JP2010004679A - Charging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a charged voltage from being consumed wastefully, and to shorten the charging time by improving the equalization speed of voltage between the respective cells in charging of a battery constituted of many cells. <P>SOLUTION: A charging system includes a main battery 41, in which a plurality of cells 41a are electrically connected at least in series, and which drives an electric motor; a main charger which charges the main battery 41; a sub-battery 42, which drives the electric motor in place of the main battery 41; and a regenerative charger 63 which charges the sub-battery 42, by utilizing excessive voltages obtained when the voltage V in the cells 41a exceeds a predetermined voltage during charging the main battery 41. The regenerative charger 63 is constituted of: regenerative discharge parts 64, each of which is connected between both positive and negative electrodes of the cell 41a, transforms the excess power input therein based on the excessive voltages, and performs power regeneration and discharge toward the sub-battery 42; and a charging control part 65 which controls the power regenerated and discharged by the regenerative discharge part 64 to charge the sub-battery 42. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging system for charging, for example, a battery that supplies electric power to an electric motor mounted as a drive source for driving a construction machine.

  In general, an engine is the main power source for construction machines, but recently, an electrically driven construction machine using an electric motor as a drive source in consideration of the surrounding environment has been proposed (see, for example, Patent Document 1). Such a construction machine is equipped with a battery for supplying electric power to the electric motor, and is provided with a control device that controls the operation of various electric components such as the electric motor. In such an electrically driven construction machine, the workable time is determined according to the chargeable capacity of the battery, so a battery having a capacity that can work for one day is mounted, and one day of work is finished. A configuration is generally adopted in which the battery is charged before the start of work on the next day. However, since the power consumption of the battery varies greatly depending on the work content of the construction machine (working device usage status, frequency, etc.), the remaining capacity of the battery is lost during the work, and the work must be interrupted. Moreover, there is a risk that the construction machine cannot be moved. In order to avoid this, a battery having a high capacity is demanded.

As such a high-capacity battery, for example, as shown in FIG. 5, a configuration in which a large number of cells 41a composed of lithium ion secondary batteries or the like are electrically connected in series and in parallel is generally used. ing. Thus, in the battery 41 composed of a large number of cells 41a, the voltage of each cell 41a may vary because the self-discharge amount varies depending on the individual cells 41a. Therefore, when charging the battery 41, it is necessary to perform charge control so that the voltage of each cell 41a does not exceed the maximum allowable voltage (hereinafter referred to as the maximum voltage) and the voltage between the cells 41a is equalized. There is. Therefore, like the control means 100 shown in the figure, when the voltage between the cells 41a reaches the maximum voltage, the voltage is lowered by conducting the resistance 101 connected between the cells 41a. That is, a method is known in which surplus power generated in the cell 41a is converted into heat by the resistor 101 and consumed.
JP 2004-225355 A

  However, when charging a battery composed of a large number of cells as described above, the surplus generated in each cell is used so that the voltage of each cell does not exceed the maximum voltage and the voltage between the cells is equalized. The method of dissipating electric power with heat has a problem that the charging voltage is wasted. In addition, there is a problem that cooling means such as a cooling fan must be taken as a countermeasure against the dissipated heat.

  The present invention has been made in view of such problems, and in charging a battery composed of a large number of cells, energy saving by preventing wasteful consumption of the charging voltage and equalization of the voltage between the cells. It is an object of the present invention to provide a charging system capable of realizing a reduction in charging time by improving speed.

  In order to achieve the above object, a charging system according to the present invention is configured by electrically connecting a plurality of cells at least in series, and includes an electric motor (for example, the pump electric motor 33 and the traveling electric motor in the embodiment). 51 and a main battery that supplies electric power for driving the turning electric motor 52), and converts AC power supplied from an AC power source into DC power, and controls the converted DC voltage to control the main battery. Charge control means for charging (for example, the main charger 61 in the embodiment), a sub-battery capable of supplying electric power for driving the electric motor instead of the main battery, and the main battery by the charge control means During the charging, the sub-battery is obtained by using an excess voltage corresponding to a cell voltage charged in the cell exceeding a predetermined voltage. Regenerative charging control means for charging (e.g., regenerative charger 63 in the embodiment) configured to include a. In addition, the regenerative charge control means is connected between the positive and negative electrodes of the cell, transforms surplus power input based on the excess voltage, and regenerative discharge unit regenerative discharge toward the sub-battery, A charge control unit configured to control the electric power regenerated by the regenerative discharge unit and charge the sub-battery.

