Patent Publication Number: US-2022224131-A1

Title: Charge control apparatus

Description:
CROSS-REFERENCE OF RELATED APPLICATIONS 
     This application is the U.S. bypass application of International Application No. PCT/JP2020/037026 filed on Sep. 29, 2020, which designated the U.S. and claims priority to Japanese Application No. 2019-182498 filed on Oct. 2, 2019, the contents of these are incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a charge control apparatus that controls a charge control of a secondary battery. 
     Description of the Related Art 
     For this type of control apparatus, a control apparatus is known in which an increase in temperature of the secondary battery is estimated based on the current temperature and charge/discharge current of the secondary battery. This control apparatus is configured to select, based on the estimated result, one upper limit charge/discharge current value from among a plurality of upper limit charge/discharge current values such that the temperature of the secondary battery does not exceed the upper limit charge/discharge limit. 
     SUMMARY 
     The present disclosure provides a charge control apparatus applied for a system provided with a secondary battery and a charger electrically connected to the secondary battery, the charge control apparatus performing a charge control of the secondary battery by operating the charger. The charge control apparatus includes: an acquiring unit that acquires a temperature of the secondary battery and a charge parameter; a learning unit that learns when the secondary battery is being charged, a temperature rising ratio and battery characteristics information including information associated with the charge parameter of the secondary battery; a storage unit that stores the learned battery characteristics information; a command value calculation unit that calculates a command value of the charge parameter; and an operation unit that operates the charger to control the charge parameter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objectives and other objectives, features and advantages of the present disclosure will be clarified further by the following detailed description with reference to the accompanying drawings. The drawings are: 
         FIG. 1  is an overall configuration of an on-board charge system according to a first embodiment; 
         FIG. 2  is a diagram showing a control unit and a sensor or the like as a periphery configuration thereof; 
         FIG. 3  is a flowchart showing a charge control process; 
         FIG. 4  is a graph showing an outline of a charge current map; 
         FIG. 5  is a graph showing a relationship between a temperature deviation and a correction quantity; 
         FIG. 6  is a flowchart showing of a learning process 
         FIG. 7  is a graph showing a relationship between an internal resistance and a temperature determination value of a secondary battery; 
         FIG. 8  is a graph showing a learning mode of a temperature rising ratio; 
         FIGS. 9A and 9B  are timing diagrams each showing an example of a charge control process; 
         FIG. 10  is a flowchart showing a charge control process according to a second embodiment; 
         FIG. 11  is a flowchart showing a learning process; 
         FIG. 12  is a graph showing a relationship between a charge current, an internal resistance and a heat quantity 
         FIG. 13  is a flowchart showing a charge control process according to a third embodiment; 
         FIG. 14  is a flowchart showing a learning process; 
         FIG. 15  is a diagram showing a relationship between a charge current, a thermal capacity and a heat quantity; 
         FIG. 16  is a flowchart showing a learning process according to a fourth embodiment; and 
         FIG. 17  is a flowchart showing a charge control process according to a fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As an example of a charge control apparatus, JP 2018-170904A discloses a charge control apparatus in which an increase in temperature of the secondary battery is estimated based on the current temperature and charge/discharge current of the secondary battery. This control apparatus is configured to select, based on the estimated result, one upper limit charge/discharge current value from among a plurality of upper limit charge/discharge current values such that the temperature of the secondary battery does not exceed the upper limit charge/discharge limit. Thus, the secondary battery is prevented from being in an overheat state during charge/discharge control of the secondary battery and further avoid degradation of the secondary battery. 
     In the case where a charge control of the secondary battery is conducted, according to the control apparatus disclosed in the above-described patent literature, an increase in the temperature of the secondary battery is estimated based on current temperature and current charge current of the secondary battery at every specific period. Thus, the upper limit charge current of the secondary current is updated at every specific period and the charge current of the secondary current can be changed. As a result, there is a concern that a charging time of the secondary battery may be significantly varied. 
     With reference to the drawings, embodiments of the present disclosure will be described. 
     First Embodiment 
     Hereinafter, a first embodiment in which a charge control apparatus according to the present disclosure is embodied will be described with reference to drawings. The charge control apparatus according to the present embodiment is mounted on a vehicle. 
