JP2002042901A - Capacity equalizing device for storage battery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacity equalizing device for a storage battery device, having a simple and low-cost system capable of equalizing the dispersion of SOC values for respective cells to avoid the deterioration of a battery by quickly detecting the sticking of switches connecting the cells in parallel and preventing an overcurrent. SOLUTION: In the state that a main switch 1 is in an open condition, on/off is alternately repeated by using an group A parallel connection switch 4a and a group B parallel connection switch 4b. When one parallel connection switch is changed over to the other, all cell parallel connection switches 4 are put into an off-state once, and after a voltage between power output terminals is detected to identify that all cell parallel connection switches 4 are in the off-state, one of the following group parallel connection switches is put into an on-state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power storage device in which a plurality of secondary battery cells are connected in series or in series / parallel, in which the variation in SOC (State Of Charge) of each cell is equalized. The present invention relates to a capacity equalizing device.

[0002]

2. Description of the Related Art EV (Electrical Vehi)
cle: electric vehicle) or HEV (Hybrid E)
In an electric vehicle (hybrid vehicle), it is necessary to mount a plurality of battery cells (hereinafter simply referred to as cells) in series as a high-voltage battery as energy storage. In such a state of the battery, if the battery is repeatedly used and left for a long time after repeated charging / discharging, variations in the charging / discharging efficiency of the cells constituting the battery and variations in the environmental temperature in which the cells are placed may cause the battery to be left in the battery. Variations in the remaining capacity of each cell (hereinafter referred to as SOC variations) occur.

In charging and discharging the battery, the cell having the highest SOC value (or cell voltage) reaches the set upper limit SOC value (or upper limit cell voltage value) from the viewpoint of ensuring the durability and safety of each cell. It is necessary to prohibit charging at a point in time and prohibit discharging when a cell having the lowest SOC value (or cell voltage) reaches a set lower limit SOC value (or lower limit cell voltage value). Therefore, when capacity variation occurs in each cell, the usable capacity of the battery is substantially reduced. For this reason, in the HEV, the so-called assist / regeneration, which replenishes the battery energy to the gasoline when climbing a hill or regenerates energy to the battery when descending a hill, becomes insufficient, and the actual vehicle power performance and fuel efficiency are reduced. become.

In order to cope with this, it is necessary to provide a means for equalizing the SOC variation of each cell and appropriately securing the usable capacity of the battery. In particular, for an energy storage such as a lithium ion battery or a supercapacitor in which the charge / discharge efficiency does not change up to the overcharge region, an additional system for performing the equalization process is essential. As a method of such equalization processing, a method of setting a bypass circuit including a voltage sensor, a bypass resistor, and a bypass switch for each cell and controlling the bypass switch by a microcomputer (a so-called bypass circuit method) has been proposed. It has been installed in HEVs and the like, and has been put to practical use.

FIG. 7 is a block diagram of a commonly used bypass circuit method. This system comprises a cell 21a,
The SOC values calculated from the voltage values sensed by the voltage sensors 22a, 22b,. Then, for example, for the cell 21a determined to have a high SOC value, the bypass switch 23a is turned on for a necessary time calculated from the SOC value to discharge the cell 21a. Thereby, the variation of the SOC value of each cell 21a, 21b... Is equalized.

[0006]

However, in the conventional bypass circuit method, each of the cells 21a, 21b.
When the equalization of the SOC values is performed, the voltage sensors 22a, 22b,.
Must be installed, and it is necessary to calculate the SOC value for each of the cells 21a, 21b,... Based on the sensed voltage value. Further, each cell 21 is calculated according to the calculated SOC value.
a, 21b ... corresponding to the bypass switches 23a, 23
Since it is necessary to perform ON / OFF control of b ..., the bypass circuit becomes complicated, and the configuration of the system becomes expensive.