  In the charging system having the above-described configuration, the regenerative discharge unit is disposed in each of the cells connected in series, and is electrically or optically connected to the other regenerative discharge unit to The charging status can be communicated, and when the variation of the cell voltage of each of the cells is larger than a predetermined range, the surplus power is regeneratively discharged, and when the variation is within the predetermined range, the surplus power is discharged. It is preferable to configure so that heat is dissipated by resistance.

  According to the charging system according to the present invention configured as described above, the surplus power generated in each cell of the main battery being charged is used for charging the sub-battery by the regenerative charging control means, so that the charging voltage is wasted. Unnecessary consumption can be prevented, and an energy saving effect can be obtained. In addition, it is not necessary to provide cooling means such as a cooling fan as a countermeasure against heat, and the system can be miniaturized.

  The regenerative discharge unit is arranged in each cell connected in series, and is configured to be electrically or optically connected to other regenerative discharge units so that the charging status of each cell can be communicated. Desirably, this makes it possible to optimize charging of the entire cell while constantly monitoring variations in the voltage of each cell. In this case, it is preferable that the surplus power is used for charging the sub-battery when the variation is larger than a predetermined range, and that the surplus power is dissipated by the discharge resistor when the variation is within the predetermined range. The voltage equalization speed in between is also increased, and the charging time can be shortened.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As an example to which the present invention is applied, FIG. 1 shows a crawler-type power shovel 1 that operates using electric power from a battery. First, the overall configuration of the power shovel 1 will be described. .

  The excavator vehicle 1 includes a traveling device 2 configured by providing traveling mechanisms 3 and 3 on the right and left of a substantially H-shaped traveling cart 4 (vehicle body) in a plan view, and a swinging portion that can swing up and down at the rear portion of the traveling cart 4. A blade 9 (earth-discharging plate) provided, a revolving body 11 (vehicle body) provided on the upper portion of the traveling carriage 4 so as to be able to turn, and a shovel mechanism 12 (working device) provided at a front portion of the revolving body 11 The driver cabin 15 is an operator cabin 15 (vehicle body) for standing on the upper part of the revolving body 11.

  A pair of left and right traveling mechanisms 3, 3 constituting the traveling device 2 is provided between a driving sprocket wheel 5 provided at the left and right front part of the traveling carriage 4 and an idler wheel 6 provided at the left and right rear parts of the traveling carriage 4. It is constructed by crawling around the crawler belt 7. The driving sprocket wheel 5 is rotationally driven by a traveling motor made up of an electric motor or a hydraulic motor.

  The blade 9 is swung by a blade cylinder 9a (see FIG. 2) formed of a hydraulic cylinder. The turning body 11 is turned by a turning motor composed of an electric motor or a hydraulic motor. The shovel mechanism 12 includes a boom 21 pivotably connected to the front portion of the swing body 11, and an arm 22 pivotally connected to the tip of the boom 21 so as to swing up and down within the undulating surface of the boom 21. And a bucket 23 pivotally connected to the tip of the arm 22 so as to swing up and down. The boom 21 is raised and lowered by a boom cylinder 24 made of a hydraulic cylinder, and the arm 22 is moved by an arm cylinder 25 made of a hydraulic cylinder. The bucket 23 is swung by a bucket cylinder 26 made of a hydraulic cylinder. In this specification, these hydraulic cylinders and hydraulic motors are collectively referred to as hydraulic actuators.

  The operator cabin 15 is formed in a rectangular box shape that is surrounded by the top, bottom, front, back, left and right, and an operator seat 16 for an operator to sit inside, and an operation for operating the traveling device 2 and the shovel mechanism 12 and the like. A device 17 is provided.

  In this power shovel 1, a pump for supplying hydraulic oil to a hydraulic actuator, a traveling device 2 (traveling mechanisms 3 and 3), and a turning body 11 are driven by an electric motor. The hydraulic unit 30 that supplies hydraulic oil to the hydraulic actuator and the power supply system 40 that supplies electric power to the pump electric motor 33, the traveling electric motor 51, and the turning electric motor 52 will be described below with reference to FIG. To do. In FIG. 2, the electrical or optical signal circuit is indicated by a solid line, and the hydraulic circuit is indicated by a dotted line.

