Patent Publication Number: US-2023133469-A1

Title: Diagnostic method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2021-180443 filed on Nov. 4, 2021, the entire contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The disclosure relates to a diagnostic method, and more particularly to a technique for diagnosing the deterioration of a battery provided in a vehicle. 
     BACKGROUND 
     For a battery, serving as a power source for a drive motor in a vehicle, and a dummy battery connected in series with the battery, there has been proposed a technique for determining the degree of deterioration of the battery by measuring the degree of deterioration of the dummy battery (see, for example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2019-509593). 
     SUMMARY 
     An aspect of the disclosure provides a diagnostic method to be implemented by a computer. The diagnostic method includes: conducting a deterioration diagnosis of a dummy battery through which a mirror current based on a current flowing through a battery used as a power source for a drive motor flows; and, in a case where it is determined in the deterioration diagnosis that the dummy battery is deteriorated, conducting a reversible deterioration diagnosis of the dummy battery based on a usage mode of the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram illustrating the configuration of a diagnostic system; 
         FIG.  2    is a diagram illustrating the configuration of a vehicle; 
         FIG.  3    is a diagram illustrating the configuration of a diagnostic apparatus; 
         FIG.  4    is a graph illustrating a reversible deterioration of a battery; and 
         FIG.  5    is a flowchart illustrating the flow of a diagnostic process. 
     
    
    
     DETAILED DESCRIPTION 
     Batteries serving as power sources for drive motors may experience a temporary capacity decrease when used at low temperatures and with high load currents, for example. When a deterioration diagnosis of a battery is conducted in the event of a temporary capacity decrease, the battery may be determined as being deteriorated despite the fact that the battery is not actually deteriorated. 
     It is desirable to improve the accuracy of determining the deterioration of a battery. 
       FIG.  1    is a diagram illustrating the configuration of a diagnostic system  1 . As illustrated in  FIG.  1   , the diagnostic system  1  includes a vehicle  10  and a diagnostic apparatus  20 . 
     The vehicle  10  is a hybrid vehicle driven by an engine and a drive motor, or an electric vehicle driven only by a drive motor. Hereinafter, the case where the vehicle  10  is an electric vehicle driven only by a drive motor will be described by way of example. 
     The diagnostic apparatus  20  indirectly diagnoses the deterioration of a battery  11  (see  FIG.  2   ) provided in the vehicle  10  by diagnosing a dummy battery  14 , as will be described in detail later. 
       FIG.  2    is a diagram illustrating the configuration of the vehicle  10 . In  FIG.  2   , an electric circuit is indicated by a solid line, and a signal circuit or a data communication circuit is indicated by a broken line. 
     As illustrated in  FIG.  2   , the vehicle  10  includes the battery  11 , a drive motor  12 , a battery control unit (BCU)  13 , the dummy battery  14 , an ammeter  15 , a thermometer  16 , and a communication unit  17 . 
     The battery  11  is a lithium-ion secondary battery, for example, and is used as a power source for the drive motor  12 . The battery  11  has cells (several tens of cells) with a rated output voltage of about several hundred V. Note that the battery  11  can be charged from an external power supply. 
     The drive motor  12  is a motor provided as a drive source for the wheels of the vehicle  10 , and is operated by receiving power supply from the battery  11  via an inverter (not illustrated). In addition, the drive motor  12  may function as a generator when the vehicle  10  decelerates. The power generated by the drive motor  12  is regenerated to the battery  11  through the inverter. 
     The BCU  13  is configured with, for example, a microcomputer including a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM). The BCU  13  performs control related to the power supply of the vehicle  10 , that is, control related to the battery  11  and the dummy battery  14 , when the CPU expands a program stored in the ROM into the RAM and executes the program. 
     The BCU  13  also includes a storage unit constituted of a non-volatile memory or the like, and various types of data may be stored in the storage unit. In addition, the BCU  13  is configured to be able to calculate the state of charge (SOC) of each of the battery  11  and the dummy battery  14 . Note that, as an SOC calculation method, various methods of the related art, such as a method using an open circuit voltage (OCV)-SOC curve indicating the relationship between OCV and SOC, or a method using the integrated value of the current at the time of charging/discharging, may be used, and thus the detailed description thereof will be omitted here. 
     The dummy battery  14  is a lithium-ion secondary battery separate from the battery  11  and is provided as a diagnostic battery. The dummy battery  14  is a scaled down version of the battery  11 , has one or more cells (several tens of cells), and a rated output voltage of about 5 V. 
