JP2001136669A - Storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize a plurality of storing means connected in series exactly and properly. SOLUTION: The respective voltages of a plurality of battery cells 16 connected in series are detected when no current run through a circuit 12. Based on the detected voltage, the determination of a charge carrying-out cell and a charge receiving cell and the calculation of equalization operating time are performed to schedule the charging equalization operation of the respective battery cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power storage device,
More specifically, the present invention relates to a power storage device in which a plurality of storage batteries are connected in series and in which the state of charge between the storage batteries can be equalized.

[0002]

2. Description of the Related Art As a power source of an electric vehicle whose technical development has been advanced in recent years, a power storage device (assembled battery) in which a plurality of storage batteries are connected in series is used. As described above, in the case of a power storage device in which a number of storage batteries are connected in series, the output depends on the battery with the lowest voltage. However, there is an inconvenience that the performance of each battery cannot be maximized.

Therefore, various voltage balancing circuits have been proposed in order to make the state of charge of each battery uniform. For example, in the device disclosed in Japanese Patent Application Laid-Open No. 10-322925, a discharge circuit is provided for each cell, the open circuit voltage of each cell is detected, and the electric circuit of each cell is detected by the discharge circuit based on the open circuit voltage. The amount is discharged and adjusted so that the charging rate of each cell becomes uniform. In the device disclosed in JP-A-11-103534, a battery that can be connected in parallel to each unit cell is provided, and after detecting the open voltage of each unit cell, a battery that charges the capacitor and receives a discharge from the capacitor. Select a battery. Then, the battery to be charged is connected to the battery to charge the battery, and then the battery to be discharged is connected to the battery to charge the battery. By performing this processing cycle a predetermined number of times (specified number of cycles), the charging rate between the cells was adjusted.

[0004]

However, the prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 10-322925 is based on the premise that the amount of discharge electricity is proportional to the time during which current flows through the discharge circuit. However, no consideration is given to the fact that the current flowing in the discharge circuit decreases as the battery voltage decreases due to the discharge. Therefore, it was not possible to discharge the amount of electricity from the battery for an exact time corresponding to the amount of electricity to be discharged. In addition, since the relationship between the resistance value of the discharge circuit and the resistance value inside the battery is not considered, when the ratio between the resistance value of the discharge circuit and the resistance value inside the battery is small, when the current flows through the main circuit, (Hereinafter referred to as "main current")
As compared with the case where the main current is not flowing, a large amount of current flows in the discharge circuit, and there is a disadvantage that a larger amount of electricity is discharged than a target amount of discharged electricity.

In the prior art disclosed in Japanese Patent Application Laid-Open No. H11-103534, each battery voltage for selecting a battery to be charged in a battery and a battery to be discharged from the battery is determined by whether a main current is flowing. Regardless of whether or not the voltage is equalized, it is detected every designated number of cycles of the voltage equalization process. Since the battery voltage fluctuates between the state where the main current is flowing and the state where the main current is not flowing, it is impossible to accurately measure the open-circuit voltage of each battery, and the battery to be charged to the battery and the battery to be discharged from the battery are accurately selected. I couldn't do that. Therefore, it is conceivable to measure the voltage when the main current is not flowing and perform the voltage equalization process.However, the designated number of cycles of the voltage equalization process is relatively short, so that the battery voltage is frequently detected and the battery is detected. The battery to be charged to the battery and the battery to be discharged from the battery must be selected. In practice, when the main current is not flowing for a long time, that is, when the vehicle is stopped, the voltage equalization process is performed. In this case, the voltage equalization processing can be performed only when the vehicle is stopped, and the effect of the voltage equalization processing cannot be sufficiently exhibited.

The present invention has been made in view of the above-described circumstances, and has as its object to provide a power storage device capable of more accurately performing voltage equalization processing of each power storage means.