In order to solve the above-mentioned problem, for example, by connecting cells constituting a battery in parallel, electric charges are transferred from a cell having a high remaining capacity to a cell having a low remaining capacity, and the variation in the remaining capacity is equalized. There is a way. This method has an advantage that a system can be realized at a much lower cost than in the past, since a switching element for connecting cells in parallel is sufficient and a complicated bypass circuit is not required.

However, in the above-described remaining capacity equalization method, a large current may locally flow inside the battery, for example, when a switch element for connecting the cells in parallel is fixed. This causes a problem that the battery is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a simple and low-cost system by connecting cells constituting a battery in parallel. In a capacity equalization device for a power storage device that can equalize the variation in values, it is possible to quickly detect a stuck switch such as a switch that connects each cell in parallel and prevent overcurrent, thereby preventing the battery from deteriorating. To provide a chemical conversion device.

[0010]

In order to solve the above-mentioned problems, a capacity equalizing device for a power storage device according to the present invention is directed to a power storage device configured by connecting a plurality of assembled batteries composed of a plurality of cells in series. A capacity equalizing device for a power storage device for equalizing the remaining capacity between the cells, wherein the battery pack is connected between series-connected circuits of the battery pack (in the embodiment, between the battery pack A and the battery pack B).
And an opening / closing means (main switch 1 in the embodiment) for connecting and disconnecting the assembled battery by an opening / closing operation (ON / OFF operation), and each of the cells constituting the assembled battery. Switching means for connecting any one of the plurality of connection terminals provided on the other connection terminal to the connection terminal of one of the assembled batteries (cell parallel connection switch 4 in the embodiment). And control means (in the embodiment, the control device 20) for controlling the connection of the switching means. After the control means sets the opening / closing means to an open state (OFF state), A capacity equalizing device for a power storage device, characterized in that control of the switching means is started after confirming that it is in an open state (OFF state).

[0011] According to the above configuration, it is possible to quickly detect the sticking of the switching means, and it is possible to prevent an overcurrent from locally flowing to the power storage device.

Further, in the capacity equalizing device for a power storage device according to the invention, the control means may change the connection combination of the switching means to a currently closed state (ON).
The switching means is in the open state (OFF state)
Then, after confirming that all the switching means are in the open state, the connection combination of the switching means is changed (in the embodiment, the group A parallel connection switch 4a and the group B parallel connection switch 4b are alternately switched). Connection). Thus, when switching the switching means, the switching means is turned on in the following combination after confirming that all the switching means are in the OFF state, so that the sticking of the switching means can be detected quickly.

Further, in the capacity equalizing device for a power storage device according to the above invention, the control means confirms that a voltage is not generated at both ends of the power storage device (in the embodiment, the voltage between the power extraction terminals). Is confirmed to be 0 V) by confirming that all the switching means are in the open state (OFF state). Thus, the control means can easily detect the sticking of the switching element without requiring a complicated processing capability.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a battery for describing a capacity equalizing device for a power storage device according to an embodiment of the present invention. The battery in the present embodiment is configured by connecting a plurality of cells in series.

In FIG. 1, the batteries are two battery packs,
An A battery pack 2 and a B battery pack 3 are connected, and the A battery pack 2 has cells A1, A2, A3... An connected in series, and the B battery pack 3 has cells B1, B2, B3. Are connected in series via the main switch 1. In this battery system, the main switch 1 is installed at the midpoint of the battery voltage. Further, a power extraction terminal 10 is provided at both ends of the battery in a state where the two assembled batteries are connected in series by turning on the main switch 1 so that the power of the battery can be extracted.

