Secondary battery voltage equalization charging device and power supply package

Abstract

In an intermittent charging device of a conventional secondary battery module, two charging periods are required, namely, a charging period for a charging capacitor and a period for charging a secondary battery by the charging capacitor. Therefore, the charging time becomes relatively long as compared with that of a general charging device which continuously charges a secondary battery. By adding a relay capacitor and a relay capacitor switch to an intermittent charging circuit, the relay capacitor is charged during a period in which a charging capacitor charges the secondary battery, and the charge is supplied to the charging capacitor in a short time after the end of charging the secondary battery, immediately starting the period in which the charging capacitor charges the secondary battery. This allows intermittent charging to be performed in a short time that is essentially the same as in continuous charging.

Description

Secondary battery voltage equalization charging device and power supply package

[0001] The present invention relates to a charging device that equalizes the voltages of the secondary batteries in a secondary battery module in which multiple secondary batteries are connected in series. In particular, the present invention relates to a charging circuit that can equalize the voltages of the secondary batteries without sacrificing charging time, and a power supply package that includes the same.

[0002] Because the voltage of each secondary battery is typically low for a given application, secondary battery modules consisting of series-connected secondary batteries are commonly used without using a boost circuit. In this case, the electrical characteristics of each secondary battery during charging and discharging must be consistent. If even one secondary battery with insufficient electrical capacity is included among the multiple series-connected secondary batteries that make up a secondary battery module, the electrical characteristics of that secondary battery will limit the charging and discharging characteristics of the entire secondary battery module.

[0003] The causes of variations in the electrical characteristics of secondary batteries include, for example, variations in initial electrical capacity, capacity reduction due to charge / discharge cycles, variations in battery internal resistance, and variations in self-discharge time. These variations are caused by variations in the manufacturing process of secondary batteries, and therefore, when using secondary battery modules, these variations in electrical characteristics cannot be avoided. Therefore, when using secondary battery modules, measures are adopted to equalize the voltages of the individual secondary batteries connected in series that make up the secondary battery module.

[0004] One of the voltage equalization measures, as shown in Non-Patent Document 1 and Patent Document 3, is to equalize the charge amounts of adjacent secondary batteries among those connected in series during discharge. This allows even a secondary battery in a secondary battery module that is prone to discharge degradation to receive a supply of insufficient charge from the adjacent secondary battery and continue discharging to the end in sync with the other secondary batteries. As a result, the secondary battery module as a whole can be discharged to the end without being dominated by the secondary battery that is prone to discharge degradation.

[0005] However, leveling the charge amount of secondary batteries during discharge does not fundamentally correct variations in the charging characteristics of secondary batteries during charging before discharge, i.e., during use, i.e., discharging. Therefore, the measures in Non-Patent Document 1 and Patent Document 3 are insufficient. In contrast, methods for suppressing variations in the charging characteristics of secondary batteries during charging are direct and effective. Specific examples of such methods include the charging methods in Patent Documents 1, 2, and 5. These prior charging methods use a circuit in which an independent charging capacitor is provided for each secondary battery to average the charge amount for each of the multiple series-connected secondary batteries that make up a secondary battery module during charging. Charge is first accumulated in the charging capacitor, and then that charge is independently supplied to each secondary battery. Because the charging capacitor charges the series-connected secondary batteries as electrically independent secondary batteries, it is effective for secondary battery modules composed of multiple series-connected secondary batteries.

[0006] If the charging voltage is set to a charge completion voltage within the maximum allowable charging voltage range, continued charging of the secondary battery that first reached its charge completion voltage will not cause deterioration of that secondary battery, while charging will continue for the secondary batteries that have not yet reached their charge completion voltage. This prevents the charging of the series-connected secondary batteries from being dominated by the secondary battery with the lowest charging (or power storage) capability, and allows the secondary battery module to charge all of the secondary batteries to the charge completion voltage.

[0007] However, in the prior charging methods of Patent Documents 1 and 2, all charging capacitors connected to the secondary batteries are first charged (i.e., "charged") from a charging power supply, and then the connection between the charging power supply and the charging capacitors is cut off. Each charging capacitor is then individually connected to a secondary battery connected in parallel, and the charge stored in the charging capacitor is supplied (i.e., "charged") to the secondary battery. After this charging operation, all charging capacitors are disconnected from their corresponding secondary batteries, and then charging is resumed from the charging power supply to all charging capacitors to compensate for the charge lost during charging of the secondary batteries. This series of operations is repeated to charge the entire secondary battery module.

[0008] In this series of operations, charging of the secondary battery from the charging power source cannot be performed while charging of the charging capacitor is in progress. Therefore, charging of the charging capacitor and charging of the secondary battery from the charging capacitor are performed alternately in this manner, and the secondary battery is charged intermittently. In this case, since periods of charging the secondary battery and periods of charging the charging capacitor are required alternately, the problem of longer charging time compared to normal continuous charging is essentially unavoidable.

[0009] In Patent Document 5, the voltage of the power supply-side relay capacitors is adjusted by supplying or discharging power to or from a charging or discharging device via a resistor, using a common local ground. Adjusting the voltage of each relay capacitor by discharging or charging through a resistor and these devices creates a time delay based on the product of the combined resistance of the resistor and these devices and the capacitance of the relay capacitor (i.e., the time constant). Therefore, the circuit disclosed in Patent Document 5 inevitably requires a longer charging time than when the relay capacitors are directly connected to a power supply and continuously charged.

[0010] In Patent Document 4, the method of charging the multiple secondary batteries that make up one secondary battery module independently does not include a method of suppressing variations in charging characteristics. Also, because each secondary battery module is charged sequentially from a single power source, there are periods when other secondary battery modules are not being charged while waiting to be charged, which essentially makes it unavoidable that the overall charging time is longer.

[0011] "Battery power balance circuit and battery system", CN103138314A "Apparatus and method for voltage equalization of storage elements", JP2007-020368A "Apparatus and method for voltage equalization of storage elements", JP2007-020368A "Active equalizing and protecting system of stackable series-connected lithium battery", CN102064568A "Cell balancing through a switched capacitor lever shifter", US2014 / 0266003 A1

[0012] “Capacitor Based Battery Balancing System”, Mohamed Daowd, Noshin Omar, Peter Van Den Bossche, Joeri Van Mierlo, World Electric Vehicle Journal Vol.5, ISSN 2032-6653, Page0385-0393

[0013] Fig. 1 shows the main circuit of the secondary battery voltage equalization charging device for a secondary battery module 100 disclosed in Patent Document 1 or Patent Document 2. The secondary batteries 20 constituting the secondary battery module 100 are connected in series, and each secondary battery 20 has an independent charging capacitor 30 connected in parallel via a charging switch 21. The charging capacitor 30 is connected to a charging power supply 50 via a charging power switch 51. Fig. 2 shows the operation of the charging switch 21 (labeled "SW1" in Fig. 2) and the charging power switch 51 (labeled "SW3" in Fig. 2).

[0014] Charging of each secondary battery 20 is performed by charging the charge accumulated in the charging capacitor 30 to the secondary battery 20 while the charging switch 21 is in a conductive state (indicated as "ON" in FIG. 2). During this period, the charging power switch 51 is in a cut-off state (indicated as "OFF" in FIG. 2), so that the charge of the secondary battery 20 does not return to the charging power supply 50, and the series connection of the secondary batteries 20 is not destroyed via the charging power switch 51 (see FIGS. 1 and 2).

