JP2000023381A - Method and controller for controlling charging of combined battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently adjust the terminal voltage variation among single batteries constituting a combined battery, and in addition, to suppress the heat generation from the batteries by detecting the terminal voltage of each single battery and charging one of the single batteries having a low terminal voltage from a standby secondary battery. SOLUTION: An overall control section 8 performs charging processing and variation processing following a basic flow. The section 8 first discriminates whether or not each single battery 1a-1d is to be charged from the voltages of the batteries 1a-1d, the state of an input - output section 15, etc., and when the section 8 discriminates that one of the batteries 1a-1d is to be charged, performs the charging processing. Secondly, the section 8 discriminates whether or not each battery 1a-1d is to be discharged, and when the section 8 discriminates that one of the batteries 1a-1d is to be discharged, it performs discharging processing. Thirdly, the section 8 discriminates whether or not the voltage differences among the batteries 1a-1d are equal to or higher than a preset limit value and, when the voltage difference between specific two batteries is equal to or higher than the limit value, additionally charges the single battery having the lower terminal voltage from a standby secondary battery 11. Since the terminal variation among the single batteries 1a-1d can be adjusted efficiently and the heat generation from the batteries 1a-1d can be suppressed, a charging controlling method and a controller suitable for an electricity storing device using a large-sized battery from which a heavy current is made to flow can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control method and a control device for a power storage device using an assembled battery comprising a plurality of secondary batteries, and detects a voltage between terminals of each battery to detect a voltage difference between terminals. The present invention relates to a charging control method and a control device that compensate for the balance between batteries by charging so as to reduce the amount.

[0002]

2. Description of the Related Art When secondary batteries are connected in series and used, the state of charge differs due to variations in characteristics between the batteries.
Since there is a risk of overcharging or overdischarging, the voltage between terminals of each battery is detected and the current at the time of charging or (and) discharging is bypassed by a circuit connected in parallel to each battery to compensate for the state of charge of each battery A method for performing this is disclosed in JP-A-5-49181 and the like.

[0003]

SUMMARY OF THE INVENTION The voltage between terminals of each battery is detected, and the charge current of a battery having a high terminal voltage is bypassed to relatively increase the charge amount of another battery, or the voltage between terminals is reduced. The conventional method of bypassing the discharge current for the low battery and relatively increasing the discharge amount of the other batteries to reduce the voltage difference between the terminals of the terminals is a simple and effective method, but in any case, When the current is bypassed, there is a loss due to the resistance and the resulting heat generation.In the case of a large battery with a large cell capacity and a large current to be bypassed, the bypass circuit becomes large and the heat generated by the bypass circuit affects the battery. It is difficult to dissipate heat to prevent the problem, and there is a problem that the efficiency is reduced due to the loss of the bypass circuit.

[0004] It is an object of the present invention to solve such a problem.

[0005]

In order to solve the above-mentioned problems, the present invention provides a power storage device using an assembled battery in which a plurality of secondary batteries are connected in series. One or more spare secondary batteries are provided separately from the secondary battery, and the spare secondary battery is charged at the same time as or prior to the assembled battery, and the voltage between the terminals of each cell constituting the assembled battery is detected. A spare secondary battery is selectively connected in parallel to the cell having a low terminal voltage only through a current limiting means until the voltage between terminals reaches a predetermined level.
It is characterized by charging from a secondary battery and reducing the voltage difference between the terminals of each unit cell.

According to the second aspect of the present invention, a limit value is provided for a voltage difference at which charging of a cell having a lower inter-terminal voltage than that of the spare secondary battery is started, and charging of the cell from the spare secondary battery is terminated. In this case, an allowable value of the voltage difference is set to restrict the voltage difference from expanding. According to the third aspect of the present invention, the voltage difference is adjusted by the spare secondary battery only during suspension of charging and discharging of the power storage device.

According to the fourth aspect of the present invention, when an equivalent internal resistance is calculated from the voltage between terminals at the end of charge / discharge, the charge / discharge current, and the voltage between terminals after the end of charge / discharge, an equivalent internal resistance is calculated. Is charged to a voltage obtained by adding a voltage drop due to the internal resistance to a voltage difference between the cells. In the invention according to claim 5, a spare secondary battery is provided for each battery module, and a single battery having a low terminal voltage is charged from the spare secondary battery for each battery module.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. It should be noted that the embodiments described below exemplify a method for embodying the technical idea of the present invention, and do not limit the claims of the present invention. Further, the following embodiment describes a case where a lithium ion secondary battery is used, but the type of the secondary battery is not limited to this.

