JP4655568B2 - Secondary battery state estimation method and system - Google Patents

Description

  The present invention relates to a state estimation method and system for a secondary battery, and more specifically, estimates a state quantity such as a remaining capacity with high accuracy for a secondary battery in which an electrode expands and contracts due to charge and discharge. It relates to a method and a system.

  Secondary batteries used for hybrid vehicles include lead batteries, nickel metal hydride (Ni-MH) batteries, lithium ion batteries, and the like. A secondary battery can be discharged again by supplying a charging current from the outside when power is consumed, and thus has been conventionally applied to various devices.

  For example, a secondary battery is mounted on a vehicle and serves as an engine starting battery that supplies power to an ignition plug, a starter, and the like of the engine at the time of starting. Recently, in electric vehicles (EV) and hybrid vehicles (HEV), it is also used as a main power source when driving a traveling motor.

  In this type of secondary battery, it is important to estimate the current remaining capacity by some method for the purpose of making the user recognize the charging time or the battery state. In particular, in a hybrid vehicle, it is required to maintain a charged state of a secondary battery serving as a vehicle driving force energy source within an appropriate range.

For this reason, SOC (State Of Charge) calculated based on the charge / discharge current and the battery state (temperature / voltage) is defined between 0% and 100% as an index representing the remaining capacity of the secondary battery. Charging / discharging of the secondary battery is controlled so that the SOC is maintained within a predetermined range. That is, in order to use the secondary battery efficiently, it is necessary to improve the estimation accuracy of the SOC.

  Conventionally, as an SOC estimation method, for example, the remaining capacity of an alkaline battery represented by a Ni-MH battery having a hydrogen storage alloy as a negative electrode is charged / discharged by directly providing a strain gauge or a pressure sensor to the negative electrode. The structure which detects and detects the volume change of the negative electrode accompanying a is proposed (for example, patent document 1).

  In addition, a configuration has been proposed in which the remaining capacity of the Ni-MH battery is estimated based on the internal pressure (hydrogen gas pressure) and temperature of the secondary battery (for example, Patent Documents 2 and 3). Furthermore, in consideration of application to an uninterruptible power supply, a configuration for detecting the life of a storage battery by detecting expansion of the storage battery has been proposed (Patent Document 4).

  In addition, since the secondary battery deteriorates in battery performance, represented by input / output power and full charge capacity (battery capacity after full charge), in the process of use, the performance changes in time series. In particular, when power input / output exceeding the battery performance is performed, the deterioration is accelerated rapidly, and there is a risk of failure if it is significant. For this reason, it is an important issue to quantitatively grasp the degree of deterioration at the present time and detect the limit amount of the secondary battery performance.

As a method for determining the deterioration of the secondary battery, as a configuration in which an easily deformable member is provided outside the battery case, by detecting the expansion of the battery case accompanying the elongation of the positive electrode lattice by the occurrence of cracks and breaks in the easily deformable member, A method for detecting deterioration of a secondary battery has been proposed (for example, Patent Document 5). Also, in order to detect the phenomenon that the internal pressure (internal pressure) of the battery rises due to the slow progress of the hydrogen storage reaction inside the battery as the secondary battery deteriorates, the differential value of the internal pressure exceeds the judgment value. In addition, a method has been proposed in which deterioration of the secondary battery is detected and the determination value is changed in accordance with the battery temperature to perform more accurate deterioration determination (for example, Patent Document 6). Similarly, a technique for detecting deterioration of a secondary battery when the battery internal pressure exceeds a predetermined determination value has been proposed (for example, Patent Document 7).
JP-A-8-194037 JP 7-63831 A JP-A-7-263033 JP 2001-166016 A JP 2002-313438 A JP-A-8-331769 Japanese Patent Laid-Open No. 2002-42896

  However, since the shrinkage / expansion of the hydrogen storage alloy is affected by the temperature, the relationship between the volume change of the negative electrode and the SOC (residual capacity) also changes according to the temperature.

  For this reason, in the SOC estimation method disclosed in Patent Document 1, since the SOC is estimated based only on the volume change of the hydrogen storage alloy constituting the negative electrode, it is difficult to estimate the SOC with high accuracy.

  Moreover, in patent documents 2 and 3, SOC is estimated by detecting the hydrogen gas pressure change accompanying a charging / discharging phenomenon by the internal pressure gas pressure measurement of a secondary battery. However, since the internal gas is dissolved in the electrode and the electrolytic solution, or is transmitted to the outside through the casing, it is difficult to estimate the SOC with high accuracy.