[0007]

To achieve the above object, a power storage device according to the present invention comprises a plurality of power storage means connected in series, and a voltage detection means for detecting a voltage of each of the power storage means. Detecting means for detecting whether or not current is flowing from the power storage means; and detecting the current not flowing by the detection means, the voltage of each of the power storage means detected by the voltage detection means when it is detected that the current is not flowing And an equalizing means for equalizing the amount of power stored in the plurality of power storage means.

According to the present invention, each voltage of the power storage means detected when no current flows from the power storage means, that is, in a state where the power storage means is not affected by its internal resistance or the like. Since the power storage means is equalized based on the accurate voltage, accurate and appropriate equalization can be performed.

Here, the term “equalization” refers to reducing the variation in the state of charge of the power storage means, and more preferably to equalizing the state of charge of the power storage means.

According to a second aspect of the present invention, the equalizing means includes a capacitor connectable to each of the power storage means, and at least one other power storage from the at least one power storage means via the power storage. A discharging means for transferring charges to the means, and a discharging means for discharging the charges and receiving the discharged charges for equalizing the amounts of charge of the plurality of power storing means based on respective voltages of the storing means. Receiving and storing means; determining means for determining an amount of charge transfer from the releasing and storing means to the receiving and storing means; and a charge moving amount determined by the determining means moving from the discharging and storing means to the receiving and storing means. The control means for controlling the moving means may be provided.

According to the present invention, the charge between the power storage means is moved based on the charge transfer amount determined by the determination means, so that the equalization processing is scheduled, and the power storage means is repeated many times. There is no need to detect the voltage of

According to a third aspect of the present invention, the deciding means sets the number of the discharging and storing means to N, the n-th voltage of the discharging and storing means to Vns, and the discharged and storing means after equalization. Vn (t), the mth voltage of the receiving and storing means is Vrms, the mth target voltage of the receiving and storing means after equalization is Vrm (t),
The electric capacity of the electric storage means is Cb, the electric capacity of the electric storage means is Cc, the period at which electric charge is transferred from the emission electric storage means to the receiving electric storage means via the electric storage means is Ti, and the discharge electric storage means from the electric storage means to the electric storage means. A time tn calculated from the following two equations, where η is a coefficient that takes into account the amount of charge loss when moving charges, and λ is a coefficient that takes into account the amount of charge loss when moving charges from the battery to the receiving and storing means. ,
The movement of the charge by the moving means for any shorter time of tm may be determined as the charge transfer amount.

[0013]

(Equation 5)

However,

[0015]

(Equation 6)

According to the present invention, the electric charge which is moved by moving the electric charge by the moving means for the shorter one of the times tn and tm calculated by the above equation is determined as the electric charge transfer amount. Therefore, the amount of electricity can be moved more accurately.

According to a fourth aspect of the present invention, the equalizing means includes a discharging means for discharging an amount of electricity from the power storage means, and the plurality of power storage means based on respective voltages of the power storage means. Discharge storage means for discharging an amount of electricity for equalizing the amount of stored electricity, determining means for determining the amount of charge discharged from the discharge storage means, and the amount of electricity determined by the determination means Control means for controlling the discharging means so as to be discharged from the power storage means.

According to the present invention, since the electric energy is discharged from the discharge power storage means based on the electric energy determined by the determination means, the equalization process is scheduled, and the power storage means is repeatedly used. There is no need to detect the voltage.

According to a fifth aspect of the present invention, the discharging means has a resistance value for consuming electric charge from the power storage means being 100 times or more the resistance value inside the power storage means. It can also be characterized by having. According to the present invention, the resistance value for consuming the electric charge from the power storage means is 100 times or more the resistance value inside the power storage means. Current flowing into the power storage means can be suppressed to a small amount, and even when a current flows through the power storage means, the equalization processing can be accurately performed.

Furthermore, as in claim 6, wherein the determining means, Vr target voltage after equalization, the capacitance Cb of the accumulator unit, the resistance value of the voltage V _S said resistor of said storage means R _BP , wherein the amount of charge discharged during one of the times tr1 and tr2 calculated from the following two equations is determined as the amount of charge discharged from the discharge storage means. Can also.