Further, individual cells A1, A2, A3... An included in one assembled battery and individual cells B1, B2, B3... Bn included in the other assembled battery are connected in parallel for each cell. For this purpose, a cell parallel connection switch 4 is provided. The parallel connection switch 4 includes an A group parallel connection switch 4a (C1, C2, C3... Cn) and a B group parallel connection switch 4b (D1, D2, D3... Dn). That is, when the A group parallel connection switch 4a is turned on, the cell A1 and the cell B1, the cell A2 and the cell B2,..., The cell An and the cell Bn are respectively connected in parallel. When the group B parallel connection switch 4b is turned on, the cells A2 and B
1, cell A3 and cell B2, ..., cell An and cell B (n-
1) are connected in parallel. However, the two cells (cell A1 and cell Bn) at both ends of the assembled battery of both the assembled battery 2 and the assembled battery 3 are connected in parallel with one cell of another assembled battery. The main switch 1 and the cell parallel connection switch 4 are ON / OFF controlled by the host controller 20.

Further, a voltage monitoring block 7 for monitoring a voltage of each cell or a plurality of cells is provided, and monitors a voltage V of a target cell. The control device 20 compares the voltages detected by the voltage monitoring block 7 with each other to detect the presence / absence of a cell voltage abnormality, and uses the same to control the variation of the cell voltage to be equal. Note that the number of cells to be measured by the voltage monitoring block 7 is determined depending on the cost and the like.

Next, an operation for equalizing the SOC value of each cell in the battery shown in FIG. 1 will be briefly described. When the main switch 1 is open, the control device 20 controls the A group parallel connection switches C1, C2, C3.
... Cn and B group parallel connection switches D1, D2, D
3... Dn are alternately turned on / off alternately. That is, in the figure, the group A parallel connection switch 4a shown by a solid line and the group B parallel connection switch 4b shown by a dotted line
Are turned ON / OFF alternately.

That is, after opening the main switch 1, the control device 20 first detects the voltage of the power extraction terminal 10, and if this terminal-to-terminal voltage (hereinafter referred to as the power extraction terminal voltage) is 0 V, By turning on the group A parallel connection switches C1, C2, C3,.
1 and cell B1, cell A2 and cell B2,... Cell An and cell Bn are connected in parallel, respectively. Thereby, the SOC values of the cells connected in parallel are equalized. Next, after a certain time has elapsed, the control device 20 switches the A group parallel connection switches C1, C2,
C3 ... Cn is turned off. Subsequently, the control device 20 confirms that the voltage between the power extraction terminals is 0 V, and then switches the group B parallel connection switches D1, D2, D3,.
By turning on Dn, cell A2 and cell B1, cell A3 and cell B2,... Cell An and cell B (n-1)
Connect them in parallel.

As a result, the SOC values of the cells connected in parallel are equalized. In this way, when the main switch 1 is open, the two sets of group parallel connection switches C1 to Cn and D1 to Dn are alternately turned on / off to change the combination of cells in the two assembled batteries. By repeating the switching of the parallel connection, the control of equalizing the variation in the SOC value is performed for all the cells of the battery. Also, when switching the parallel connection switch,
First, after confirming that the voltage between the power extraction terminals is 0 V, the cell parallel connection switch in the OFF state is turned on.
Since the state is the N state, it is possible to prevent the battery from being deteriorated due to an overcurrent flowing through the wiring.

Next, FIG. 2 shows the voltage generated at the power extraction terminal 10 according to the ON / OFF state of each switch when the voltage of the battery is PV. As shown in this figure, when any of the switches is in the OFF state, the voltage between the power extraction terminals is 0V. On the other hand, when one of the switches is in the ON state, some voltage is generated at the power extraction terminal 10. Therefore, the control device 20 can confirm that all the switches are in the OFF state by confirming that the voltage between the power extraction terminals is 0 V.

Next, the basic operation of the SOC equalization process according to the present embodiment will be described with reference to an example of two cells connected in parallel as shown in FIG. As shown in FIG. 3, a high SOC cell 11 having a cell voltage of 4.0 V and a low SOC cell 12 having a cell voltage of 3.0 V include a switch 13 and a low SOC cell 12.
They are connected in parallel via a 7Ω resistor 14. When current is applied between the cells by the switch 13 using such a parallel circuit of cells, a current flows from the high SOC cell 11 to the low SOC cell 12, the voltages of the two cells 11 and 12 become equal, and the SOC is equalized. Is done. In such an equalization method, it is not necessary to monitor the cell voltage, and it is not necessary to calculate the SOC for the equalization.