  Further, in the configuration disclosed in Patent Document 4, when the expansion of the secondary battery casing exceeds a certain amount, the life of the battery is detected before the secondary battery is damaged. There is no disclosure of a method for estimating the remaining capacity (SOC).

  Further, as described above, the volume change amount (expansion) of the electrode and the battery case changes depending on the temperature, so that the deterioration is detected only by the deformation of the easily deformable member on the surface of the battery case without taking the temperature into consideration. In the secondary battery degradation determination method disclosed in No. 5, accurate degradation determination is difficult. Similarly, in Patent Documents 6 and 7, since the deterioration is detected based on the measurement of the internal pressure of the battery, it is difficult to accurately determine the deterioration because of the dissolution or leakage of the internal gas as described above.

  In particular, in the methods disclosed in Patent Documents 5 to 7, although the deterioration determination of the secondary battery can be executed in a binary manner, the degree of deterioration can be quantitatively grasped, and the input / output power at that time or The limit amount of the full charge capacity cannot be detected.

  The present invention has been made to solve such problems, and an object of the present invention is to estimate a state quantity of a battery represented by a remaining capacity (SOC) with a simple configuration with high accuracy. A secondary battery state estimation method and system are provided.

  A state estimation method for a secondary battery according to the present invention is a state estimation method for a secondary battery in which a positive electrode and a negative electrode are housed in a casing, the step of detecting a volume change of at least one of the positive electrode and the negative electrode, And a step for detecting the temperature of at least one of the negative electrodes, and a step for estimating the state of the secondary battery from a preset correlation based on the detected volume change and temperature.

  According to the state estimation method for the secondary battery described above, it is possible to accurately estimate various battery states that change in relation to the volume change of the electrode by considering that the volume change characteristic of the electrode changes depending on the temperature. . In addition, since the estimation is performed based on the measurement of the temperature and volume change of the electrode, the state estimation can be executed during charging / discharging without being influenced by the energization state of the secondary battery.

  Preferably, in the secondary battery state estimation method according to the present invention, the remaining capacity estimation value is calculated as the state of the secondary battery from the correlation.

  According to the state estimation method for the secondary battery, the remaining capacity (SOC) can be estimated taking into consideration that the volume change characteristic of the electrode changes depending on the temperature, so that the estimation accuracy can be improved.

  Preferably, in the secondary battery state estimation method according to the present invention, an estimated value of a state quantity that changes as a state of the secondary battery reflecting the degree of deterioration is calculated from the correlation.

  According to the secondary battery state estimation method described above, the amount of state that changes with the progress of battery deterioration, for example, the input power, output power, and full charge capacity, reflects the degree of battery deterioration at that time. Value can be grasped. Thereby, taking into consideration the degree of deterioration, it becomes possible to more precisely perform charge restriction and discharge restriction in charge / discharge control of the secondary battery, so that overdischarge and overcharge can be stably avoided. In particular, when a hybrid vehicle is mounted, there is a possibility that more efficient energy distribution control can be performed with the internal combustion engine by expanding the usable range of the battery.

  In the secondary battery state estimation method according to the present invention, the correlation is based on the relationship between the volume change, the temperature, and the state quantity indicating the state of the secondary battery, which is experimentally obtained in advance for the secondary battery. It is preferable that the two-dimensional map is set.

  According to the secondary battery state estimation method, the state quantity indicating the secondary battery state, such as the estimated remaining capacity, can be calculated by a simple calculation with a small processing load.

  A state estimation system for a secondary battery according to the present invention includes a secondary battery in which a positive electrode and a negative electrode are housed in a housing, a pressure measuring unit attached to the outer surface of the housing, and a housing and the pressure measuring unit. A restraining means for restraining the pressing force to be generated, a temperature measuring unit for detecting the temperature of at least one of the positive electrode and the negative electrode, and a state estimating means are provided. The state estimation means estimates the state of the secondary battery from a preset correlation based on the pressure measured by the pressure measuring unit and the temperature measured by the temperature measuring unit.