  The hydraulic unit 30 includes a tank 31 that stores hydraulic oil, a hydraulic pump 32 that is driven by a pump electric motor 33 to discharge hydraulic oil at a predetermined hydraulic pressure and flow rate, and the hydraulic oil discharged from the hydraulic pump 32 is operated by the operating device 17. Control valve 34 for performing control to supply each hydraulic actuator (blade cylinder 9a, boom cylinder 24, arm cylinder 25, and bucket cylinder 26) with a supply direction and supply amount according to the pressure, and hydraulic oil returning from the control valve 34 to the tank 31 It is comprised from the hydraulic oil generator 35 which receives the flow of this and is rotationally driven and produces electric power. The hydraulic oil generator 35 includes, for example, a rotating blade disposed in a return oil passage from the control valve 34 to the tank 31 and a generator that is rotated by receiving the rotational force of the rotating blade.

  The power supply system 40 includes a main battery 41 configured by a secondary battery such as a lithium ion battery or an organic radical battery, a sub battery 42 configured by a secondary battery such as a lead storage battery, and the main battery 41 or the sub battery 42. Output control device 43 that supplies the AC power to the pump electric motor 33, the traveling electric motor 51, and the turning electric motor 52, and the main battery 41 or sub battery. And a connection switching unit 44 that selectively connects the output control unit 44 to the output control unit 43. The hydraulic unit 30 and the power supply system 40 are disposed on the revolving unit 11 so as to be covered with the cover member 50.

  The main battery 41 is configured by electrically connecting a plurality of cells 41a, 41a,... In series and in parallel (see FIG. 5), and as described above, the pump electric motor 33 and the travel electric motor 51. It functions as a power source for the electric motor 52 for turning, and is set to a high capacity at a high rated voltage. In the main battery 41 of the present embodiment, a parallel cell group 41A in which a plurality of cells 4.2a having a maximum allowable voltage (a cell voltage at full charge, hereinafter referred to as a maximum voltage) DC4.2V is connected in parallel is provided. 80 columns are connected in series, and the rated voltage is set to DC4.2V × 80 columns = DC336V. When the sub-battery 42 is connected to the output control device 43 by the connection switcher 44, the rated voltage and capacity capable of driving the pump electric motor 33, the traveling electric motor 51, and the turning electric motor 52 are set. However, it is set to a low rated voltage (for example, rated voltage DC15V) and a low capacity for the purpose of use to be described later.

  The electric motor 33 for pumps consists of AC motors, such as an IPM motor (permanent magnet synchronous motor). Therefore, by applying AC power having an arbitrary frequency exchanged by the output control device 43 to the pump electric motor 33, the output torque of the pump electric motor 33 is controlled and the predetermined hydraulic pressure is supplied from the hydraulic pump 32. Can do. At this time, the power supply is normally performed by the main battery 41, but the pump electric motor 33 is driven by the power supply from the sub-battery 42 by connecting the sub-battery 42 to the output control device 43 by the connection switch 44. You can also do it. Similarly, the traveling electric motor 51 and the turning electric motor 52 can be driven by supplying electric power from the sub-battery 42.

  The traveling electric motor 51 and the turning electric motor 52 are composed of a motor generator, and are driven by power supply from the main battery 41 (or the sub battery 42) via the output control device 43. At the time of decelerating traveling by the device 2, the traveling electric motor 51 acts as a generator by receiving the deceleration force, and the generated power is output to the sub-battery 42 via the sub-charger 62 described later and charged. Similarly, when the turning body 11 decelerates and turns, the turning electric motor 52 acts as a generator in response to the deceleration force, and the generated electric power is output to the sub-battery 42 via the sub-charger 62 to charge it. . In FIG. 2, the hydraulic oil generator 35, the traveling electric motor 51, and the turning electric motor 52 are shown in two places for easy understanding of the explanation, but these are actually the same.

  Next, a charging system 60 for charging the main battery 41 and the sub battery 42 will be described with reference to FIG. The charging system 60 includes a connector 61a connected to a commercial power source. The main charger 61 that connects the connector 61a to the commercial power source and receives AC power from the connector 61a to charge the main battery 41; and hydraulic oil power generation The sub-charger 62 that charges the sub-battery 42 by receiving the generated power output from the machine 35, the electric motor 51 for traveling, and the electric motor 52 for turning, and each cell 41a in the main battery 41 that is being charged by the main charger 61. It comprises a regenerative charger 63 that charges the sub-battery 42 using surplus power generated in each parallel cell group 41A. Here, “surplus power” refers to power based on the excess voltage v (see FIG. 4A) corresponding to the cell voltage V of each cell 41a exceeding the maximum voltage DC4.2V.

