thermal conductivity, the temperature of the point S and the temperature of the portion where the temperature sensor 23 is attached are substantially equal.

  In the present embodiment, the temperature sensor 23 is attached to the outer surface of the unit cell 11 so that the temperature at the point S is regarded as the temperature detected by the temperature sensor 23, but the present invention is not limited to this. That is, the temperature sensor 23 can be arranged at a position away from the outer surface of the unit cell 11. In this case, it is necessary to consider the heat transfer in the air layer existing between the unit cell 11 and the temperature sensor 23. If heat transfer between the unit cell 11 and the temperature sensor 23 is specified in advance based on experiments or the like, the temperature on the outer surface of the unit cell 11 (the temperature at the point S) is determined from the temperature detected by the temperature sensor 23. Can be estimated.

  In this embodiment, as shown in FIG. 5, attention is paid to the thickness direction (X direction) of the unit cell 11, but the present invention is not limited to this. Since the power generation element 111 is a three-dimensional rectangular parallelepiped, not only the position in the X direction but also the position in the Z direction or the Y direction can be considered. Here, the position to be considered varies depending on the heat transfer path of the unit cell 11.

  The heat transfer path is also affected by dimensions, heat transfer area, material of the unit cell 11, presence or absence of an air layer, and the like. In this embodiment, as an example, the heat transfer path along the X direction is the most dominant as the heat transfer path inside the single battery 11.

  Next, a method for specifying the lattice point i indicating the performance temperature of the unit cell 11 will be described. FIG. 8 is a flowchart for explaining a method of specifying the lattice point i indicating the performance temperature. A method for specifying the lattice point i will be described with reference to the flowchart shown in FIG.

  In step S101, a map showing the relationship between the resistance and temperature of the unit cell 11 is created. Specifically, the relationship between resistance and temperature in the single battery 11 is acquired. Here, as the unit cell 11, a unit in which the temperature variation in the unit cell 11 is reduced is used. That is, regardless of the position in the X direction, the resistance of the unit cell 11 is measured after the temperature inside the unit cell 11 is set to a substantially uniform temperature. In order to set the entire cell 11 to a substantially uniform temperature, for example, the cell 11 may be left at a specific temperature for a sufficient time. If the resistance is measured while changing the temperature of the unit cell 11, for example, a map shown in FIG. 9 is obtained. When the SOC fluctuates in the pattern shown in FIG.

  The map shown in FIG. 9 shows that the resistance (internal resistance) of the unit cell 11 and the performance temperature are in a correspondence relationship. If the resistance is measured using the unit cell 11 in which the temperature variation is sufficiently suppressed, the correspondence between the internal resistance of the unit cell 11 and the performance temperature can be found. And if the map shown in FIG. 9 is used, performance temperature can be specified by measuring the resistance of the cell 11. FIG.

  In step S102 of FIG. 8, the performance temperature of the unit cell 11 is specified. This performance temperature is used to specify the lattice point i.

  First, based on the pattern shown in FIG. 10 and FIG. 11, the temperature of the cell 11 is detected based on the output of the temperature sensor 23 by charging and discharging the cell 11, and the map shown in FIG. 9 is used. To determine the performance temperature. 10 and 11, the horizontal axis indicates time, and the vertical axis indicates the current value. Here, when the cell 11 is charged, the current value is a positive value, and when the cell 11 is discharged, the current value is a negative value.

  The charge / discharge of the pattern shown in FIG. Charging / discharging of the pattern shown in FIG. 11 is performed in a period (temperature relaxation period) in which the temperature variation of the unit cells 11 is relaxed. After the charge / discharge of the pattern shown in FIG. 10 is performed, the charge / discharge of the pattern shown in FIG. 11 is performed.

  In the heat generation period, as shown in FIG. 10, charging / discharging of the first pattern Pc and the second pattern Ph is set as one cycle, and this cycle is repeated. The first pattern Pc is used for measuring the resistance of the unit cell 11. The 2nd pattern Ph is used in order to make the cell 11 (power generation element 111) generate heat. The number of charge / discharge cycles shown in FIG. 10 can be set as appropriate. Specifically, the charge / discharge cycle can be repeated until the unit cell 11 is heated and the temperature of the unit cell 11 hardly changes.

  In this embodiment, the resistance after 2 seconds from the start of charge / discharge of the first pattern Pc is measured. Note that the measurement of resistance is not limited to 2 seconds after the start of charging / discharging of the first pattern Pc, but may be set at another time. The timing for measuring the resistance may be the same timing in each cycle.