  According to the above-described secondary battery state estimation system, the state quantity of the secondary battery can be estimated based on the housing pressure and the electrode temperature reflecting the volume change of the electrode inside the housing. Taking into consideration that the volume change characteristic changes, it is possible to accurately estimate various states that change in relation to the volume change of the electrode. In particular, by disposing the pressure measuring unit outside the housing, the sensor mounting structure can be simplified, the manufacturing cost can be reduced, and high-precision estimation reflecting the volume change of the entire electrode can be performed.

  Preferably, in the state estimation system for a secondary battery according to the present invention, the state estimation means calculates an estimated remaining capacity value as the state of the secondary battery from the correlation.

  According to the state estimation system of the secondary battery, the remaining capacity (SOC) can be estimated taking into consideration that the volume change characteristic of the electrode changes depending on the temperature, so that the estimation accuracy can be improved.

  Preferably, in the state estimation system for a secondary battery according to the present invention, the state estimation means estimates a state quantity that changes to reflect the deterioration state from the correlation. In particular, as the state quantity that reflects the deterioration state, the input / output power of the secondary battery or the full charge capacity of the secondary battery is estimated.

  According to the above secondary battery state estimation system, the amount of state that changes with the progress of battery deterioration, for example, input power, output power, and full charge capacity, reflects the degree of battery deterioration at that time. Value can be grasped. Thereby, taking into consideration the degree of deterioration, it becomes possible to more precisely perform charge restriction and discharge restriction in charge / discharge control of the secondary battery, so that overdischarge and overcharge can be stably avoided. In particular, when a hybrid vehicle is mounted, there is a possibility that more efficient energy distribution control can be performed with the internal combustion engine by expanding the usable range of the battery.

  Preferably, in the state estimation system for a secondary battery according to the present invention, the state estimation means includes a measurement value, a measurement temperature, and a quantitative value indicating the state of the secondary battery, which are experimentally obtained in advance for the secondary battery. A quantitative value is calculated with reference to a two-dimensional map based on the relationship between the two.

  According to the secondary battery state estimation system, the state quantity (quantitative value) indicating the state of the secondary battery can be calculated by a simple calculation with a small processing load.

  Preferably, in the state estimation system for a secondary battery according to the present invention, the temperature measurement unit is provided corresponding to a portion of the outer surface of the housing that changes its temperature according to the temperature of at least one of the electrodes. ing.

  According to the state estimation system for a secondary battery described above, the temperature measuring unit can be arranged outside the housing to detect the electrode temperature, so that the sensor mounting structure is simplified and the manufacturing cost can be reduced.

  Alternatively, preferably, in the state estimation system for a secondary battery according to the present invention, a plurality of secondary batteries are electrically connected to each other, and the pressure measuring unit is attached to a housing of at least one secondary battery. It is done. The restraint means includes a plurality of secondary batteries and a restraint plate disposed on both sides of the pressure measuring unit, and a restraint rod that couples the restraint plates.

  According to the secondary battery state estimation system described above, even when a module is formed by an assembly of a plurality of secondary battery cells, the restraint structure necessary for pressure measurement can be realized in a compact manner. Can be downsized.

  Preferably, the secondary battery is configured by a single cell, and the pressure measuring unit is attached to the casing of the secondary battery. Further, the restraining means includes a restraining plate disposed on both sides of the secondary battery and the pressure measuring unit, and a restraining rod that couples between the restraining plates.

  According to the state estimation system for a secondary battery described above, even when the secondary battery is configured by a single cell, the restraint structure necessary for pressure measurement can be realized in a compact manner, and thus the system can be miniaturized.

  According to the present invention, it is possible to provide a state estimation method and system for a secondary battery capable of estimating an internal state quantity such as a remaining capacity (SOC) with a simple configuration with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(Application to SOC estimation)
FIG. 1 is a schematic diagram showing a configuration of a remaining capacity estimation system shown as a representative example of a state estimation system for a secondary battery according to the present invention. In the remaining capacity estimation system described below, the remaining capacity (SOC), which is a representative state quantity of the secondary battery, is estimated.

  Referring to FIG. 1, remaining capacity estimation system 10 includes secondary battery cells 20 a to 20 d, restraint plates 30 and 31, restraint rod 40, pressure sensor 50, bus bars 60 to 64, and temperature sensor 70. And an ECU (Electronic Control Unit) 100.

  Each of the secondary battery cells 20a to 20d has a positive electrode 21 and a negative electrode 22 housed in a casing. In the positive electrode 21 and the negative electrode 22, expansion / contraction occurs with charge / discharge, and a volume change occurs.