[0021]

(Equation 7)

[0022]

(Equation 8)

However, according to the present invention, α = 1 / (Cb · R _BP ) According to the present invention, the amount of charge discharged during one of the times tr1 and tr2 calculated by the above equation is calculated as follows. Since it is determined as the amount of charge discharged from the discharge storage means, a more accurate amount of electricity can be discharged.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] As shown in FIG.
Power storage device 10 according to the present embodiment includes a plurality of lithium ion secondary batteries (hereinafter referred to as “battery cells”) as power storage means.
16A, 16B, 16C, and 16N are configured as an assembled battery 16 in which a large number are connected in series. In addition,
Although only four battery cells are shown in FIG. 1 for the sake of illustration, a large number of battery cells (not shown) are actually connected, and a total of several tens of battery cells (this embodiment Are connected in series).
At one end of the assembled battery 16, an ammeter 14 is installed as monitoring means for monitoring whether current is supplied from the power storage device 10, that is, whether a main current is flowing through the circuit 12. . Battery cells 16A, 16B,
16C,... 16N plus terminals 26A, 26C, 26
A changeover switch connectable to one end 28A of the charge pump capacitor 24 is connected to E and 26M, and the negative terminals 26B, 26D, 26F and 26N of the battery cells 16A, 16B, 16C,. A changeover switch that can be connected to the other end 28 </ b> B of the capacitor 24 is connected, and forms a changeover connection section 22. The switching connection unit 22 is connected to a control circuit 20 that controls switching between the charge pump capacitor 24 and each battery cell. As a switch of the switching connection unit 22, a field effect transistor (FET), a relay switch, or the like can be used. Also, battery cell 1
6A, 16B, 16C,... 16N have voltage measuring devices 18A, 18B for measuring the voltage of each battery cell.
18C and # 18N are connected, and the voltage measuring device 1
8A, 18B, 18C and # 18N are connected to the control circuit 20.

Next, the operation of this embodiment will be described.
This will be described with reference to the drawings.

In the present embodiment, the state of charge between the battery cells is equalized by transferring electricity from the battery cells having a higher state of charge to the battery cells having a lower state of charge through the charge pump capacitor 24. That is,
Electricity is transferred from a battery cell or a battery cell group having a high state of charge (hereinafter referred to as a "take-out cell group") to charge the charge pump capacitor 24, and the charged electricity is charged to a battery cell or a group of battery cells having a low state of charge (hereinafter referred to as a battery cell group). The operation of discharging to the “receiving cell group” is repeated. This charge state equalization process will be described with reference to the flowchart shown in FIG.

First, at step 30, it is determined by the ammeter 14 whether a main current is flowing through the circuit 12.
When the main current is not flowing, the voltage of each of the battery cells 16A, 16B, 16C, and # 16N measured by the voltage meters 18A, 18B, 18C, and # 18N is read in step 32, and the control circuit 20 In the voltage table (not shown). Here, when measuring the voltage of each battery cell, the amount of electricity in the battery cell is substantially proportional to the voltage. Therefore, it is considered that this voltage value indicates the amount of electricity in the battery cell, that is, the state of charge of the battery cell. Because it can be done. If the main current is flowing, the measurement of the voltage is not performed, and the process waits until the main current stops flowing. The reason why the voltage needs to be measured when the main current does not flow is that when the main current flows, an accurate open-circuit voltage cannot be measured due to the internal resistance of each battery cell.

In step 34, a target voltage to be reached when the voltage of each battery cell is equalized is set based on the measured voltage value of each battery cell. This setting is specifically performed as follows.