[0015] On the other hand, when charging the charging capacitor 30 from the charging power source 50, the charging switch 21 is turned off and the charging power switch 51 is turned on, allowing the charging capacitor 30 to be charged by the charging power source 50. However, because the charging switch 21 is turned off, the secondary battery 20 is not charged by the charging power source 50 (see Figures 1 and 2), and the series connection of the secondary batteries is not destroyed via the charging power source 50. Therefore, none of the secondary batteries are destroyed electrically, and all of the secondary batteries 20 can be safely charged. Here, the charging switch 21 and the charging power switch 51 are composed of linked multi-pole switches SW1 and SW3. Because of this linked operation, all of the charging switches 21 and charging power switches 51 are simultaneously turned on or off.

[0016] In order to distinguish this intermittent charging method and device using a charging capacitor and a charging switch from a general charging method and device that performs continuous charging, they will be referred to as intermittent charging and intermittent charging device, respectively.

[0017] In Patent Document 1 and Patent Document 2, as described above, each secondary battery 20 constituting a secondary battery module 100 is charged independently and equally. It is important here that the charging capacitor 30 is intermittently charged with electric charge from the charging power source 50. To achieve this, as shown in FIGS. 1 and 2 , the secondary batteries must be charged during a period when the charging switch 21 and the charging power source switch 51 are not simultaneously in a conductive state. This allows the secondary batteries constituting the secondary battery module to be charged independently and equally, thereby achieving the electrical output of the secondary battery module 100 achieved by connecting the secondary batteries 20 in series.

[0018] In this type of intermittent charging, even if a secondary battery module contains secondary batteries with different charging characteristics, they are intermittently charged independently to the same voltage as the other normal secondary batteries. Therefore, the secondary battery module as a whole can be charged to completion without being dominated by such secondary batteries. In other words, even if some secondary batteries are difficult to charge, the power supply capacity of the secondary battery module is not significantly affected. Therefore, even if there are multiple secondary battery modules in which multiple secondary batteries containing different secondary batteries are connected in series, variation in the power supply capacity of the secondary battery modules can be suppressed.

[0019] However, in the intermittent charging devices shown in Patent Documents 1 and 2, the charging switch 21 and the charging power switch 51 are not in a conductive state at the same time as shown in Figure 2, so that during the period when the charging capacitor 30 is being charged from the charging power source 50, each secondary battery 20 is not charged from the charging capacitor 30. Because this period is a non-charging period for the secondary batteries 20, the total charging time for the secondary batteries is relatively longer than with a general charging device that charges continuously. The total charging period is the sum of the period for charging the secondary batteries 20 and the period for charging the charging capacitor 30, so roughly speaking, the charging period with such an intermittent charging device is twice as long as the period for continuous charging.

[0020] That is, a problem with such conventional intermittent charging devices is that the charging time is longer than that of continuous charging devices that charge continuously. Therefore, the problem to be solved by the present invention is to correct the problem of long charging times during intermittent charging operations that include non-charging periods, even for series-connected secondary batteries 20, and to have charging capacitor 30 charge secondary batteries 20. This makes it possible to achieve charging of secondary battery modules with an intermittent charging device that is substantially equivalent to that of a continuous charging device.

[0021] One possible means for correcting the conventional intermittent charging operation is to provide a relay capacitor for storing charge for charging the charging capacitor 30 so that the charging capacitor 30 can continuously maintain its charging capacity even while the charging capacitor 30 is charging each secondary battery 20, and to supply charge for the next charging to the charging capacitor via the relay capacitor immediately after charging a secondary battery 20. This is because adopting such a means makes it possible to eliminate the non-charging period mentioned above.

[0022] As the above means, the present invention provides a relay capacitor 40 and a relay capacitor switch 32. FIG. 3 shows the circuit of a secondary battery voltage equalization charging device 110 according to the present invention. The secondary batteries 20 constituting the secondary battery module 104 are connected in series, and an independent charging capacitor 30 is connected in parallel to each secondary battery 20 via a charging switch 22. Each charging capacitor 30 is connected to a relay capacitor 40 via a relay capacitor switch 32, and the relay capacitor 40 is connected to a DC charging power supply 50 via a charging power switch 52. FIG. 4 shows the operation of the charging switch 22 (labeled "SW1" in FIG. 4), the relay capacitor switch 32 (labeled "SW2" in FIG. 4), and the charging power supply switch 52 (labeled "SW3" in FIG. 4). Note that all charging power supplies, including the charging power supply 50, appearing in the following description have DC output unless otherwise specified.

[0023] In the secondary battery voltage equalization charging device 110 according to the present invention, the charging switches 22, relay capacitor switches 32, and charging power supply switches 52 used for each secondary battery are implemented as multi-pole switches SW1, SW2, and SW3. These switches perform conduction and interruption operations simultaneously in conjunction with each other, but are electrically independent for each secondary battery. Therefore, although multiple secondary batteries are charged by a single charging power supply 50, the positive and negative poles of the multiple batteries are not short-circuited.

[0024] Each secondary battery 20 is charged during the charging period, i.e., the period during which the charging switch 22 (or SW1) is in the conductive state, by supplying the charge accumulated in the charging capacitor 30 to the secondary battery 20. At this time, the charging power supply switch 52 (or SW3) is in the conductive state in synchronization with the charging switch 22 (or SW1), and the relay capacitor 40 is also charged by the charging power supply 50. However, during this period, the charging capacitor switch 32 (or SW2) is in the cut-off state (see FIG. 4), so the charge of the secondary battery 20 does not return to either the relay capacitor 40 or the charging power supply 50, and the series connection of the secondary batteries 20 is not destroyed.

[0025] During the charging period, the charging capacitor 30 is not directly charged from the charging power source 50. However, during the relay period (the period when SW2 is "ON"), the charge stored in the relay capacitor 40 is supplied to the charging capacitor 30 via the relay capacitor switch 32 (or SW2). This relay period of charge via the relay capacitor 40 is achieved by coupling (so-called capacitor coupling) the relay capacitor 40 and the charging capacitor 30 via the relay capacitor switch 32 (or SW2), and therefore the relay period is much shorter than the charging period for the secondary battery (see FIG. 4).

[0026] During this charge relay period (i.e., while SW2 is ON), the charging switch 22 (or SW1) and the charging power switch 52 (or SW3) are synchronized and in an OFF state, so the secondary batteries 20 are not directly charged from the charging power source 50 (see FIG. 4), and the series connection relationship of the secondary batteries 20 in the secondary battery module 104 is not destroyed via the charging power source 50. Therefore, none of the secondary batteries 20 are destroyed electrically, and the secondary batteries 20 can be safely charged.

[0027] Next, we will consider how much shorter the time it takes to charge a secondary battery module using the secondary battery voltage equalization charging device of the present invention compared to intermittent charging using the prior art equalization charging device of Figure 1 (the operation of which is shown in Figure 2).

[0028] For this study, a lithium-ion battery was selected as the secondary battery and its charging characteristics were analyzed. Figure 5 shows the charging characteristics of a lithium-ion battery as a representative secondary battery. The horizontal axis represents charging time.