  Typically, as the secondary battery cell, a nickel metal hydride battery in which a hydrogen storage alloy is used for the negative electrode 22 is applied. However, as will be apparent from the following description, the remaining capacity estimation according to the present invention can be applied to a secondary battery in which a volume change accompanying charging / discharging occurs in at least one of the electrodes. That is, the secondary battery cells 20a to 20d shown in FIG. 1 are not limited to nickel metal hydride batteries, and may be constituted by lead batteries, lithium ion batteries, or the like.

  Secondary battery cells 20a to 20d are connected in series by bus bars 61 to 63 to constitute a single module. That is, a voltage of four cells is generated between the bus bar 60 connected to the negative electrode of the secondary battery cell 20a and the bus bar 64 connected to the positive electrode of the secondary battery cell 20d.

  Bus bars 60 and 64 are connected to a load (not shown). Bus bars 60 and 64 are also connected to a charging device (not shown), for example, a generator in an automobile. For this reason, the secondary battery cells 20a to 20d can supply voltage to the load and be charged from the charging device.

  The restraint plates 30 and 31 are arranged on both sides of the plurality of secondary battery cells 20a to 20d so as to correspond to surfaces having a relatively large housing area. The restraining rod 40 couples between the restraining plates 30 and 31.

  2 is a cross-sectional view taken along the line II-II in FIG.

  Referring to FIG. 2, the housings of the secondary battery cells 20 a to 20 d and the pressure sensor 50 are integrally restrained between restraining plates 30 and 31 provided on both sides. Therefore, the pressure sensor 50 can measure the pressure acting on the casings of the secondary battery cells 20a to 20d in a state where the pressing force is applied to the casing.

  Inside each housing, volume changes occur in the positive electrode 21 and the negative electrode 22 due to expansion / contraction associated with the charge / discharge phenomenon. Therefore, the measured values by the pressure sensor 50 are the positive electrode 21 in the entire secondary battery cells 20a to 20d. It reflects the volume change of both the negative electrode 22 and the negative electrode 22. As shown in FIG. 1, the pressure detection value P by the pressure sensor 50 is sent to the ECU 100.

  Since the secondary battery cells 20a to 20d and the pressure sensor 50 are integrally restrained by the restraining plates 30, 31 and the restraining rod 40, the restraint structure necessary for pressure measurement can be realized in a compact manner, so that the remaining capacity The overall estimation system 10 can be reduced in size.

  Referring to FIG. 1 again, temperature sensor 70 is provided in at least one of secondary battery cells 20a to 20d in order to detect the temperature of positive electrode 21 and negative electrode 22. In the configuration example of FIG. 1, the temperature sensor 70 is disposed outside the housing of the secondary battery cell 20 a so as to correspond to a part where the temperature changes according to the temperature of the positive electrode 21 or the negative electrode 22 to be measured. The The temperature detection value T by the temperature sensor 70 is sent to the ECU 100.

  ECU 100 calculates an SOC that serves as an index of the remaining capacity of the secondary battery, based on pressure detection value P from pressure sensor 50 and temperature detection value T from temperature sensor 70. For example, the ECU 100 combines a ROM, RAM, etc. (not shown) for storing predetermined program data, etc., and a CPU, MPU, etc. (not shown) for sequentially executing arithmetic processing according to the program. Consists of a microcomputer.

  Here, the correspondence between the configuration shown in FIG. 1 and the configuration of the present invention will be described. Each of the secondary battery cells 20a to 20d corresponds to the “secondary battery” of the present invention, and the restraint plate 30 , 31 and the restraining rod 40 correspond to the “restraining means” of the present invention. Further, the pressure sensor 50 and the temperature sensor 70 correspond to the “pressure measurement unit” and the “temperature measurement unit” of the present invention, and the ECU 100 corresponds to the “state estimation unit” of the present invention.

  In each of the secondary battery cells 20a to 20d, since the positive electrode 21 and the negative electrode 22 expand by charging and contract by discharging, the SOC increases in a region where the volume is relatively large, and the volume is relatively high. In a very low region, the SOC becomes small.

  Referring to FIG. 3, such a change in volume of positive electrode 21 and negative electrode 22 is detected by pressure sensor 50 as a change in pressure acting on the casings of secondary battery cells 20a to 20d. Therefore, the SOC increases in a region where the pressure detection value P by the pressure sensor 50 is high, and the SOC decreases in a region where the pressure detection value P is small.