  For example, the resistance in 1 second or 10 seconds can be measured after charging / discharging of the first pattern Pc is started. Further, by charging / discharging the second pattern Ph, the unit cell 11 can generate heat and the resistance after a predetermined time can be measured. In this case, charging / discharging of the first pattern Pc can be omitted. Furthermore, the unit cell 11 can also generate heat by charging and discharging the first pattern Pc.

  The pattern used for measuring the resistance of the unit cell 11 is not limited to the pattern shown in FIG. In the first pattern Pc shown in FIG. 10, charging and discharging pulses are generated, but it is also possible to generate only charging or discharging pulses. Further, for the second pattern Ph shown in FIG. 10, it is also possible to only generate a charge or discharge pulse. For the second pattern Ph, it is only necessary that the unit cell 11 can generate heat.

  In addition, if charging and discharging are alternately performed so that the amount of coulomb is equal as in the first pattern Pc and the second pattern Ph shown in FIG. 10, the SOC (State Of Charge) of the unit cell 11 is maintained substantially constant. can do. In this case, regarding the map shown in FIG. 9, it is possible to omit obtaining the SOC dependency.

  After the charge / discharge cycle shown in FIG. 10 ends, in other words, after the heat generation period ends, the charge / discharge cycle shown in FIG. 11 is repeated. In the charge / discharge shown in FIG. 11, only the charge / discharge of the first pattern Pc is performed as one cycle, and this cycle is repeated. The cell 11 (the power generation element 111) is provided with a sufficient resting time (a time during which no charging / discharging is performed) after the first pattern Pc is charged / discharged until the next charging / discharging is performed. The temperature change is very small.

  The number of charge / discharge cycles shown in FIG. 11 can be set as appropriate. Specifically, after stopping the heat generation of the cell 11, the charge / discharge cycle shown in FIG. 11 can be repeated until the temperature of the cell 11 hardly changes.

  FIG. 12 shows the resistance measured during the heat generation period and the temperature relaxation period. In FIG. 12, the vertical axis represents the resistance of the unit cell 11, and the horizontal axis represents the number of charge / discharge cycles (in other words, time). As shown in FIG. 12, when the heat generation period is switched to the temperature relaxation period, the resistance of the unit cell 11 is increased. Based on the resistance shown in FIG. 12 and the map shown in FIG. 9, the performance temperature can be specified.

  FIG. 13 shows the relationship between the temperature Ts detected by the temperature sensor 23 and the performance temperature Tp specified using the map shown in FIG. In FIG. 13, the vertical axis represents temperature, and the horizontal axis represents the number of charge / discharge cycles (in other words, time). Further, the distribution indicated by the alternate long and short dash line in FIG. 13 indicates the temperature Ts detected by the temperature sensor 23, and the distribution indicated by the solid line in FIG. 13 indicates the performance temperature Tp.

  As shown in FIG. 13, the detected temperature Ts and the performance temperature Tp show similar behavior, but the performance temperature Tp is higher than the detected temperature Ts during the heat generation period. Further, the difference between the performance temperature Tp and the detection temperature Ts during the temperature relaxation period is smaller than the difference between the performance temperature Tp and the detection temperature Ts during the heat generation period.

  In step S103 of FIG. 8, the lattice point i indicating the temperature change closest to the temperature change of the performance temperature Tp is specified. Based on the temperature Ts detected by the temperature sensor 23 and the heat conduction equation shown in Equation (2), the temperature of each lattice point can be calculated.

  Specifically, in FIG. 6 and FIG. 7, the temperature at the point S becomes the detected temperature Ts. Therefore, if the heat conduction equation shown in the equation (2) is used, the temperature of the lattice point adjacent to the point S is calculated. Can do. Further, the temperature of the lattice point adjacent to the lattice point can be calculated based on the temperature of the lattice point adjacent to the point S.

  With this calculation method, temperatures at a plurality of lattice points can be calculated. If the temperature closest to the performance temperature Tp is identified among the temperatures at the plurality of lattice points, the lattice point indicating the performance temperature can be identified. Information regarding the identified grid points can be stored in the memory 30a.