     As shown in  FIG. 1 , a vehicle  10  is provided with a secondary battery  11  and a rotary electric machine  12 . The secondary battery  11  is, for example, a lithium ion battery or a nickel hydrogen battery, and a battery pack is intended to be utilized according to the present embodiment. The rotary electric machine  12  is driven with power supplied by the secondary battery  11 , and serves as a travelling power source of the vehicle  100 . 
     The vehicle  10  is provided with a battery supervising device  13 , a charger  14  and a control unit  15 . The battery supervising device  13  has a function of detecting a terminal voltage of each battery cell that constitutes the secondary battery  11  and a function of calculating a SOC or the like of each battery cell. The charger  14  is configured to charge the secondary battery  11  with a power supplied from power supply equipment provided outside the vehicle  10 . 
     As shown in  FIG. 2 , the vehicle  10  is provided with a temperature sensor  20 , a voltage sensor  21  and a current sensor  22 . The temperature sensor  20  detects the temperature of the secondary battery  11 , the voltage sensor  21  detects the terminal voltage of the secondary battery  11  and the current sensor  22  detects the current flowing through the secondary battery  11 . The detection values of respective sensors  20  to  22  and the information such as SOC calculated by the battery supervising device  13  is transmitted to the control unit  15 . 
     The control unit  15  performs a charge control process for charging the secondary battery  11  from the charger  14  based on the received detection value and the information thereof. Note that the function of the control unit  15  can be provided, for example, by software stored in a tangible memory device and a computer that executes the software, or by hardware, or combination thereof. 
       FIG. 3  shows the charge control process. The charge control process is executed when the control unit  15  determines that a charge request of the secondary battery  11  is present. 
     Prior to an activation of the charging of the secondary battery  11 , the processes of steps S 10  to S 12  are executed. At step S 10 , the process acquires an initial temperature Tini which is the temperature detected by the temperature sensor  20  prior to the activation of the charging of the secondary battery  11 . Then, the initial temperature Tini is subtracted from a limit temperature Tblimit of the secondary battery  11 , thereby acquiring an allowable temperature rise quantity ΔTlimit. The limit temperature Tblimit is set to be, for example, an allowable upper limit temperature of the secondary battery  11  capable of preventing the secondary battery from being deteriorated. 
     At step S 11 , the allowable temperature rise quantity ΔTlimit is divided by a prescribed period TL, thereby calculating a limit temperature rising ratio ΔTtgt. According to the present embodiment, the prescribed period TL is set to be a period for charging the secondary battery  11  with a constant current control. 
     At step S 12 , the process calculates a command charge current Itgt of the secondary battery  11  based on a charge current map where the command charge current Itgt is defined correlating with the initial temperature Tini and a temperature rising ratio ΔT. The temperature rising ratio ΔT defines an amount of temperature rise at the secondary battery  11  from a time when a charging of the secondary battery starts to a time when a prescribed period TL elapses. At step S 12 , the command charge current Itgt is calculated by selecting a command charge current Itgt among command charge current Itgt defined in the charge current map which corresponds to the initial temperature Tini acquired at step S 10 , and the temperature rising ratio ΔT which is the same value as the limit temperature rising ratio ΔTtgt. Note that processes of steps S 10  to S 12  correspond to command value calculation unit. 
     In the charge current map, as shown in  FIG. 4 , the larger the temperature rising ratio ΔT, the larger the command charge current Itgt is. The charge current map is stored in a memory  15   a  (corresponds to storage unit) included in the control unit  15 . The memory  15   a  is a non-transitory tangible recording media excluding ROM (e.g. non-volatile memory excluding ROM). The charge current map is updated by a learning process which will be detailed later. 
     Referring back to explanation of  FIG. 3 , at step S 13 , the process starts to operate the charger  14  such that the charge current of the secondary battery  11  is controlled to be the command charge current Itgt calculated at step S 12 , thereby starting the charging of the secondary battery  11  with a constant current control. The operation of the control unit corresponds to operation unit. Hereinafter, processes at steps S 14  to S 23  are repeatedly executed at a predetermined control period until the process determines, at step S 23 , that the charging of the secondary battery  11  is completed. 