  In this embodiment, the pressure sensor 50 is disposed outside the housing, and the volume change of the electrode is measured as the pressure acting on the housing. As a result, as compared with the configuration in which the sensor is directly provided on the electrode inside the casing as in Patent Document 1, there is a problem of the electrolytic solution resistance of the sensor and the signal extraction wire and the sealing resistance at the portion of the wire penetrating through the casing. This eliminates the need to consider this problem, so that the sensor can be easily installed.

  In addition, since it is not necessary to wire the inside of the housing or to provide a recess for arranging the sensor in the separator, the secondary battery cell can be easily designed, and inexpensive and highly reliable pressure measurement can be performed.

  Further, in the configuration in which the sensor is directly provided on the electrode as in Patent Document 1, a charge / discharge reaction at the sensor arrangement portion cannot be expected, so a sensor as small as possible is required. For this reason, it is impossible to measure the pressure over the entire surface of the electrode, and only a local volume change of the electrode can be measured. For this reason, the SOC of the entire secondary battery is estimated based on the pressure at the local portion of the electrode. On the other hand, according to the configuration in which the pressure sensor is arranged outside the housing as in this embodiment, pressure detection can be performed on the entire side surface of the cell, which reflects the volume change of the entire electrode. The SOC can be estimated for the entire secondary battery.

  Further, as shown in FIG. 3, the characteristic line indicating the relationship between pressure P and SOC changes using electrode temperature T # as a parameter.

  For example, in the case of a nickel metal hydride battery, the hydrogen storage amount of the hydrogen storage alloy changes according to the temperature. For this reason, even if the SOC is the same, the ratio of the amount present in the hydrogen storage alloy to the amount present as gas for the hydrogen present in the housing varies depending on the temperature. Moreover, the volume change of the electrode (negative electrode) comprised with the hydrogen storage alloy depends on the hydrogen storage amount. For this reason, even if the volume of the electrode is the same, that is, the detected pressure value P is the same, the SOC varies depending on the electrode temperature T #. It has been confirmed by the inventor that the above characteristic line also changes with the electrode temperature T # as a parameter when data is experimentally collected for other secondary batteries.

  In addition, it is preferable to use the electrode temperature T # obtained by directly measuring the temperature of the positive electrode 21 and the negative electrode 22 for the estimation of the state quantity of the battery including the SOC estimation. However, it is difficult to directly measure the temperature of the electrode in an actual system configuration.

  Therefore, in this embodiment, as shown in FIG. 1, temperature measurement is performed on a housing outer surface portion showing a temperature close to the electrode temperature. That is, the temperature sensor 70 is structurally close to the electrodes 21 and 22 on the outer surface of the housing and has a part with good thermal conductivity from the electrodes, that is, a part or space having low thermal conductivity between the electrode and the temperature measuring part. It is preferable to arrange in the part which is not.

  A plurality of temperature sensors 70 may be arranged in a single cell or a plurality of temperature sensors.

  If necessary, the temperature of the arrangement site of the temperature sensor 70 and the electrode temperature can be experimentally obtained in advance and reflected in the SOC estimation.

  Thus, in the remaining capacity estimation according to the present invention, ECU 100 calculates SOC by further using temperature detection value T reflecting the electrode temperature in addition to pressure detection value P reflecting the volume change of the electrode.

  The SOC calculation in the ECU 100 can be performed by the following method, for example, based on the characteristic line shown in FIG.

  FIG. 4 is a flowchart for explaining the SOC estimation routine by the ECU.

  Referring to FIG. 4, the SOC estimation routine is started every predetermined cycle. When the SOC estimation routine is started, the measurement value of the pressure sensor 50 is first sampled (step S100). Thereby, the pressure detection value P in FIG. 3 is sent to the ECU 100. As described above, since the volume change of the electrode inside the housing is reflected in the pressure detection value P, this step S100 corresponds to a step of detecting the volume change of the electrode (at least one of the positive electrode and the negative electrode). .

  Further, the measurement value of the temperature sensor 70 is sampled, and the temperature detection value T is sent to the ECU 100 (step S110). As described above, since electrode temperature T # in FIG. 3 is reflected in temperature detection value T, step S110 corresponds to a step of detecting the temperature of the electrode (at least one of the positive electrode and the negative electrode).