[0029] The charging operation of a secondary battery does not start from 0% charge capacity, but from a state with a margin of around 10% to 20%. Even for so-called full charge, the end point of charging is not 100% charge capacity, but rather when the battery reaches a voltage just below that. This starting and ending of charging is intended to prevent overcharging and overdischarging, which would shorten the life of the secondary battery. Within this range of charge capacity, the charging operation of a secondary battery is nearly linear with respect to the steady-state charging current. Therefore, the charging process of a secondary battery can be treated approximately as an equivalent series circuit of an internal resistance and a capacitor.

[0030]

[0031] The validity of treating the charging equivalent circuit as a linear circuit lies in the linear relationship between the charging time and charging capacity of a lithium-ion battery shown in Figure 5. However, even if a secondary battery other than a lithium-ion battery is used and the characteristics of that secondary battery do not have such a linear relationship but simply have a monotonically increasing relationship with time, the analysis shown below is applicable because the comparison between the intermittent charging operation of the prior art and the intermittent charging operation of the present invention is a relative comparison of charging times.

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] The equivalent circuit of the intermittent charging circuit for one secondary battery according to the present invention during charging is configured as shown in Figure 9. That is, in the conventional charging equivalent circuit shown in Figure 6, a relay capacitor 40 is inserted between the charging power supply PS and the charging capacitor 30 together with the relay capacitor switch SW2.

[0039] Even when the charging capacitor 30 is charging the secondary battery RBC, the switch SW3 is turned on and the relay capacitor 40 receives charge from the charging power supply PS. This charge is a charge that supplements the charge supplied by the charging capacitor 30 to the secondary battery RBC.

[0040] The charging operation of this charging device is an intermittent charging operation as shown in FIG.

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] If the charging rate of each relay capacitor 40 by the charging power supply PS is faster than the charging rate of the secondary battery RBC by the charging capacitor 30, the conduction period of SW3 may be set within the conduction (ON) period of SW1 and shorter than the conduction (ON) period of SW1. Normally, the output impedance of the charging power supply PS is smaller than the internal resistance of the secondary battery, so the condition that the charging rate for the relay capacitors 40 is faster than the charging rate for the secondary battery RBC is met.

[0050] As described above, the secondary battery charge equalization device according to the present invention charges each secondary battery in a secondary battery module consisting of multiple secondary batteries, thereby enabling the power supply capacity of the secondary battery module as a whole to be fully utilized without being dominated by the secondary battery with the lowest charging capacity, and since the charging switch SW1 is only turned off for a very short time, the charging time is approximately the same as that for continuous charging. Such short charging times are possible due to the use of the relay capacitor and the capacitor coupling between the relay capacitor and the charging capacitor, which are means of the present invention.

[0051] Furthermore, with the intermittent charging circuit of the present invention, even if the output voltage of the charging power source is lower than the voltage of the secondary battery module to be charged, the secondary battery module can still be charged as long as it is higher than the charging voltage of the secondary battery alone. This is due to the advantage of being able to charge each secondary battery independently by using a relay capacitor and a charging power switch.

[0052] FIG. 1 is a circuit diagram of the main components of a secondary battery voltage equalization charging device for a secondary battery module disclosed in Patent Document 1 or Patent Document 2. FIG. 2 is a diagram illustrating the operation of the charging switch (SW1) and charging power switch (SW3) of the secondary battery voltage equalization charging device of FIG. 1. FIG. 3 is a circuit diagram of a secondary battery voltage equalization charging device of the present invention. FIG. 4 is a diagram illustrating the operation of the charging switch (SW1), relay capacitor switch (SW2), and charging power switch (SW3) of the secondary battery voltage equalization charging device of the present invention. FIG. 5 is a diagram illustrating the charging characteristics of a lithium-ion battery. FIG. 6 is a charging equivalent circuit diagram of the intermittent charging circuit disclosed in Patent Document 1 or Patent Document 2. FIG. 7 is a diagram illustrating the operation of switches SW1 and SW3 of the intermittent charging circuit disclosed in Patent Document 1 or Patent Document 2. FIG. 8 is a diagram illustrating the operation of each switch and the change in battery voltage of the secondary battery during intermittent charging disclosed in Patent Document 1 or Patent Document 2. FIG. 9 is an equivalent circuit diagram of the intermittent charging circuit of the present invention during charging. FIG. 10 is a diagram showing the operation of the charging switch (SW1), relay capacitor switch (SW2), and charging power switch (SW3) of the intermittent charging circuit of the present invention. FIG. 11 is a diagram showing the operation of the individual switches (SW1, SW2, SW3) during intermittent charging, and the changes in the relay capacitor voltage and secondary battery voltage. FIG. 12 is a circuit diagram of a secondary battery voltage equalizing charging device of the present invention using electrical connectors. FIG. 13 is a circuit diagram of a secondary battery voltage equalizing charging device of the present invention using a current limiting device. FIG. 14 is a circuit diagram of a secondary battery voltage equalizing charging device of the present invention using a constant current diode. FIG. 15 is a circuit diagram of a secondary battery voltage equalizing charging device of the present invention using a current and voltage limiting device. FIG. 16 is a specific example of the current and voltage limiting device shown in FIG. 15. FIG. 17 is a circuit diagram of a power supply package and load connection in which a secondary battery module is connected to a secondary battery voltage equalizing charging device of the present invention. FIG. 18 is a circuit diagram of a secondary battery voltage equalizing charging device and power supply package in which a secondary battery is used as an input power source to drive a DC-DC converter, which serves as another DC power source for the secondary battery voltage equalizing charging device. FIG. 19 is a circuit diagram of a secondary battery voltage equalization charging device and power supply package that utilizes a DC-AC converter.Figure 20 is a circuit diagram of a secondary battery voltage equalization charging device that uses a main power supply switch to equalize secondary battery voltages during charging and discharging. Figure 21 is a circuit diagram of a secondary battery voltage equalization charging device that uses an electrical connector to equalize secondary battery voltages during charging and discharging. Figure 22 is a circuit diagram of an embodiment of a secondary battery voltage equalization charging device according to the present invention that omits a charging switch. Figure 23 is a circuit diagram of a secondary battery voltage equalization charging device circuit that omits a charging switch and uses an electrical connector 25 to equalize secondary battery voltages during charging and discharging. Figure 24 is a circuit diagram of an embodiment of a secondary battery voltage equalization charging device that omits a charging switch, uses a main power supply switch, and further includes a current limiting device and a bypass switch to equalize secondary battery voltages during charging and discharging. Figure 25 is a circuit diagram of a secondary battery voltage equalization charging device that omits a charging switch, uses an electrical connector, and further includes a current / voltage limiting device and a bypass switch to equalize secondary battery voltages during charging and discharging. Figure 26 is a diagram of a secondary battery voltage equalization regenerative charging device that uses regenerative power. FIG. 27 is a diagram showing the configuration of a secondary battery voltage equalizing regenerative charging device used in a charging device for the auxiliary motor and secondary battery of an electrically assisted bicycle.

[0053] An embodiment to which the basic circuit of the present invention is applied will be described below.

[0054] The voltage of the charging power source 50 of the secondary battery voltage equalizing charging device 110 of the present invention shown in Figure 3 is set in accordance with the maximum allowable charging voltage of the secondary battery. This setting may be variable within a range not exceeding the maximum allowable charging voltage of the secondary battery 20 being charged. By limiting the voltage of the charging power source in this way, it is possible to prevent accidents such as fire or explosion of the secondary battery 20 during charging, and further to prevent a reduction in the service life of the secondary battery due to overcharging.