FIG. 1 is a block diagram of an embodiment of the present invention. 1
Reference numerals a, 1b, 1c, and 1d denote unit cells composed of lithium ion secondary batteries, which are connected in series to form a battery pack 2. Both terminals of each of the cells 1a, 1b, 1c, 1d are composed of a voltage detecting means 3 and two sets of interlocking changeover switches, and are respectively connected to changeover connection means 4 for performing tap changeover by a signal from the overall control unit 8. Switching connection means 4
A common terminal of a battery changeover switch 5a connected to the positive electrodes of the cells 1a, 1b, 1c, 1d is connected to the cathode of a diode 6 for preventing backflow.
The current limiting means 7 is connected to the common terminal of the battery changeover switch 5b connected to the negative electrodes of the cells 1a, 1b, 1c, 1d.
Is connected.

The anode side of the diode 6 and the other end of the current limiting means 7 are each composed of an interlocking two-pole switch element, and one end of a switch element in the opening / closing means 9 which performs an opening / closing operation by a signal from the overall control unit 8 is connected. Each is connected,
Each of the other ends of the switch elements in the opening / closing means 9 is constituted by an interlocking two-pole transfer changeover switch element,
It is connected to a transfer changeover switch element in charge / discharge changeover means 10 for changing over according to a signal from the overall control unit 8.

A spare secondary battery 11 is connected between the transfer switch elements in the charge / discharge switching means 10, and spare battery voltage detecting means 12 is connected to both ends of the spare secondary battery 11. The terminal voltage of the spare secondary battery 11 is constantly monitored. The spare battery voltage detecting means 12 is connected via an insulating means such as a photocoupler for exchanging information with the overall control unit 8. Charge / discharge switching means 1
0 is connected to the spare battery charge control unit 13 for controlling the voltage, current, and time during the charging of the spare secondary battery 11 and to the negative electrode side of the assembled battery 2, and constitutes a charging path for the spare secondary battery 11. I have.

The spare battery charge control unit 13 is connected to the general control unit 8 and performs a charge control operation based on a signal from the general control unit 8. The positive electrode side of the battery pack 2 is connected to a charge / discharge control unit 14 for controlling the charge / discharge of the battery pack 2, and the charge / discharge control unit 14 is connected to the overall control unit 8, and The charge / discharge control operation is performed by the signal of (1). The charge / discharge control unit 14, the spare battery charge control unit 13, the overall control unit 8, and the negative electrode side of the battery pack 2 are connected to an input / output unit 15 for controlling the exchange of charge / discharge power with the outside. Make up.

Next, the operation of the thus configured power storage device at the time of charging and discharging will be described with reference to FIGS. 2 to 4 in addition to the configuration diagram of FIG. FIG. 2 is a basic operation flow at the time of charging / discharging, and FIG. 3 is a graph of the terminal voltage of the unit cell 1 at the time of charging / discharging. This shows the characteristics when the equivalent internal resistance of the cell 1 varies. FIG. 4 is a graph of charging / discharging current when charging / discharging is performed under the above conditions. The illustrated graph starts from a state of ending discharging and waiting for charging, constant current charging, constant voltage charging, waiting for discharging to complete charging, and discharging. , A case where a charge / discharge cycle waiting for discharge completion charge is performed once.

The overall control unit 8 performs a charge / discharge process and a variation adjustment process according to a basic operation flow. First, whether or not to charge is determined from the voltage of each of the cells 1a, 1b, 1c, 1d and the state of the input / output unit 15 (16). When charging, the charging process is performed (17), and then discharging is performed. It is checked whether or not the battery is discharged (18), and if it is discharged, a discharging process is performed (19). Then, it is checked whether or not the voltage difference between the cells 1a, 1b, 1c, 1d is equal to or larger than a preset limit value (20). If the voltage difference is greater than the limit value, reserve 2 until the voltage difference falls within the allowable value.
The unit cell having an inter-terminal voltage lower than that of the next battery 11 is additionally charged (21), and then the process proceeds to the next process.