  When estimating the temperature of the unit cell 11, the temperature of the lattice point i corresponding to the performance temperature is calculated based on the temperature detected by the temperature sensor 23 and the heat conduction equation shown in the equation (2). This calculation process is performed by the controller 30 (see FIGS. 1 and 2). Thereby, the temperature corresponding to the internal resistance of the unit cell 11 can be estimated. The temperature of the lattice point i is used for various controls of the unit cell 11 as the temperature of the unit cell 11.

  In the present embodiment, the temperature of the lattice point i corresponding to the performance temperature is calculated based on the temperature detected by the temperature sensor 23 and the heat conduction equation, but the present invention is not limited to this. The temperature of the lattice point i corresponding to the performance temperature may be calculated based on the temperature on the outer surface of the unit cell 11 and the heat conduction equation. For example, if the temperature on the outer surface of the unit cell 11 can be specified or estimated without using the temperature sensor 23, the lattice point corresponding to the performance temperature based on the specified or estimated temperature and the heat conduction equation. The temperature of i can be calculated.

  Next, processing for controlling charging / discharging of the assembled battery 10 will be described with reference to a flowchart shown in FIG. The process shown in FIG. 14 is executed by the controller 30.

  When charging / discharging the assembled battery 10, for example, charging / discharging is controlled so that the input power and the output power of the assembled battery 10 do not exceed a predetermined upper limit value. The upper limit value is a predetermined value for protecting the assembled battery 10 (unit cell 11), and is set as appropriate. That is, charging / discharging of the assembled battery 10 is permitted until the input power and output power of the assembled battery 10 reach the upper limit values.

  For example, when discharging the assembled battery 10, if the output power of the assembled battery 10 reaches an upper limit value (upper limit value corresponding to the output), the discharge of the assembled battery 10 is limited. When limiting the discharge of the battery pack 10, the upper limit value is lowered. If the upper limit value is lowered, the power allowed as the output of the assembled battery 10 is suppressed. If the upper limit value is reduced to 0 [kW], the assembled battery 10 is not discharged.

  Moreover, when charging the assembled battery 10, if the input power of the assembled battery 10 reaches an upper limit value (upper limit value corresponding to input), charging of the assembled battery 10 is limited. When limiting the charging of the battery pack 10, the upper limit value is lowered. If the upper limit value is lowered, the power allowed as the input of the assembled battery 10 is suppressed. If the upper limit value is reduced to 0 [kW], the battery pack 10 is not charged.

  In charge / discharge control of the assembled battery 10, for example, the state of the assembled battery 10 may be monitored to control charge / discharge, or the state of the single battery 11 may be monitored to control charge / discharge. The state of the assembled battery 10 or the single battery 11 includes voltage, current, and temperature.

  The process shown in FIG. 14 is a process for setting an upper limit value used in charge / discharge control of the battery pack 10.

  In step S201, the controller 30 calculates (estimates) the temperature of the lattice point i corresponding to the performance temperature as described above. In step S202, the controller 30 estimates the SOC (State of Charge) of the unit cell 11. The SOC indicates the ratio of the current charging capacity of the single battery 11 to the full charging capacity of the single battery 11. The SOC of the unit cell 11 can be estimated using any one of various known methods.

  For example, the controller 30 acquires the current value when the cell 11 is charged / discharged from the output of the current sensor 22. The controller 30 can estimate the SOC of the unit cell 11 by integrating the acquired current values. Here, for example, regarding the value detected by the current sensor 22, the charging current can be a positive value and the discharging current can be a negative value.

  On the other hand, the OCV (Open Circuit Voltage) of the unit cell 11 can be measured, and the SOC can be estimated from the measured OCV. Since OCV and SOC are in a correspondence relationship, if a map showing this correspondence relationship is prepared in advance, the SOC can be specified by measuring the OCV.

  In step S203, the controller 30 sets an upper limit value for discharging (outputting) and charging (inputting) the unit cell 11 based on the temperature calculated in step S201 and the SOC estimated in step S202. FIG. 15 is a map showing the relationship between the temperature and SOC of the cell 11 and the upper limit value (referred to as the output upper limit value) when the cell 11 is discharged. “High” and “low” indicated by arrows in FIG. 15 indicate the level relationship of the output upper limit value. The map shown in FIG. 15 can be prepared in advance and stored in the memory 30a.

  FIG. 15 shows changes in the output upper limit when the SOC and temperature change. Specifically, when the SOC does not change, the output upper limit value decreases as the temperature decreases. Since the chemical reaction at the time of discharge is suppressed as the temperature decreases, it is preferable to suppress the output of the unit cell 11. Therefore, the output upper limit value is lowered as the temperature is lowered. The map shown in FIG. 15 may include a case where the output upper limit value does not change even if the temperature changes.