It is assumed that the voltage (Vn) of each battery cell measured at a certain time is distributed as shown in FIG. Since the equalization of the battery cells is performed by moving the electricity from the high-charged battery cells to the low-charged battery cells, the equalization of the battery cells is performed by moving the amount of electricity in the portion equal to or higher than the minimum voltage (Vmin). Become. At this time, if the electricity transfer efficiency is 100% (without loss), the idealized average voltage (V ^img _avg ) after equalization is:
Since it is considered to be equal to the sum of the minimum voltage (Vmin) and the average voltage of a portion equal to or higher than the minimum voltage (Vmin) of each battery cell, it is calculated by the following equation (1-1).

[0031]

(Equation 9)

Here, it is considered that due to a loss in the circuit, the amount of electricity flowing out of the taken-out cell group is larger than the amount of electricity flowing out of the charge pump capacitor 24. At this time, the amount of electricity flowing out of the taken-out cell group is charged. It is expressed as the quantity of electricity flowing out of the pump condenser 24 multiplied by the increment coefficient λ (> 1). It is also assumed that the receiving cell group can receive electricity from the charge pump capacitor 24 only at a predetermined efficiency η (<1). Therefore, the calculation is performed in consideration of the case where the moving efficiency is 100% (1-
1) modifications to the added, to calculate the expected average voltage after equalization (V ^{re al} _avg) by the following equation (1-2). Note that λ and η used here are measured by experiments and set in advance.

[0033]

(Equation 10)

The expected average voltage (V ^real ) thus calculated
_avg ) is the target attained voltage.

In the above example, the expected average voltage (V
^real _avg ) is set as the target attainment voltage, but the present invention is not limited to this. For example, it is also possible to obtain an average value (Vavg) of all battery cell voltages and set this as the target attainment voltage. is there.

At step 36, a cell group to be taken out is selected. The number of battery cells selected here is two,
The battery cell in which the sum of the voltages of the two adjacent battery cells is the largest is selected as a cell group to be taken out.

At step 38, a receiving cell group is selected. The number of battery cells selected here is one,
The battery cell with the minimum voltage is received and selected as a cell group.

The number of cells to be taken out and the number of cells to be received are not limited to those described above.
Any number can be used. In addition, the method of selecting the export cell group and the reception cell group is not limited to the above-described method.For example, in the adjacent cell group including the battery cell having the maximum or minimum voltage, the sum of the voltages is maximum or minimum. Can be selected as the export cell group and the reception cell group, respectively. Further, as the carry-out cell group, a minimum voltage cell among adjacent cell groups including the battery cell having the maximum voltage is compared, and a cell group including the highest voltage among the cells is selected, and a receiving cell group is selected. Alternatively, the maximum voltage cell among the adjacent cell groups including the battery cell with the minimum voltage may be compared, and the cell group including the lowest voltage cell among the cells may be selected.

In step 40, when the receiving cell group is charged from the taken-out cell group via the charge pump capacitor 24, an expected arrival time T0 as a time until the target reaching voltage is reached is set. The expected arrival time T0 is calculated based on the following concept.

First, consider a case where the number of taken-out cell groups is 2, the corresponding battery cells are 16A and 16B, and the number of receiving cell groups is 1 and the corresponding battery cells are 16N. The equalizing operation between the take-out cell group and the receiving cell group is performed by first connecting the take-out cell group and the charge pump capacitor 24 in parallel to charge the charge pump capacitor 24, and then connecting the charge pump capacitor 24 to the charge pump capacitor 24. The receiving cell group is charged from the charge pump capacitor 24 by switching to the parallel connection with the receiving cell group. By repeating this equalizing operation, the voltages of the brought-out cell group and the receiving cell group are equalized. In this equalizing operation, if the amount of electricity moved by the charge pump capacitor 24 is assumed to be ΔQ, and an amount of electricity of ΔQ1 flows from the battery cell 16A and ΔQ2 from the battery cell 16B, then ΔQ = ΔQ1 + ΔQ2 (2-1) ). Here, ΔV1: voltage change amount of battery cell 16A (unit: V) ΔV2: voltage change amount of battery cell 16B (unit: V) C1: electric capacity of battery cell 16A (unit: F) C2: battery cell 16B Electric capacity (unit: F)
Then, ΔQ = C1 · ΔV1 + C2 · ΔV2 (2-2) The battery cells used here are of the same standard, and since there are usually no significant differences in characteristics such as electric capacity and internal resistance, C1 = C2 = Cb and ΔV1 = ΔV2
And