At this time, the charging operation of the power storage device according to the present embodiment is performed in such a manner that an external power supply is received by the input / output unit 15 and the charge / discharge control unit 14 receives the upper limit of the charging current and the charging voltage based on a signal from the overall control unit 8. The constant current,
The battery pack 2 is charged by constant voltage charging. At this time,
The spare battery charge controller 13 is controlled by a signal from the overall controller 8 to charge the spare secondary battery 11. Each cell 1a, 1
b, 1c, 1d and the voltage between the terminals of the spare secondary battery 11 are respectively detected by the voltage detecting means 3 and the spare battery voltage detecting means 12
, So that each battery is not overcharged.

When the spare secondary battery 11 is fully charged, the spare battery charge control unit 13 stops the charging process, and the charge / discharge switching means 10 switches from the charged state to the discharged state.
When the charging of the assembled battery 2 is completed and the charging / discharging control unit 14 stops the charging process, it is checked whether or not to discharge, and if the discharging is not performed, each of the cells 1 a,
The inter-terminal voltages of 1b, 1c and 1d are compared by the overall control unit 8, and if there is a voltage difference larger than the limit value, the battery switching of the switching connection means 4 is performed so as to connect to a battery having a lower inter-terminal voltage. The switches 5a and 5b are switched, and then the opening / closing means 9 is closed to additionally charge the unit cell having a low inter-terminal voltage from the spare secondary cell 11.

When discharging, the charge / discharge control unit 14 performs a discharge process based on a signal from the general control unit 8 and supplies the load to the load via the input / output unit 15. When the discharging process is completed, each cell 1a, 1 detected by the voltage detecting means 3
The voltage between the terminals b, 1c and 1d is compared by the overall control unit 8, and if there is a voltage difference equal to or larger than the limit value, the battery switching of the switching connection means 4 is performed so as to connect to a battery having a low terminal voltage. The switches 5a and 5b are switched, and then the opening / closing means 9 is closed to additionally charge the unit cell having a low inter-terminal voltage from the spare secondary cell 11.

FIG. 3 shows an example of a charging / discharging curve of the cell 1 when there is a difference in terminal voltage between the cells, and charging / discharging of a cell having a high terminal voltage caused by a difference in equivalent internal resistance. Curve 22 and charge / discharge curve 2 of a cell with low terminal voltage
3 is shown.

FIG. 4 shows the change of the charging / discharging current at this time, which is a charging current curve 24 at the time of constant current and constant voltage charging and a discharging current curve 25 at the time of constant current discharging. Since the equivalent internal resistance of the cell 1 increases as the charging rate decreases, the change in the inter-terminal voltage at the end of charging / discharging is larger at the end of discharging and at the start of charging than at the end of charging and at the start of discharging.

During charging, the state of charge of the battery body is difficult to understand due to the effect of the voltage drop due to the equivalent internal resistance that changes depending on the charging rate, and when the charge / discharge control is of a switching type such as when the battery is large. Since it is difficult to control the voltage of the battery body during charging and discharging with high accuracy because the ripple due to switching is superimposed on the charging and discharging current, the equivalent internal resistance and the ripple during charging and discharging are used in this embodiment. The standby secondary battery 11 is used at the time of charging / discharging standby which can eliminate the influence of the battery, and the cells 1a, 1b, 1c, 1d at the end of charging / discharging.
The overall control unit 8 calculates the equivalent internal resistance from the terminal voltage of the terminal and the terminal voltage after the end of charge / discharge, additionally charges the cell having a low terminal voltage, and determines the voltage difference of the terminal voltage by the equivalent internal resistance. Charge to the value obtained by adding the voltage drop at the time of additional charge by
This is to correct the difference between the voltages of the battery bodies of the cells 1a, 1b, 1c, 1d within an allowable value.

FIG. 5 is a block diagram of a power storage device according to a second embodiment of the present invention, showing a fifth embodiment of the present invention. The configuration of the second embodiment will be described. A battery 2 in which a plurality of cells composed of lithium ion secondary batteries are connected in series is provided with a voltage detecting means 3 for detecting a voltage between terminals of each cell in the battery. And switching connection means 4 for switching the connection when additional charging is performed from the spare secondary battery 11 when there is a single cell having a low inter-terminal voltage, and the switching connection means 4 controls the charging current at the time of additional charging. Current limiting means 7 for limiting
A spare secondary battery 11 is connected to the secondary battery 11 via a spare battery voltage detecting means 12 for detecting the voltage of the spare secondary battery 11 and a spare battery for controlling the charging of the spare secondary battery 11. The charging control unit 13 is connected.

