Abstract:
Disclosed is a battery system that, in a laminated part of a power generating element in a lithium ion rechargeable battery, can properly detect a temperature and the distribution of a temperature change occurring in a positive-negative extending direction and can utilize the detected data in the control of the battery. Also disclosed are a vehicle and a battery-mounting device comprising the battery system. A battery system comprises a lithium ion rechargeable battery. The lithium ion rechargeable battery comprises a power generating element comprising a laminated part, a positive electrode extended part, and a negative electrode extended part. The battery system further comprises a control means and a central temperature detecting means that detects the temperatures of a central laminated part in the laminated part, and at least one of a positive-side temperature detecting means that detects the temperatures of a positive-side laminated part in the laminated part and a negative-side temperature detecting means that detects the temperatures of a negative-side laminated part in the stacked part. The control means controls the lithium ion rechargeable battery using the temperature of the central laminated part, and at least one of the temperature of the positive-side laminated part and the temperature of the negative-side laminated part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a national phase application based on the PCT International Patent Application No. PCT/JP2009/057754 filed on Apr. 17, 2009, the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a battery system including a lithium ion secondary (rechargeable) battery including a power generating element, a temperature detecting means for detecting the temperature of the power generating element, and a control means for controlling the lithium ion secondary battery. The present invention further relates to a vehicle and a battery-mounting device, each of which includes the battery system. 
       BACKGROUND ART 
       [0003]    Recently, a lithium ion secondary battery (hereinafter, simply also referred to as a battery) is utilized as a power source for driving a hybrid vehicle or a portable electronic device such as a notebook-sized personal computer, a video camera corder, etc. 
         [0004]    As one of such batteries, Patent Literature 1 discloses a lithium ion secondary battery in which a thermocouple is embedded in a predetermined portion of a battery main body (a power generating element). 
       CITATION LIST 
     Patent Literature 
       [0005]    Patent Literature 1: JP10(1998)-55825 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    Meanwhile, of the power generating element of the battery, a laminated part functioning as a battery and including a positive electrode and a negative electrode both being laminated by interposing a separator therebetween has a spread or extent in a parallel direction to a surface of the positive electrode and others. Accordingly, it has been found that the laminated part has, locally in the above direction, nonuniform concentration of an electrolyte solution retained between the positive and negative electrodes, nonuniform current density during operation, nonuniform temperature resulting from a local difference in heat radiation characteristics. 
         [0007]    Further, it has also been found that, in a positive-negative electrode extending direction that joins a positive electrode extended part which is a part of the positive electrode plate extending from the laminated part and a negative electrode extended part which is a part of the negative electrode plate extending from the laminated part, assuming that this laminated part is divided into a central laminated part, a positive-side laminated part located closer to the positive electrode extended part than the central laminated part is, and a negative-side laminated part located closer to the negative electrode extended part than the central laminated part is, the above nonuniformity is distributed differently between the three parts in many cases. 
         [0008]    Furthermore, it has also been revealed that the occurrence of various nonuniformity occurring in the laminated part can be detected from temperatures of the central laminated part, the positive-side laminated part, and the negative-side laminated part, a temperature change before and after discharge or before and after charge, and the battery could be controlled based on a detection result. 
         [0009]    However, as to the battery disclosed in Patent Literature 1, only a predetermined portion of the laminated part of the power generating element could be measured. Thus, the various nonuniformity occurring in the laminated part cannot be detected appropriately. 
         [0010]    The present invention has been made to solve the above problems and has a purpose to provide a battery system capable of appropriately detecting a temperature and a temperature change distribution occurring in a laminated part of a power generating element of a lithium ion secondary battery in a positive-negative extending direction to utilize a detection result for control of the battery. Another purpose is to provide a vehicle and a battery-mounting device each including the battery system. 
       Solution to Problem 
       [0011]    To achieve the above purpose, one aspect of the invention provides a battery system comprising: a lithium ion secondary battery having a power generating element including a positive electrode plate, a negative electrode plate, and a separator, the power generating element including a laminated part in which the positive electrode plate and the negative electrode plate are laminated by interposing the separator therebetween, a positive extended part formed of a part of the positive electrode plate extending from the laminated part, and a negative extended part formed of a part of the negative electrode plate extending from the laminated part in an opposite direction to the positive extended part; control means for controlling the lithium ion secondary battery; when a positive and negative extending direction is defined as a direction joining the positive extended part and the negative extended part, central temperature detecting means for detecting a temperature of a central laminated part located in the center of the laminated part in the positive and negative extending direction; and at least one of: positive-side temperature detecting means for detecting a temperature of a positive-side laminated part of the laminated part, the positive-side laminated part being located closer to the positive extended part in the positive and negative extending direction than the central laminated part is, and negative-side temperature detecting means for detecting a temperature of a negative-side laminated part of the laminated part, the negative-side laminated part being located closer to the negative extended part in the positive and negative extending direction than the central laminated part is, the control means being arranged to control the lithium ion secondary battery by use of the temperature of the central laminated part and at least one of the temperature of the positive-side laminated part, and the temperature of the negative-side laminated part. 
         [0012]    The above battery system comprises the central temperature detecting means, at least one of the positive-side temperature detecting means, and the negative-side temperature detecting means, and the control means. Thus, by use of the temperature of the central laminated part and the temperature of the positive-side laminated part or the negative-side laminated part, for example, it is possible to calculate a temperature difference between the parts, a difference in temperature rise amount before and after discharge between the parts, and others. The battery can therefore be appropriately controlled based on the calculation results. 
         [0013]    The above battery system uses the temperature of each part and hence can more easily detect various nonuniformity occurring in the laminated part than in the case where a lithium ion concentration of an electrolyte solution and others in each part is directly detected. 
         [0014]    The type of the power generating element may include a winding type that a positive electrode plate and a negative electrode plate, each having a strip shape, are wound by interposing a separator therebetween and a laminated type that positive electrode plates and negative electrode plates, having a rectangular plate-like shape respectively, are laminated by interposing separators therebetween. Further, as the central temperature detecting means, the positive-side temperature detecting means, and the negative-side temperature detecting means, for example, a thermocouple and a thermistor may be adopted. 
         [0015]    The control to be executed by the control means may include the control of battery current during charge and discharge, the control of temperature of the central laminated part, the positive-side laminated part, and the negative-side laminated part by use of a heater or a cooling element, etc. 
         [0016]    In performing the control by use of the temperature of the central laminated part and others, the control means utilizes the temperature itself of each part and besides can use a difference in temperature between the parts and a difference in temperature rise amount generated before and after the discharge of the battery between the parts. 