     Moreover, the dummy battery  14  is configured as a battery in a separate housing from the battery  11 . For example, the battery  11  is relatively firmly attached with bolts or the like under the floor of the compartment of the vehicle  10 . In contrast, the dummy battery  14  is attached to a certain position in the vehicle  10  so as to be relatively easily removable through an attachment/detachment mechanism such as a hook. 
     The ammeter  15  measures the current value of a current charged/discharged from the battery  11  and outputs the measured current value to the BCU  13 . 
     The thermometer  16  measures the temperature of the battery  11  or the ambient temperature of the battery  11 , and outputs the measured temperature to the BCU  13 . Note that the ambient temperature is the temperature of a space in which the battery  11  is provided, that is, the atmospheric temperature of the battery  11 . 
     The communication unit  17  is connected with the BCU  13 , and is connectable by wire to a vehicle diagnostic terminal (not illustrated). The communication unit  17  allows data transmission/reception to be performed between the BCU  13  and the vehicle diagnostic terminal. 
     The BCU  13  stores usage state data indicating the usage state of the battery  11  as needed. Note that the usage state of the battery  11  includes the state of the battery  11  in use, such as the environment in which the battery  11  is placed and/or how the battery  11  is used. In one example, the BCU  13  stores the current value measured by the ammeter  15 , the temperature measured by the thermometer  16 , and the SOC as usage state data in the storage unit at certain intervals. 
     The BCU  13  also generates a mirror current based on the current flowing through the battery  11 . In one example, the BCU  13  generates a mirror current based on the current value of a current flowing through the battery  11 , which is measured by the ammeter  15 . Here, a “mirror current” refers to a current that changes in conjunction with the current flowing through the battery  11  in order to simulate the usage state of the battery  11  in the dummy battery  14 . 
     As an example, it is conceivable to generate, with regard to the temperature of the battery  11  due to Joule heat, a mirror current so that the temperature of the battery  11  and the temperature of the dummy battery  14  become equal. 
     In one example, the BCU  13  generates a mirror current so as to satisfy the following condition: “(current of battery  11 ) 2 ×(heat capacity of battery  11 )=(current of dummy battery  14 ) 2 ×(heat capacity of dummy battery  14 )”. 
     As another example, it is conceivable to generate a mirror current so that the SOC of the battery  11  and the SOC of the dummy battery  14  become equal. 
     In one example, the BCU  13  generates a mirror current so as to satisfy the following condition: “(current of battery  11 )/(initial capacity of battery  11 )=(current of dummy battery  14 )/(initial capacity of dummy battery  14 )”. 
     Moreover, it is conceivable to generate a mirror current as having been given a coefficient corresponding to the difference in capacity or the like between the battery  11  and the dummy battery  14 . In one example, in the case where the cell size or capacity of the dummy battery  14  is 1/10 of the cells of the battery  11 , the BCU  13  generates, as a mirror current, a current with a current value that is 1/10 of the current value of a current flowing through the battery  11 . 
     As described above, a mirror current may be any current as long as the usage state of the battery  11  is simulated in the dummy battery  14 . 
     The BCU  13  allows the generated mirror current to flow through the dummy battery  14 . By allowing the mirror current of a current flowing through the battery  11  to flow through the dummy battery  14 , the usage state of the battery  11  is reproduced in the dummy battery  14 . That is, the BCU  13  simulates the deterioration state of the battery  11  in the dummy battery  14 . 
       FIG.  3    is a diagram illustrating the configuration of the diagnostic apparatus  20 . In  FIG.  3   , an electric circuit is indicated by a solid line, and a signal circuit or a data communication circuit is indicated by a broken line. 
     As illustrated in  FIG.  3   , the diagnostic apparatus  20  includes a control unit  21 , a charge/discharge device  22 , a heater  23 , a voltmeter  24 , an ammeter  25 , a thermometer  26 , and a communication unit  27 . 
     The control unit  21  is configured with, for example, a microcomputer including a CPU, ROM, and RAM, and controls each unit of the diagnostic apparatus  20  when the CPU expands a program stored in the ROM into the RAM and executes the program. 
     Under control of the control unit  21 , the charge/discharge device  22  charges and discharges the dummy battery  14  removed from the vehicle  10 . 
     Under control of the control unit  21 , the heater  23  heats the dummy battery  14 . 
     The voltmeter  24  measures the voltage value of the dummy battery  14  and outputs the measured voltage value to the control unit  21 . 
     The ammeter  25  measures the current value of a current charged/discharged from the dummy battery  14  and outputs the measured current value to the control unit  21 . 