The spare battery voltage detecting means 12, the spare battery charging control section 13 and the voltage detecting means 3 are
6, the battery pack 2, the voltage detecting means 3, the switching connection means 4, the current limiting means 7, and the spare secondary battery 1
1, spare battery voltage detecting means 12, spare battery charge control unit 1
3 and the module controller 26 constitute a battery module 27a. The power of the control circuit in the battery module 27a is supplied from the battery pack 2.

The battery module 27a having the same configuration as the battery module 27a is connected in series, and the battery module 2
7a is connected to the input / output unit 15 via the charge / discharge control unit 14, the battery module 27b is connected to the input / output unit 15, and the battery modules 27a, 27b are connected to the overall control unit 8 via the insulating means. The overall control unit 8 is connected to the charge / discharge control unit 14 and the input / output unit 15 to constitute a power storage device. In such a power storage device, the overall control unit 8 performs status management of each battery module 27a, 27b, charge / discharge management, and input / output instructions. Each battery module 27a, 2
The voltage difference between the cells in the battery module 7b is adjusted in the battery modules 27a and 27b according to the instruction of the module control unit 26 in the battery modules 27a and 27b. The voltage difference between the terminals of the unit cells is managed by the overall control unit 8, and when the voltage difference between the battery modules 27a and 27b exceeds the limit value, an instruction is given from the overall control unit 8 and the Each unit cell of the battery module 27 having a low overall voltage is additionally charged, and the voltage difference between the battery modules is reduced to be within an allowable value.

[0024]

As described above, according to the present invention, in a power storage device using an assembled battery in which a plurality of cells composed of secondary batteries are connected in series, separately from the secondary batteries constituting the assembled battery, At least one spare secondary battery is provided, the spare secondary battery is charged at the same time as or prior to the assembled battery, and the inter-terminal voltage of each cell constituting the assembled battery is detected. A spare secondary battery is selectively connected in parallel via current limiting means only to low cells until the terminal voltage reaches a predetermined level, and the cells having low terminal voltage are charged from the spare secondary battery. It is characterized by reducing the voltage difference between the terminals, and the charge for adjusting the voltage difference between the cells is also used for charging the cells, so there is no extra loss as in the bypass method. A spare secondary battery that does not have a large voltage difference from the cell to be charged Since additional charging, the variation in inter-terminal voltage between the unit cells can be efficiently adjusted, so heat generation is also reduced, it is possible to provide a suitable charge control method and control device to the power storage device using a large-sized battery to flow a large current.

In addition, a limit value of a voltage difference for performing additional charging from the spare secondary battery is provided, an allowable value of a voltage difference for stopping the additional charging is provided, and a difference in terminal voltage between each unit cell is determined by a predetermined value. By limiting the range, the battery can be used at a high utilization rate while increasing the noise allowance of the voltage detection means. Also,
The effect on the detection accuracy of the voltage detecting means due to the ripple of the switching circuit at the time of charging / discharging is performed by charging the unit cell having a lower terminal voltage than the spare secondary battery only during the period when the power storage device is not charging / discharging. Can be prevented.

Further, the terminal voltage of each cell at the end of charge / discharge and after the end of charge / discharge is detected, and the equivalent internal resistance of each cell is calculated from these values and the current value immediately before the end. When additional charging is performed on cells with a low inter-voltage, the battery is charged to a voltage obtained by adding the voltage drop due to the equivalent internal resistance to reduce the voltage difference between the cells. Can be adjusted well.

Also, a battery module is constructed by providing a spare secondary battery in an assembled battery in which a plurality of unit cells are connected in series, and in a power storage device using a plurality of battery modules connected in series, By detecting the voltage between the terminals of the batteries and charging the cells having a low voltage between the terminals from each of the battery modules from the spare secondary battery, the voltage regulator between the cells can be constituted by a low-voltage circuit. Standardization is easy and repair is easy.