Therefore, ΔQ = Cb · ΔV1 + Cb · ΔV1 (2-3) ΔV1 = ΔV2 = ΔQ / 2 · Cb (2-4)

Next, the voltage change of each cell is expressed by a mathematical formula. Here, V1 (t): voltage of battery cell 16A at time t (unit: V) V2 (t): voltage of battery cell 16B at time t (unit: V) Vr (t): voltage of battery cell 16N Voltage at time t (unit: V) V1s: Initial voltage of battery cell 16A (unit: V) V2s: Initial voltage of battery cell 16B (unit: V) Vrs: Initial voltage of battery cell 16N (unit: V) Cc : Electric capacity of charge pump capacitor 24 (unit: F) Ti: Period of charge / discharge cycle (unit: sec)
Then

[0043]

[Equation 11]

Is as follows.

The battery cell 16 which is a receiving cell
The electric capacity Cr of N is also equal to the above Cb, and Cr = Cb
And

In this case, the amount of electricity flowing out from the cell group to the charge pump capacitor 24 is actually larger than the amount of electricity charged in the charge pump capacitor 24 due to the loss in the circuit.
4 is multiplied by an increment coefficient λ (> 1). On the other hand, the receiving cell group can receive electricity only with a certain efficiency, and the receiving cell group is charged with the charge pump capacitor 2
The amount of electricity charged from 4 is the charge pump capacitor 2
4 is smaller than the amount of electricity flowing out of the charge pump capacitor 24,
Represented by multiplying by 1).

The change of each battery cell voltage in consideration of the increment coefficient λ and the decrease coefficient η is as follows.

[0048]

(Equation 12)

Is as follows.

FIG. 9 is a block diagram showing this equation.

Here, the electric capacity Cb of the battery cell 16
Also, since the electric capacitance Cc of the charge pump capacitor 24 is almost constant regardless of the elapsed time, (2-6)
By solving equations (2-7) and (2-8), V1 (t),
The time change of V2 (t) and Vr (t) can be calculated.

Solve using Laplace transform or the like.

[0053]

(Equation 13)

In other words,

[0055]

[Equation 14]

Is as follows.

With the equations (2-10) to (2-12), it is difficult to find the time t at which the target voltage V1 (t) is reached when the target voltage V1 (t) or the like is given. Is linearized and approximated by the following method.

Here, the approximation is made as follows: f (t) = e ^−at ≒ 1− ^at (2-13) According to this approximation method, as shown in FIG. 10, the smaller the value of at, the higher the degree of approximation, and it is estimated to be larger than the actual change.
The change is expected to be on the safe side. Further, in practice, the voltage is not used until the voltage finally converges, and only the region where at is small is used, so it seems that there is no problem in practical use.

It can be seen that this approximation has been replaced in the block diagram of FIG. 9 by making it proportional to time t instead of integration.

Using the equation (2-13), (2-10)
-12)

[0061]

(Equation 15)

This can be simplified as follows.

Here, when V1 (t), V2 (t), Vr (t), etc. are given, the times at which they are reached are t1, t2,
tr is

[0064]

(Equation 16)

Is obtained as follows.

In the above example, the number of cells taken out is two.
And the number of received cells is one, but when the number of cells taken out is N and the number of received cells is M,
(2-14), (2-16) and (2-17), (2-19)
The equation can be expressed as:

[0067]

[Equation 17]

[0068]

(Equation 18)

Therefore, in this step 40, the shorter of (2-22) and (2-23) is set as the estimated arrival time T0.