         [0017]    In the above battery system, preferably, the control means includes limitation changing means for changing limitation of charge and discharge current to be allowed to flow in the lithium ion secondary battery during high-rate charge and discharge based on a rise amount difference between a temperature rise amount of the temperature rise in the central laminated part and at least one of a temperature rise amount of the temperature rise in the positive-side laminated part and a temperature rise amount of the temperature rise in the negative-side laminated part, the difference being generated by the high-rate discharge. 
         [0018]    For instance, it has been found that when high-rate discharge or charge with a current of 10C for example is performed, a current density is distributed according to a lithium ion concentration distribution of an electrolyte in the laminated part, and also a heating amount in each part is distributed. Accordingly, by comparing the temperature rise amounts in the parts occurring during the high-rate discharge, it is possible to acquire a difference in current density between the parts and hence a difference in lithium ion concentration of the electrolyte solution. 
         [0019]    In the above battery system, the control means includes the above limitation changing means. Accordingly, based on at least one of the difference in temperature rise amount between the central laminated part and the positive-side laminated part and the difference in temperature rise amount between the central laminated part and the negative-side laminated part, the limitation changing means changes the limitation of discharge current for the high-rate discharge. This makes it possible to perform appropriate control to battery deterioration caused by the high-rate discharge. 
         [0020]    Furthermore, in the above battery system, preferably, the limitation changing means changes the control to relatively decrease a discharge current of subsequent high-rate discharge when the temperature rise amount of the central laminated part is smaller than one of the temperature rise amount of the positive-side laminated part and the temperature rise amount of the negative-side laminated part. 
         [0021]    Meanwhile, it has been found that when the battery is repeatedly discharged with a relatively large current (high-rate) of 10C for example, battery deterioration (high-rate deterioration) such as an increase in internal resistance is caused. 
         [0022]    In a battery in which no high-rate deterioration has occurred, a temperature rise amount that occurs during high-rate discharge is larger in the central laminated part than in the positive-side laminated part and the negative-side laminated part. On the other hand, as the high-rate deterioration resulting from the high-rate discharge progresses, the temperature rise amount in the central laminated part decreases, whereas the temperature rise amounts in the positive-side laminated part and the negative-side laminated part increase. Accordingly, the temperature rise amount of the central laminated part finally becomes equal to those of the positive-side laminated part and the negative-side laminated part. Thereafter, reversely, the temperature rise amount of the central laminated part becomes smaller than those of the positive-side laminated part and the negative-side laminated part. 
         [0023]    In consideration of the above knowledge, the limitation changing means of the above battery system changes the control to relatively decrease the discharge current for the subsequent high-rate discharge when the temperature rise amount of the central laminated part becomes smaller than the temperature rise amounts of the positive-side laminated part and the negative-side laminated part. This can restrain progression of the battery high-rate deterioration, i.e., increase in the internal resistance. Furthermore, in some cases, the high-rate deterioration caused in the battery can be restored. 
         [0024]    For relatively reducing the detecting current for the high-rate discharge, it may be achieved by a technique of limiting the value of a peak discharge current in the high-rate discharge generated under rapid acceleration to a smaller value, a technique of shortening a period of a larger discharge current than a predetermined value, etc. 
         [0025]    Alternatively, in the above battery system, preferably, the battery system includes the negative-side temperature detecting means, and the limitation changing means changes the control to relatively increase a discharge current of subsequent high-rate discharge when the temperature rise amount of the central laminated part is smaller than the temperature rise amount of the negative-side laminated part. 
         [0026]    The present inventors found out that when the battery was subjected to repeated high-rate discharge, the internal resistance increased once but then decreased and became stable. Consequently, when the high-rate deterioration is forced to progress, thereby causing the battery to go through a high internal resistance state, a rather preferable (a low internal resistance) state can be established later. For a period in which the internal resistance is high while the high-rate deterioration is progressing, the temperature rise amount of the central laminated part becomes smaller than the temperature rise amounts of the positive-side laminated part and the negative-side laminated part. For a period in which the internal resistance decreases past the above period, the temperature rise amount of the positive-side laminated part decreases. 
         [0027]    Accordingly, it has been found that the temperature rise amount of the central laminated part is smaller than the temperature rise amount of the negative-side laminated part but almost equal to the temperature rise amount of the positive-side laminated part. 
         [0028]    Based on the above knowledge, in the above battery system, the control changing means changes the control to relatively increase the discharge current for the subsequent high-rate discharge in the case where the temperature rise amount of the central laminated part is smaller than the temperature rise amount of the negative-side laminated part. By relatively increasing the discharge current for the high-rate discharge as above, the high-rate deterioration of the battery is prompted. Thus, the battery is caused to quickly go through a high internal resistance state and then can be used in a low internal resistance state. 
         [0029]    For relatively increasing a discharge current for the high-rate discharge, it may be achieved by a technique of changing the value of a peak discharge current in the high-rate discharge to a larger value, a technique of lengthening a period of a larger discharge current than a predetermined value, etc. 
         [0030]    Alternatively, the above battery system, preferably, includes: central temperature changing means for changing a temperature of the central laminated part of the power generating element; positive-side temperature changing means for changing a temperature of the positive-side laminated part of the power generating element; and negative-side temperature changing means for changing a temperature of the negative-side laminated part of the power generating element, wherein the control means includes temperature control means for controlling the central temperature changing means, the positive-side temperature changing means, and the negative-side temperature changing means. 
         [0031]    The above battery system includes the above temperature changing means and also the control means includes the temperature control means. Accordingly, based on the temperature of the central laminated part of the measured power generating element and at least one of the temperature of the positive-side laminated part and the temperature of the negative-side laminated part, the temperatures of the central laminated part, the positive-side laminated part, and the negative-side laminated part can be appropriately changed. This enables appropriate temperature control by for example controlling the temperatures to eliminate nonuniformity of lithium ion concentration generated in the laminated part and others. 
         [0032]    As the central temperature changing means, the positive-side temperature changing means, and the negative-side temperature changing means, for instance, a heater that generates heat when energized and a Peltier element that absorbs heat when energized may be adopted. 
         [0033]    Alternatively, another aspect of the invention provides a vehicle including one of the aforementioned battery systems. 
         [0034]    The above vehicle includes the aforementioned battery system. Thus, the vehicle can calculate a temperature difference between the parts, a difference in temperature rise amount before and after in each part based on the temperatures of the central laminated part, the positive-side laminated part, and the negative-side laminated part, and hence appropriately control the battery based on a calculation result. 
         [0035]    It is to be noted that the vehicle may be any vehicle using electric energy of the battery in the whole or part of its power source. For instance, the vehicle may be an electric vehicle, a plug-in hybrid vehicle, a hybrid railroad vehicle, a forklift, an electric-driven wheel chair, an electric bicycle, an electric scooter, etc. 
         [0036]    Alternatively, another aspect of the invention provides a battery-mounting device including one of the aforementioned battery systems. 
