Title of Invention

CHARGING SYSTEM FOR BATTERY SET

Abstract

A charging system for a battery set of the invention includes a temperature detecting device 15, a charging device 12 and a control device 13 for controlling the charging device 12 based on a battery temperature. The control device 13 carries out a temperature feedback charge with "a quantity relying on Temperature" (AT/At) as a desired value (Y). Thus, the batteries can be charged in a fully charged state or close to the fully charged state while preventing performance of the batteries from being deteriorated due to the heat caused by the charge.

Full Text

FIELD OF THE Owenton This invention relates to a charging technology for batteries to be mounted on an electric motor vehicle represented by an electric car, more particularly, a charging system for allowing the batteries to be charged in a fully charged state or close to the fully charged state while preventing performance of the batteries from being deteriorated through the heat generated by the charge. PRIOR ART As shown in Fig. 1, a conventional charging system 9 for an electric car includes' a battery set 91; a charging device 92 for charging the battery set 91; a control device 93; a charging current detecting device 94 for detecting the charging current of the battery set 91 a battery temperature detecting device 95 for detecting a temperature of the battery set 91; and a charging voltage detecting device 96 for detecting terminal voltages of electric cells for constituting the battery set 91. The battery set 91, as shown in Fig. 2, is formed of a plurality of modules M’, Mg, . . . Mn2, and further the module is constituted of a plurality of electric cells Q, Cg, . . . The charging device 92 includes an AC/DC converter 921 and a current supply portion 922. The AC/DC converter 921 is connected to a commercial electric power supply (here, single phase 100 V electric power supply) G’’,. The current supply poison 922 generates a pulse IP of a predetermined duty from the DC output of the AC/DC converter 921 based on a control signal (charging current command CC ‘f) from the control device 93 (described later) and suppress the pulse IP to the battery set 91 to charge. The control device 93 makes reference to a value of a charging current I’ detected by the charging current detecting device 94, and outputs the control signal (charging current command 00’.’’) to the charging device 92 so that the charging current I’ becomes a predetermined value (allowable maximum current value). Also, the control device 93 determines whether a full charge is attained or not, based on a AV peak (described later) of the charging voltage V’- detected by the charging voltage detecting device 96, or based on a time-rate-of-change (AT/At) of temperature T of the battery set 91 detected by the battery temperature detecting device 95. The charging voltage detecting device 96, as shown in Fig. 3, conveniently estimates the charging voltage per electric cell by detecting the series connection voltage of a plurality of modules. The battery temperature detecting device 95 is formed of a sensor 951 and an AD converter 952. Generally, for a charging start condition, an upper limit is defined for the battery temperature Tg (for example, in case an initial temperature is over 45 X, the start of charge is controlled.) Therefore, it is required to check the battery temperature Tg. Fig. 4 is a graph showing a relationship among the charging voltage Vc, charging current Ic and battery temperature Tg from an empty state to reach a fully charged state of the normal secondary batteries of the nickel’ metal hydride (Ni-MH) and the like to be used for the electric car. When the charge starts (refer to t’ in Fig, 4), the charging voltage V’ starts rising (hereinafter, an inclination caused by the rise will be referred to as ‘the first inclination'). When the charging voltage V’ passes through the first inclination (refer to tg in Fig, 4), the charging voltage V’ and the battery temperature Tg make a slightly gradual increase. When the charge to the battery set 91 comes up to a fully charged state (for example, 80 to 90% of the fully charged state), the charging voltage V’ starts rising (refer to t3 in Fig. 4; hereinafter, an inclination caused by the rise will be referred to as 'the second inclination') and, slightly later, the battery temperature Tg starts rising (refer to t4 in Fig. 4). When the charge proceeds further, the charging voltage Vf’ reaches a peak, which is called as "AV peak" (refer to t- in Fig. 4). In the conventional charging system 9, normally, the AV peak is detected and when a voltage downward movement value (which is represented by "-AV") reaches a predetermined value, the charge is terminated (refer to tg in Fig. 4). Incidentally, without resort to the AV peak detection, when the time-rate-of-change (ATg/At) of the battery temperature Tg exceeds a predetermined value, the charge may be terminated Incidentally, in the secondary battery, it has been generally known that when the charge is carried out, an excessive rise in th’ battery temperature has an adverse affect on the performance and duration of life of the battery. In the conventional charging system 9 shown in Fig. 1, as shown in Fig. 4, since the charge is terminated at a time tg not long