     According to the present embodiment, a value calculated at step S 12  is basically used as the command charge current Itgt for a period from a time when the charging of the secondary battery  11  starts to a time when the prescribed period TL elapses. This is because, according to the present embodiment, a fan for cooling the secondary battery  11  and a cooling apparatus such as cooling water passage are not provided in the vehicle  10 . Specifically, in this case, when the temperature of the secondary battery  11  once becomes high during the charging of the secondary battery  11 , since the temperature cannot be decreased soon, the temperature of the secondary battery  11  may exceed the limit temperature Tblimit. In particular, when the charging is conducted during the vehicle is stopped, an air cooling effect of the second battery  11  accompanying with the travelling of the vehicle cannot be utilized. Hence, the temperature of the secondary battery  11  may exceed the limit temperature Tblimit. Therefore, prior to starting the charging of the secondary battery  11 , the command charge current Itgt which prevents the temperature of the secondary battery  11  from exceeding the limit temperature Tblimit is determined by processes at steps S 10  to S 12 , and this command charge current Itgt is used for a constant current control period. 
     At step S 14 , the process calculates the temperature estimated value Test of the secondary battery  11  based on the initial temperature Tinit, the limit temperature rising ratio ΔTtgt and the elapse time from a time when the charge starts at step S 13 . In more detail, the initial temperature Tini is added to a value where the limit temperature rising ratio and the elapse time are multiplied, thereby calculating the temperature estimating value Test. Note that the process at step S 14  corresponds to temperature estimating unit. 
     At step S 15 , the process acquires the current temperature detected value Tb of the secondary battery  11  detected by the temperature sensor  20 . 
     At step S 16 , the temperature estimated value Test is subtracted from the temperature detected value Tb, thereby calculating the temperature deviation Terr. 
     At step S 17 , the process determines whether the temperature deviation Terr is larger than or equal to a threshold Tth (&gt;0). Note that the threshold Tth at step S 17  corresponds to first threshold. 
     When the determination at step S 17  is affirmative, the process proceeds to step S 18 , and sets the command value correction quantity ΔIchg to be negative value. In more detail, as shown in  FIG. 5 , the command value correction quantity ΔIchg is set such that the larger the absolute value of the temperature deviation Terr in the positive side, the larger the absolute value of the command value correction quantity ΔIchg in the negative side is. 
     The process proceeds to step S 19  after executing the process at step S 18 , and adds the command value correction quantity ΔIchg set at step S 18  to the command charge current Itgt calculated at step S 12 , thereby calculating the command charge current Itgt which is a value after the correction. Thus, the command charge current Itgt calculated at step S 12  is corrected to be decreased. Thereafter, the charge current of the secondary battery  11  is controlled to be the corrected command charge current Itgt. 
     At step S 17 , when the process determines that the temperature deviation Terr is smaller than the threshold Tth, the process proceeds to step S 20  and determines whether the temperature deviation Terr is less than or equal to −Tth. Note that −Tth at step S 20  corresponds to a second threshold. 
     When the determination at step S 20  is affirmative, the process proceeds to step S 21  and sets the command value correction quantity ΔIchg to be a positive value. In more detail, as shown in  FIG. 5 , the process sets the absolute value of the command value correction quantity ΔIchg such that the larger the absolute value of the temperature deviation Terr in the negative side, the larger the command value correction quantity ΔIchg in the positive side is. 
     The process proceeds to step S 19  after executing the process at step S 21 , and adds the command value correction quantity ΔIchg set at step S 21  to the command charge current Itgt calculated at step S 12 , thereby calculating the command charge current Itgt which is a value after the correction. Thus, the command charge current Itgt calculated at step S 12  is corrected to be increased. Thereafter, the charge current of the secondary battery  11  is controlled to be the corrected command charge current Itgt. Note that processes at steps S 17  to S 21  correspond to correction unit. 
     In the case where the temperature deviation Terr is determined to be larger than −Tth at step S 20 , the process proceeds to step S 22  and sets the command value correction quantity ΔIchg to be 0 (see  FIG. 5 ). In the case where the process proceeds to step S 19  after executing the process at step S 22 , the process does not execute the correction of the command charge current Itgt calculated at step S 12  The process proceeds to step S 23  after executing the process at step S 19 , and determines whether the charging of the secondary battery with the constant current control is completed. That is, the process determines whether the prescribed period TL has elapsed. When the determination at step S 19  is negative, the process proceeds to step S 14 . On the other hand, when the determination at step S 19  is affirmative, the process proceeds to a process of charge control of the secondary battery  11  with the constant voltage control. 
     Subsequently, with reference to  FIG. 6 , a learning process will be described. This process is repeatedly executed at a predetermined control period by the control unit  15 , for example. 
     At step S 30 , the process determines whether the charging of the secondary battery  11  is started similar to the process at step S 13  shown in  FIG. 3 . 
     At step S 31 , the process acquires current charge current detection value Ib (corresponds to charge parameter) of the secondary battery which is detected by the current sensor  22  and current temperature detection value Tb of the secondary battery  11  which is detected by the temperature sensor  20 . 