  On the other hand, when the temperature does not change, the output upper limit value decreases as the SOC decreases. As the SOC of the unit cell 11 decreases, the unit cell 11 is less likely to be discharged. Therefore, the output upper limit value is decreased as the SOC decreases. The map shown in FIG. 15 may include a case where the output upper limit value does not change even if the SOC changes.

  The temperature in the map shown in FIG. 15 is the temperature calculated in step S201. The SOC in the map of FIG. 15 is the SOC estimated in step S202. If the temperature and SOC of the unit cell 11 can be specified, the output upper limit value can be specified from the map shown in FIG. And discharge control of the cell 11 (assembled battery 10) is performed on the basis of the set output upper limit.

  FIG. 15 shows the upper limit value when discharging the unit cell 11, but a map corresponding to FIG. 15 may be prepared for the upper limit value when charging the unit cell 11. Then, an upper limit value (referred to as an input upper limit value) for charging the unit cell 11 can be specified by a method similar to the method for specifying the output upper limit value.

  When the SOC of the unit cell 11 does not change, the input upper limit value can be decreased according to the decrease in the temperature of the unit cell 11. Here, even if the temperature changes, the input upper limit value may not be changed. Further, when the temperature does not change, the input upper limit value can be lowered in accordance with the increase in the SOC. As the SOC of the unit cell 11 increases, it becomes more difficult to charge the unit cell 11, so the input upper limit value is lowered in accordance with the increase in the SOC. Based on the set input upper limit value, charging control of the single battery 11 (the assembled battery 10) is performed.

  In this embodiment, the output upper limit value is specified using the map shown in FIG. 15, but the present invention is not limited to this. Specifically, when the output upper limit value is expressed by a function using the temperature of the cell 11 and the SOC as variables, the output upper limit value can be calculated using this function. In this case, information related to the function using temperature and SOC as variables may be stored in the memory 30a.

  In the present embodiment, the upper limit value of the charge / discharge control is set based on the temperature and SOC of the unit cell 11, but the present invention is not limited to this. Specifically, the upper limit value of the charge / discharge control can be set based only on the temperature of the single battery 11.

  According to the present embodiment, since the upper limit value (output upper limit value or input upper limit value) corresponding to the performance temperature of the unit cell 11 is set, charging / discharging according to the input / output characteristics of the unit cell 11 can be performed. it can. The performance temperature of the cell 11 is a temperature corresponding to the internal resistance of the cell 11, and the input / output characteristics of the cell 11 depend on the internal resistance of the cell 11. Therefore, if an upper limit value corresponding to the performance temperature of the unit cell 11 is set, charging / discharging according to the performance of the unit cell 11 can be performed.

  As described with reference to FIG. 5, the surface temperature of the unit cell 11 (the temperature at the point S) tends to be lower than the performance temperature of the unit cell 11. For this reason, if the output upper limit value or the input upper limit value is set based on the surface temperature of the unit cell 11, charging / discharging of the unit cell 11 may be excessively limited. On the other hand, the temperature at the center of the unit cell 11 (power generation element 111) tends to be higher than the performance temperature. For this reason, if the output upper limit value and the input upper limit value are set based on the center temperature (the highest temperature) of the unit cell 11, the unit cell 11 may be excessively charged / discharged.

  On the other hand, the temperature of the unit cell 11 can be adjusted based on the temperature (performance temperature) of the lattice point i. If the temperature of the lattice point i has risen, the temperature rise of the unit cell 11 can be suppressed by supplying a cooling heat exchange medium to the unit cell 11.

  Further, the SOH of the unit cell 11 can be estimated based on the temperature (performance temperature) of the lattice point i. In Japanese Patent Application Laid-Open No. 2004-257781, SOH is estimated based on an open circuit voltage and an integrated amount of electricity, and the open circuit voltage is corrected by temperature. In this case, the performance temperature described in this embodiment can be used as temperature information for correcting the open circuit voltage.

  According to the present embodiment, the temperature corresponding to the internal resistance of the unit cell 11 can be estimated. Moreover, if the internal state (SOC etc.) of the single cell 11 is estimated based on the estimated temperature (performance temperature), the estimation accuracy of the internal state can be improved. In particular, when the temperature is lowered and the SOC is lowered, the estimation accuracy of the SOC can be improved.