  The main charger 61 can be connected to a commercial power source via the connector 61a, converts AC power supplied from the commercial power source into DC power, and charges the DC voltage (supply voltage) to the main battery 41. A charge control unit (not shown) for control is provided. The sub-charger 62 performs control for charging the sub-battery 42 with the generated power output from the hydraulic oil generator 35, the traveling electric motor 51, and the turning electric motor 52, whereby the sub-battery 42 is powered. The excavator vehicle 1 is intermittently charged while operating. When the sub-battery 42 is fully charged, the sub-charger 62 that monitors the sub-battery 42 uses the generated power output from the hydraulic oil generator 35, the traveling electric motor 51, and the turning electric motor 52 as the main battery. 41, and the main battery 41 is charged.

  As shown in FIG. 3, the regenerative charger 63 regenerates the surplus power generated in each parallel cell group 41 </ b> A (each cell 41 a) of the main battery 41 being charged by the main charger 61 toward the sub battery 42. It is comprised from the discharge part 64 and the charge control part 65 which controls so that the output voltage from the regenerative discharge part 64 can charge the sub-battery 42. The regenerative discharge unit 64 is provided in each parallel cell group 41A (the same number of regenerative discharge units 64 as the parallel cell group 41A are provided). In the main battery 41 of the present embodiment, as described above. Since the parallel cell groups 41a are connected in 80 columns in series, the regenerative charger 63 includes a total of 80 regenerative discharge units 64.

  The regenerative discharge unit 64 is a primary winding on the input side of the switching transformer T that transforms (boosts) power (surplus voltage) for the excess voltage v generated in the diode D for rectification and the cell 41a (parallel cell group 41A). The first switching element S1 composed of Ta, a field effect transistor (FET), and the like is configured to be connected in series in a closed circuit connected between the positive and negative electrodes of one cell 41a in the parallel cell group 41A. The secondary winding Tb on the output side of the switching transformer T is connected to the charging control unit 65 via a diode bridge DB and an electrolytic capacitor C provided in parallel with each other. Similarly to the discharge resistor R and the first switching element S1, a second switching element S2 configured by an FET or the like is connected in parallel with the diode D, the switching transformer T (primary winding Ta) and the first switching element S1. ing.

  The regenerative discharge unit 64 monitors the cell voltage V of the cells 41a constituting the parallel cell group 41A, and outputs a control signal (for example, a pulse signal) according to the cell voltage V, so that the first switching element S1 And the overvoltage control part 66 which performs intermittent control (ON / OFF control) of 2nd switching element S2 is comprised. The overvoltage control unit 66 is arranged in parallel with the other overvoltage control units 66, 66,... In each regenerative discharge unit 64, 64,... By an electrical or optical signal as indicated by a one-dot chain line arrow in FIG. The charging state (cell voltage V) of the cell group 41A (cell 41a) is configured to be communicable.

  The operation of the power shovel 1 configured as described above will be described below. The power shovel 1 is operated when an operator seated on an operator seat 16 in an operator cabin 15 operates an operating device 17. Specifically, the two operation devices 17 provided upright from the floor in front of the central portion constitute a travel operation lever for operating the travel mechanisms 3, 3 and are provided on the left and right sides of the operator seat 16. The pair of left and right operating devices 17 constitute a work operating lever for operating the shovel mechanism 12.

  For this reason, when the travel operation lever (operation device 17) is operated, AC power having an arbitrary frequency exchanged by the output control device 43 is supplied to the travel electric motor 51 based on the operation signal, thereby The output torque of the electric motor 51 is controlled, and the left and right traveling mechanisms 3 and 3 are driven to control the excavator vehicle 1 to travel. In the case where the control for running the power shovel vehicle 1 is performed in this way, when the vehicle is decelerated, energy regeneration is performed by the electric motor for traveling 51 to generate deceleration torque. The electric power generated in this way is supplied to the sub-battery 42 via the sub-charger 62 to charge it. At this time, power supply control to the pump electric motor 33 is performed by the output control device 43 according to the operation, and the hydraulic pump 32 is driven by the motor 33 so that the operating hydraulic pressure is supplied to the control valve 34. Yes.