     At step S 32 , the process sets a high temperature side determination value Ta (n) based on the acquired temperature detection value Tb. As shown in  FIG. 7 , the high temperature side determination value Ta (n) is selected from among a plurality of temperature determination values which divides a temperature range where the temperature detection value Tb can take. According to the present embodiment, each temperature range is set such that the lower the temperature detection value Tb, the narrower the temperature range is. This is determined based on a fact that the lower the temperature of the secondary battery  11 , the larger an amount of increase in the internal resistance R per an amount of decrease in the unit temperature of the secondary battery  11 .  FIG. 7  exemplifies first to fourth temperature determination values Ta 1  to Ta 4 . 
     At step S 32 , the process sets, among the plurality of temperature determination values, the temperature determination value which is the closet value to the acquired temperature detection value Tb and higher than the acquired temperature detection value Tb, to be a high temperature side determination value Ta (n). When updating the temperature determination value Ta (n) at step S 32 , the process sets the high temperature side determination value Ta (n) set immediately before the updating to be a low temperature side determination value Ta (n−1). For example, in the current control period, when updating the high temperature side determination value Ta (n) to be a third temperature determination value Ta 3  from a second temperature determination value Ta 2 , the process sets the second temperature determination value Ta 2  which is a value immediately before the updating, to be the low temperature side determination value Ta (n−1). 
     At step S 33 , the process determines whether the acquired temperature detection value Tb reaches the high temperature side determination value Ta (n) set at step S 32 . When determined that the acquired temperature detection value Tb does not reach the high temperature side determination value Ta (n) at step S 33 , the process proceeds to step S 31 , and proceeds to step S 34  when determined that the acquired temperature detection value Tb reaches the high temperature side determination value Ta (n). 
     At step S 34 , the process divides a value where the current low temperature side determination value Ta (n−1) is subtracted from the current high temperature side determination value Ta (n) by a time TT required for the temperature detection value Tb to reach the high temperature side determination value Ta (n) from a time when the temperature detection value Tb becomes the low temperature side determination value Ta (n−1), thereby calculating the temperature rising ratio ΔT. 
     At step S 35 , the process learns the temperature rising ratio ΔT associating with the charge current detection value Ib and the current low temperature side determination value Ta (n−1) which are acquired at step S 31 . Then, the process stores the learned temperature rising ratio ΔT, the command charge current Itgt having the same value as the acquired charge current detection value Ib and the initial temperature Tini having the same value as the current low temperature side determination value Ta (n−1) into the memory  15   a  while being associated with each other, thereby updating the charge current map. Note that the process at step S 35  corresponds to learning unit. 
     At step S 36 , similar to step S 23  shown in  FIG. 3 , the process determines whether the charging of the secondary battery  11  with the constant current control is completed. 
       FIG. 8  shows an example of learning process of the temperature rising ratio ΔT. In  FIG. 8 , the charge current detection value Ib is set to be constant. 
     At time t 0  to t 1 , the high temperature side determination value Ta (n) is set to be the second temperature determination value Ta 2 , and the low temperature side determination value Ta (n−1) is set to be the first temperature determination value Ta 1 . Hence, in the case where Ta 2 -Ta 1  in a period from t 0  to t 1  is defined as dT 1 , a period from t 0  to t 1  is defined as dL 1 , the temperature rising ratio ΔT 1  is learned as dT 1 /dL 1 . Then, the learned temperature rising ratio ΔT 1  is stored in the memory  15   a  associating with the command charge current Itgt of which the value is the same as the acquired charge current detection value Ib and the initial temperature Tini of which the value is the same as the first temperature determination value Ta 1 , thereby updating the charge current map. Similarly, the learning process is executed for a period from t 1  to t 2 , a period from t 2  to t 3 , and a period from t 3  to t 4 . 
       FIGS. 9A and 9B  show an example of a charge control process.  FIG. 9A  shows a change in the command charge current Itgt of the secondary battery  11  and  FIG. 9B  shows a change in the temperature detected value Tb and the temperature estimated value Test of the secondary battery  11 . 
     The process calculates the allowable temperature rise quantity ΔTlimit based on the initial temperature Tini and the limit temperature Tblimit prior to time t 1  at which a charge starts. Then, the process calculates the limit temperature rising ratio ΔTtgt based on the calculated allowable temperature rise quantity and the prescribed period TL, and calculates the command charge current Itgt based on the calculated limit temperature rising ratio ΔTtgt, the initial temperature Tini and the charge current map. Thereafter, at time t 1 , the charging of the secondary battery  11  is started based on the calculated command charge current Itgt. 