  In the embodiment described above, among the plurality of lattice points provided in the thickness direction of the unit cell 11, the lattice point corresponding to the performance temperature is identified, and the temperature of the identified lattice point is set as the temperature of the unit cell 11. Estimated as temperature. Here, the performance temperature of the unit cell 11 can be calculated using only three lattice points.

  FIG. 16 shows the relationship between the position of the unit cell 11 in the thickness direction and the temperature when three lattice points are set. In the example shown in FIG. 16, among the three lattice points, the temperature of the lattice point inside the unit cell 11 is the performance temperature Tp, and the temperature of the lattice point on the surface of the unit cell 11 is the detection temperature Ts by the temperature sensor 23. . Here, the temperature of another lattice point can be used instead of the detected temperature Ts.

  Here, the heat conduction equation when three lattice points are set can be simplified as the following equation (3).

  Moreover, Formula (3) can be represented by following formula (4).

  Here, α and β are represented by the following formulas (5) and (6).

  In equations (3), (5), and (6), k1 and k2 indicate correction coefficients, and can be determined by, for example, the method described below.

  As described with reference to FIG. 13, the performance temperature of the unit cell 11 is calculated. Next, the temperature (estimated temperature) estimated as the performance temperature is calculated using the equations (3) and (4) while changing each of the correction coefficients k1 and k2. Then, correction coefficients k1 and k2 that minimize the difference between the performance temperature and the estimated temperature are specified.

  FIG. 17 shows a relationship (one example) between the performance temperature and the estimated temperature. In the heat generation period, the unit cells 11 are heated by alternately charging and discharging the first pattern Pc and the second pattern Ph (see FIG. 10). In the temperature relaxation period, by charging / discharging only the first pattern Pc (see FIG. 11), the temperature of the unit cell 11 reaches the temperature corresponding to the environment without causing the unit cell 11 to generate heat.

  In addition, by charging and discharging the second pattern Ph, the unit cell 11 can generate heat and the resistance after a predetermined time can be measured. In this case, charging / discharging of the first pattern Pc can be omitted. Moreover, the unit cell 11 can also generate heat by charging and discharging the first pattern Pc.

  During the heat generation period and the temperature relaxation period, the resistance of the unit cell 11 is measured, and the performance temperature can be specified using the measured resistance and the map shown in FIG. The distribution of performance temperature is shown by the solid line in FIG. On the other hand, the estimated temperature is specified by substituting the detected temperature of the temperature sensor 23 acquired during the heat generation period and the temperature relaxation period into the heat conduction equation shown in Expression (3) and appropriately setting the correction coefficients k1 and k2. A distribution (an example) of the estimated temperature is indicated by a dotted line in FIG.

  As shown in FIG. 17, when the estimated temperature is higher than the performance temperature, the correction coefficients k1 and k2 are changed so that the estimated temperature is lowered to approach the performance temperature. In addition, when the estimated temperature is lower than the performance temperature, the correction coefficients k1 and k2 are changed so that the estimated temperature is raised to approach the performance temperature. That is, the correction coefficients k1 and k2 are determined so that the difference ΔT between the estimated temperature and the performance temperature approaches zero.

  Here, the process of determining the correction coefficients k1 and k2 is performed based on the difference ΔT between the estimated temperature and the performance temperature during the heat generation period, or based on the difference ΔT between the estimated temperature and the performance temperature during the temperature relaxation period. Can do. The obtained correction coefficients k1, k2 (or α and β) can be stored in the memory 30a. Thereby, if the temperature Ts detected by the temperature sensor 23 is acquired, the performance temperature Tp can be calculated based on the equation (3).

  In the battery system of the present embodiment, after the charging / discharging of the assembled battery 10 is stopped, the temperature variation inside the unit cell 11 is alleviated. By relaxing the temperature variation, the temperature on the outer surface of the unit cell 11, in other words, the temperature detected by the temperature sensor 23 and the performance temperature of the unit cell 11 become substantially equal.

  Immediately after stopping the charging / discharging of the battery pack 10, temperature variation occurs inside the unit cell 11. That is, as described with reference to FIG. 5, the temperature inside the unit cell 11 is higher than the temperature on the outer surface of the unit cell 11. On the other hand, as the time for stopping charging / discharging of the battery pack 10 becomes longer, the temperature variation in the unit cell 11 is reduced. That is, the temperature inside the unit cell 11 is substantially equal to the temperature on the outer surface of the unit cell 11.