According to the equalization as in this method,
Unlike the conventional bypass circuit method shown in FIG. 7 in which the equalization is performed by consuming the energy of the high SOC cell as heat with the bypass resistor, the low SOC signal is applied from the high SOC cell 11.
Since the configuration is such that charges are transferred to the OC cell 12, energy can be effectively used without consuming energy as heat during the equalization process.

FIG. 4 is a characteristic diagram showing a state of SOC equalization by the cell parallel connection circuit shown in FIG. In this figure, the horizontal axis represents the energization time of the switch 13 for connecting the cells 11 and 12 in parallel, the left vertical axis represents the cell voltage (V), and the right vertical axis represents the current (A) flowing between the cells. Initially, the voltage of the low SOC cell 12 is 3 V and the high SOC
Since the voltage of the cell 11 is 4 V, a large charging current of about 1.2 A flows from the cell 11 to the cell 12 while being limited by the resistor 14 of 0.7Ω. Then, as the time elapses, the voltages of the cells 11 and 12 approach each other. After about the time T3, the voltages of the cells 11 and 12 become about 3.6 V, and the equalization is almost completed. Further, the charging current flowing from the high SOC cell 11 to the low SOC cell 12 also decreases as the voltages of both cells approach, and is less than 0.1 A near time T3.

Next, a case will be described in which the above-described remaining power detection device for a power storage device according to an embodiment of the present invention is applied to an HEV or an EV. Usually, in HEV or EV, the main switch 1 is turned off immediately after the ignition is turned off. As a result, the ignition OF
At the time of F, the system connected to the power extraction terminal 10 of the battery is cut off from the high voltage, and safety is ensured. The main switch 1 is a switch for shutting off a high voltage circuit of a system connected to a battery and ensuring safety when an ignition is turned off.

Next, a variation equalizing process in an HEV or an EV equipped with the power storage device variation equalizing device of the present invention will be specifically described with reference to FIG. FIG.
9 is a flowchart showing a flow of processing for equalizing control of cells. The following control is performed by the control device 20.
Is a process performed by executing a predetermined program.

First, in step S1, when the ignition is turned off, the main switch 1 is turned off immediately thereafter. In the following step S2, based on the difference between the voltages V detected by the respective voltage monitoring blocks 7,
The number of repetitions of ON / OFF of the cell parallel connection switch 4 is set. Here, the larger the difference between the voltages V, the longer the (processing) time required for equalization, and thus the number of repetitions is set to be large. Next, in step S3, it is determined whether the voltage between the power extraction terminals is 0V.
As a result, when it is determined that the voltage between the power extraction terminals is 0 V, the process proceeds to step S4, and only the group A parallel connection switch 4a is turned on while the group B parallel connection switch 4b is kept off. Thus, the cells A1 and B1, the cells A2 and B2,..., The cells An and Bn are connected in parallel, and the cells are equalized.

Next, in step S5, it is checked whether a preset time has elapsed. As a result, if the set time has not elapsed, steps S4 and S5 are looped, and as a result, the switching state of step S4 is maintained until the set time has elapsed.

When it is determined that the set time has elapsed and the set time has elapsed in step S5, the A-group parallel connection switch 4a is turned off. Then, in step S6, the voltage between the power extraction terminals is set to 0V. Is determined. As a result, the terminal voltage becomes 0 V
If it is determined that the above condition is satisfied, the process proceeds to step S7, where the B group parallel connection switch 4b is turned on. Thus, the cells A2 and B1, the cells A3 and B2,..., The cells An and the cells B (n-1) are connected in parallel, and the cells are equalized. Subsequently, in step S8, it is checked whether or not a preset time has elapsed. As a result, if the set time has not elapsed, steps S7 and S8 are looped, and the current switching state is maintained until the set time is reached.