Further, a control means for comparing and managing the voltage difference between the battery modules is provided, and when a voltage difference exceeding a preset limit value is generated between the battery modules, an instruction signal is issued from the control means, and a low voltage is output. Each cell in the battery module is additionally charged from the spare secondary battery in the battery module to reduce the voltage difference between the battery modules within a predetermined allowable value, thereby facilitating voltage adjustment between the battery modules. I can do it.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a battery pack charging control device according to a first embodiment.

FIG. 2 is a flowchart illustrating a basic operation at the time of charging and discharging of FIG. 1;

FIG. 3 is a graph showing an example of a terminal voltage of a unit cell during constant current / constant voltage charging and constant current discharging.

FIG. 4 is a graph showing an example of a current of a cell at the time of constant current / constant voltage charging and constant current discharging.

FIG. 5 is a block diagram of a battery pack charging control apparatus according to a second embodiment.

[Explanation of symbols]

1a, 1b, 1c, 1d: single cell, 2: assembled battery, 3: voltage detecting means, 4, switching connection means, 5a, 5b: battery switching switch, 6: diode, 7: current limiting means, 8: overall control Part, 9 opening / closing means, 10 charging / discharging switching means, 11
... spare secondary battery, 12 ... spare battery voltage detecting means, 13 ...
Spare battery charge control unit, 14 charge / discharge control unit, 15 input / output unit, 22, 23 charge / discharge curve, 24 charge current curve, 25 discharge current curve, 26 module control unit
27a, 27b: Battery module.

Claims (6)

[Claims] 1. A power storage device using an assembled battery in which a plurality of unit cells composed of secondary batteries are connected in series, one or more spare secondary batteries are provided separately from the secondary batteries constituting the assembled battery.
The spare secondary battery is charged at the same time as or prior to the assembled battery, the voltage between terminals of each unit cell constituting the assembled battery is detected, and the spare secondary battery is connected only to the unit cell having a low terminal voltage. Selectively and parallel-connected via the current limiting means until the inter-voltage reaches a predetermined level, and charge the cells having a low inter-terminal voltage from the spare secondary battery to reduce the voltage difference between the terminals of the individual cells. A charge control method for a battery pack, comprising: 2. A power storage device using an assembled battery in which a plurality of secondary batteries are connected in series, comprising one or more spare secondary batteries in addition to the unit batteries constituting the assembled battery.
A voltage detecting means for detecting a terminal voltage of each cell constituting the battery pack, and both ends of the spare secondary battery are switched between predetermined terminals of each cell constituting the battery pack via a current limiting means. Switching connection means for connecting, and when the voltage difference between the terminals of the cells constituting the assembled battery becomes equal to or greater than a preset limit value, the spare secondary battery is switched by the switching connection means to reduce the terminal voltage. A charging control apparatus for a battery pack, comprising: a function of connecting the cells in parallel with each other and adjusting the voltage difference between the terminals of each cell so as to be within a predetermined allowable value. 3. The battery according to claim 1, wherein the battery is charged only during a period in which the power storage device is suspended from charging and discharging. A charging control method for a battery pack or a control device thereof. 4. The terminal voltage of each cell and the charging current or (and) discharging current at the end of charging or (and / or discharging), and the terminal of each cell after completion of charging or (and / or discharging). Calculate the equivalent internal resistance of each cell at the end of charging or (and / or at the end of discharging) from the voltage difference and the current value of each cell, and charge the cell with low terminal voltage from the spare secondary battery. The battery according to any one of claims 1 to 3, wherein the battery is charged to a voltage obtained by adding a voltage drop due to an equivalent internal resistance to reduce a voltage difference between the cells. A charge control method and a control device for a battery pack. 5. A power storage device comprising a plurality of unit cells connected in series and a spare secondary battery provided in a battery pack, and a plurality of such battery modules connected in series. The assembled battery according to any one of claims 1 to 4, wherein the inter-terminal voltage of the unit cell is detected, and a unit cell having a low inter-terminal voltage is charged from a spare secondary battery for each battery module. Charge control method and its control device. 6. The charging control method and control device according to claim 5, further comprising control means for comparing and managing a voltage difference between the battery modules, wherein a voltage difference greater than a preset limit value occurs between the battery modules. Then, an instruction signal is issued from the control means, and each single cell in the battery module with a low voltage is additionally charged from the spare secondary battery in the battery module to reduce the voltage difference between the battery modules to within a predetermined allowable value. A charge control method for a battery pack and a control device thereof.