after the AV peak (tg), the electric cells for constituting the battery set 91 do not reach a battery temperature (hereinafter referred to as 'critical temperature") causing the performance decrement on the graph. Also, in the charging system 9, since the battery temperature Tg is detected by the battery temperature detecting device 95, the electric cells or modules appear not to reach the critical temperature. However, as described above, the AV peak is not detected with respect to each electric cell or module. Therefore, for example, the following problems are generated based on the variation of the capacity when the electric cells or modules are produced, or due to the variation of the capacity based on the temperature difference (which takes place where the electric cell is disposed in the whole battery set). Namely, there is apt to take place such a situation that although an electric cell or module as a non-meaning object has akeady reached the AVpeak, another electric cell or module as a misaiming object of the sensor 951 does not yet reach the AVpeak. Also, there is apt to take place a situation that in case a plurality of electric cells or modules is connected in series and the AV peak is detected, although some of the electric cells or modules as the measuring objects of the sensor 951 have already passed the AV peak a long time ago, the electric cells or modules as an entire series connection does not yet reach the AV peak. With respect to each of the electric cells or modules, after it passes the AV peak, since the terminal voltage thereof is lowered, such a situation further tends to take place. Also, while the actual temperature of an electric cell is relied on that the electric cell is disposed on a position where the electric cell is easily cooled off or not, the temperature of each of the electric cells or modules is not detected by the battery temperature detecting device 95. Therefore, there is a case where the actual temperature of a certain electric cell is higher than the temperature detected by the battery temperature detecting device 95. Moreover, in the conventional charging system, as shown in Fig. 4, when the charge is completed (t’ in Fig. 4), there may be a case that the battery temperature Tg is higher than the initial temperature, for example, by about 10 to 40 T. Because of this, some of the electric cells have exceeded the critical temperature before the charge is completed. Especially, in the electric car, since the battery set is formed of a plurality of the electric cells connected in series, deterioration of some of the electric cells is directly linked to a great functional decrement of the electric car itself. Also, in case such a functional decrement takes place, it is hard to find out which electric cell is in trouble. In case the number of the module groups (series connection of the modules) for detecting the charging voltage is increased to two or more (in case a plurality of the charging voltage detecting devices is provided), the above described problems are dissolved to some extent. However, in the method of this settlement, the number of the AD converters to be used for detection is required as many as the number of the charging voltage detecting devices. Since the value of "-AV" is a very small, such as several mill-volts, per battery cell, an expensive (i.e. high precision) AD converter has to be used. In the conventional power supply device, how the production cost is to be reduced has been one of the research tasks. For this purpose, in the above-described method where the number of the module groups for detecting the charains voltage is increased to two or more, the number of the AD converters is increased, which results in a hoi cost of the charisma system and is not realistic. In view of the above defects, the present invention has been made and an object of the invention is to provide a charging system for a batter>' set, wherein all the electric cells for constituting the battery set do not reach the critical temperature or the risk of reaching the critical temperature can be lowered, and the charge can be made to a full charged state, without raising the costs. Further objects and advantages of the invention will be apparent from the following description of the invention. Accordingly, the present invention provides a charging system for charging a battery-set, comprising a temperature detecting device for detecting a battery temperature; a charging device; and a control device for controlling the charging device based on the battery temperature, said control device performing a temperature feedback charge and continuously controlling a charge current of the charging device with a quantity representing the temperature as a target value. BRIEF DESCRIPTION OF THE DRAWINGS With reference to the accompanying drawings in which : Fig. 1 is a block diagram showing a conventional charging system; 2 is an explanatory diasram showing a batter to be used in the conventional charging system as shown in Fig. I; Fig. 3 is an electric connection diagram of batter modules for detecting a charging voltage per electric cell by a charging voltage detecting device in the conventional charging s\stem shown in Fig. 1; Fig. 4 is a graph showing a relationship among the charging current. batter\' temperature and