Subsequently, the set time elapses, and step S8 is executed.
If it is determined that the set time has elapsed, the process proceeds to step S9, and it is checked whether the ON / OFF of the cell parallel connection switch 4 has been repeated the specified number of times set in step S2. As a result, if the ON / OFF of the cell parallel connection switch 4 has not been repeated the specified number of times, the process returns to the step S3 to repeat the above-described processing.

On the other hand, if it is determined in step S9 that the ON / OFF of the cell parallel connection switch 4 has been repeated a specified number of times, the process proceeds to step S10, in which the A group parallel connection switch 4a and the B group parallel connection switch 4b
Are turned off, and in a succeeding step S11, it is confirmed whether or not the voltage difference between all the voltage monitoring blocks 7 is within a specified value. If there is a voltage monitoring block 7 in which the inter-block voltage difference does not fall within the specified value, the process returns to step S2, and based on the current inter-block voltage difference, the ON / OF of the cell parallel connection switch is again performed.
The number of F repetitions is set, and the above processing is performed again. On the other hand, if all the voltage differences detected by the voltage monitoring block 7 are within the specified value, the cell equalization processing is terminated as it is.

The above-described steps S3 and S3
In step 6, if the voltage between the power extraction terminals is not 0 V, the process proceeds to step S12, in which it is determined that the system has failed and the operation of the equalization process is stopped, and the main switch and the cell parallel connection switch 4 are turned on. Operation is prohibited. Further, when the ignition is turned on next time, the warning light is turned on to notify the driver.

As described above, the A group parallel connection switch 4a and the B group parallel connection switch 4b are alternately switched according to the voltage difference measured by each voltage monitoring block 7.
The equalization process for all cells is performed by repeating ON / OFF for a set time by a specified number of times.

The ON / O of the cell parallel connection switch 4
After the FF is repeated a specified number of times, if the voltage difference between the voltage monitoring blocks 7 is equal to or greater than a set value (for example, 1 V), the A group parallel connection switches 4a and B
The ON / OFF of the group parallel connection switch 4b is repeated to perform the associated control. If the voltage difference between the voltage monitoring blocks 7 increases during the operation of the above-described cell equalization processing, it is determined that the system has failed and the operation of the equalization processing is stopped, and the next operation is performed. When the ignition is turned on, a warning light is turned on to notify the driver.

FIG. 6 is a timing chart showing ON / OFF timing of each switch and detection timing for detecting the voltage of the power extraction terminal 10 when the above-described processing is performed. FIG. 6A shows the O of the main switch 1.
6B shows ON / OFF timing of the A group parallel connection switch 4a, and FIG. 6C shows ON / OFF of the B group parallel connection switch 4b.
FIG. 6D shows the timing of the FF and the timing of detecting the voltage between the power extraction terminals.

In the figure, when the main switch 1 is turned off at time t0, it is detected at next time t1 whether the voltage between the power extraction terminals is 0V. Thereafter, if the voltage between the power extraction terminals is 0 V, the time t2
, The group A parallel connection switch 4a is turned on. The ON state is continued for the set time, and at time t3, when the switches are turned OFF, at the same time, the voltage between the power extraction terminals is detected, and all the switches are turned OFF.
It is confirmed whether the state is the FF state. As a result, if the voltage between the power extraction terminals is 0 V, at time t4, B
The group parallel connection switch is turned on.

The ON state is continued for the set time, and when the switch is turned OFF at time t5, the voltage between the power extraction terminals is simultaneously detected. When the switching of the cell parallel connection switch 4 is performed a predetermined number of times, and it is confirmed that the remaining capacities between the cells have been equalized, the equalization processing ends at time t6. Thereafter, when the ignition is turned on at time t7, the voltage between the power extraction terminals is simultaneously detected, and when it is confirmed that all the switches are in the OFF state, the main switch 1 is turned off at time t8.
N.