         [0037]    The above battery-mounting device includes the aforementioned battery system, so that the battery-mounting device can calculate a temperature difference between the parts, a difference in temperature rise amount before and after each part based on the temperatures of the central laminated part, the positive-side laminated part, and the negative-side laminated part, and hence appropriately control the battery based on a calculation result. 
         [0038]    It is to be noted that the battery-mounting device may be any device mounted with the battery and utilizes the battery as at least one of energy sources. For example, the device may be any one of various battery-driven home electric appliances, office equipment, and industrial equipment such as a personal computer, a cell phone, a battery-driven electric tool, an uninterruptible power supply system. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0039]      FIG. 1  is a perspective view of a vehicle in Embodiment 1, Embodiment 2, and Modified example 1; 
           [0040]      FIG. 2  is a perspective view of a lithium ion secondary battery in Embodiment 1 and Modified example 1; 
           [0041]      FIG. 3  is a cross-sectional view of the lithium ion secondary battery in Embodiment 1 and Modified example 1 (a cross-sectional view along A-A in  FIG. 2 ); 
           [0042]      FIG. 4A  is a cross-sectional view of the lithium ion secondary battery in Embodiment 1 and Modified example 1 (a cross-sectional view along B-B in  FIG. 3 ); 
           [0043]      FIG. 4B  is an enlarged cross-sectional view of the lithium ion secondary battery in Embodiment 1 and Modified example 1 (a part C in  FIG. 4A ); 
           [0044]      FIG. 5  is an explanatory view of a temperature in Embodiment 1 and Modified example 1; 
           [0045]      FIG. 6  is a graph showing a relationship between internal resistance of the lithium ion secondary battery and the number of cycles in a charge and discharge cycle test; 
           [0046]      FIG. 7  is a graph showing lithium ion concentration in each laminated part of the lithium ion secondary battery; 
           [0047]      FIG. 8  is a graph showing a temperature rise amount in each laminated part of the lithium ion secondary battery; 
           [0048]      FIG. 9  is a flowchart in Embodiment 1; 
           [0049]      FIG. 10  is a flowchart in Embodiment 1 and Modified example 1; 
           [0050]      FIG. 11  is a graph showing a relationship between internal resistance of the lithium ion secondary battery and the number of cycles in the charge and discharge cycle test; 
           [0051]      FIG. 12  is a graph showing lithium ion concentration in each laminated part of the lithium ion secondary battery; 
           [0052]      FIG. 13  is a flowchart in Modified example 1; 
           [0053]      FIG. 14  is a perspective view of a lithium ion secondary battery in Embodiment 2; 
           [0054]      FIG. 15  is a cross-sectional view of the lithium ion secondary battery in Embodiment 2 (a cross-sectional view along D-D in  FIG. 14 ); 
           [0055]      FIG. 16  is a flowchart in Embodiment 2; and 
           [0056]      FIG. 17  is a perspective view of a hammer drill in a Embodiment 3. 
       
    
    
     REFERENCE SIGNS LIST 
       [0000]    
       
           1 ,  3  Battery (Lithium ion secondary battery) 
           20  Power generating element 
           20 L Laminated part 
           20 LX Positive-side laminated part 
           20 LY Negative-side laminated part 
           20 LZ Central laminated part 
           21  Positive electrode plate 
           21   f  Positive lead part (Positive electrode extended part) 
           22  Negative electrode plate 
           22   f  Negative lead part (Negative electrode extended part) 
           23  Separator 
           40 X First element (Temperature control means) 
           40 Y Second element (Temperature control means) 
           40 Z Third element (Temperature control means) 
           50 X First thermocouple (Central temperature detecting means) 
           50 Y Second thermocouple (Positive-side temperature detecting means) 
           50 Z Third thermocouple (Negative-side temperature detecting means) 
           100 ,  200 ,  300  Vehicle 
           130  Control unit (Control means) 
           400  Hammer drill (Battery-mounting device) 
           410  Battery pack 
         DA First direction (Positive-negative extending direction) 
         DC Discharge current (Charge and discharge current, Discharge current) 
         DTX Positive-side rise amount (Temperature rise amount (of positive-side laminated part)) 
         DTY Negative-side rise amount (Temperature rise amount (of negative-side laminated part)) 
         DTZ Central rise amount (Temperature rise amount (of central laminated part)) 
         F 1  First rise amount difference (Temperature rise amount difference) 
         F 2  Second rise amount difference (Temperature rise amount difference) 
         M 1 , M 2 , M 3  Battery system 
         TX 0  Positive-side temperature (Temperature (of positive-side laminated part), Temperature (of laminated part)) 
         TX 1  Positive-side preceding temperature (Temperature (of positive-side laminated part), Temperature (of laminated part)) 
         TX Positive-side post-discharge temperature (Temperature (of positive-side laminated part), Temperature (of laminated part)) 
         TY 0  Negative-side temperature (Temperature (of negative-side laminated part), Temperature (of laminated part)) 
         TY 1  Negative-side preceding temperature (Temperature (of negative-side laminated part), Temperature (of laminated part)) 
         TY 2  Negative-side post-discharge temperature (Temperature (of negative-side laminated part), Temperature (of laminated part)) 
         TZ 0  Central temperature (Temperature (of central laminated part), Temperature (of laminated part)) 
         TZ 1  Central preceding temperature (Temperature (of central laminated part), Temperature (of laminated part)) 
         TZ 2  Central post-discharge temperature (Temperature (of central laminated part), Temperature (of laminated part)) 
       
     
       DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       [0095]    A detailed description of a first preferred embodiment of the present invention will now be given referring to the accompanying drawings. 
         [0096]    Firstly, a vehicle  100  in Embodiment 1 is explained.  FIG. 1  is a perspective view of the vehicle  100 . 
         [0097]    This vehicle  100  is a hybrid electric vehicle including a plurality of lithium ion secondary batteries (hereinafter, also simply referred to as batteries)  1  constituting a battery pack  120 , thermocouples  50 X,  50 Y, and  50 Z for detecting the temperatures of a power generating element  20  of each battery  1  respectively, and a control unit  130 . In addition, the vehicle  100  includes an engine  150 , a front electric motor  141 , a rear electric motor  142 , a cable  160 , a first inverter  171 , a second inverter  172 , and a vehicle body  190 . The thermocouples  50 X,  50 Y, and  50 Z are connected to a battery monitor  122 . A battery system M 1  in Embodiment 1 is constituted of the batteries  1 , the thermocouples  50 X,  50 Y, and  50 Z (the battery monitor  122  connected to them), and the control unit  130 . 