     Thereafter, at time  2 , the process determines that the temperature deviation Terr is larger than the temperature estimated value Test by the threshold Tth or more. Hence, the command charge current Itgt is corrected to be decreased. At this moment, in order to avoid a rapid change in the command charge current Itgt, the command charge current may preferably be gradually changed. After time T 3  at which the prescribed period TL elapses from time T 1 , the charging is performed for the secondary battery  11  with the constant current control. 
     According to the present embodiment described in detail, the following effects and advantages can be obtained. 
     The limit temperature rising ratio ΔTtgt is calculated based on the allowable temperature rise quantity ΔTlimit and the prescribed period TL. Then, the command charge current Itgt is calculated based on the calculated limit temperature rising ratio ΔTtgt, the initial temperature Tini and the charge current map. Hence, in the prescribed period TL from the charge start timing of the secondary battery  11 , the command charge current Itgt which prevents the temperature of the secondary battery  11  from exceeding the limit temperature Tblimit can be determined, and the secondary battery  11  can be prevented from being in an overheating state in an overheat state during charge/discharge control process. Here, learning of the temperature rising ratio ΔT used for calculating the command charge current Itgt is performed based on the temperature detected value Tb and the charge current detection value Ib. Accordingly, accuracy of calculating the command charge current Itgt which prevents the temperature of the secondary battery  11  from exceeding the limit temperature Tblimit can be enhanced. 
     Also, prior to the charging start of the secondary battery  11 , the process calculates the command charge current Itgt for the prescribed period from the charge start timing. Hence, the charge period of the secondary battery  11  can be prevented from being significantly changed from the prescribed period TL. 
     In a period from the charging of the secondary battery is started to a time when the prescribed period TL elapses, learning for the temperature rising ratio ΔT is performed for each temperature range where the acquired temperature detection value Tb passes through, among respective temperature ranges divided by respective temperature determination values. Hence, learning process for the temperature rising ratio ΔT can be frequently performed when the charge control process is performed. As a result, in the case where the charge control process is performed in the next cycle, the calculation accuracy of the command charge current Itgt based on the charge current map can be improved. 
     After starting the charging of the secondary battery  11 , when the temperature deviation Terr, which is a difference between the acquired temperature detection value Tb and the temperature estimated value Test, is larger than or equal to the threshold Tth, the command charge current Itgt is corrected to be decreased. On the other hand, when the temperature deviation Terr is lower than or equal to −Tth, the command charge current Itgt is corrected to be increased. Thus, even in the case where the command charge current Itgt determined prior to start of the charging us varied from the appropriate value, the temperature of the secondary battery  11  can be prevented from exceeding the limit temperature Tblimit. 
     Modifications of the First Embodiment 
     The absolute value of the threshold (&gt;0) used for step S 17  shown in  FIG. 3  and the absolute value of the threshold (&lt;0) used for step S 20  may be set to be different values. 
     Second Embodiment 
     Hereinafter, with reference to the drawings, for the second embodiment, configurations different from the first embodiment will be mainly described. According to the present embodiment, a learning process for the internal resistance as battery characteristics information of the secondary battery  11  is also performed. 
       FIG. 10  shows a procedure of the charge control process according to the present embodiment. In  FIG. 10 , processes same as those shown in  FIG. 3  will be applied with the same reference symbols for the sake of convenience. 
     After executing the process at step S 12 , the process proceeds to step S 24  and calculates the internal resistance R based on the internal resistance map where the internal resistance R of the secondary battery  11  is defined associated with the temperature of the secondary battery  11  and the charge current of the secondary battery  11 . In more detail, among the internal resistance defined in the internal resistance map, an internal resistance R corresponding to a temperature value the same as the initial temperature Tini acquired at step S 10  and a charge current value which is the same as the command charge current Itgt calculated at step S 12  is selected, thereby calculating the internal resistance R. 
     At step S 25 , a reference temperature increasing quantity ΔTcal represented by the following equation (eq1) based on the command charge current Itgt calculated at step S 12 , the internal resistance R calculated at step S 24 , the thermal capacity C of the secondary battery  11  and a heat dissipation quantity Qdis. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Math 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       Δ 
                       ⁢ 
                       