  Therefore, when the charging / discharging of the assembled battery 10 is resumed, the method for estimating the performance temperature of the unit cell 11 can be changed according to the time during which the charging / discharging of the assembled battery 10 is stopped. FIG. 18 is a flowchart illustrating a process for estimating the performance temperature of the unit cell 11. The process shown in FIG. 18 is executed by the controller 30.

  In step S301, the controller 30 confirms that the ignition switch has been switched from on to off. Information relating to turning on and off the ignition switch is input to the controller 30. When the controller 30 receives information related to turning off the ignition switch, the controller 30 switches the system main relays SMR-B and SMR-G from on to off in the battery system shown in FIG. Thereby, the connection between the assembled battery 10 and the load is cut off, and charging / discharging of the assembled battery 10 is stopped.

  In step S302, the controller 30 starts measuring the time t_off using a timer from the timing when the ignition switch is switched from on to off. In addition, the controller 30 acquires the temperature Ts1 detected by the temperature sensor 23 at the timing when the ignition switch is switched from on to off. Information about the detected temperature Ts can be stored in the memory 30a.

  In step S303, the controller 30 confirms that the ignition switch has been switched from OFF to ON. By inputting information related to the ignition switch on to the controller 30, the controller 30 can confirm that the ignition switch is on.

  In step S304, the controller 30 ends the measurement of the time t_off and acquires the detected temperature Ts2 by the temperature sensor 23. The detected temperature Ts2 is the temperature of the unit cell 11 after charging / discharging of the assembled battery 10 (unit cell 11) is stopped. Information regarding the detected temperature Ts2 can be stored in the memory 30a.

  In step S305, the controller 30 determines whether or not the measurement time t_off is longer than the predetermined time t_th. The predetermined time t_th is a predetermined time from the viewpoint of eliminating the temperature variation inside the unit cell 11. By conducting an experiment in which the unit cell 11 dissipates heat in a state where charging / discharging of the unit cell 11 is stopped, it is possible to obtain a time during which the temperature variation within the unit cell 11 is eliminated. Information regarding the predetermined time t_th can be stored in the memory 30a.

  The predetermined time t_th may be a fixed value or may be changed. When changing the predetermined time t_th, for example, the predetermined time t_th can be changed according to the detected temperature Ts1 acquired in step S302. Specifically, a map indicating the relationship between the detected temperature Ts1 and the predetermined time t_th is obtained in advance, and the predetermined time t_th corresponding to the detected temperature Ts1 acquired in step S302 can be specified using this map. A map showing the correspondence between the detected temperature Ts1 and the predetermined time t_th can be stored in the memory 30a.

  In step S305, when the measurement time t_off is longer than the predetermined time t_th, the process proceeds to step S306. When the measurement time t_off is shorter than the predetermined time t_th, the process proceeds to step S307.

  In step S306, the controller 30 determines that the performance temperature Tp of the unit cell 11 is equal to the temperature Ts2 detected by the temperature sensor 23. When charging / discharging of the battery pack 10 is resumed, the controller 30 assumes that the performance temperature Tp is the detected temperature Ts2, and estimates the internal state of the battery cell 11 or inputs / outputs the battery cell 11 (the battery pack 10). And can be controlled.

  In step S307, the controller 30 determines that the performance temperature Tp of the single battery 11 is different from the temperature Ts2 detected by the temperature sensor 23. In this case, the controller 30 can estimate the performance temperature Tp of the unit cell 11 using the detected temperature Ts2.

  According to the processing shown in FIG. 18, as shown in FIG. 19, the temperature Ts1 detected by the temperature sensor 23 when the ignition switch is switched from on to off, and the temperature sensor 23 when the ignition switch is switched from off to on. The detected temperature Ts2 can be acquired.

  If the detected temperatures Ts1, Ts2 can be acquired, the performance temperature Tp of the unit cell 11 can be estimated when the ignition switch is switched from off to on. For example, if a relationship in which the temperature change while the ignition switch is off is linear or exponential with respect to time is obtained in advance by experiment, while the ignition switch is off (while the detection temperature Ts1 changes to the detection temperature Ts2) ) Is defined only, and the amount of change in the performance temperature Tp can be calculated by using Equation (4) by complementing the detected temperature of the temperature sensor 23 at this time.

  In this embodiment, it is determined whether or not the temperature variation in the unit cell 11 has been eliminated based on whether or not the measurement time t_off is longer than the predetermined time t_th. However, the present invention is not limited to this. .