         [0098]    The control unit  130  of the vehicle  100  has a CPU, a ROM, and a RAM not shown, and includes a microcomputer that is operated by a predetermined program. This control unit  130  communicates with the front motor  141 , the rear motor  142 , the engine  150 , the first inverter  171 , the second inverter  172 , and the battery monitor  122 , respectively, each of which is mounted in the vehicle  100 . This control unit  130  controls the front motor  141 , the rear motor  142 , the engine  150 , the first inverter  171 , and the second inverter  172 . 
         [0099]    The battery pack  120  of the vehicle  100  includes a battery pack part  121  in which the batteries  1  are arranged and the battery monitor  122  (see  FIG. 1 ). The battery monitor  122  obtains the temperatures of the power generating element of each battery  1  via the thermocouples  50 X,  50 Y, and  50 Z. 
         [0100]    Further, the battery part  121  contains the batteries  1  fastened to a bus bar (not shown) with bolts and thus connected in series with each other. 
         [0101]    Each battery  1  is a winding-type lithium ion secondary battery having the power generating element  20  including a positive electrode plate  21 , a negative electrode plate  22 , and a separator  23  (see  FIGS. 2-4 ). The power generating element  20  is housed in a rectangular box-shaped battery case  10 . 
         [0102]    This power generating element  20  is configured such that the positive electrode plate  21  and the negative electrode plate  22 , each having a strip shape, are wound in flat form by interposing the strip-shaped separator  23  made of polyethylene therebetween (see  FIG. 2 ). This power generating element  20  includes, as shown in  FIG. 4A , a laminated part  20 L in which the positive electrode plate  21 , the negative electrode plate  22 , and the separator  23  are laminated, a positive lead part  21   f  of the positive electrode plate  21 , extending upward from this laminated part  20 L in  FIG. 4A , and a negative lead part  22   f  of the negative electrode plate  22 , extending downward in  FIG. 4A . The positive lead part  21   f  is joined with a positive current collector  71  having a crank-like bent plate shape (see  FIG. 3 ). A positive terminal  71 A located at a leading end (upper in  FIG. 3 ) of the positive current collector  71  protrudes upward from the battery case  10  in  FIG. 3 . The negative lead part  22   f  is joined with a negative current collector  72  having a crank-like bent plate shape (see  FIG. 3 ). A negative terminal  72 A located at a leading end of the negative current collector  72  (upper in  FIG. 3 ) protrudes upward from the battery case  10  in  FIG. 3 . 
         [0103]    The positive electrode plate  21  is made from a strip-shaped aluminum foil  21 A and positive active material layers  21 B. This positive electrode plate  21  carries the positive active material layers  21 B on both surfaces of the aluminum foil  21 A excepting the positive lead part  21   f  (see  FIGS. 4A and 4B ). 
         [0104]    The negative electrode plate  22  is made from a strip-shaped copper foil  22 A and direction active material layers  22 B. This negative electrode plate  22  carries the negative active material layers  22 B on both surfaces of the copper foil  22 A excepting the negative lead part  22   f  (see  FIGS. 4A and 4B ). 
         [0105]    In Embodiment 1, as shown in  FIG. 3 , assuming that a direction joining the positive lead part  21   f  to the negative lead part  22   f  (a direction along a winding axis) is a first direction DA, the laminated part  20 L of the power generating element  20  is divided in a perpendicular direction to this first direction DA into three sections. Specifically, the laminated part  20 L is assumed to include a central laminated part  20 LZ located at the center in the first direction DA, a positive-side laminated part  20 LX which is located closer to the positive lead part  21   f  than the central laminated part  20 LZ is, and a negative laminated part  20 LY which is located closer to the positive lead part  21   f  than the central laminated part  20 LZ is (see  FIG. 3 ). 
         [0106]    In the laminated part  20 L, the first thermocouple  50 X is placed in the positive-side laminated part  20 LX, the second thermocouple  50 Y is placed in the negative-side laminated part  20 LY, and the third thermocouple  50 Z is placed in the central laminated part  20 LZ (see  FIG. 3 ). 
         [0107]    Specifically, a rectangular plate member  50 B made of resin, on which the first thermocouple  50 X, the second thermocouple  50 Y, and the third thermocouple  50 Z are arranged and fixed, is inserted in an axial core of the wound power generating element  20  (see  FIGS. 3 and 4A ). In this plate member  50 B, as shown in  FIG. 5 , a leading end of the first thermocouple  50 X, that is, a measuring junction thereof is fixed to a right portion of the plate member  50 B in the figure with an insulation tape TP. A measuring junction of the second thermocouple  50 Y is fixed to a left portion of the plate member  50 B in the figure with an insulation tape TP and a measuring junction of the third thermocouple  50 Z is fixed to a central portion of the plate member  50 B in the first direction DA with an insulation tape TP. 
         [0108]    Those first, second, and third thermocouples  50 X,  50 Y, and  50 Z are all Type K thermocouples (Chromel-Alumel). Further, those first, second, and third thermocouples  50 X,  50 Y, and  50 Z are extended in a bundle out of the battery case  10  and connected to the battery monitor  122 . 
         [0109]    Meanwhile, the present inventors found the following fact. When high-rate discharge is repeated by supply of a high-rate current as large as 10C for example, the battery  1  deteriorates (High-rate deterioration). Simultaneously, the lithium ion concentrations of the electrolyte in the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ of the laminated part  20 L of the power generating element  20 , which were uniform at the time of battery manufacture, come to differ from each other. 
         [0110]    Specifically, the battery  1  was first subjected to a cycle test in which high-rate discharge, that is, pulse charge and discharge are repeated by charging at a constant current of 100 A for 10 seconds and then charging at a constant current of 10 A for 100 seconds. The value of internal resistance of the battery  1  was measured after a predetermined number of cycles. 
         [0111]    This test result is shown in  FIG. 6 . The value of internal resistance of the battery  1  greatly increases as the number of cycles approaches 700 and becomes maximum when the number of cycles reaches around 1700. 
         [0112]    In addition to the measurement of the internal resistance of the battery  1 , the lithium ion concentration of the electrolyte in each portion of the laminated part  20 L was measured at the test start time and at the number of cycles of 1700, respectively. 
         [0113]    Measurement results are shown in  FIG. 7 .  FIG. 7  is a graph showing the lithium ion concentration in each of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ. This graph reveals that the lithium ion concentrations in the positive-side laminated part  20 LX and the negative-side laminated part  20 LY at the number of cycles of 1700 are higher than at the test start time. On the other hand, the lithium ion concentration in the central laminated part  20 LZ at the number of cycles of 1700 is lower than at the test start time. 
         [0114]    It is found that when the high-rate discharge is further performed in this state, the heating values are distributed in each place. This is conceivably because a current density is distributed according to the distribution of the lithium ion concentration of the electrolyte in the laminated part  20 L. 