                         T 
                         cal 
                       
                     
                     = 
                     
                       
                         
                           
                             I 
                             
                               t 
                               ⁢ 
                               g 
                               ⁢ 
                               t 
                             
                             2 
                           
                           · 
                           R 
                         
                         - 
                         
                           Q 
                           
                             d 
                             ⁢ 
                             i 
                             ⁢ 
                             s 
                           
                         
                       
                       C 
                     
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                   ( 
                   eq1 
                   ) 
                 
               
             
           
         
       
     
     In the above-equation (eq1), for the thermal capacity C and the heat dissipation quantity Qdis, predetermined values determined by experiment or the like are utilized. The above equation (eq1) is derived from the following equation (eq2) indicating a relationship between the heat quantity Qf, the heat dissipation quantity Qdis and the thermal capacity C of the secondary battery  11 , and the following equation (eq3) indicating a relationship between the heat quantity Qf, the charge current and the internal resistance R of the secondary battery  11 . 
       [Math 2] 
         Q   f   −Q   dis   =C·ΔT   cal   (eq2)
 
       [Math 3] 
         Q   f   =I   tgt   2   ·R   (eq3)
 
     Thereafter, at step S 26 , the process calculates the temperature estimated value Test of the secondary battery  11  based on the initial temperature Tini, the reference temperature increasing quantity ΔTcal calculated at step S 25  and the elapsed time from a time when the charge starts at step S 13 . Specifically, the initial temperature Tini is added to a value where the reference temperature increasing quantity ΔTcal and the elapsed time are multiplied, thereby calculating the temperature estimated value Test. 
     Note that the reference temperature increasing quantity ΔTcal used for step S 26  may preferably be updated based on the current temperature detection value Tb and the command charge current Itgt with a method similar to that of steps S 24  and S 25 . 
     Subsequently, with reference to  FIG. 11 , a learning process will be described. This process is repeatedly executed by the control unit  15  at a predetermined period, for example. In  FIG. 11 , processes the same as those shown in  FIG. 6  will be applied with the same reference symbols for the sake of convenience. 
     After executing the process at step S 35 , the process proceeds to step S 37  and calculates, based on the temperature rising ratio ΔT calculated at step S 34 , the current charge current detection value Ib, the thermal capacity C and the heat dissipation quantity Qdis, the internal resistance R with the following equation (eq4). 
     
       
         
           
             
               
                 
                   [ 
                   
                     Math 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     R 
                     = 
                     
                       
                         
                           
                             C 
                             · 
                             Δ 
                           
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           T 
                         
                         + 
                         
                           Q 
                           
                             d 
                             ⁢ 
                             i 
                             ⁢ 
                             s 
                           
                         
                       
                       
                         I 
                         b 
                         2 
                       
                     
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                   ( 
                   eq4 
                   ) 
                 
               
             
           
         
       
     
     At step S 38 , the process learns the internal resistance R associating with the charge current detection value Ib acquired at step S 31  and the low temperature side determination value Ta (n−1). The learned internal resistance R is stored into the memory  15   a  associating with a charge current value which is the same as the acquired charge current detection value Ib and a temperature value which is the same as the current low temperature side determination value Ta (n−1), thereby updating the internal resistance map. The above-described learning process for the internal resistance R is performed based on a fact that the heat quantity Qf of the secondary battery  11  becomes larger when the internal resistance R is large compared to a case of low internal resistance R as shown in  FIG. 12   
     According to the above-described embodiment, since the temperature estimated value Test is calculated based on the learned internal resistance R, accuracy of estimating the temperature during the charge control process can be enhanced. 
     Third Embodiment 
     Hereinafter, with reference to the drawings, for the third embodiment, configurations different from the second embodiment will be mainly described. According to the present embodiment, in the learning process, instead of the internal resistance, a learning process for the thermal capacity of the secondary battery  11  is performed. 
       FIG. 13  shows a charge control process according to the present embodiment. In  FIG. 13 , processes same as those shown in  FIG. 10  will be applied with the same reference symbols for the sake of convenience. 
     After executing the process at step S 12 , the process proceeds to step S 27  and calculates the thermal capacity C based on the thermal capacity map where the thermal capacity C of the secondary battery  11  is defined associating with the temperature of the secondary battery  11  and the charge current of the secondary battery  11 . In more detail, the process selects, among the thermal capacity C defined in the thermal capacity map, a thermal capacity C corresponding to a temperature value which is the same as the initial temperature Tini acquired at step S 10  and a charge current value which is the same as a command charge current Itgt calculated at step S 12 , thereby calculating the thermal capacity C. 
     At step S 28 , the process calculates, based on the command charge current Itgt calculated at step S 12 , the thermal capacity C calculated at step S 27 , the internal resistance R of the secondary battery  11  and the heat dissipation quantity Qdis from the secondary battery, the reference temperature increasing quantity ΔTcal expressed by the above equation (eq1). In this case, predetermined values determined by an experiment or the like may be used for the internal resistance R and the heat dissipation quantity Qdis. 
     Thereafter, at step S 29 , the process calculates, based on the initial temperature Tini, the reference temperature increasing quantity ΔTcal calculated at step S 28  and the elapsed time from a time when the charge starts at step S 13 , the temperature estimated value Test of the secondary battery  11 . Specifically, the initial temperature Tini is added to a value where the reference temperature increasing quantity ΔTcal and the elapse time are multiplied, thereby calculating the temperature estimated value Test. 
     Note that, similar to the second embodiment, the reference temperature increasing quantity ΔTcal used for step S 26  may preferably be updated, based on the current temperature detection value Tb and the command charge current Itgt, with a method similar to steps S 27  and S 28 . 
     Next, with reference to  FIG. 14 , a learning process will be described. This process is repeatedly executed at a predetermined control period, for example. In  FIG. 14 , processes same as those shown in  FIG. 11  will be applied with the same reference symbols for the sake of convenience. 
     After executing the process at step S 35 , the process proceeds to step S 39  and calculates, based on the temperature rising ratio ΔT calculated at step S 34 , the current charge current detection value Ib, the internal resistance R and the heat dissipation quantity Qdis, with the following equation (eq5). 
     