     The thermometer  26  measures the temperature of the dummy battery  14  or the ambient temperature of the dummy battery  14 , and outputs the measured temperature to the control unit  21 . 
     The communication unit  27  is connected with the control unit  21  and is connected by wire to the vehicle diagnostic terminal (not illustrated). The communication unit  27  performs data transmission/reception between the control unit  21  and the vehicle diagnostic terminal. 
     When the dummy battery  14  is set in the diagnostic apparatus  20 , the control unit  21  first conducts a deterioration diagnosis of the dummy battery  14 . 
     For the sake of confirmation, a “deterioration diagnosis” here refers to, with regard to an evaluation index related to the deterioration state of a battery, at least comparing an evaluation index value serving as a reference and an actually measured evaluation index value. 
     Methods of the related art may be used for diagnosing the deterioration of a battery. Hereinafter, the case of conducting a diagnosis based on the capacity maintenance rate of a battery will be discussed by way of example. 
     The control unit  21  calculates the capacity maintenance rate Rc (%), which is indicated in equation (1) below, of the dummy battery  14  in a deterioration diagnosis based on the capacity maintenance rate: 
       “capacity maintenance rate  Rc =current full charge capacity ( Ah )/reference full charge capacity×100”.   (1)
 
     Note that the reference full charge capacity is, for example, a full charge capacity determined in advance to be used as a reference, such as a full charge capacity measured at the time of shipment from a factory (the initial full charge capacity of the dummy battery  14 ). 
     In addition, the full charge capacity in equation (1) is obtained by equation (2) below: 
       “full charge capacity ( Ah )=cumulative amount of charge current ( Ah )/(SOC after charge−SOC before charge)×100”  (2)
 
     Note that the SOC of the dummy battery  14  can be calculated based on the voltage value measured by the voltmeter  24 . 
     Here, the dummy battery  14  is charged by the charge/discharge device  22 . The control unit  21  calculates the above-mentioned capacity maintenance rate Rc in response to the fact that the dummy battery  14  has become fully charged, that is, the charging of the dummy battery  14  is completed, and conducts a deterioration diagnosis of the dummy battery  14  based on the capacity maintenance rate Rc. 
     As a deterioration diagnosis, the control unit  21  determines whether the capacity maintenance rate Rc is greater than or equal to a certain capacity threshold Th, for example. Note that the capacity threshold Th is set to a capacity maintenance rate at which the battery  11  is reusable, for example. 
     Here, if the capacity maintenance rate Rc is greater than or equal to the capacity threshold Th, it is determined that the dummy battery  14  is not deteriorated, that is, the battery  11  is not deteriorated and is reusable. In contrast, if the capacity maintenance rate Rc is less than the capacity threshold Th, it is determined that the dummy battery  14  is deteriorated, that is, the battery  11  is deteriorated and is not reusable. 
       FIG.  4    is a graph illustrating a reversible deterioration of the battery  11 . By the way, when high-load currents frequently flow through the battery  11  at low temperatures, such as when slipping and gripping are frequently performed on frozen mountain roads, a reversible deterioration occurs. 
     A reversible deterioration is a phenomenon in which the battery  11  experiences a temporary decrease in capacity or increase in resistance, mainly because the charge is concentrated only on the surface of the negative electrode, making it difficult to accumulate electricity inside the battery  11 . Such a reversible deterioration is gradually resolved over time. 
     For example, as illustrated in  FIG.  4   , suppose that a capacity decrease, which is one form of reversible deterioration, occurs in the battery  11  at time T 1 . Then, suppose that the capacity decrease in the battery  11  is resolved over time, and the capacity decrease is completely eliminated at time T 2 . 
     In such a case, suppose that the dummy battery  14  is removed from the vehicle  10  between time T 1  and time T 2  and a deterioration diagnosis is conducted. Then, because the dummy battery  14  is in the same usage state as the battery  11 , the dummy battery  14  experiences a reversible deterioration, like the battery  11 . 
     Therefore, when a deterioration diagnosis of the dummy battery  14  is conducted between time T 1  and time T 2 , the capacity maintenance rate of the dummy battery  14  is determined to be less than the capacity threshold Th where the dummy battery  14  is not usable, for example. That is, the battery  11  is falsely determined to be not reusable due to a reversible deterioration. 
     Therefore, when it is determined that the dummy battery  14  is deteriorated in the deterioration diagnosis, the control unit  21  conducts a reversible deterioration diagnosis to determine whether there is a possibility that the dummy battery  14  is reversibly deteriorated based on the usage state of the battery  11 . 