         [0115]    Therefore, in addition to the measurement of the internal resistance of the battery  1 , the temperature of each of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ was measured before and after the high-rate discharge, at the time just after the test start (the number of cycles=1), at the number of cycles of 700, and at the number of cycles of 1700 by use of the first thermocouple  50 X, the second thermocouple  50 Y, and the third thermocouple  50 Z. To be concrete, the temperature before the high-rate discharge was measured, and then the battery  1  was discharged with a constant current of 100 A and the temperature after 10 seconds from the start of discharge was measured. 
         [0116]    Based on the above temperatures, a temperature rise amount (a difference between a temperature after the high-rate discharge and a temperature immediately before the high-rate discharge) in each of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ was calculated. 
         [0117]    Calculation results are shown in  FIG. 8 .  FIG. 8  is a graph showing a temperature rise amount in each of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ. This graph reveals that the temperature rise amounts in the positive-side laminated part  20 LX and the negative-side laminated part  20 LY at the number of cycles of 700 and 1700 are higher than at the time just after the test start (the number of cycles=1). On the other hand, the temperature rise amount in the central laminated part  20 LZ at the number of cycles of 700 and 1700 is lower than at the time just after the test start. 
         [0118]    In the battery  1  in which no high-rate deterioration has occurred yet, at the time just after the test start, the temperature rise amount in the central laminated part  20 LZ occurring at the high-rate discharge is slightly larger than in the positive-side laminated part  20 LX and the negative-side laminated part  20 LY. This is conceivably because the central laminated part  20 LZ is more unlikely to radiate heat than the positive-side laminated part  20 LX and the negative-side laminated part  20 LY and therefore the temperature increases. 
         [0119]    As the high-rate deterioration advances by the high-rate discharge, the temperature rise amount in the central laminated part  20 LZ gradually decreases, whereas the temperature rise amounts in the positive-side laminated part  20 LX and the negative-side laminated part  20 LY increase. Accordingly, at the number of cycles of 500 prior to 700, the temperature rise amount becomes equal between the central laminated part  20 LZ and the positive-side laminated part  20 LX or the negative-side laminated part  20 LY. Furthermore, at the later number of cycles of 700 and 1700, reversely, the temperature rise amount in the central laminated part  20 LZ becomes smaller than those in the positive-side laminated part  20 LX and the negative-side  20 LY. 
         [0120]    Based on the above experimental results, the control of the battery  1  in the battery system M 1  in Embodiment 1 will be explained in detail with reference to flowcharts in  FIGS. 9 and 10 . 
         [0121]    When the vehicle  100  is started to operate (Key ON) (step S 1 ), the control unit  130  of the vehicle  100  is activated. In step S 2 , it is judged whether or not the control unit  130  stored at the preceding stop time of operation of the vehicle  100  that the control was changed to the control to limit a discharge maximum current value allowed to flow from the battery  1  to a lower value. It is to be noted that “Limiting the discharge maximum current value to a lower value” indicates limiting a maximum value of discharge current DC allowed to flow in the battery  1  for discharge, to a lower value than before this limitation. 
         [0122]    If NO in this step, that is, if it was not stored that the discharge maximum current value was limited to a lower one, the flow advances to step S 4 . On the other hand, if YES, that is, if it was stored that the discharge maximum current value was limited to a lower one, the flow advances to step S 3  in which the discharge maximum current value of the discharge current DC of the battery  1  is limited to a lower one during the present operation, and then goes to step S 4 . 
         [0123]    In step S 4 , successively, it is judged whether or not the stop of operation (Key OFF) of the vehicle  100  is instructed. 
         [0124]    If NO in this step, that is, if the operation of the vehicle  100  is not stopped (not 
         [0125]    Key OFF), the flow advances to step S 7 . On the other hand, if YES, that is, if the operation of the vehicle  100  is stopped (Key OFF), the flow goes to step S 5  in which it is judged whether or not the discharge maximum current value has been limited to be lower at the present operation stop time. 
         [0126]    If NO in this step, that is, if the discharge maximum current value has not been limited to be lower at the present operation stop time, the operation is stopped directly. On the other hand, if YES, that is, if the discharge maximum current value has been limited to a lower one at the present operation stop time, the flow goes to step S 6  in which the control unit  130  stores that the discharge maximum current value has been limited to a lower value, and then the operation is stopped. 
         [0127]    In step S 7 , on the other hand, it is determined whether or not the battery  1  is subjected to high-rate discharge. 
         [0128]    If NO in this step, the battery  1  is not subjected to the high-rate discharge, the flow returns to step S 4  to continue the operation of the vehicle  100 . On the other hand, if YES, i.e., if the battery  1  is subjected to the high-rate discharge, the flow goes to a temperature difference calculation sub-routine in step S 20  mentioned later to calculate temperature rise amounts DTX, DTY, and DTZ generated in the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ by the high-rate discharge. 
         [0129]    The temperature difference calculation sub-routine in step S 20  is explained with reference to  FIG. 10 . 
         [0130]    In step S 21 , firstly, a positive-side preceding temperature TX 1  of the positive-side laminated part  20 LX immediately before the battery  1  is subjected to the high-rate discharge in step S 7  is measured by the first thermocouple  50 X. Similarly, a preceding temperature TY 1  of the negative-side laminated part  20 LY is measured by the second thermocouple  50 Y and a preceding temperature TZ 1  in the central laminated part  20 LZ is measured by the third thermocouple  50 Z immediately before the battery  1  is subjected to the high-rate discharge. 
         [0131]    In step S 22 , thereafter, a positive-side post-discharge temperature TX 2  in the positive-side laminated part  20 LX is measured by the first thermocouple  50 X after the termination of the high-rate discharge in step S 7 . Specifically, the temperature of the positive-side laminated part  20 LX after 10 seconds from the start of high-rate discharge is measured. 
         [0132]    Similarly, a negative-side post-discharge temperature TY 2  in the negative-side laminated part  20 LY is measured by the second thermocouple  50 Y and a central post-discharge temperature TZ 2  in the central laminated part  20 LZ is measured by the third thermocouple  50 Z. 
         [0133]    In step S 23 , successively, based on the positive-side preceding temperature TX 1  and the positive-side post-discharge temperature TX 2 , a positive-side rise amount DTX in the positive-side laminated part  20 LX, which is caused by the high-rate discharge, is calculated (DTX=TX 2 −TX 1 ). Similarly, a negative-side rise amount DTY in the negative-side laminated part  20 LY, which is caused by the high-rate discharge, is calculated based on the negative-side preceding temperature TY 1  and the negative-side post-discharge temperature TY 2 . A central rise amount DTZ in the central laminated part  20 LZ, which is caused by the high-rate discharge, is calculated based on the central preceding temperature TZ 1  and the central post-discharge temperature TZ 2 . After calculation, the temperature difference calculation sub-routine is terminated. The flow then returns to a main routine. 