As described above, when each switch is turned on, it is confirmed that all the switches are in the OFF state once, and then the switch to be turned on next is turned on, thereby fixing the switch. Can be quickly detected, and an overcurrent can be prevented from flowing through the wiring.

[0039]

As described above, according to the capacity equalizing device for a power storage device of the present invention, the control means makes the switching means all open after opening the switching means. Since the control of the switching means is started after the confirmation, the sticking of the switching means can be detected quickly. Thus, an overcurrent can be prevented from locally flowing to the power storage device, so that an effect of preventing battery deterioration can be obtained.

Further, according to the capacity equalizing device for a power storage device of the present invention, when changing the connection combination of the switching means, the control means sets the switching means, which is currently closed, to the open state, After confirming that all the switching means are in the open state, the connection combination of the switching means is changed, so that even when the switching means is switched, the fixation of the switching means can be quickly detected, and the deterioration of the power storage device is deteriorated. Can be prevented.

According to the capacity equalizing device for a power storage device of the present invention, the control means confirms that no voltage is generated at both ends of the power storage device, so that the switching means are all open. Therefore, it is possible to obtain the advantage that the control means can easily detect the sticking of the switching element without requiring a complicated processing capability, and the device can be realized at a low price.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a battery according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a voltage generated at a power extraction terminal according to an ON / OFF state of each switch when a battery voltage is PV.

FIG. 3 is an explanatory diagram for describing a basic operation of an SOC equalization process according to the embodiment;

FIG. 4 is a diagram illustrating an SOC using the cell parallel connection circuit shown in FIG. 3;
It is a characteristic view which shows the situation of equalization.

FIG. 5 is a flowchart illustrating an operation of the battery voltage detection device according to the present embodiment.

6 is a timing chart showing ON / OFF timing of each switch and detection timing for detecting a voltage of the power extraction terminal 10, and FIG. 6A shows ON / OFF timing of the main switch 1; (B)
6C shows ON / OFF timing of the A group parallel connection switch 4a, FIG. 6C shows ON / OFF timing of the B group parallel connection switch 4b, and FIG. 6D shows timing of detecting the voltage between the power extraction terminals. Is shown.

FIG. 7 is a configuration diagram of a commonly used bypass circuit method.

[Explanation of symbols]

A1, A2, A3 ... An, B1, B2, B3 ... Bn Cell 1 Main switch (opening / closing means) 2 A battery pack 3 B battery pack 4 Cell parallel connection switch (switching means) 4a A group parallel connection switch 4b B group parallel Connection switch 7 Voltage monitoring block 10 Power extraction terminal 20 Control device (control means)

Claims (3)

[Claims] 1. A capacity equalizing device for a power storage device configured to equalize a remaining capacity between cells in a power storage device configured by connecting a plurality of assembled batteries including a plurality of cells in series. An opening / closing means provided between the series connection circuits of the batteries for connecting and disconnecting the assembled battery by an opening / closing operation; a connection terminal provided between each of the cells constituting the assembled battery; A plurality of switching means for connecting any of the plurality of connection terminals provided on the other battery pack to the connection terminal of the battery; and a control means for controlling connection of the switching means, The control means, after opening the opening / closing means, confirms that the switching means are all open, and then starts controlling the switching means. Quantity equalizer. 2. When changing the connection combination of the switching means, the control means checks that all the switching means are in the open state after opening the currently closed switching means. 2. The capacity equalizing device for a power storage device according to claim 1, wherein a combination of the connections of the switching means is changed after that. 3. The control device according to claim 1, wherein the control unit confirms that no voltage is generated at both ends of the power storage device, thereby confirming that the switching units are all open. A capacity equalizing device for a power storage device according to claim 2.