charging voltage from an empty state to reach a fully charged state of the conventional charging system as shown in Fig. 1; Fig. 5 is a block diagram showing an embodiment of a charging system according to the present invention; Fig. 6 is a block diagram showing the batteries-set used with the enforcement form of the charge svstem of Fig. 5.; Fig. 7 is a control block diagram in a temperature feedback charging mode of the charging system, as shown in Fig. 5, of the present invention; Fig. 8 is a graph showing a relationship among the charging current, battery temperature and charging voltage from an empty state to a fully charged state of the charging system as shown in Fig. 5; and Fig. 9 is a graph showing measured results of the charging current, charging voltage and battery temperature in the temperature feedback charging mode. THE BEST FORM FOR EMBOD With reference to Figs. 5 through 9, an embodiment of a charging system according to the present invention will be described. Fig. 5 is an explanatory view showing the entire embodiment of the invention. In the drawing, a charging system 1 includes a battery set 11; a charging device 12 for supplying charging current to the battery set 11; a control device 13 for controlling the charging device 12; a charging current detecting device 14 for detecting the charging current of the battery set 11; a battery temperature detecting device 15 for measuring a temperature of the battery set U; and a charging voltage detecting device 16. As shown in Fig. 2, the battery set 11 is formed of a plurality of modules M’ M2,. . ., l’p and each module includes a plurality of electric cells C’, Q, . . ., C’. In the present embodiment, as the electric cell, nickel-metal hydride (Nineveh) is used As shown in Fig. 5, the charging device 12 includes an AC/DC converter 121 and a current supply portion 122. In the present embodiment, a commercial power source (single phase lOO power source) G’’’ is connected to the AC/DC converter 121. The current supply portion 122 generates a pulse IP of a predetermined duty from a DC output of the AC/DC converter 121 based on a control signal (charging current command 00’.’’) from the control device 13 to supply the battery set 11. The control device 13 includes a AT/At calculating portion 131; a charging rate operation portion 132; and an average value operation device 133. Also, the control device 13 has a temperature feedback charging mode TFB-CM and a low current charging mode TCL-CM, as a control mode, and the charging current command Chef is outputted to the charging device 12 according to the respective modes. The control device 13 controls the charging device 12 through the feedback control with a time-rate-change of a temperature as a desired value in the temperature feedback charging mode TFB- In the present embodiment, " a time-rate-change of a temperature’' is a value showing a time-rate-of-change (AT/At) of the temperature 1Q of the battery set 11. In the present embodiment, the average value operation device 133 calculates an average temperature value of N-pieces of modules as a battery temperature Tg. Fig. 7 shows a control block diagram of a temperature feedback charging mode TFB-CM of the charging system 1 of the invention. First, the battery temperature Tg is detected by the battery temperature detecting device 15 and sent to the control device 13. The time-rate-of-change (AT/At)j,’ of the battery temperature Tg is operated by the AT/At calculating portion 131 in the control device 13. The charging rate operation portion 132 outputs the charging current command to the charging device 12 based on a deviation E between the time-rate-of-change (AT/At) T-.B and the desired value Y. The charging device 12 supplies the charging current I’ to the battery set 11 based on the charging current command 00’.’’. In the low current charging mode TCL-CM, the control device 13 controls the charging device 12 so that the charge is carried out with a predetermined maintenance current Ij Incidentally, the transition conditions from the temperature feedback charging mode TFB-CM to the low current charging mode TCL-CM will be described later. The battery temperature detecting device 15 includes a temperature sensor 151 and an AD converter 152. The charging voltage detecting device 16 detects the charging voltage V’ of the battery set 11, but it does not detect the AV peak or -AV, different from the conventional technology described with reference to Figs. 1 through 4. As described above, while detection of the AV peak or-AV requires a high-precision (i.e. expensive) AD converter, since such an expensive AD converter is not necessary in the present embodiment, a lower price AD converter for constituting the charging voltage detecting device 16 can be used. Incidentally, in the present embodiment, the charging voltage detecting device 16 is used for checking or managing the lower limit voltage*upper limit voltage of the battery set 11. Fig. 8 is a graph showing a relationship among the charging current I’, battery temperature Tg, and charging voltage V’, from an empty state to reach a fully charged state of the charging system 1 as shown in Fig. 5. When the charge of the battery set 11 is started (refer to t’ in Fig. 8), the charging voltage Vc starts elevating, and when it passes through