         [0134]    In step S 8  of the main routine, it is judged whether a first rise amount difference F 1  (=DTZ−DTX) is a negative value or a second rise amount difference F 2  (=DTZ−DTY) is a negative value, in which F 1  is a difference between the central rise amount DTZ and the positive-side rise amount DTX and F 2  is a difference between the central rise amount DTZ and the negative-side rise amount DTY. 
         [0135]    If NO in this step, that is, if the first rise amount difference F 1  is zero or a positive value and the second rise amount difference F 2  is zero or a positive value, the flow goes to step S 9 . This is because the high-rate deterioration of the battery  1  has not progressed yet. 
         [0136]    On the other hand, if YES, that is, if the first rise amount difference F 1  is a negative value or the second rise amount difference F 2  is a negative value, the flow goes to step S 11 . This is conceivably because the high-rate deterioration of the battery  1  has progressed to some extent and thus further progression has to be prevented. 
         [0137]    In step S 9 , successively, it is determined whether or not the discharge maximum current value has been limited to a lower one. 
         [0138]    If NO in this step, i.e., if the discharge maximum current value has not been limited to a lower one, the flow directly returns to step S 4 . If YES, on the other hand, i.e., if the discharge maximum current value has been limited to a lower one, the flow advances to step S 10  in which the limitation is removed and the flow returns to step S 4 . 
         [0139]    In step S 11 , on the other hand, the discharge maximum current value of the discharge current DC flowing in the battery  1  is limited to a lower value. For instance, an upper limit value of the discharge current DC is changed from 10C maximum to 7C maximum. Then, the flow returns to step S 4  to continue the operation of the vehicle  100 . Consequently, in the next high-rate discharge, the discharge maximum current value of the discharge current DC is to be limited to a lower value. 
         [0140]    The battery system M 1  in Embodiment 1 includes the first thermocouple  50 X, the second thermocouple  50 Y, the third thermocouple  50 Z, and the control unit  130 . Accordingly, by using the temperatures of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ of the battery  1  (the positive-side preceding temperature TX 1 , the positive-side post-discharge temperature TX 2 , the negative-side preceding temperature TY 1 , the negative-side post-discharge temperature TY 2 , the central preceding temperature TZ 1 , and the central post-discharge temperature TZ 2 ), it is possible to calculate the rise amount differences F 1  and F 2  and others of the temperature rise amounts DTX, DTY, and DTZ before and after the high-rate discharge in each of the parts. Thus, the battery  1  can be appropriately controlled based on the calculated results. 
         [0141]    Furthermore, the battery system M 1  uses the temperature in each part (the positive-side preceding temperature TX 1 , the positive-side post-discharge temperature TX 2 , the negative-side preceding temperature TY 1 , the negative-side post-discharge temperature TY 2 , the central preceding temperature TZ 1 , and the central post-discharge temperature TZ 2 ). Accordingly, it is possible to more easily detect various nonuniformity (nonuniformity of lithium ion concentration) occurring in the laminated part  20 L for example than in the case where the lithium ion concentration of the electrolyte in each part is directly detected. 
         [0142]    Furthermore, the control unit  130  includes limitation changing means S 8  and S 9 . Based on the rise amount difference (the first rise amount difference F 1  and the second rise amount difference F 2 ) in the temperature rise amount (the positive-side rise amount DTX, the negative-side rise amount DTY, and the central rise amount DTZ) between the central laminated part  20 LZ and the positive-side laminated part  20 LX and between the central laminated part  20 LZ and the negative-side laminated part  20 LY, the limitation changing means S 8  and S 9  change the limitation so as to reduce the discharge current DC for high-rate discharge. Accordingly, it is possible to appropriately control the high-rate deterioration of the battery  1  caused by the high-rate discharge. 
         [0143]    The limitation changing means S 8  and S 9  of the battery system M 1  in Embodiment 1 change the control to relatively reduce the discharge current DC of the high-rate discharge subsequently flowing in the battery  1  (the control in step S 9  to limit the discharge maximum value to a lower value), when the first rise amount difference F 1  or the second rise amount difference F 2  is negative, that is, when the central rise amount DTZ in the central laminated part  20 LZ becomes smaller than the positive-side rise amount DTX in the positive-side laminated part  20 LX or the negative-side rise amount DTY in the negative-side laminated part  20 LY. This makes it possible to restrain the progression of high-rate deterioration of the battery  1 , namely, the increase in internal resistance. The high-rate deterioration occurring in the battery  1  can also be restored. 
         [0144]    The vehicle  100  in Embodiment 1 includes the aforementioned battery system M 1 . Therefore, by using each temperature in the central laminated part  20 LZ, the positive-side laminated part  20 LZ, or the negative-side laminated part  20 LY (the positive-side preceding temperature TX 1 , the positive-side post-discharge temperature TX 2 , the negative-side preceding temperature TY 1 , the negative-side post-discharge temperature TY 2 , the central preceding temperature TZ 1 , and the central post-discharge temperature TZ 2 ), it is possible to calculate for example the temperature rise amounts DTX, DTY, and DTZ before and after discharge in each part and also a difference (the first rise amount difference F 1  and the second rise amount difference F 2 ) therebetween. Based on this, the vehicle  100  can appropriately control the battery  1 . 
       Modified Example 1 
       [0145]    A vehicle  200  in Modified example 1of the present invention will be explained referring to  FIGS. 1-5  and  10 - 13 . 
         [0146]    Modified example 1 is identical to Embodiment 1 mentioned above excepting that a control changing means of a battery system changes the control to relatively increase the value of discharge current. 
         [0147]    The following explanation is therefore given with a focus on differences from Embodiment 1. Like parts to those in Embodiment 1 are not explained or are briefly described. It is to be noted that identical or similar parts to those in Embodiment 1 provide the same operations and advantages as in Embodiment 1. The identical or similar parts are given with the same reference numbers as those in Embodiment 1 in the following explanation. 
         [0148]    Meanwhile, the present inventors found that when the battery  1  was repeatedly subjected to the high-rate discharge more times than in Embodiment 1, the internal resistance of the battery  1  increased once, and then decreased and became constant (see  FIG. 11 ). 
         [0149]    This result reveals that when the high-rate deterioration of the battery  1  is forcibly progressed to pass through a high internal resistance state, the internal resistance then comes to a rather preferable state (with low internal resistance). 
         [0150]    To check this, the internal resistance of the battery  1  was measured and the temperature of each of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ was measured before and after the high rate discharge at the test start time and at each of the number of cycles of 700, 1700, and 4000. Respective temperature rise amounts were calculated. 