  Specifically, while the ignition switch is off, the controller 30 acquires the detected temperature Ts every time the predetermined period Δt elapses. The detected temperature Ts acquired at the predetermined period Δt can be stored in the memory 30a. The controller 30 calculates a change amount ΔTs of the detected temperature Ts when the predetermined period Δt has elapsed, and calculates a ratio (ΔTs / Δt) of the change amount ΔTs with respect to the predetermined period Δt. Based on whether the ratio (ΔTs / Δt) is smaller than the threshold value, the controller 30 can determine whether or not the temperature variation in the unit cell 11 has been eliminated.

  The predetermined period Δt can be set as appropriate. The shorter the predetermined period Δt, the easier it is to track the behavior of the detected temperature Ts, but the amount of data of the detected temperature Ts stored in the memory 30a increases. On the other hand, as the predetermined period Δt is lengthened, the amount of data of the detected temperature Ts stored in the memory 30a can be reduced, but it becomes difficult to track the behavior of the detected temperature Ts changing. In consideration of this point, the predetermined period Δt can be set.

  When the temperature variation within the unit cell 11 begins to disappear, the ratio (ΔTs / Δt) begins to decrease. For this reason, by determining whether or not the ratio (ΔTs / Δt) is smaller than the threshold value, it is possible to determine whether or not the temperature variation in the unit cell 11 has been eliminated. The threshold value can be set as appropriate in consideration of variations in the detected temperature Ts. When the temperature variation is completely eliminated and the temperature difference ΔTs does not change, the ratio (ΔTs / Δt) becomes zero. Therefore, if the threshold value is set to 0, it can be determined that the temperature variation has been completely eliminated.

  When the ratio (ΔTs / Δt) is smaller than the threshold value, the controller 30 can determine that the temperature variation in the unit cell 11 has been eliminated. When the temperature variation is eliminated, the process of step S306 can be performed. Further, when the ratio (ΔTs / Δt) is larger than the threshold value, the controller 30 can determine that the temperature variation in the unit cell 11 has not been eliminated. When the temperature variation is not eliminated, the process of step S307 can be performed. For example, the performance temperature Tp can be estimated from the time measured periodically and the history of the temperature detected by the temperature sensor 23 using Equation (4). The estimation (calculation) of the performance temperature Tp may be performed simultaneously with turning on the ignition switch.

  According to the present embodiment, when the ignition switch is switched from OFF to ON, in other words, when charging / discharging of the assembled battery 10 (unit cell 11) is resumed, the temperature variation in the unit cell 11 is eliminated. Accordingly, the performance temperature of the unit cell 11 can be specified.

  In the present embodiment, the temperature of the lattice point i corresponding to the performance temperature is calculated based on the temperature on the outer surface of the unit cell 11 and the heat conduction equation, but the present invention is not limited to this. Specifically, the temperature outside the unit cell 11 is acquired, and the temperature of the lattice point i corresponding to the performance temperature can be calculated using an equation representing heat transfer.

  The temperature outside the unit cell 11 includes not only the temperature on the outer surface of the unit cell 11 but also the temperature at a position away from the outer surface of the unit cell 11. The temperature at a position away from the outer surface of the unit cell 11 can be detected using the temperature sensor 23. As a position away from the outer surface of the unit cell 11, for example, when a heat exchange medium (gas or liquid) is supplied to the unit cell 11 and the temperature of the unit cell 11 is adjusted, the heat exchange medium is supplied to the unit cell 11. (For example, the supply port of the heat exchange medium).

  The expression representing the heat transfer is an expression representing the heat transfer from the outside of the unit cell 11 to the lattice point i corresponding to the performance temperature. In addition to the heat conduction equation described in the present embodiment, for example, an expression representing heat transfer and an expression based on a model of a heat equivalent circuit are included in the expression representing heat transfer.

  When acquiring the temperature at a position away from the outer surface of the unit cell 11, heat transfer from a position away from the outer surface of the unit cell 11 to the outer surface of the unit cell 11 and heat conduction inside the unit cell 11 are considered. Thus, the temperature of the lattice point i corresponding to the performance temperature can be calculated. Here, heat transfer and heat conduction can be individually evaluated to calculate the temperature of the lattice point i, or both heat transfer and heat conduction can be evaluated together to calculate the temperature of the lattice point i. You can also.