       
         
           
             
               
                 
                   [ 
                   
                     Math 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   C 
                   = 
                   
                     
                       
                         
                           I 
                           
                             t 
                             ⁢ 
                             g 
                             ⁢ 
                             t 
                           
                           2 
                         
                         · 
                         R 
                       
                       - 
                       
                         Q 
                         
                           d 
                           ⁢ 
                           i 
                           ⁢ 
                           s 
                         
                       
                     
                     
                       Δ 
                       ⁢ 
                       T 
                     
                   
                 
               
               
                 
                   ( 
                   eq5 
                   ) 
                 
               
             
           
         
       
     
     At step S 38 , the process learns the thermal capacity C associating with the charge current detection value Ib acquired at step S 31  and the low temperature side determination value Ta (n−1). The learned thermal capacity C is stored into the memory  15   a  associating with a charge current value which is the same as the acquired charge current detection value Ib and a temperature value which is the same as the current low temperature side determination value Ta (n−1), thereby updating the thermal capacity map. The above-described learning process for the thermal capacity C is performed based on a fact that the heat quantity Qf with higher thermal capacity C is smaller than a case of smaller thermal capacity C as shown in  FIG. 15   
     According to the above-described embodiment, effects and advantages similar to those in the second embodiment can be obtained. 
     Fourth Embodiment 
     Hereinafter, with reference to the drawings, for the fourth embodiment, configurations different from the first embodiment will be mainly described. According to the present embodiment, when occurrence of an abnormality in the secondary battery  11  is determined, the learning process is discontinued. 
       FIG. 16  shows a learning process according to the present embodiment. For example, this process is repeatedly executed at a predetermined control process by the control unit  15 . In  FIG. 16 , processes the same as those shown in  FIG. 6  will be applied with the same reference symbols for the sake of convenience. 
     When determination at step S 33  is affirmative, the process proceeds to step S 50  and determines whether an abnormality has occurred in the secondary battery  11 . A method for determining an abnormality of the secondary battery  11  can be accomplished by various known methods. Note that the process at step S 50  corresponds to an abnormality determination unit. 
     When determined that no abnormality has occurred at step S 50 , the process proceeds to step S 34 . On the other hand, when determined that no abnormality has occurred at step S 50 , the process proceeds to step S 51  and discontinue the process. 
     According to the above-described present embodiment, erroneous learning of the temperature rising ratio ΔT can be avoided. 
     Fifth Embodiment 
     Hereinafter, with reference to the drawings, for the fifth embodiment, configurations different from the first embodiment will be mainly described. According to the present embodiment, the contents of the correction process is changed. 
       FIG. 17  shows a charge control process according to the present embodiment. In  FIG. 17 , processes same as those shown in  FIG. 3  will be applied with the same reference symbols for the sake of convenience. 
     At step S 60 , the process determines, when a predetermined period elapsed from a time when the process at step S 19  is executed, whether the absolute value of the temperature deviation Terr is larger than or equal to a predetermined value TA. The predetermined value TA corresponds to a first predetermined value which is set to be larger than 0 and smaller than or equal to the threshold Tth. According to the present embodiment, the predetermined value TA is set to be smaller than the threshold Tth. 
     When the determination at step S 60  is negative, the process proceeds to step S 23 . On the other hand, when the determination at step S 60  is affirmative, the process proceeds to step S 61  and sets the absolute value of the command value correction quantity ΔIchg to be multiplied by α (α&gt;1) while maintaining the sign of the command value correction quantity ΔIchg set at step S 18  or S 21 . 
     According to the process at step S 61 , after executing the process of step S 18 , the command charge current Itgt is further corrected to be decreased. On the hand, after executing the process of step S 21 , the command charge current Itgt is further corrected to be increased. Thus, the temperature of the secondary battery  11  can be reliably prevented from exceeding the limit temperature Tblimit 
     Modifications of Fifth Embodiment 
     In the process shown in  FIG. 17 , the predetermined value used for step S 60  after executing the process of step S 18  and the predetermined value used for step S 60  after executing the process of step S 21  may be set to be different values. 
     Other Embodiment 
     Note that the above-described respective embodiments may be modified in the following manners. 
     In the charge current map, the command charge current Itgt may be defined associating with at least one of the number of charging of the secondary battery  11  and the SOC of the secondary battery  11  in addition to the temperature rising ratio ΔT. 
     In the internal resistance map, the internal resistance value R may be defined associating with at least one of the number of chargings of the secondary battery  11  and the SOC of the secondary battery  11  in addition to the charge current and the temperature of the secondary battery  11 . Further, in the thermal capacity map, the thermal capacity C may be defined associating with at least one of the number of chargings of the secondary battery  11  and the SOC of the secondary battery  11  in addition to the charge current and the temperature of the secondary battery  11 . 
     The present disclosure may be applied to a system without being mounted on a vehicle. 