the first inclination (refer to to in Fig. 8), the charging voltage V’ generally becomes a steady state. At this time, the battery temperature Tg is also generally-in a steady state. Incidentally, in Fig, 8, the initial value of the battery temperature Tg is substantially the same as the battery temperature Tg at the steady state. When the charge to the battery set 11 proceeds and approaches a full charge (for example, when the battery set 11 is charged up to 80% of the full charge), the battery temperature Tg starts rising (refer to t’ in Fig. 8). The control device 13 controls the charging device 12 with Y as a desired value in the temperature feedback charging mode TFB-CM, as explained in Fig. 7. At this time, as shown in Fig. 7, the charging rate operation portion 132 outputs to the charging device 12 a charging current command CCj-ef of which charging current (charging rate) I’ satisfies, for example, the following equation (1)'. Ic = Is X [l-(Gp • E + Gi • /Edt + G, • AE)] ... (1) wherein Ic '- charging current Is", rated current E : deviation (= Y - (AT/At)’’’ AE: deviation difference Gp.' proportional gain G’'. integration gain Gj: derivation gain. After the charging current I’ passes through the peak, it gradually lowers. In the present embodiment, when the charging current becomes I’ (refer to t’ in Fig. 8), it changes to the low current charging mode TCL-Ql. Fig. 9 shows measurement results of the charging current I’, charging voltage V’ and battery temperature Tg, in the temperature feedback charging mode TFB-CM. Incidentally, in the measurement, the control in the low current charging mode TCL-Q! was not carried out. In the above equation (l), I’ (rated current) =5[A], Y (desired value) -0. 1 [X/minute], Gp (proportional gain) = 5.0, G’ (integration gain) = 5.0, G’ (derivation gain)'= 0. Also, when the time-rate-of-change (AT/At)’:’’ of the temperature was calculated and when the deviation E, the deviation product /Edt and the deviation difference AE were renewed, each period was set at 10 seconds, the damping time constant was set at one minute, and the lower limit value of the charging current I’ was set at 0. 5A. The charging completion was determined to be 30 minutes since the value of the charging current Ic became less than lA for the first time. As can be seen from Fig. 9, 0. 12 °C/minute of the battery temperature Tg was obtained with respect to 0. 1 °C/minute of the desired value Y; the temperature upsurge breadth T’ from the start to the completion of the charge was 7 °C; and the time from the empty state to the charge completion was 110 minutes. Also, after completion of the charge, a discharge test was carried out to obtain a battery capacity, which was substantially the same as that obtained in the conventional charging system. Also, in the above measurement, the temperature upsurge breadth T was about 70 °C irrespective of the charging initial temperature of the battery set 11, i.e. outside air terrtperature. Also, in case the outside air temperature is abruptly increased during the charge, the charging rate, i.e. charging current command 00’.’’ is temporarily lowered. In the present invention, since the charging device 12 is controlled so that the time-rate-of-change AT/At of the temperature of the battery set 11 becomes a steady value (Y), the charging rate lowered as described above restores. As shown in Fig. 4, since the conventional charging system has a temperature upsurge breadth T’of about 12 "C, there has been a very high chance that a certain electric cell reaches a critical temperature. Therefore, in the conventional charging system, it is required that, for example, a plurality of battery temperature detecting devices is prepared, and that the electric cell or module, which reaches the critical temperature, is found at an early stage. Also, when the charge is carried out, in case its initial temperature is high, it is required that the charge is not started. In the present embodiment, since it is also possible to carry out such a charge that temperatures of all the electric cells can be controlled to be sufficiently lower than the critical temperature, the risk that a certain electric cell reaches the critical temperature can be reduced. Therefore, even if the initial temperature is high to a certain extent and the charging is carried out, it is possible to allow all the electric cells not to reach the critical temperature, INDSTRIAL APPLICABILITY It is impossible or hard to become such a situation that any electric cell reaches the critical temperature due to the charge. Also, unnecessary stress is not applied to any electric cell, or it is considered unlikely that’ the unnecessary stress is applied thereto. Therefore, the durations of lives of the respective electric cells or modifies for constituting the battery set are expected to be longer and uniformed. Since the present charging system can be applied to a system wherein secondary batteries having a characteristic that the temperature is raised at a terminal stage of the charge are used, the present charging system can be applied to various instruments using the secondary batteries in addition to the electric car. Since the AV peak is not detected, in the present system, as an AD converter to be used in the charging voltage detecting device, a low-priced