  On the other hand, when the work operation lever (operation device 17) is operated, the operation of the control valve 34 is controlled based on the operation signal, and the hydraulic pressure applied to the blade cylinder 9a, the boom cylinder 24, the arm cylinder 25, and the bucket cylinder 26. Supply control is performed and the shovel mechanism 12 is actuated. Further, the output control device 43 performs power supply control to the turning electric motor 52 based on the operation signal, and the turning operation of the turning body 11 is performed. At this time, when turning is stopped, energy is regenerated by the turning electric motor 52 to decelerate the turning, and the electric power generated in this way is supplied to the sub battery 42 via the sub charger 62. Charge this. Also at this time, the power control to the pump electric motor 33 is performed by the output control device 43 according to the operation, and the hydraulic pump 32 is driven by the motor 33 and the hydraulic pressure is supplied to the control valve 34. Yes.

  When the excavator 1 travels and the work by the excavator mechanism 12 is performed in this way, the power of the main battery 41 is consumed. Therefore, when the remaining capacity is reduced, the connector 61a is connected to the commercial power source and is connected to the commercial power source. Is supplied to the main battery 41 via the main charger 61 to be charged. At this time, the cell voltage V of each parallel cell group 41A in the main battery 41 may vary, and when charging is performed in this case, as shown in FIG. 4A, in a certain parallel cell group 41A, Then, the cell voltage V reaches the maximum voltage Vmax (4.2 V), and thereafter, an overcharge state occurs in which an excess voltage v corresponding to the maximum voltage Vmax is generated.

  Here, when the variation of the cell voltage V of each parallel cell group 41A is larger than a predetermined range (for example, 0.05V), in the parallel cell group 41A that has reached the maximum voltage Vmax, the cell voltage V exceeds the maximum voltage Vmax. When the excess voltage v is generated, the power for the excess voltage v (surplus power) is discharged toward the sub-battery 42 via the regenerative discharge unit 64 and the charge control unit 65. That is, the surplus power generated in the parallel cell group 41A is used for charging the sub-battery 42 by the regenerative charger 63 (this is called regenerative discharge).

  Specifically, in the regenerative discharge unit 64, when the cell voltage V exceeds the maximum voltage Vmax (when the excess voltage v is generated), the overvoltage control unit 66 that monitors the cell voltage V controls the first switching element S1. A signal (pulse signal) is output to cause intermittent operation. By the intermittent operation of the first switching element S1, a current corresponding to the surplus power generated in the parallel cell group 41A is conducted to the rectifying diode D and the primary winding Ta of the switching transformer T. At this time, in the switching transformer T, the surplus power input from the parallel cell group 41A is boosted using alternating current, and the boosted surplus power is output from the secondary winding Tb. The surplus power (AC power) output from the secondary winding Tb of the switching transformer T is full-wave rectified by the diode bridge DB, reconverted to DC power, and further smoothed by the electrolytic capacitor C to be charged. 65 is input.

  In the charge control unit 65, the surplus power output from each parallel cell group 41A is joined and input via each regenerative discharge unit 64 as described above, and the surplus power input in this way is controlled to The battery 42 is supplied and charged. The overvoltage control unit 66 can monitor the cell voltage V of the parallel cell group 41A and can communicate the charging status of each parallel cell group 41A with the other overvoltage control units 66, 66,. The variation of the cell voltage V of each parallel cell group 41A is also monitored.

  In the main battery 41 being charged, by performing regenerative discharge in the overcharged parallel cell group 41A as described above, as shown in FIG. 4B, the variation in the cell voltage V of each parallel cell group 41A varies. The voltage gradually decreases, and the variation in the cell voltage V becomes within a predetermined range (for example, 0.05 V) and becomes stable. Thus, when the variation of the cell voltage V is within the predetermined range, in the parallel cell group 41A that has reached the maximum voltage Vmax, when the cell voltage V exceeds the maximum voltage Vmax (when the excess voltage v occurs), the excess voltage v The amount of power (surplus power) is switched to regenerative discharge to the sub-battery 42 and consumed in the regenerative discharge unit 64.

  Specifically, in the regenerative discharge unit 64, when the cell voltage V exceeds the maximum voltage Vmax, the overvoltage control unit 66 outputs a control signal to the second switching element S2 to be turned on. At this time, no control signal is output to the first switching element S1 (the first switching element S1 is not intermittently operated). When the second switching element S2 is turned on, a current corresponding to surplus power generated in the parallel cell group 41A is conducted to the discharge resistor R, and this surplus power is converted into heat by the discharge resistor R and consumed.

  In this way, the main battery 41 is supplied with power from the commercial power supply via the main charger 61 in a state where the variation in the cell voltage V of each parallel cell group 41A is within a predetermined range and is stable. When the total voltage of the cell voltages V of the group 41A reaches the rated voltage DC336V (DC4.2V × 80 columns), the charging by the main charger 61 is terminated.