         [0151]    Measurement results are shown in  FIG. 12 . According to this graph, at the number of cycles of 1700 at which the internal resistance is high, the temperature rise amount of the central laminated part  20 LZ is smaller than the temperature rise amounts of the positive-side laminated part  20 LX and the negative-side laminated part  20 LY. On the other hand, at the number of cycles of 4000 at which the internal resistance is low, the temperature rise amount of the positive-side laminated part  20 LX is also low. This reveals that the temperature rise amount of the central laminated part  20 LZ is smaller than the temperature rise amount of the negative-side laminated part  20 LY and almost equal to the temperature rise amount of the positive-side laminated part  20 LX. 
         [0152]    Based on the above experimental results, the control of the battery  1  in the battery system M 2  in Modified example 1 will be explained in detail referring to flowcharts in  FIGS. 13 and 10 . 
         [0153]    Firstly, when the vehicle  200  is started (Key ON) to operate (step S 31 ), a control unit  130  of the vehicle  200  is activated (see  FIG. 13 ). In S 32 , it is determined whether or not the control unit  130  stored at the preceding stop time of operation of the vehicle  200  that the control was changed the control to increase the discharge maximum current value allowed to flow from the battery  1 . It is to be noted that “Changing the discharge maximum current value to a higher value” indicates changing a maximum value of discharge current DC allowed to flow in the battery  1  for discharge, to a higher value than before this changing. 
         [0154]    If NO in this step, that is, if it was not stored that the discharge maximum current value was changed to a higher one, the flow advances step S 34 . On the other hand, if YES, that is, if it was stored that the discharge maximum current value was changed to a higher one, the flow advances to step S 33  where the discharge maximum current value of the discharge current DC of the battery  1  is changed to a higher value during the present operation, and then the flow goes to step S 34 . 
         [0155]    In step S 34 , successively, it is determined whether the stop of operation (Key OFF) of the vehicle  200  is instructed. 
         [0156]    If NO in this step, that is, if the operation of the vehicle  200  is not stopped (not Key OFF), the flow advances to step S 37 . On the other hand, if YES, that is, if the operation of the vehicle  200  is stopped (Key OFF), the flow goes to step S 35  in which it is determined whether or not the discharge maximum current value has been changed to a higher one at the present operation stop time. 
         [0157]    If NO in this step, i.e., if the discharge maximum current value was not changed to a higher one at the present operation stop time, the operation is directly stopped. On the other hand, if YES, i.e., if the discharge maximum current value has been changed to a higher one at the present operation stop time, the flow goes to step S 36  in which the control unit  130  stores that the discharge maximum current value has been changed to a higher one, and then the operation is terminated. 
         [0158]    In step S 37 , on the other hand, it is determined whether or not the battery  1  is subjected to high-rate discharge. 
         [0159]    If NO in this step, i.e., if the battery  1  is not subjected to the high-rate discharge, the flow returns to step S 34  to continue the operation of the vehicle  200 . If YES, on the other hand, that is, if the battery  1  is subjected to the high-rate discharge, the flow goes to a temperature difference calculating sub-routine (see  FIG. 10 ) in step S 20  similar to that in Embodiment 1. Thus, the temperature rise amounts DTX, DTY, and DTZ of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ caused by the high-rate discharge are calculated. Herein, the explanation of the temperature difference calculating sub-routine is not repeated. 
         [0160]    In step S 38 , it is determined whether or not the discharge maximum current value has been changed to a higher one. 
         [0161]    If NO in this step, i.e., if the discharge maximum current value has not been changed to a higher one, the flow goes to step S 39 . On the other hand, if YES, i.e., if the discharge maximum current value has been changed to a higher one, the flow goes to step S 41 . 
         [0162]    In step S 39 , it is determined whether or not a first rise amount difference F 1  (=DTZ−DTX) that is a difference between the central rise amount DTZ and the positive-side rise amount DTX is a negative value or a second rise amount difference F 2  (=DTZ−DTY) that is a difference between the central rise amount DTZ and the negative-side rise amount DTY is a negative value. 
         [0163]    If NO in this step, i.e., if the first rise amount difference F 1  is zero or a positive value and the second rise amount difference F 2  is zero or a positive value, the flow returns to step S 34 . 
         [0164]    On the other hand, if YES, i.e., if the first rise amount difference F 1  is a negative value or the second rise amount difference F 2  is a negative value, the flow goes to step S 40 . The high-rate deterioration of the battery  1  is assumed to have progressed. Thus, the discharge maximum current value is changed to a higher value to prompt this high-rate deterioration. 
         [0165]    In step S 40 , the discharge maximum current value of the discharge current DC flowing in the battery  1  is changed to a higher value. For instance, an upper limit of the discharge current DC is changed from 10C maximum to 13C maximum. Then, the flow returns to step S 34  to continue the operation of the vehicle  200 . 
         [0166]    On the other hand, in step S 41 , it is determined whether or not the first rise amount difference F 1  is zero, i.e., DTZ=DTX. 
         [0167]    If NO in this step, that is, if the first rise amount difference F 1  is not zero, i.e., DTZ≠DTX, the flow directly returns to step S 34 . If YES, on the other hand, that is, if the first rise amount difference F 1  is zero, i.e., DTZ=DTX, the flow goes to step S 42  where the change is removed, and then the flow returns to step S 34 . 
         [0168]    As above, the control changing means S 39  and S 40  of the battery system M 2  of the vehicle  200  in Modified example 1 change the control to increase the subsequent discharge current DC of the high-rate discharge flowing in the battery  1  (the control to limit the discharge maximum current value to a higher value in step S 40 ) when the first rise amount difference F 1  or the second rise amount difference F 2  is negative, that is, the central rise amount DTZ is smaller than the positive-side rise amount DTX or the negative-side rise amount DTY. This makes it possible to make the battery  1  quickly go through a high internal resistance state to enable the use of the battery  1  in a low internal resistance state. 
       Embodiment 2 
       [0169]    A vehicle  300  in Embodiment 2 of the present invention will be explained referring to FIGS.  1  and  14 - 16 . 
         [0170]    Embodiment 2 is different from Embodiment 1 in that a battery further includes a central temperature changing means, a positive-side temperature changing means, and a negative-side temperature changing means, and they are controlled by a control means. 
         [0171]    Specifically, a battery  3  in Embodiment 2 is identical in structure to the battery  1  in Embodiment 1 mentioned above and further includes three rectangular plate-like Peltier elements (a first element  40 X, a second element  40 Y, and a third element  40 Z) arranged in front of a power generating element  20  in  FIG. 14  in a battery case  10  as shown in  FIGS. 14 and 15 . The first element  40 X is fixedly placed in contact with a positive-side laminated part  20 LX, the second element  40 Y is fixedly placed in contact with a negative-side laminated part  20 LY, and the third element  40 Z is fixedly placed in contact with a central laminated part  20 LZ, respectively. Those first, second, and third elements  40 X,  40 Y, and  40 Z are connected to a control unit  130  through a cable  40 C, so that they are energized and controlled. Accordingly, the elements  40 X,  40 Y, and  40 Z are controlled by the control unit  130  to absorb heat from each of the laminated parts  20 LX,  20 LY, and  20 LZ of the power generating element  20  to cool them. 