[0055] 4 shows the operation of the charging switch 22 (SW1), relay capacitor switch 32 (SW2), and charging power switch 52 (SW3) that make up the secondary battery voltage equalizing charging device 110. That is, the charging device is made up of a charging capacitor 30 electrically connected in parallel to each secondary battery 20 of a secondary battery module 104 via a first switch 22, a relay capacitor 40 electrically connected in parallel to the charging capacitor 30 via the relay capacitor switch 32, and one DC power supply 50 electrically connected in parallel to the relay capacitor 40 via the charging power switch 52 (SW3), and the relay capacitor 40 has a larger capacitance than the charging capacitor 30. Furthermore, as shown in FIG. 4, the charging switch 22 and the charging power switch 52 are synchronized, repeating the cycle of conducting when the relay capacitor switch 32 is cut off and cutting off when the relay capacitor switch 32 is conducted, and the charging switch 22 and the third switch are not simultaneously conducting with the relay capacitor switch 32, and the above-mentioned conduction and cutting off are performed simultaneously in conjunction with all of the charging switches 22, all of the relay capacitor switches 32, and all of the charging power switches 52.

[0056] Alternatively, charging power supply 50 may be provided with a constant current and constant voltage function. In this case, the current limit value of the constant current is set to a value obtained by multiplying the maximum allowable charging current of the series-connected secondary batteries 20 constituting secondary battery module 104 by the number of series connections, and the voltage limit value of the constant voltage is set to the maximum allowable charging voltage of secondary batteries 20. Use of a charging power supply with such a constant current and constant voltage function can prevent accidents such as fire or explosion of secondary batteries 20 and further prevent a reduction in the service life of secondary batteries 20 due to overcharging.

[0057] The charging power source 50 is used when charging the secondary battery modules 104, and even if it is separated from the secondary battery voltage equalizing charging device 110, there is no problem in using it as a power source for the secondary battery modules 104. In this case, the charging switch 22 (SW1), relay capacitor switch 32 (SW2), charging power switch 52 (SW3), and charging capacitor 30 operate to equalize the voltage when the secondary battery modules 104 are discharged. This part of the secondary battery voltage equalizing charging device 110 without the charging power source 50 is called a secondary battery voltage equalizing charging circuit 135 ( FIG. 3 ).

[0058] In the case where the secondary battery modules 104 are connected to the secondary battery voltage equalizing charging device 120 of the present invention only during charging, an embodiment may be adopted in which each secondary battery 20 is connected to the secondary battery voltage equalizing charging device 121 using an electrical connector 24, as shown in Figure 12. Unless the secondary battery modules 104 are to be removed from the secondary battery voltage equalizing charging device 121 and moved, a switch that can make and break electrical connection may be used instead of the electrical connector 24.

[0059] The secondary battery 20 is equivalent to a capacitor during charging, and its storage capacity A is much larger than the capacitance of the charging capacitor. Therefore, the initial voltage when charging the secondary battery 20 is low (and therefore the charging start voltage is also low). At the beginning of charging the secondary battery 20 with the charging capacitor 30, the input resistance of the charging capacitor is extremely small, so the current flowing from the charging capacitor 30 to the secondary battery 20 may exceed the maximum allowable charging current. Charging with such an excessive charging current will cause the secondary battery 20 to deteriorate, its electrical capacity to decrease, and its battery life to be shortened. This is known as degradation of storage capacity due to overcharging current.

[0060] To avoid this, a current limiting device 80 with a rated limiting current equal to or less than the maximum allowable charging current of the secondary battery is inserted in the current path between the charging capacitor and the secondary battery to prevent excessive current from flowing between the charging capacitor and the secondary battery (FIG. 13). Such a current limiting device 80 prevents the current from exceeding the rated limiting current of the current limiting device 80, even when the current flowing from the charging capacitor to the secondary battery is excessive. Due to the effect of this current limiting, an overcharging current does not flow even in a secondary battery with an extremely low initial charging voltage, and the battery can be charged without deteriorating its storage efficiency.

[0061] One example of such a current limiting device 80 is a constant current diode 81 whose rated current is equal to or less than the limiting current, which is used between each charging capacitor 30 and secondary battery 20. Fig. 14 shows a secondary battery voltage equalization charging device 112 according to the present invention that uses a constant current diode 81.

[0062] By using such a current limiting device 80 or constant current diode 81, it is possible to prevent a decrease in charging capacity and a shortened lifespan even for secondary batteries with extremely low initial charging voltages, and as a result, it is possible to prevent a deterioration in the lifespan of the entire secondary battery module made up of individual secondary batteries connected in series.

[0063] A DC constant current, constant voltage power supply is often used as the charging power source. However, the secondary batteries that make up a secondary battery module basically have different electrical characteristics. Therefore, even if the entire secondary battery module is charged using a charging power supply with constant current, constant voltage characteristics, it is not guaranteed that each secondary battery will be charged within the rated safe charging range.

[0064] Therefore, as shown in Figure 15, it is possible to protect each secondary battery 20 by using a secondary battery voltage equalization charging device 113 in which a current / voltage limiting device 90 is inserted in the current path between each charging capacitor 30 and each secondary battery 20. In this case, the rated limiting current and rated limiting voltage of the current / voltage limiting device 90 are set to be equal to or less than the maximum allowable charging current and maximum allowable charging voltage of the secondary battery, respectively. With these settings, the secondary batteries can be safely charged without exceeding their maximum ratings. Furthermore, if a secondary battery module is composed of secondary batteries with different ratings, safe charging can be achieved by setting the current / voltage limiting device 90 to be equal to or less than the maximum allowable charging current and maximum allowable charging voltage of each secondary battery.

[0065] 16 shows an example of a specific circuit for current / voltage limiting device 90. Constant current operation is achieved by Zener diode ZD2, n-channel MOS transistor 27, operational amplifier OP2, and resistors R2 and R3. The limiting current value for the constant current operation is the product of the resistance of resistor R3 and the current flowing through that resistor R3, i.e., the current when the voltage drop across resistor R3 becomes equal to the Zener voltage of Zener diode ZD2.

[0066] On the other hand, constant voltage operation is realized by Zener diode ZD1, p-channel MOS transistor 26, operational amplifier OP1, and resistor R1. The Zener voltage appearing across Zener diode ZD1 is the limit voltage for the voltage applied to secondary battery 20 in constant voltage operation.

[0067] In this example, a single power supply is used for the operational amplifiers OP1 and OP2. In practice, auxiliary capacitors are required to suppress parasitic oscillations, but these are omitted in FIG. 16 for simplicity. VDD for the operational amplifiers OP1 and OP2 and VSS for the operational amplifier OP1 are supplied from the positive and negative voltage sources of the secondary battery module 104 shown in FIG. 16. VSS for the operational amplifier OP2 is supplied from the negative power supply of the secondary battery module 104 or an external DC power supply with a lower voltage. When the voltage between the positive and negative terminals of the secondary battery module 104 is higher than the voltage between the VDD and VSS terminals of the operational amplifiers OP1 and OP2, the voltages for VDD and VSS may be supplied from an external power supply with a voltage lower than the maximum allowable voltage between VDD and VSS.