AD converter can be employed. Thus, the cost of the entire system can be lowered. As described hereinabove, an object of the present invention is to provide a charging system wherein all the electric cells for constituting the battery set do not reach the critical temperature or the risk of reaching the critical temperature can be lowered, and the charge can be made to a full charge state, without raising the costs. The suitable embodiment of the invention will be described below. In a conventional charging system, the reason why the battery temperature is abruptly increased after the second inclination, is considered that at the time immediately after the second inclination, since the charge of the battery set is mostly (specifically about 80%) completed, the injected current is consumed as heat, i. e. the charging efficiency is lowered. Also, the reason why some of the electric cells reach the critical temperature is that the charging completion is determined based on the AV peak characteristically showing the full charge or based on the time-rate-of-change of the battery temperature. In view of the above defects, the inventors of the present invention have made the present invention based on the knowledge obtained by establishing a relationship between the battery temperature and the charging current, so that: (1) the abrupt increase in the charging voltage can be prevented; and (2) the chances that some electric cells reach the critical temperature are completely removed or lowered without relying on the AV peak and, moreover, the fully charged state, called in the conventional system, or the state comparable with the fully charged state, can be definitely obtained. The charging system according to the present invention includes: a temperature detecting device for detecting the battery temperature; a charging device; and a control device for controlling the charging device. The control device controls the charging device based on the battery temperature. A battery set of an electric car is formed of a plurality of electric cells. For example, the battery set is constituted of a plurality of modules, and each module includes a plurality of the electric cells. The temperature detecting device detects a value typically showing the temperatures of the modules constituting the battery set or the temperatures of the electric cells, as a ‘battery temperature'. The temperature detecting device contact a temperature of one module among the modules as the '"'battery temperature', or can detect an average value of more than two modules as the 'battery temperature". Also, the temperature detecting device can detect a temperature of one electric cell among a plurality of the electric cells as the "battery temperature", or can detect an average value of more than two electric cells as the "battery temperature". The temperature detecting device, specifically, includes a temperature sensor and an AD converter, and in case the average value of more than two modules is detected as the battery temperature, an average value operation device may be included therein. Incidentally, the function of the average value operation device can be assumed by an appropriate processor, such as CPU of the control device. Incidentally, although substantially the same, more specifically, although there is nothing but difference how to define "the temperature detecting device", the average value operation device may be included in the control device, not in the temperature detecting device. The control device can control the charging device through the temperature feedback with "the time-rate-of-change (AT/At) of the temperature T", as a desired value. The control device can control the charging device through the temperature feedback with the quantity based on the temperature, such as '‘the time-rate-of-change (AT/At) of the temperature T\ as a desired value. In other words, by controlling the charging current so that the time-rate-of-change of the temperature T does not exceed a steady value, the abrupt rising of the temperatures of all the electric cells constituting the battery set can be controlled, i. e. the respective electric cells can be prevented from reaching the critical temperature. In the conventional charging system, since the charging is terminated when the time-rate-of-change (AT/At) of the battery temperature Tg exceeds a predetermined value, in case the ‘original AT/At' is erroneously detected due to elevation of the outdoor air temperature, the charge is terminated although the full charge is not attained. However, in the charging system according to the present invention, in case the 'original AT/At" is erroneously detected due to elevation of the outdoor air temperature, since the charging device is controlled by the control device through the temperature feedback, the charging temperature is once lowered down. Then, in case the "AT/At" is lowered, the charging current can be again increased. Incidentally, the characteristics of the invention, as described above, reside in that the control device, basically, controls the charging device through the temperature feedback. However, the control device controls such that the output current becomes a constant current charge before the time-rate-of-change (AT/At) of the temperature T based on the battery