     Instead of the charge current map, a command charge power Ptgt of the secondary battery  11  may be calculated based on the charge power map where the command charge power Ptgt of the secondary battery  11  is defined associating with the initial temperature Tini and the temperature rising ratio ΔT. In this case, the control unit may operate the charger  14  to control the charge power from the charge start timing of the secondary battery  11  to be calculated command charge power Ptgt. Hereinafter, a charge power map will be described with reference to the process shown in  FIG. 6 . 
     The control unit  15  calculates the charge power Pb (charging parameter) during the charging of the secondary battery based on the charge current detection value Ib and the voltage detection value Vb of the voltage sensor  21 . 
     The control unit  15  learns, at step S 35 , the temperature rising ratio ΔT associated with the calculated charge power Pb and the current low temperature side determination value Ta (n−1). The process stores the learned temperature rising ratio ΔT into the memory  15   a  associating with the command charge power Ptgt of which the value is the same as the acquired charge power Pb and the initial temperature Tini of which the value is the same as the current low temperature side determination value Ta (n−1), thereby updating the charge power map. For process other than the updating process of the charge power map, in the above-described respective embodiments, instead of the charge current detection value Ib and the command charge current Itgt, the charge power Pb and the command charge current Ptgt may be utilized respectively. 
     The control unit and method thereof disclosed in the present disclosure may be accomplished by a dedicated computer constituted of a processor and a memory programmed to execute one or more functions embodied by computer programs. 
     Alternatively, the control unit and method thereof disclosed in the present disclosure may be accomplished by a dedicated computer provided by a processor configured of one or more dedicated hardware logic circuits. Further, the control unit and method thereof disclosed in the present disclosure may be accomplished by one or more dedicated computer where a processor and a memory programmed to execute one or more functions, and a processor configured of one or more hardware logic circuits are combined. Furthermore, the computer programs may be stored, as instruction codes executed by the computer, into a computer readable non-transitory tangible recording media. 
     The present disclosure has been described in accordance with the embodiments. However, the present disclosure is not limited to the embodiments and structure thereof. The present disclosure includes various modification examples and modifications within the equivalent configurations. Further, various combinations and modes and other combinations and modes including one element or more or less elements of those various combinations are within the range and technical scope of the present disclosure. 
     CONCLUSION 
     As described, the present disclosure provides a charge control apparatus capable of preventing a charge period of a secondary battery from being significantly varied while preventing the secondary battery from being in an overheating state. 
     Specifically, the present disclosure provides a charge control apparatus applied for a system provided with a secondary battery and a charger electrically connected to the secondary battery, the charge control apparatus performing a charge control of the secondary battery by operating the charger. The charge control apparatus includes: an acquiring unit that acquires a temperature of the secondary battery and a charge parameter which is either a charge current or a charge power of the secondary battery; a learning unit that learns when the secondary battery is being charged, based on the acquired charge parameter and the temperature of the secondary battery, a temperature rising ratio which is a temperature rise quantity of the secondary battery in a prescribed period elapsed from a time when a charging of the secondary battery starts, and battery characteristics information including information associating with the charge parameter of the secondary battery; a storage unit that stores the learned battery characteristics information; a command value calculation unit that calculates, prior to an activation of a charging of the secondary battery, a command value of the charge parameter through the prescribed period elapsed from a charge start timing of the secondary battery, based on a limit temperature rising ratio calculated in accordance with a difference between an initial temperature of the secondary battery and a limit temperature of the secondary battery and the prescribed period, and the battery characteristics information stored in the storage unit; and an operation unit that operates the charger to control the charge parameter from the charge start timing of the secondary battery to be the calculated command value. 
     According to the present disclosure, a command value of the charge parameter is calculated based on the temperature rising ratio calculated in accordance with a difference between the initial temperature of the secondary battery and the limit temperature and the battery characteristics information stored in the storage unit. Hence, as the command value used for the prescribed period from the charge start timing of the secondary battery, a command value can be determined where the temperature of the secondary battery does not exceed the limit temperature. Thus, the secondary battery can be prevented from being in an overheating state during the charge control. According to the present disclosure, the battery characteristics information including the temperature rising ratio used when calculating the command value is learned based on the temperature and the charge parameter of the secondary battery. Accordingly, calculation accuracy of the command value where the temperature of the secondary battery does not exceed the limit temperature can be improved. 
     Also, according to the present disclosure, prior to start of charging of the secondary battery, the command value is calculated for a prescribed period from the charge start timing, and the calculated command value is basically used through the prescribed period. Therefore, the charge period of the secondary battery can be prevented from being significantly varied from the prescribed period. 
     According to the above-described preset disclosure, the charging period of the secondary battery can be prevented from being significantly varied while preventing the secondary battery being in an overheating state.