     In one example, the control unit  21  obtains usage state data from the vehicle  10  via the vehicle diagnostic terminal. Then, the control unit  21  determines whether there is a possibility that the dummy battery  14  is reversibly deteriorated by referring to a frequency map set in advance for the obtained usage state data. 
     Here, the frequency map defines a range within which a reversible deterioration can occur for three parameters: current value, temperature, and SOC. The control unit  21  counts the number of times the combination of the current value, temperature, and SOC stored in the usage state data is within the range specified in the frequency map. Then, the control unit  21  determines that the dummy battery  14  may be reversibly deteriorated when the counted value is greater than or equal to a preset count threshold. 
     When it is determined that the dummy battery  14  may be reversibly deteriorated, the control unit  21  conducts a deteriorated electrode diagnosis to determine a deteriorated electrode in the dummy battery  14 . 
     In one example, the control unit  21  controls the charge/discharge device  22  to charge and discharge the dummy battery  14 , during which a voltage value is measured by the voltmeter  24  and a current value is measured by the ammeter  25 , and a charge/discharge curve (capacity and voltage) is calculated based on the voltage value and the current value. Moreover, the control unit  21  calculates a dQ/dV curve by taking the derivative of the charge/discharge curve. 
     It is known that whether the positive electrode or the negative electrode of a battery is deteriorated can be estimated based on the slope of the dQ/dV curve, that is, the charge/discharge curve. In one example, because the position (capacity) at which the charge/discharge curve changes abruptly during charging or discharging differs between the positive electrode deterioration and the negative electrode deterioration, whether the positive electrode or the negative electrode is deteriorated can be estimated based on the position (capacity) at which the charge/discharge curve changes abruptly. 
     Accordingly, the control unit  21  determines whether the positive electrode or the negative electrode is deteriorated based on the calculated dQ/dV curve. 
     When the negative electrode of the dummy battery  14  is deteriorated, because lithium ions are unevenly accumulated at the negative electrode of the dummy battery  14 , the control unit  21  controls the charge/discharge device  22  to refresh discharge the dummy battery  14 . Note that refresh discharging refers to forcibly discharging electricity accumulated in the dummy battery  14 . 
     While the dummy battery  14  is being refresh discharged, the control unit  21  heats the dummy battery  14  with the heater  23  to about 60° C., for example. This can accelerate the reaction of the dummy battery  14 . 
     In contrast, when the positive electrode of the dummy battery  14  is deteriorated, because lithium ions are unevenly detached from the positive electrode of the dummy battery  14 , the control unit  21  controls the charge/discharge device  22  to refresh charge the dummy battery  14 . Note that refresh charging refers to forcibly charging the dummy battery  14  with electricity. 
     While the dummy battery  14  is being refresh charged, the control unit  21  heats the dummy battery  14  with the heater  23  to about 60° C., for example. This can accelerate the reaction of the dummy battery  14 . 
     As described above, the control unit  21  allows the dummy battery  14  to recover from a reversible deterioration by refresh discharging or refresh charging the dummy battery  14  according to the deteriorated electrode of the dummy battery  14 . 
     After that, the control unit  21  again conducts a deterioration diagnosis of the dummy battery  14 . Here, when the dummy battery  14  is reversibly deteriorated, it is determined that the capacity of the dummy battery  14  has recovered and the dummy battery  14  is not deteriorated. That is, the battery  11  is determined to be reusable. 
     In contrast, when the dummy battery  14  is not reversibly deteriorated, it is again determined that the dummy battery  14  is deteriorated because the capacity of the dummy battery  14  has not recovered. That is, the battery  11  is determined to be not reusable. 
       FIG.  5    is a flowchart illustrating the flow of a diagnostic process. Note that the process illustrated in  FIG.  5    is executed by the control unit  21  based on a program stored in the ROM or the like. 
     As illustrated in  FIG.  5   , in step S 1 , the control unit  21  conducts a deterioration diagnosis of the dummy battery  14 . In one example, the control unit  21  calculates a capacity maintenance rate using equation (1). Then, in step S 2 , the control unit  21  determines whether the capacity maintenance rate is greater than or equal to the capacity threshold Th. 
     In the case where the capacity maintenance rate is greater than or equal to the capacity threshold Th (Yes in step S 2 ), the control unit  21  determines in step S 3  that the battery  11  is reusable, and ends the process. 