  When using an equation representing heat transfer, an equation representing heat transfer can be appropriately determined in consideration of heat transfer from a position away from the outer surface of the unit cell 11 to the outer surface of the unit cell 11. When evaluating the heat conduction inside the unit cell 11 and the heat transfer from the position away from the outer surface of the unit cell 11 to the outer surface of the unit cell 11, in addition to the heat conduction equation described in this embodiment, A model of a thermal equivalent circuit can be used. In the model of the thermal equivalent circuit, the heat capacity C and the thermal resistance R can be used in consideration of how heat is transmitted. Based on the model of the heat equivalent circuit, equations representing heat conduction and heat transfer can be determined as appropriate.

10: assembled battery 11: single battery (storage element)
111: Power generation element 111a: Positive electrode plate 111b: Negative electrode plate 11c: Separator 112: Battery case 113: Positive electrode terminal 114: Negative electrode terminal 21: Voltage sensor 22: Current sensor 23: Temperature sensor 30: Controller 30a: Memory 31: Inverter 32: Motor generator

Claims (15)

A power storage element for charging and discharging; and
A temperature sensor for obtaining a temperature outside the storage element;
A controller that calculates a temperature at a reference point indicating a temperature corresponding to an internal resistance of the power storage element, using a temperature outside the power storage element and an expression representing heat transfer;
The controller is
When resuming charging / discharging of the electricity storage element, it is determined whether or not temperature variation within the electricity storage element has been resolved,
When the temperature variation is eliminated, the surface temperature on the surface of the electricity storage element is used as the temperature of the reference point, and when the temperature variation is not eliminated, the temperature of the reference point is calculated. Power storage system.   2. The power storage system according to claim 1, wherein the controller calculates the temperature of the reference point by using a temperature on an outer surface of the power storage element and a heat conduction equation when the temperature variation is not eliminated. .   The controller measures an elapsed time while the storage element is not being charged / discharged, and determines that the temperature variation is eliminated when the elapsed time is longer than a predetermined time. The power storage system according to claim 1 or 2.   The controller acquires the surface temperature in a predetermined cycle while the power storage element is not being charged / discharged, and the temperature variation is eliminated when the amount of change in the surface temperature in the predetermined cycle is smaller than a threshold value. The power storage system according to claim 1, wherein it is determined that the power storage system is operating.   The controller calculates a temperature of the reference point using a temperature change from when charging / discharging of the power storage element is stopped to when charging / discharging of the power storage element is restarted. Item 5. The power storage system according to any one of Items 1 to 4.   The power storage system according to any one of claims 1 to 5, wherein the controller estimates an internal state of the power storage element using a temperature of the reference point.   The power storage system according to claim 6, wherein the internal state is SOH.   The power storage system according to any one of claims 1 to 7, wherein the power storage element outputs energy used for running the vehicle. Obtaining a temperature outside the storage element that performs charging and discharging; and
When resuming charging / discharging of the electricity storage element, determining whether or not temperature variation within the electricity storage element has been eliminated;
When the temperature variation is eliminated, the surface temperature on the surface of the electricity storage element is used as the reference point temperature indicating the temperature corresponding to the internal resistance of the electricity storage element, and when the temperature variation is not eliminated, Calculating the temperature of the reference point using a temperature outside the energy storage element and an expression representing heat transfer;
The temperature estimation method of the electrical storage element characterized by this.   The temperature estimation method for a power storage element according to claim 9, wherein when the temperature variation is not eliminated, the temperature of the reference point is calculated using a temperature and a heat conduction equation on the outer surface of the power storage element. .   The elapsed time while the storage element is not being charged / discharged is measured, and when the elapsed time is longer than a predetermined time, it is determined that the temperature variation is eliminated. The temperature estimation method of the electrical storage element of Claim 10.   When the surface temperature is acquired at a predetermined cycle while the power storage element is not being charged / discharged, and the amount of change in the surface temperature at the predetermined cycle is smaller than a threshold value, the temperature variation is eliminated. The temperature estimation method for a storage element according to claim 9 or 10, wherein the temperature is determined.   The temperature of the reference point is calculated using a temperature change from when charging / discharging of the power storage element is stopped to when charging / discharging of the power storage element is resumed. The temperature estimation method of the electrical storage element as described in any one of these.   The temperature estimation method for a power storage element according to any one of claims 9 to 13, wherein the temperature of the reference point is used to estimate an internal state of the power storage element. The method of claim 14, wherein the internal state is SOH.