  Note that the execution order of the above steps S100 and S110 is not particularly defined, and it is preferable to carry out both in parallel.

  Next, based on the sampled pressure detection value P and temperature detection value T, the SOC is calculated from the preset correlation, specifically referring to the map shown in FIG. 5 (step S130).

  FIG. 5 is an example of the SOC estimation map according to the embodiment of the present invention.

  Referring to FIG. 5, the SOC estimation map is constituted by a two-dimensional map corresponding to pressure detection value P and temperature detection value T, and is stored in ECU 100 in advance.

  Corresponding to the temperature detection value T, for example, the correlation between the pressure detection value P and the SOC in increments of 10 ° C. of T = −20 ° C., −10 ° C., 0 ° C., 10 ° C., 20 ° C., 30 ° C. and 40 ° C. A relationship is set. For example, in each temperature range, the pressure detection value P corresponding to the SOC in the range of 0 (%) to 100 (%) is set in increments of 10%. The map value may be determined based on data obtained in advance through experiments.

  In step S130 in FIG. 4, one row is selected from the two-dimensional map according to the temperature detection value T, and the SOC corresponding to the pressure detection value P is calculated using the map value of the selected row. . That is, step S130 corresponds to the “step of estimating the state of the secondary battery” in the present invention.

  As an example, when the temperature detection value T is 20 ° C., the pressure detection value P is compared with Pa0 to Pa10, and the corresponding SOC (%) is calculated by interpolation between map values. It should be noted that the interpolation between the map values is preferably a linear interpolation in terms of calculation load, but may be a non-linear interpolation.

  When the temperature detection value T is an intermediate value of a predetermined step size, two rows are selected from the two-dimensional map corresponding to the range of the temperature detection value, and the calculation is performed for each selected row. The final estimated SOC may be calculated by further interpolating the two SOC values with the temperature.

  Thus, according to the state estimation method and system of the secondary battery according to the present invention, the remaining capacity (SOC) can be estimated with high accuracy because the volume change characteristic of the electrode changes with temperature. Further, since the estimation is performed based on the measurement of the temperature and volume change of the electrode, the remaining capacity (SOC) can be estimated even during charging / discharging regardless of the energized state of the secondary battery.

  Furthermore, since the pressure sensor and the temperature sensor are arranged outside the casing of the secondary battery cell, the remaining capacity (SOC) can be estimated with a low-cost configuration without complicating the sensor mounting structure. Can be realized.

  In addition, since the SOC is calculated with reference to a two-dimensional map created in advance based on experimental data or the like, compared with the case where the SOC is calculated by directly substituting it into an arithmetic expression such as non-linearity, the ECU 100 It is possible to simplify the calculation and reduce the processing load.

  In the configuration example shown in FIG. 1, a configuration in which a plurality of secondary battery cells 20a to 20d are connected in series is representatively shown, but the connection form of the secondary battery cells is not particularly limited when the present invention is applied. . For example, even with respect to one secondary battery cell or a configuration in which a plurality of secondary battery cells are connected in parallel or in series and parallel, a pressure sensor constrained with respect to the casing is used to It is possible to apply the configuration of the present invention that estimates the state quantity of a battery represented by

  The secondary battery cell constraining structure is not limited to the example shown in FIG. 1, and a change in the volume of the electrode inside the cell is detected by a pressure sensor attached outside the cell casing (outer tank). Any structure can be applied if possible.

(Applicable to grasping quantitative deterioration level)
In the state estimation system of the secondary battery having the same configuration as the remaining capacity estimation system shown in FIG. 1, it is possible to estimate other state quantities of the secondary battery by appropriately preparing a map. For example, it is also possible to estimate state quantities such as input possible power, output possible power, and full charge capacity, which change according to battery deterioration.

  The electrode material of the secondary battery changes with time in the process of use due to the progress of so-called deterioration reaction. There are various types of degradation reactions, such as cracking of the active material itself and irreversible chemical changes, chemical changes between the active material and non-active materials such as electrolytes and binders, binders, etc. Degradation progresses by combining various chemical changes such as chemical changes in the constituent materials that are unrelated to charge / discharge.

  Since many of these chemical changes are accompanied by a volume change, the deterioration of the secondary battery appears as a volume change of the electrode. In the state estimation system having the constraint structure as described above, the volume change of the electrode is reflected in the pressure detection value P (restraint stress) measured by the pressure sensor 50.