[0068] In addition, the current limiting device and constant current diode of Example 3 and the current / voltage limiting device of Example 4 may be inserted either between the charging switch 22 and the charging capacitor 30 or between the charging switch 22 and the secondary battery 20, as long as they are within the current path between the secondary battery 20 and the charging capacitor 30.

[0069] The secondary battery voltage equalizing charging device according to the present invention is basically a charger that simply charges secondary battery modules. Furthermore, as shown in Figure 17, the secondary battery voltage equalizing charging device according to the present invention can be used as a power supply to supply power to a load 60 by connecting a secondary battery module to the power supply package 140. The connection to the load 60 can be direct or by using a switch 61 as shown in Figure 17. The switch 61 can be a single-pole switch that operates on either pole of the secondary battery module.

[0070] In the secondary battery voltage equalization charging device according to the present invention, the input power supply of the intermittent charging device, i.e., the charging power supply, basically limits the charging voltage to a value that does not exceed the maximum allowable charging voltage of the secondary batteries. Meanwhile, the secondary battery module is made up of two or more secondary batteries connected in series. Therefore, the voltage of the secondary battery module is always higher than the charging voltage of each individual secondary battery.

[0071] 18, it is also possible to use the secondary battery module 104 as an input power source, and drive a DC-DC converter 70 whose output voltage is the charging voltage of the secondary battery, to serve as another charging power source for the secondary battery voltage equalizing charging device 130. A secondary battery module 104 can also be further connected to this secondary battery voltage equalizing charging device 130 to form a power supply package 150.

[0072] In this way, the choice of whether to use the secondary battery module 104 as the self-power source of the secondary battery voltage equalizing charging device or the external DC power source 50 is made by selecting the electrical connection using the double-pole double-throw switch 62. In the circuit of this embodiment, the secondary battery module 104 supplies power to the load while simultaneously equalizing the voltages of its own secondary batteries, so that differences in the discharge characteristics of the secondary batteries can be corrected by equalizing charging. As a result, some deteriorated secondary batteries within the secondary battery module 104 can function in the same way as the other secondary batteries, allowing the power of the secondary battery module 104 to be used up to the end.

[0073] When using an AC input DC charging power supply 55 in which the input of the charging power supply is AC input, a secondary battery voltage equalizing charging device 131 as shown in FIG. 19 can be used. In this case, by using a DC-AC converter 75 instead of a DC-DC converter, the DC-AC converter 75 can be used as a power supply that supplies AC power other than the AC input DC charging power supply 55, and the secondary battery voltage equalizing charging device of the present invention can be used with uniform AC power utilization. A multi-polar selection switch 72 switches between AC input sources. The advantage of this embodiment is that AC power can be utilized uniformly.

[0074] A power supply package 150 can be formed by further connecting a secondary battery module 104 to this secondary battery voltage equalizing charging device 131 .

[0075] While the above-described examples all demonstrate the function of the secondary battery voltage equalizing charging device of the present invention during intermittent charging, the circuit that realizes the intermittent charging operation of the present invention does not perform the charging function when the charging power source is disconnected, but it can still perform the function of equalizing the voltage of the secondary batteries that make up the secondary battery module during discharge.

[0076] Specifically, the circuit configuration of the secondary battery voltage equalizing charging device 110 in Figure 3 is modified, for example, to form a secondary battery voltage equalizing charging device 111 shown in Figure 20, in which a main power supply switch 53 is added to the output path of the charging power source 50. The voltage equalizing operation process executed here achieves voltage equalization during discharge of the secondary battery. The voltage equalizing operation is described below.

[0077] Each charging capacitor 30 connected in parallel to each secondary battery 20 constituting the secondary battery module 104 maintains the voltage of the secondary battery 20 to which it is connected during discharging. The charge maintaining that voltage is transferred to the relay capacitor 40 via the relay capacitor switch 32. Similarly, the charge maintaining the voltage of the other secondary batteries 20 constituting the secondary battery module 104 during discharging is transferred to the other charging capacitor 30 connected to it, and then to the other relay capacitor 40 via the other relay capacitor switch 32. The voltages of all these secondary batteries 20 during discharging and the charge maintaining that voltage are then temporarily transferred to and stored in the relay capacitor 40.

[0078] Then, if the main power supply switch 53 is turned off and the charging power supply 50 is not connected, the charging power supply switch 52 is turned on, and the voltages of all discharging secondary batteries 20 and the charges maintaining them are leveled out (i.e., made equal to each other) in all relay capacitors 40 connected in parallel via the charging power supply switch 52.

[0079] The leveled voltage and charge of the relay capacitor 40 are then transferred in reverse to the individual charging capacitors 30 via the individual relay capacitor switches 32. These leveled voltage and charge are then transferred to the individual secondary batteries 20 via the individual charging switches 22. The transfer of the leveled voltage and charge to the secondary batteries serves to compensate for the insufficient charge when the charge supply capacity of the secondary battery is degraded compared to the other batteries during discharge. On the other hand, when the charge supply capacity of the secondary battery is not degraded, the secondary battery supplies charge to the charging capacitor 30 to increase (i.e., restore) the leveled voltage.

[0080] Then, the voltages and charges of all relay capacitors 40 connected in parallel are again equalized via the charging power switch 52. At this time, if the secondary battery module 104 continues to discharge, the new voltage of the secondary battery 20 generated by the discharge is equalized. Then, the equalized voltage and charge are used to compensate for the insufficient charge of the secondary battery whose charge supply capacity has deteriorated.

[0081] By repeating this cycle, the secondary battery module as a whole can discharge to the end while minimizing limitations imposed by secondary batteries with deteriorated charge supply capabilities. Note that the relative operations of the charging switch 22 (SW1), relay capacitor switch 32 (SW2), and charging power switch 52 (SW3) are the same as those shown in Figure 4 or the upper diagram of Figure 11. The basic principle is that when the charging power switch 52 (SW3) is turned on, its conduction does not create a DC path leading to the secondary battery 20, and the on / off times of all switches, including the other switches, may be changed as appropriate.

[0082] 21 shows another example of the eighth embodiment. In this example, a DC charging power source 50 for charging is connected to a secondary battery voltage equalization charging device circuit 160 by an electrical connector 25 instead of a main power supply switch 53. When the DC charging power source 50 is connected by the electrical connector 25, the secondary battery voltage equalization charging device circuit 160 performs a voltage equalization function for the secondary battery modules 104 during charging, and when the DC charging power source 50 is disconnected from the electrical connector 25, the secondary battery voltage equalization charging device circuit 160 performs a secondary battery voltage equalization function during discharging.

[0083] In either function, the secondary battery module 104 can exert its overall power supply capacity until the end of discharging without being dominated by the secondary battery with the lowest charging / discharging capacity among the secondary batteries 20.

[0084]

[0085] The "ON" state of relay capacitor switch SW2 is sufficiently shorter than the above product and the "ON" state of SW3. Therefore, even if the charging capacitor 30 and secondary battery 20 are always in a conductive state, the relay capacitor and relay capacitor switch according to the present invention can achieve the effect of intermittent charging. Therefore, intermittent charging can be performed even if the charging switch SW1 is omitted and the charging capacitor 30 and secondary battery 20 are always in a conductive state. In this case, the secondary battery voltage equalizing charging device of the present invention has a two-system switch circuit configuration, as shown in Figure 22, in which the relay capacitor switch 32 is the first switch and the charging power switch 52 is the second switch, simplifying switch control.