  When the power of the main battery 41 is consumed by the traveling of the power shovel 1 and work by the shovel mechanism 12 and the remaining capacity is reduced, the sub battery 42 is connected to the output control device 43 by the connection switch 44, It is also possible to control the electric power of the sub-battery 42 by the output control device 43 and supply it to the traveling electric motor 51 to drive it. As a result, when the remaining capacity of the main battery 41 is exhausted, the electric motor 51 for traveling is controlled using the electric power of the sub-battery 42, the left and right traveling mechanisms 3, 3 are driven, and the power shovel vehicle 1 is charged. It is possible to cope with the vehicle running to a certain point (commercial power source) and charging the main battery 41 with this charging facility. Since the sub-battery 42 plays such a role, its capacity is smaller than that of the main battery 41 as described above.

  According to the charging system 60 configured as described above, surplus power generated in each cell 41a (parallel cell group 41A) of the main battery 41 being charged is used for charging the sub battery 42 by the regenerative charger 63. Therefore, useless consumption of the charging voltage supplied from the commercial power supply via the main charger 61 can be prevented, and an energy saving effect can be obtained. In addition, it is not necessary to provide cooling means such as a cooling fan as a countermeasure against heat, and the system can be miniaturized.

  Moreover, the regenerative discharge part 64 is provided in each parallel cell group 41A, respectively, and the overvoltage control part 66 which comprises the regenerative discharge part 64 is electrically or optically connected with the other overvoltage control parts 66, 66, .... Thus, the charging status of each cell 41a (parallel cell group 41A) can be communicated. As a result, it is possible to optimize charging of the entire cell 41a while constantly monitoring variations in the cell voltage V of each cell 41a. Further, when the variation of the cell voltage V is larger than the predetermined range, the surplus power is used for charging the sub-battery 42, and when the variation of the cell voltage V is within the predetermined range, the surplus power is radiated by the discharge resistor R. It is configured as follows. As a result, the equalization speed of the cell voltage V between the cells 41a is increased, and the charging time can be shortened.

  Note that the charging system according to the present invention is not limited to charging a battery mounted on a construction machine as described in the above embodiment, but for charging a battery composed of a large number of cells. Various charging systems can be used.

1 is a perspective view of a power shovel vehicle equipped with a charging system according to the present invention. It is a block diagram which shows the structure of the hydraulic unit of the said power shovel vehicle, a power supply system, and a charging system. It is a circuit diagram which shows the structure of the regenerative charger of the said charging system. It is the figure which showed the cell voltage of each parallel cell group which comprises the main battery currently charged by the said charging system, (a) is a figure in case the variation in cell voltage is larger than a predetermined range, (b) is It is a figure in case the variation of a cell voltage is in a predetermined range. It is a circuit diagram which shows the structure of the principal part of the conventional charging system.

Explanation of symbols

33 Electric motor for pump (electric motor)
41 Main battery 42 Sub battery 41a Cell 41A Parallel cell group 51 Electric motor for travel (electric motor)
52 Electric motor for turning (electric motor)
60 Charging system 61 Main charger (charging control means)
63 Regenerative charger (regenerative charge control means)
64 regenerative discharge unit 65 charge control unit

Claims (2)

A main battery configured to electrically connect a plurality of cells at least in series and supplying electric power for driving the electric motor;
Charge power control means for converting the AC power supplied from the AC power source into DC power and charging the main battery by controlling the converted DC voltage;
A sub-battery capable of supplying electric power for driving the electric motor instead of the main battery;
Regenerative charge control means for charging the sub-battery using an excess voltage of a cell voltage charged to the cell exceeding a predetermined voltage during charging of the main battery by the charge control means,
The regenerative charge control means is
A regenerative discharge unit connected between the positive and negative electrodes of the cell and transforming surplus power input based on the excess voltage and regeneratively discharging toward the sub-battery;
A charging system comprising: a charging control unit configured to control electric power regenerated and discharged by the regenerative discharging unit and charge the sub battery.   The regenerative discharge unit is disposed in each of the cells connected in series, and can be electrically or optically connected to the other regenerative discharge unit to communicate the charging status of each cell. When the variation of the cell voltage of each of the cells is larger than a predetermined range, the regenerative discharge of the surplus power is performed, and when the variation is within the predetermined range, the surplus power is radiated by a discharge resistor. The charging system according to claim 1.

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