     In contrast, in the case where the capacity maintenance rate is not greater than or equal to the capacity threshold Th (No in step S 2 ), the control unit  21  determines in step S 4  whether it is after the refresh discharging of the dummy battery  14  in step S 9  described below or after the refresh charging of the dummy battery  14  in step S 10  described below. Hereinafter, refresh discharging and refresh charging are collectively referred to as refreshing. 
     In the case where the dummy battery  14  is not after being refreshed (No in step S 4 ), in step S 5 , the control unit  21  obtains the usage state data from the vehicle  10  via the vehicle diagnostic terminal, refers to the frequency map, and conducts a reversible deterioration diagnosis of the dummy battery  14 . 
     Next, in step S 6 , the control unit  21  determines whether there is a possibility that the dummy battery  14  is reversibly deteriorated as a result of the reversible deterioration diagnosis in step S 5 . As a result, when there is a possibility that the dummy battery  14  is reversibly deteriorated (Yes in step S 6 ), the control unit  21  conducts a deteriorated electrode diagnosis of the dummy battery  14  in step S 7 . In one example, the control unit  21  controls the charge/discharge device  22  to charge and discharge the dummy battery  14 , calculates the charge/discharge curve and the dQ/dV curve during the charging and discharging, and determines whether the positive electrode or the negative electrode is deteriorated based on the calculated dQ/dV curve. 
     In step S 8 , the control unit  21  determines whether the negative electrode of the dummy battery  14  is deteriorated as a result of the deteriorated electrode diagnosis in step S 7 . As a result, in the case where the negative electrode of the dummy battery  14  is deteriorated (Yes in step S 8 ), in step S 9 , the control unit  21  refresh discharges the dummy battery  14  and heats the dummy battery  14  with the heater  23 . 
     In contrast, in the case where the negative electrode of the dummy battery  14  is not deteriorated (No in step S 8 ), that is, in the case where the positive electrode of the dummy battery  14  is deteriorated, in step S 10 , the control unit  21  refresh charges the dummy battery  14  and heats the dummy battery  14  with the heater  23 . 
     Then, in the case where the dummy battery  14  is refreshed in step S 9  or step S 10 , the process returns to step S 1 . 
     In the case where the dummy battery  14  is after being refreshed (Yes in step S 4 ), and in the case where there is no possibility that the dummy battery  14  is reversibly deteriorated (No in step S 6 ), the control unit  21  determines in step S 11  that the battery  11  is not reusable, and ends the process. 
     Here, the embodiment is not limited to the specific examples described above and can be configured in various modifications. 
     For example, it has been described above that a mirror current flowing through the dummy battery  14  is generated by software processing performed by the BCU  13 . However, a mirror current can also be generated using an analog circuit such as a current mirror circuit, for example. 
     In the above embodiment, the case where the diagnostic apparatus  20  is provided separately from the vehicle  10  has been described. However, the diagnostic apparatus  20  may be provided in the vehicle  10 , and a diagnostic process may be performed without removing the dummy battery  14 . 
     In the above embodiment, if it is determined that there is a possibility that the dummy battery  14  is reversibly deteriorated, the dummy battery  14  is refresh discharged or refresh charged. However, the control unit  21  may only heat the dummy battery  14  with the heater  23  without refresh discharging or refresh charging the dummy battery  14 . Moreover, the control unit  21  may neither refresh discharge or refresh charge the dummy battery  14  nor heat the dummy battery  14  with the heater  23 . In such a case, however, in order for the dummy battery  14  to recover from a reversible deterioration, it is necessary to allow more time to elapse than in the case where refresh discharging or refresh charging is performed, and then to conduct a deterioration diagnosis again. 
     Although the temperature of the battery  11  is measured with the thermometer  16  in the above embodiment, the thermometer  16  may measure the temperature of the dummy battery  14 . 
     In the above embodiment, the case where the vehicle  10  is connected to the diagnostic apparatus  20  via the vehicle diagnostic terminal has been described. However, the vehicle  10  and the diagnostic apparatus  20  may be connected by wire or wirelessly, or the usage state data may be uploaded to a cloud from the vehicle  10 , and may be downloaded by the diagnostic apparatus  20 . 
     In the above embodiment, the control unit  21  conducts a deterioration diagnosis based on the capacity maintenance rate of the dummy battery  14 . However, the control unit  21  may conduct a deterioration diagnosis based on a resistance increase rate. 