  Therefore, with regard to state quantities such as input possible power, output possible power, and full charge capacity that change according to the degree of deterioration of the battery, experimental changes in restraint stress (pressure detection value) and state quantities accompanying the progress of deterioration It is possible to obtain a correspondence between the two by measuring in advance. In addition, since the temperature affects the volume change and restraint stress of the electrode, a two-dimensional table similar to that shown in FIG. 5 is created for the input power, output power, and full charge capacity of the battery. Similarly to the remaining capacity (SOC), the state quantity can be estimated with high accuracy.

  FIG. 6 is a flowchart for explaining a deterioration degree estimation routine by the ECU.

  Referring to FIG. 6, the deterioration degree estimation routine is started every predetermined period. After the activation, the measurement value sampling of the pressure sensor 50 (step S100) and the measurement value of the temperature sensor 70 are sampled (step S110) as in the SOC estimation routine.

  Furthermore, based on the sampled pressure detection value P and temperature detection value T, the degree of deterioration was estimated from the preset correlation, specifically by referring to the maps shown in FIGS. Inputtable power, outputable power, and full charge capacity are estimated (step 130). That is, step S130 corresponds to the “step of estimating the state of the secondary battery” in the present invention.

  As shown in FIG. 7, the estimated map of the input power and the output power is a two-dimensional map and is stored in advance in ECU 100.

  In this two-dimensional map, in correspondence with the temperature detection value T, for example, the correlation between the pressure detection value P and the input power (or output power) in increments of 10 ° C. in the range of T = −20 ° C. to 40 ° C. A relationship is set. For example, in each temperature range, the pressure detection value P corresponding to the range where the input power (or output power) is 0 (%) to 100 (%) is 10% increments based on data obtained in advance by experiments. Set by. Here, 100 (%) corresponds to input possible power (or output possible power) in the initial state (no deterioration). That is, the amount of decrease from 100 (%) corresponds to a quantitative amount of deterioration related to input possible power (or output possible power).

  As an example, when the temperature detection value T is 20 ° C., the pressure detection value P is compared with Pb0 to Pb10, and the corresponding input possible power (or output possible power) is calculated by interpolation between the map values. . It should be noted that the interpolation between the map values is preferably a linear interpolation in terms of calculation load, but may be a non-linear interpolation. Further, as described above, the final estimated value may be calculated by interpolating the estimated values respectively obtained from the two map rows.

  In the map setting, the power that can be input (or power that can be output) may be directly defined by the amount of power (W) instead of the ratio (%) to the initial state.

  Further, as shown in FIG. 8, the full charge capacity estimation map is also composed of a two-dimensional map and stored in advance in the ECU 100.

  Also in this two-dimensional map, for example, the correlation between the full charge capacity and the pressure detection value P is set in increments of 10 ° C. within a range of T = −20 ° C. to 40 ° C. For example, in each temperature range, the pressure detection value P corresponding to the range where the full charge capacity is 0 (%) to 100 (%) is set in increments of 10% based on data obtained by experiments in advance. Here, 100 (%) corresponds to the full charge capacity in the initial state (no deterioration). That is, the amount of decrease from 100 (%) corresponds to a quantitative deterioration amount related to the full charge capacity.

  As an example, when the temperature detection value T is 20 ° C., the pressure detection value P is compared with Pc0 to Pc10, and the corresponding full charge capacity is calculated by interpolation between map values. It should be noted that the interpolation between the map values is preferably a linear interpolation in terms of calculation load, but may be a non-linear interpolation. Further, as described above, the final estimated value may be calculated by interpolating the estimated values respectively obtained from the two map rows.

  In the map setting, the full charge capacity may be directly defined by the capacity value (Ah) instead of the ratio (%) to the initial state.

  In this way, the charge limit in the charge / discharge control of the secondary battery is obtained by grasping the input possible power, output possible power and full charge capacity at that time, which is the state quantity that reflects the degree of deterioration of the battery. In addition, overdischarge and overcharge can be stably avoided by more precisely limiting the discharge. In particular, when a hybrid vehicle is mounted, there is a possibility that more efficient energy distribution control can be performed with the internal combustion engine by expanding the usable range of the battery.