         [0172]    A battery system M 3  in the discharge embodiment includes batteries  3 , thermocouples  50 X,  50 Y, and  50 Z, the Peltier elements  40 X,  40 Y, and  40 Z, and the control unit  130 . 
         [0173]    The control of the battery  3  in the battery system M 3  will be described in detail referring to a flowchart in  FIG. 16 . 
         [0174]    Firstly, the vehicle  300  is started (Key ON) to operate (step S 51 ), the control unit  130  of the vehicle  300  is activated. In S 52 , by use of the first thermocouple  50 X, the second thermocouple  50 Y, and the third thermocouple  50 Z, a positive-side temperature TX 0 , a negative-side temperature TY 0 , and a central temperature TZ 0  of the laminated part  20 L of each battery  3  are measured. This measurement is performed at regular intervals by use of a built-in timer (not shown) in the control unit  130 . 
         [0175]    In step S 53 , it is determined whether or not the positive-side temperature TX 0 , the negative-side temperature TY 0 , and the central temperature TZ 0  are equal or uniform (TX 0 =TY 0 =TZ 0 ). 
         [0176]    If YES in this step, the flow returns to step S 52  to wait a next measurement timing. On the other hand, if NO, that is, if the positive-side temperature TX 0 , the negative-side temperature TY 0 , and the central temperature TZ 0  are unequal or nonuniform (e.g., TX 0 =TY 0 &lt;TZ 0 ), the flow goes to step S 54 . 
         [0177]    In step S 54 , any one of the Peltier elements (the first element  40 X, the second element  40 Y, the third element  40 Z) fixedly placed in the laminated part  20 L is energized and controlled in order to cool any one of the positive-side laminated part  20 LX, the negative-side laminated part  20 LY, and the central laminated part  20 LZ. For instance, if TX 0 =TY 0 &lt;TZ 0 , the third element  40 Z is energized and controlled to cool the central laminated part  20 LZ higher in temperature than others so that the central temperature TZ 0  becomes equal to other temperatures (the positive-side temperature TX 0  and the negative-side temperature TY 0 ). 
         [0178]    After cooling, it is determined in step S 55  whether or not the positive-side temperature TX 0 , the negative-side temperature TY 0 , and the central temperature TZ 0  are equal. 
         [0179]    If NO in this step, that is, if the positive-side temperature TX 0 , the negative-side temperature TY 0 , and the central temperature TZ 0  are not equal, the flow returns to step S 54  where the Peltier elements (the first element  40 X, the second element  40 Y, the third element  40 Z) are continuously energized and controlled so that the positive-side temperature TX 0 , the negative-side temperature TY 0 , and the central temperature TZ 0  become equal. On the other hand, if YES, that is, the positive-side temperature TX 0 , the negative-side temperature TY 0 , and the central temperature TZ 0  are equal to each other, the flow returns to step S 52 . 
         [0180]    The battery system M 3  of the vehicle  300  in Embodiment 2 includes the aforementioned Peltier elements (the first element  40 X, the second element  40 Y, the third element  40 Z) and the control unit  130  includes the temperature control means S 54 . Accordingly, it is possible to appropriately change the temperatures (TZ 0 , TX 0 , TY 0 ) of the central laminated part  20 LZ, the positive-side laminated part  20 LX, and the negative-side laminated part  20 LY based on measurement results of the central temperature TZ 0  of the central laminated part  20 LZ, the positive-side temperature TX 0  of the positive-side laminated part  20 LX, and the negative-side temperature TY 0  of the negative-side laminated part  20 LY of the power generating element  20 . This enables appropriate temperature control by controlling the temperature to eliminate nonuniformity of lithium ion concentration and others occurring in the laminated part  20 L. 
       Embodiment 3 
       [0181]    A hammer drill  400  in Embodiment 3 mounts a battery pack  410  containing one of the aforementioned battery systems M 1 , M 2 , and M 3 . The hammer drill  400  is a battery mounting device having the battery pack  410  and a main body  420  as shown in  FIG. 17 . The battery pack  410  is removably housed in a pack housing part  421  of the main body  420  of the hammer drill  400 . 
         [0182]    The hammer drill  400  in Embodiment 3 includes the aforementioned battery system M 1 , M 2 , or M 3 . Accordingly, the hammer drill  400  is able to calculate a difference between the temperatures TX 0 , TY 0 , and TZ 0  of the parts, the temperature rise amounts DTX, DTY, and DTZ of the parts before and after discharge and a difference (a first rise amount difference F 1 , a second rise amount difference F 2 ) therebetween by use of the temperatures of the central laminated part  20 LZ, the positive-side laminated part  20 LX, and the negative-side laminated part  20 LY (a positive-side temperature TX 0 , a negative-side temperature TY 0 , a central temperature TZ 0 , a positive-side preceding temperature TX 1 , a positive-side post-discharge temperature TX 2 , a negative-side preceding temperature TY 1 , a negative-side post-discharge temperature TY 2 , a central preceding temperature TZ 1 , and a central post-discharge temperature TZ 2 ), and appropriately control the batteries  1  and  3  by use of a calculation result. 
         [0183]    The present invention is explained in Embodiment 1, Embodiment 2, Embodiment 3, and Modified example 1 but the present invention is not limited thereto. The present invention may be embodied in other specific forms without departing from the essential characteristics thereof. 
         [0184]    For instance, in Embodiment 1, the first thermocouple, the second thermocouple, and the third thermocouple are inserted in the position of the axial core of the power generating element to detect the temperatures of the positive-side laminated part, the negative-side laminated part, and the central laminated part. An alternative is to place the first thermocouple, the second thermocouple, and the third thermocouple on the outer surface(s) of the power generating element or between layers of the laminated parts of the power generating element to detect the temperatures of the positive-side laminated part, the negative-side laminated part, and the central laminated part. 
         [0185]    In Embodiment 2, the central temperature TZ 0 , the positive-side temperature TX 0 , and the negative-side temperature TY 0  of the power generating element  20  are controlled to be equal to eliminate nonuniformity of lithium ion concentration. Reversely, for example, they may be controlled to produce a temperature difference between the central temperature TZ 0  and the positive-side temperature TX 0  and the negative-side temperature TY 0  in order to prompt the high-rate deterioration of the battery. The Peltier elements that absorb heat when energized are used as the central temperature changing means, the positive-side temperature changing means, and the negative-side temperature changing means. As an alternative, a heater that generates heat when energized may be used.