[0086] Even if an intermittent charging circuit such as this embodiment, in which the charging switch SW1 is omitted and a two-system switch circuit configuration is used instead of the three-system switch circuit configuration, it is possible to configure the secondary battery voltage equalizing charging device and power supply package of Examples 1 to 8 above and achieve the same effects.

[0087] Figure 23 shows a case where a two-system switch circuit configuration is applied to the secondary-battery voltage equalization charging device circuit 160 (see Figure 21) that performs voltage leveling during discharge according to the eighth embodiment. In this case, the secondary-battery voltage equalization charging device of the present invention has a two-system switch circuit configuration in which the relay capacitor switch 32 is the first switch and the charging power switch 52 is the second switch, simplifying switch control. Furthermore, in the circuit of Figure 20 according to the eighth embodiment, the main power supply switch 53 is the third switch.

[0088] With respect to secondary battery voltage equalization by voltage leveling during discharge in Example 8, when using the current limiting device 80 during charging in Example 3 (see FIG. 13) or the current / voltage limiting device 90 during charging in Example 4 (see FIG. 15) in voltage equalization during charging, a bypass switch is required. This is because, while the secondary battery voltage equalization circuit limits the current supply and current direction to the secondary battery 20 during charging, two current directions are required during discharge: current release and current supply to the deteriorated secondary battery 20.

[0089] Therefore, during discharge, it is necessary to release the restriction on the direction of current to the secondary battery 20 by the current limiting device 80 and the current / voltage limiting device 90. For this reason, a switch is required to bypass the current limiting device 80 and the current / voltage limiting device 90 during discharge.

[0090] As an example of such an added bypass, Fig. 24 shows a case where the current limiting device 80 is applied to the embodiment of Fig. 20 and the secondary battery voltage equalizing charging device 111 is a two-system switch circuit (however, a constant current diode 81 is used as the current limiting device 80). Fig. 25 shows a case where the current / voltage limiting device 90 is applied to the embodiment of Fig. 21 and the secondary battery voltage equalizing charging device circuit 160 is a two-system switch circuit (Fig. 23).

[0091] The bypass switch 54 in Figure 24 is synchronized with the main power supply switch 53 and is cut off when the main power supply switch 53 is on and the secondary battery module 104 is in a charging state, and is on when the main power supply switch 53 is off and the secondary battery 20 is discharging or not charging.

[0092] The bypass switch 54 in FIG. 25 is cut off when the charging power source 50 is connected via the electrical connector 25, and is conductive when the charging power source 50 is not connected.

[0093] Even in the case of a current limiting device 80 or a current / voltage limiting device 90 in a secondary battery voltage equalizing charging device or a secondary battery voltage equalizing charging device circuit based on a two-system switch circuit configuration that omits the charging switch SW1, the operation of the bypass switch 54 is the same as in the case of a three-system switch circuit configuration.

[0094] In both the secondary battery voltage equalization charging devices of Example 6 (FIG. 18) and Example 7 (FIG. 19), the charging power source is either an external DC power source or the secondary battery module 104 to be charged is used as its own power source via a DC-DC converter 70 or a DC-AC converter 75. On the other hand, in an application product that uses the secondary battery module 104 as a power supply, for example, a product that uses an electric motor, the regenerative current (or regenerative power) of the electric motor can be used to charge the secondary battery module 104. This can extend the usable life of the secondary battery module 104 after charging.

[0095] The problem with using regenerative current to charge the secondary battery modules 104 is that the voltage of the motor that generates the regenerative current is lower than the voltage of the motor's drive power supply, i.e., the voltage of the secondary battery modules 104, so the regenerative current cannot be used directly to charge the secondary battery modules 104. However, in the secondary battery voltage equalization charging device of the present invention, the charging power supply charges each of the secondary batteries 20 that make up the secondary battery module 104, rather than the entire secondary battery module 104. Therefore, the charging power supply only needs to be higher than the full-charge voltage of each secondary battery 20, not the voltage provided by the secondary battery module 104. The full-charge voltage is roughly the voltage obtained by dividing the voltage of the secondary battery module 104, which is composed of secondary batteries connected in series, by the number of secondary batteries.

[0096] Therefore, the secondary battery voltage equalization charging device circuit according to the present invention can directly use the regenerative current to charge the secondary battery modules 104. Figure 26 shows a secondary battery voltage equalization regenerative charging device 170 that uses regenerative power.

[0097] Specifically, a secondary battery voltage equalization charging circuit 160 is connected to the secondary battery module 104 via an electrical connector 24, and a power relay capacitor 45 is connected in parallel to the charging power supply side. When charging the secondary battery module 104, a DC power supply 50 is connected to the electrical connector 25. At this time, the charging switch 22 (SW1), relay capacitor switch 32 (SW2), and charging power switch 52 (SW3) operate according to the sequence shown in FIG. 4 to independently charge the secondary battery 20. During drive, a selectable double-throw motor switch SWM connects to drive contact PD to supply power from the secondary battery module 104 to the electric motor RDM. During regeneration, the motor switch SWM connects to regeneration contact PR, and the electric motor RDM charges the regenerated power in the form of electric charge in the power relay capacitor 45 via the rectifier 82. The selective operation of this switch SWM does not need to be synchronized with the charging switch 22, relay capacitor switch 32, and charging power switch 52.

[0098] The electromotive voltage of the electric motor RDM during regeneration starts at a voltage lower than the voltage of the secondary battery module 104, and as the rotation of the electric motor RDM decreases during regeneration, the electromotive voltage decreases. That is, the initial electromotive voltage during regeneration is relatively high, and becomes lower as time passes. Even during the high voltage period, when charging operation begins, the charge of the power relay capacitor 45 moves to the secondary battery 20 via the charging power switch 52, relay capacitor switch 32, and charging switch 22. At this time, the electromotive voltage of the electric motor RDM itself is not directly applied to the secondary battery 20, and the power relay capacitor 45 is connected in parallel to the relay capacitor 40. Therefore, as the charge of the power relay capacitor 45 moves, the initial electromotive voltage is divided by the multiple relay capacitors 40.

[0099] As long as the voltage of the charge transferred to the charging capacitor 30 is higher than the charging completion voltage of the secondary battery 20, the regenerative power is used to charge the secondary battery 20. Conversely, if the voltage is lower than the charging completion voltage of the secondary battery 20, the regenerative power is not used to charge the secondary battery 20. Even in this case, the charging capacitor 30, relay capacitor 40, and power relay capacitor 45 function to equalize the voltages of the individual secondary batteries 20 when they are discharging.

[0100] On the other hand, as the regenerative power weakens, the electromotive voltage of the electric motor RDM also decreases, and when the voltage of the charge transferred to the charging capacitor 30 becomes lower than the electromotive voltage of the secondary battery 20, the charge transferred to the charging capacitor 30 no longer has the charging capacity, and charging no longer occurs. Even in this case, the charging capacitor 30, relay capacitor 40, and power relay capacitor 45 maintain the same function of equalizing the voltage during discharge of the secondary battery 20 as described above. Due to the effect of the rectifier 82, regardless of the magnitude of the electromotive voltage of the electric motor RDM, the charge of the power relay capacitor 45 does not flow back to the electric motor RDM, and the voltage equalization function during charging and discharging of the secondary battery 20 is maintained.