  The secondary battery state estimation method and system according to the present invention described above are typically applied to hybrid vehicles that require precise SOC management and charge / discharge control, but the state (remaining capacity) of the secondary battery is determined. The present invention can also be applied in common to secondary batteries mounted on devices and systems that need to be managed and controlled.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is the schematic which shows the structure of the remaining capacity estimation system of the secondary battery according to this invention. It is II-II sectional drawing in FIG. It is a conceptual diagram which shows the qualitative relationship between the housing | casing pressure of a secondary battery cell, electrode temperature, and SOC. It is a flowchart explaining SOC calculation operation | movement by ECU. It is a figure which shows the example of the SOC estimation map used for embodiment of this invention. It is a flowchart explaining degradation degree estimation operation | movement by ECU. It is a figure which shows the example of the input / output possible electric power estimation map used for embodiment of this invention. It is a figure which shows the example of the full charge capacity estimation map used for embodiment of this invention.

Explanation of symbols

  10 remaining capacity estimation system, 20a to 20d secondary battery cell, 21 positive electrode, 22 negative electrode, 30, 31 restraint plate, 40 restraint rod, 50 pressure sensor, 60 to 64 bus bar, 70 temperature sensor, P pressure detection value, T temperature Detected value, T # electrode temperature.

Claims (13)

A method for estimating a state of a secondary battery in which a positive electrode and a negative electrode are stored in a housing,
Detecting a volume change of at least one of the positive electrode and the negative electrode;
Detecting the temperature of at least one of the positive electrode and the negative electrode;
Estimating the state of the secondary battery from a preset correlation based on the detected volume change and the temperature.   The secondary battery state estimation method according to claim 1, wherein an estimated remaining capacity value is calculated as the state of the secondary battery from the correlation.   The state estimation method for a secondary battery according to claim 1, wherein an estimated value of a state quantity that reflects a degree of deterioration as the state of the secondary battery is calculated from the correlation.   The correlation is set in a two-dimensional map based on a relationship between the volume change, the temperature, and a state quantity indicating the state of the secondary battery, which is experimentally obtained in advance for the secondary battery. The state estimation method of the secondary battery of Claim 1. A secondary battery in which a positive electrode and a negative electrode are housed in a housing;
A pressure measurement unit attached to the outer surface of the housing;
Restraining means for restraining the pressing force to be generated between the housing and the pressure measuring unit;
A temperature measuring unit for detecting the temperature of at least one of the positive electrode and the negative electrode;
A state estimation system for a secondary battery, comprising state estimation means for estimating the state of the secondary battery from a preset correlation based on the pressure measured by the pressure measurement unit and the temperature measured by the temperature measurement unit .   6. The state estimation system for a secondary battery according to claim 5, wherein the state estimation means calculates an estimated remaining capacity value as the state of the secondary battery from the correlation.   6. The state estimation system for a secondary battery according to claim 5, wherein the state estimation unit estimates a state quantity that reflects a deterioration state based on the correlation.   The secondary battery state estimation system according to claim 7, wherein the state estimation unit estimates input / output possible power of the secondary battery as a state quantity that changes to reflect the deterioration state.   The secondary battery state estimation system according to claim 7, wherein the state estimation unit estimates a full charge capacity of the secondary battery as a state quantity that changes to reflect the deterioration state.   The state estimating means refers to a two-dimensional map based on a relationship among the measured pressure, the measured temperature, and a quantitative value indicating the state of the secondary battery, which is experimentally obtained in advance for the secondary battery. The state estimation system for a secondary battery according to claim 5, wherein the quantitative value is calculated.   The state estimation of the secondary battery according to claim 5, wherein the temperature measuring unit is provided corresponding to a portion of the outer surface of the housing where its temperature changes according to the temperature of the at least one electrode. system. A plurality of the secondary batteries are electrically connected to each other and arranged.
The pressure measuring unit is attached to a housing of at least one secondary battery,
The restraining means is
A constraining plate disposed on both sides of the plurality of secondary batteries and the pressure measuring unit, which are continuously disposed;
The state estimation system for a secondary battery according to claim 5, further comprising a restraining rod that couples between the restraining plates. The secondary battery is composed of a single cell,
The pressure measuring unit is attached to a casing of the secondary battery,
The restraining means includes restraining plates disposed on both sides of the secondary battery and the pressure measuring unit,
The state estimation system for a secondary battery according to claim 5, further comprising a restraining rod that couples between the restraining plates.

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