temperature exceeds a predetermined value, and after it exceeds the predetermined value, the control device can also control the charging device through the temperature feedback. The control device can control the charging device, in the control through the temperature feedback, so that the charging current becomes zero or a low current charge is carried out when the charging current is lowered to a certain value. Here, the 'low current charge' is defined as a charge with a current value on the Drier of not having an adverse affect on the battery life. Also, the charging device can also be controlled so that the charging current becomes 2ero or the low current charge is carried out when a predetermined time has passed since the charging current lowered to a certain value. Further, the charging device can also be controlled so that the charging current becomes zero or the low current charge is carried out when the battery temperature reaches a certain value. Or, the charging device can also be controlled so that the charging current becomes zero or the low current charge is carried out when the battery temperature has been raised by a ‘predetermined value since the battery temperature reached a certain value. While the invention has been explained with reference to the specific embodiments )f the invention, the explanation is illustrative and the invention is limited only 3y the appended claims. WE CLAIM : 1. A charging system for charging a battery-set, comprising a temperature detecting device for detecting a battery' temperature; a charging device; and a control device for controlling the chagrins device based on the battery temperature, said control device perfuming a temperature feedback charge and continuously controlling a charge current of the charging device with a quantity-representing the temperature as a target value. 2. The charging system for charging a battery-set as claimed in claim 1, wherein said control device controls the charging device in \a temperature feedback control in one of control methods such that a charging current becomes zero when the charge current becomes below a certain value; that the charging current becomes zero after a predetermined time is elapsed since the charge current becomes below a certain value; that the charging current becomes zero when the battery temperature reaches a certain value; and that the charging current becomes zero when the battery temperature increases by a predetermined value after the battery temperature reaches a certain value. 3. The charging system for charging a battery-set as claimed in claim I, wherein said control device controls the charging device in a temperature feedback control with one of methods such that when a charge current becomes below a certain value, low current charge is performed; that after a predetermined time TO since the charge current becomes below a certain value, the low current charge is performed; that when the battery temperature reaches a certain value, the low current charge is performed; and that when the battery temperature increases by a predetermined value since the battery temperature reaches a certain value, the low current charge is performed; and that when the battery' temperature increases by a predetermined value since the battery temperature reaches a certain value, the low current charge is performed. 4. The char sins system for charging a batter set as claimed in claim 1, wherein said battery-set is formed of a plurality of batter\' cells, and wherein said temperature detecting device detects the batter temperature based on a part of the battery cells. 5. The charging system for charging a battery -set as claimed in claim 1, wherein said battery-set is formed of a plurality of modules and the modules are formed of a plurality of battery cells, and wherein said temperature detecting device detects, as the batter}^ temperature, a temperature of one module in the plurality of the modules or a temperature of one battery cell in the plurality of the battery cells, or a temperature based on temperatures of more than two modules in the plurality of modules or a temperature based on temperatures of more than two battery cells in the plurality of the batterv^ cells. 6. The charging system for charging a batter)-set as claimed in claim 7 or 8, wherein said temperature detecting device detects an average of temperatures of more than two modules more than two battery cells in the plurality of the battery cells detects a maximum temperature of the plurality of the battery cells as the battery temperature. 7. The charging system for charging a battery-set as claimed in claim 1, wherein said charging system is installed in an electric motor vehicle. 8. A charging system for charging a battery-set substantially as herein described with reference to lures 5 to 9 of the accompanying drawings.

Documents:

994-chenp-2003-abstract.pdf

994-chenp-2003-claims filed.pdf

994-chenp-2003-claims granted.pdf

994-chenp-2003-correspondnece-others.pdf

994-chenp-2003-correspondnece-po.pdf

994-chenp-2003-description(complete)filed.pdf

994-chenp-2003-description(complete)granted.pdf

994-chenp-2003-drawings.pdf

994-chenp-2003-form 1.pdf

994-chenp-2003-form 19.pdf

994-chenp-2003-form 26.pdf

994-chenp-2003-form 3.pdf

994-chenp-2003-form 5.pdf

994-chenp-2003-pct.pdf