[0101] Incidentally, the charging switch 22 can be omitted and the circuit configuration can be simplified by using a two-system switch in which the relay capacitor switch 32 is the first switch and the charging power switch 52 is the second switch, as shown in Figures 22 and 23.

[0102] As a specific application of the use of regenerative power, Fig. 27 shows a secondary battery voltage equalization regenerative charging device 171 in which the electric motor RDM is used as an auxiliary electric motor for an electrically assisted bicycle, the electric power of the secondary battery module 104 is used as driving power, and the regenerative power of the electric motor RDM is used to charge the secondary battery 20. The difference from Example 11 is that three operating modes - driving power and regenerative power of the electric motor RDM, and disconnection from the secondary battery voltage equalization regenerative charging device 171 - are selected depending on the pedaling and braking of the bicycle.

[0103] Table 1 shows the operation of the electric motor RDM in response to combinations of pedaling and braking, i.e., the relationship between auxiliary drive of the bicycle, regenerative power generation, and electrical disconnection from the secondary battery 20. Here, the soft brake switch SWB is a switch that turns ON when the brake lever is slightly depressed before physically applying the brakes to the wheel. The pedal switch SWP is a single-throw switch that turns ON when the pedal is depressed and OFF when the pedal is not depressed. The soft brake switch SWB is a double-throw switch that selects between the drive contact PD and the regenerative contact PR.

[0104] When the brakes are not applied, i.e., when the soft brake switch SWB is not engaged (OFF), and the pedals are depressed, the soft brake switch SWB selects the drive contact PD, and the electric motor RDM assists the bicycle in power-on drive in response to the load on the pedals. The degree of assistance can be controlled by a separately provided controller. When the soft brake switch SWB is engaged (ON), the soft brake switch SWB selects the regeneration contact PR. When the pedals are not depressed, the pedal switch SWP is disconnected (OFF), and the electric motor RDM enters regeneration mode, with the regenerative current charging the secondary battery 20. Otherwise, the electric motor RDM is electrically disconnected from the secondary battery voltage equalization charging circuit 160 and the secondary battery module 104.

[0105] The operation of the soft brake switch SWB and the pedal switch SWP does not need to be synchronized with the operation of the charging switch 22, the relay capacitor switch 32, and the charging power switch 52.

[0106] Incidentally, the charging switch 22 can be omitted and the circuit configuration can be simplified by using a two-system switch in which the relay capacitor switch 32 is the first switch and the charging power switch 52 is the second switch, as shown in Figures 22 and 23.

[0107] The present invention includes combinations of the above-mentioned multiple derivatives and product forms. These combinations may be selected based on the objectives and technologies of the present invention. That is, these derivatives may include partial or complete combinations of a three-system switch or a two-system switch, the addition of a current limiting device, the addition of a current / voltage limiting device, the addition of a DC-DC converter or a DC-AC converter, the addition of an electrical connector or a main power supply switch, the addition of a discharge operation, and the addition of a discharge bypass switch. The product options of the present invention reflect these derivatives and include a secondary battery voltage equalization charging device including a charging power source, a secondary battery voltage equalization charging device circuit without a charging power source, and a power supply package including a secondary battery module to be charged by the secondary battery voltage equalization charging device.

[0108] Furthermore, the present invention also includes a utilization invention that extends the operating life of a secondary battery module by utilizing a secondary battery voltage equalization regenerative charging device that uses regenerative power from an electric motor driven by a secondary battery module connected to a voltage equalization charging device as a power source to charge the secondary battery. As an application of this, the present invention exemplifies an auxiliary drive device for an electrically assisted bicycle.

[0109] In any of the above embodiments except for Example 9 (FIG. 22) and Example 10 (FIG. 23), the charging switch 22 may be a single-pole switch for either the positive or negative electrode of each secondary battery 20, or a bipolar switch for both the positive and negative electrodes, which may be selected in accordance with the use of the secondary battery voltage equalization charging device of the present invention.

[0110] In any of the above embodiments, the charging switch, relay capacitor switch, and charging power switch may be solid state switches.

[0111] Both the intermittent charging device and the secondary battery voltage equalizing charging device according to the present invention can be configured using existing electronic components, and can be manufactured and used in the field of charging technology.

[0112] DESCRIPTION OF SYMBOLS 20, RBC: Secondary battery 21, 22: Charging switch 24, 25: Electrical connector 26: P-channel MOS transistor 27: N-channel MOS transistor 30: Charging capacitor 32: Relay capacitor switch 40: Relay capacitor 45: Power relay capacitor 50, PS: Charging power supply 51, 52: Charging power supply switch 53: Main power supply switch 54: Bypass switch 55: AC input DC charging power supply 60: Load 61: Switch 62: Two-pole three-way switch 70: DC-DC converter 72: Multi-pole selection switch 75: DC-AC converter 80: Current limiting device 81: Constant current diode 82: Rectifier 90: Current / voltage limiting device 100, 104: Secondary battery module 110, 111, 112, 113, 120, 121, 130, 131 ... Secondary battery voltage equalization charging device 135, 160 ... Secondary battery voltage equalization charging circuit 140, 150 ... Power supply package 170, 171 ... Secondary battery voltage equalization regenerative charging device OP1, OP2 ... Operational amplifier R1, R2, R3 ... Resistors SW1, SW2, SW3 ... Multi-pole switch ZD1, ZD2 ... Zener diodes RDM ... Electric motor SWB ... Soft brake switch SWM ... Electric motor switch SWP ... Pedal switch PD ... Drive contact PR ... Regenerative contact

Claims

1. A charging device comprising a first capacitor electrically connected in parallel via a first switch to each secondary battery of a secondary battery module consisting of multiple secondary batteries connected in series; a second capacitor electrically connected in parallel to the first capacitor via a second switch; and one DC power source electrically connected in parallel to the second capacitor via a third switch, wherein the second capacitor has a larger capacitance than the first capacitor; the first switch and the third switch are synchronized, repeatedly conducting when the second switch is cut off and cutting off when the second switch is conducting, and the first switch and the third switch are never conducting at the same time as the second switch; and the above conduction and cutting are linked for all of the first switches, all of the second switches, and all of the third switches.

2. A secondary battery voltage equalization charging device comprising: a first capacitor electrically connected in parallel to each secondary battery of a secondary battery module consisting of multiple secondary batteries connected in series; a second capacitor electrically connected in parallel to the first capacitor via a first switch; and a DC power supply electrically connected in parallel to the second capacitor via a second switch, wherein the second capacitor has a larger capacitance than the first capacitor; the first switch and the second switch are configured such that when one switch is conducting the other switch is cut off, but both switches are never conducting simultaneously; and the above conduction and cut-off are linked for all of the first switches and all of the second switches.

3. A power supply package comprising the secondary battery voltage equalization charging device according to claim 1 or 2 connected to the secondary battery module.

4. A secondary battery voltage equalization charging device as set forth in claim 1 or claim 2, characterized in that it includes a DC-DC converter whose input is the output of a secondary battery module made up of secondary batteries charged by said secondary battery voltage equalization charging device, and the output of said DC-DC converter is used as another DC power source for said secondary battery voltage equalization charging device.