     In a deterioration diagnosis based on a resistance increase rate, the resistance increase rate Rr (%), which is indicated in equation (3) below, of the dummy battery  14  is calculated: 
       “resistance increase rate  Rr =latest battery resistance value (Ω)/reference battery resistance value (Ω)×100”  (3)
 
     The battery resistance value in equation (3) is calculated by equation (4) below: 
       “battery resistance value=average value of change in battery current/average value of change in voltage between two terminals of battery”  (4)
 
     In this case, the control unit  21  calculates the battery resistance value of the dummy battery  14  using equation (4). That is, while the vehicle  10  is in operation, the control unit  21  obtains a current flowing through the dummy battery  14  for a certain period of time, and detection information of a voltage between two terminals, and calculates the battery resistance value of the dummy battery  14  in accordance with equation (4). 
     Note that, as the reference battery resistance value, like the reference full charge capacity mentioned above, a battery resistance value determined in advance to be used as a reference, such as a battery resistance value measured at the time of shipment from a factory (the initial battery resistance value of the dummy battery  14 ), is used. 
     Then, as a deterioration diagnosis, the control unit  21  determines whether the resistance increase rate Rr is greater than or equal to a certain threshold. 
     As described above, in a diagnostic method according to an embodiment, a computer (control unit  21 ) conducts a deterioration diagnosis of the dummy battery  14  through which a mirror current based on a current flowing through the battery  11  used as a power source for the drive motor  12  flows, and, if it is determined in the deterioration diagnosis that the dummy battery  14  is deteriorated, conducts a reversible deterioration diagnosis of the dummy battery  14  based on the usage mode of the battery  11 . 
     Accordingly, even if it is determined in a deterioration diagnosis that the dummy battery  14  is deteriorated, the diagnostic apparatus  20  is able to determine whether there is a possibility that the capacity of the dummy battery  14  will recover by determining whether the dummy battery  14  is reversibly deteriorated. 
     Therefore, the diagnostic apparatus  20  is able to improve the accuracy of determining the deterioration of the battery  11 . 
     In addition, if it is determined in a reversible deterioration diagnosis that the dummy battery  14  is reversibly deteriorated, the computer conducts a deteriorated electrode diagnosis of the dummy battery  14 . 
     Accordingly, the diagnostic apparatus  20  is able to determine whether the cause of the reversible deterioration of the dummy battery  14  is the positive electrode deterioration or the negative electrode deterioration. 
     Thus, the diagnostic apparatus  20  is able to cause a recovery from a reversible deterioration at an early stage in accordance with the deteriorated electrode of the dummy battery  14 . 
     In addition, the computer refresh discharges the dummy battery  14  when it is determined in a deteriorated electrode diagnosis that the negative electrode is deteriorated, and refresh charges the dummy battery  14  when it is determined in a deteriorated electrode diagnosis that the positive electrode is deteriorated. 
     Accordingly, the diagnostic apparatus  20  is able to cause a recovery from a reversible deterioration at an early stage in accordance with the deteriorated electrode of the dummy battery  14 . 
     The computer also heats the dummy battery  14  while refresh discharging or refresh charging the dummy battery  14 . 
     Accordingly, the diagnostic apparatus  20  is able to increase the reaction speed while refresh discharging or refresh charging the dummy battery  14 . 
     Therefore, the diagnostic apparatus  20  is able to allow the dummy battery  14  to recover from a reversible deterioration at an early stage. 
     The computer also conducts a reversible deterioration diagnosis of the dummy battery  14  based on the current value, temperature, and SOC of the battery  11  or the dummy battery  14 . 
     This enables the diagnostic apparatus  20  to determine a state of use in which a reversible deterioration is likely to occur, such as when in use at low temperatures and with high load currents. 
     The control unit  21  illustrated in  FIG.  3    can be implemented by circuitry including at least one semiconductor integrated circuit such as at least one processor (e.g., a central processing unit (CPU)), at least one application specific integrated circuit (ASIC), and/or at least one field programmable gate array (FPGA). At least one processor can be configured, by reading instructions from at least one machine readable tangible medium, to perform all or a part of functions of the control unit  21 . Such a medium may take many forms, including, but not limited to, any type of magnetic medium such as a hard disk, any type of optical medium such as a CD and a DVD, any type of semiconductor memory (i.e., semiconductor circuit) such as a volatile memory and a non-volatile memory. The volatile memory may include a DRAM and a SRAM, and the non-volatile memory may include a ROM and a NVRAM. The ASIC is an integrated circuit (IC) customized to perform, and the FPGA is an integrated circuit designed to be configured after manufacturing in order to perform, all or a part of the functions of the modules illustrated in  FIG.  3   .