5. A secondary battery voltage equalization charging device as set forth in claim 1 or claim 2, comprising a DC-DC converter whose input is the output of a secondary battery module made up of secondary batteries charged by said secondary battery voltage equalization charging device, and wherein the output of said DC-DC converter is used as another DC power source for said secondary battery voltage equalization charging device.

6. A secondary battery voltage equalization charging device according to claim 1 or 2, characterized in that a current limiting device whose rated limit current is equal to or smaller than the maximum allowable charging current of each secondary battery is inserted in the current path between each secondary battery and the first capacitor.

7. A secondary battery voltage equalization charging device as claimed in claim 1 or claim 2, characterized in that a current / voltage limiting device is inserted in the current path between each of the secondary batteries and the first capacitor, and the current output from the current / voltage limiting device is limited to a value equal to or less than the maximum allowable charging current of the secondary batteries, and the output voltage is limited to a value equal to or less than the maximum allowable charging voltage of the secondary batteries.

8. A secondary battery voltage equalization charging device as set forth in claims 1 and 2, characterized in that a fourth switch is inserted between said one DC power source and the third switch provided on each of said secondary batteries, and a third switch is inserted between said second switch and said third switch, and when said secondary battery module is being charged, said fourth switch and said third switch are respectively conductive, and when said secondary battery module is being discharged, said fourth switch and said third switch are respectively cut off.

9. A secondary battery voltage equalization charging device as set forth in claims 1 and 2, characterized in that a connector is further inserted between said one DC power source and the third switch and the second switch provided on each of said secondary batteries, and said DC power source is connected to said electrical connector when charging said secondary battery module, and said DC power source is disconnected from said electrical connector when discharging.

10. A secondary battery voltage equalization charging device as claimed in claim 8, characterized in that it includes a DC-DC converter whose input is the output of a secondary battery module comprising secondary batteries charged by said secondary battery voltage equalization charging device, and the output of said DC-DC converter is used as another DC power source for said secondary battery voltage equalization charging device.

11. A secondary battery voltage equalization charging device according to claim 8, comprising a DC-DC converter whose input is the output of a secondary battery module made up of secondary batteries charged by said secondary battery voltage equalization charging device, and the output of said DC-DC converter is used as another DC power source for said secondary battery voltage equalization charging device.

12. A secondary battery voltage equalization charging device as claimed in claim 8, characterized in that a current limiting device is inserted in the current path between each of the secondary batteries and the first capacitor, and a bypass circuit via a bypass switch is provided in parallel with the current limiting device, the bypass switch is cut off when the secondary battery module is being charged, and the bypass switch is turned on when the secondary battery module is being discharged, and the rated limiting current of the current limiting device is equal to or less than the maximum allowable charging current of the secondary batteries.

13. A secondary battery voltage equalization charging device as claimed in claim 8, wherein a current / voltage limiting device is inserted in the current path between each of the secondary batteries and the first capacitor, a bypass circuit via a bypass switch is provided in parallel with the current / voltage limiting device, the bypass switch is cut off when the secondary battery module is being charged, and the bypass switch is turned on when the secondary battery module is being discharged, and the current / voltage limiting device limits the current output from the current / voltage limiting device to a maximum allowable charging current of the secondary batteries or less, and limits the output voltage to a maximum allowable charging voltage of the secondary batteries or less.

14. A secondary battery voltage equalization charging circuit comprising a first capacitor electrically connected in parallel via a first switch to each secondary battery of a secondary battery module consisting of a plurality of secondary batteries connected in series, and a second capacitor electrically connected in parallel to the first capacitor via a second switch, the second capacitor being electrically connected in parallel to an external DC power source via a third switch, the second capacitor having a larger capacitance than the first capacitor, the first switch and the third switch being synchronized to repeat the cycle of conducting when the second switch is cut off and cutting off when the second switch is conducting, the first switch and the third switch never being conducted simultaneously with the second switch, and the above conduction and cutting are linked for all first switches, all second switches, and all third switches, further comprising a third capacitor connected in parallel to the end of the third switch on the external DC power source side, the secondary battery modules are connected to an electric motor via a double-throw switch, and the third capacitor is connected to the electric motor via a rectifier and the double-throw switch, and when charging the secondary battery modules, the external DC power source is connected across the third capacitor.

15. A secondary battery voltage equalization charging circuit comprising: a first capacitor electrically connected in parallel to each secondary battery of a secondary battery module formed by connecting a plurality of secondary batteries in series; and a second capacitor electrically connected in parallel to the first capacitor via a first switch; the second capacitor is electrically connected in parallel to an external DC power source via a second switch; the second capacitor has a larger capacitance than the first capacitor; the first switch and the second switch are configured such that one switch is turned on while the other is turned off, and both switches are not turned on simultaneously; and the above-mentioned conduction and cut-off are linked for all first switches and all second switches; further, a third capacitor is connected in parallel to the end of the second switch on the external DC power source side; the secondary battery module is connected to an electric motor via a double-throw switch, and the third capacitor is connected to the electric motor via a rectifier and the double-throw switch; a third capacitor connected to the external DC power supply when charging the secondary battery module; 16. A secondary battery voltage equalization charging circuit comprising a first capacitor electrically connected in parallel via a first switch to each secondary battery of a secondary battery module consisting of a plurality of secondary batteries connected in series, and a second capacitor electrically connected in parallel to the first capacitor via a second switch, the second capacitor being electrically connected in parallel to an external DC power source via a third switch, the second capacitor having a larger capacitance than the first capacitor, the first switch and the third switch being synchronized, repeating the cycle of conducting when the second switch is cut off and cutting off when the second switch is conducting, the first switch and the third switch never being conducted simultaneously with the second switch, and the above conduction and cutting are linked for all first switches, all second switches, and all third switches, further comprising a third capacitor connected in parallel to the end of the third switch on the external DC power source side, the secondary battery module is connected to the electric motor via a double-throw switch, and the third capacitor is connected to the electric motor via a rectifier, the double-throw switch, and a single-throw switch; an external power source is connected to both ends of the third capacitor when charging the secondary battery module; the double-throw switch is linked to the brake of a bicycle driven by the electric motor, and the single-throw switch is linked to the pedaling movement of the bicycle.

17. A secondary battery voltage equalization charging circuit comprising: a first capacitor electrically connected in parallel to each secondary battery of a secondary battery module formed by connecting a plurality of secondary batteries in series; and a second capacitor electrically connected in parallel to the first capacitor via a first switch; the second capacitor is electrically connected in parallel to an external DC power source via a second switch; the second capacitor has a larger capacitance than the first capacitor; the first switch and the second switch repeatedly turn on when one switch is on and the other switch is off, and both switches are never turned on simultaneously; and the above-mentioned turn-on and turn-off are linked for all first switches and all second switches; further, a third capacitor is connected in parallel to the end of the second switch on the external DC power source side; the secondary battery module is connected to an electric motor via a double-throw switch; and the third capacitor is connected to the electric motor via a rectifier, the double-throw switch, and a single-throw switch; A secondary battery voltage equalization regenerative charging device is characterized in that an external power source is connected to both ends of the third capacitor when charging the secondary battery module, the double-throw switch is linked to the brake of the bicycle driven by the electric motor, and the single-throw switch is linked to the pedal movement of the bicycle.

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