In step 42, the equalizing operation shown in FIG. 3 is performed. More specifically, in step 52, the terminal 26A of the battery cell and the charge pump capacitor 24 are connected in parallel so that the cell group of the battery cells 16A and 16B having the maximum voltage sum is connected in parallel with the charge pump capacitor 24.
Of the battery cell, and the terminal 28B of the charge pump capacitor 24. Then, the charge pump capacitor 24 is charged from the taken-out cell group,
At step 54, it is determined whether or not the amount of electricity corresponding to the capacity is stored in the charge pump capacitor 24. When the amount of electricity corresponding to the capacity is stored in the charge pump capacitor 24, the connection between the take-out cell group and the charge pump capacitor 24 is released, and in step 56, the receiving cell group and the charge pump capacitor 24 are connected in parallel. . Here, the terminal 26M of the battery cell and the terminal 28A of the charge pump capacitor 24 are connected to the terminal 2 of the battery cell.
The switching connection unit 22 is controlled so that 6N is connected to the terminal 28B of the charge pump capacitor 24. Then, charging is performed from the charge pump capacitor 24 to the battery cells 16 </ b> N as the receiving cell group. In step 58, it is determined whether or not the charging of the receiving cell group has been completed. If the charging of the receiving cell group has been completed, the process proceeds to step 44 in FIG. Here, one equalizing operation shown in FIG. 3 is one cycle of charge and discharge, and the time required for this one cycle corresponds to the cycle Ti of one charge and discharge cycle described above.

At step 44 in FIG. 2, it is determined whether or not the expected arrival time T0 has been reached. If the expected arrival time T0 has not been reached, both the cell group taken out and the cell group received
Since the set target voltage has not been reached, step 4
2 is repeated. If the estimated arrival time T0 has been reached, the voltage values after the equalization operation of the battery cells 16A and 16B, which were the cell groups taken out, and the battery cell 16N, which was the reception cell group, based on the estimated arrival time T0 in step 46. Is calculated, and in step 48, the voltage values in the voltage table are replaced. Here, the voltage of the battery cell whose voltage value has reached the target voltage is deleted from the voltage table. In step 50, it is determined whether or not the next cell group should be equalized. Here, whether to equalize the next cell group is determined as follows. That is, since the battery cells that have reached the target voltage are sequentially deleted from the voltage table, if all of the battery cells in either the carry-out cell group or the reception cell group are deleted, the next cell group will be evenly distributed. This processing is terminated without performing the conversion. If both the export cell group and the reception cell group remain in the voltage table, the process returns to step 36 and the following processing is repeated to perform the next equalization processing.

According to the present embodiment, the voltage of the battery cell is measured when the main current is not flowing, so that a more accurate open-circuit voltage of the battery cell can be measured.
Therefore, a more appropriate take-out cell group and a receiving cell group can be selected based on the accurate open-circuit voltage.

As described above, when the main current is not flowing, the voltage of the battery cell is measured, and based on this voltage, the target voltage, the expected arrival time, and the battery cell voltage after voltage equalization are calculated. Since the equalization process is scheduled, it is not necessary to measure the battery cell voltage every one equalization cycle, and the battery cell voltage is equalized when necessary regardless of whether the main current is flowing. Can be. Furthermore, since the calculation of the estimated arrival time is performed using a method of approximating the voltage change of the battery cell voltage during the voltage equalization operation, the voltage equalization process can be performed more accurately.

[Second Embodiment] In the second embodiment, the same parts as those in the first embodiment will be described.
Description is omitted.

The operation according to the present embodiment will be described with reference to FIGS.

The cell voltage reading routine shown in FIG. 5 starts at a fixed time (for example, every 10 minutes). Step 3
0, in step 32, the voltage of each battery cell is stored in the voltage table as in the first embodiment. In step 70, a voltage data flag indicating that the voltage table has been updated is set, and the cell voltage reading routine ends. The voltage equalization process shown in FIG. 4 is performed based on the stored battery cell voltage data.

At step 60, the voltage data stored in the voltage table is read. In step 62, the set voltage data flag is reset. Steps 34 to 48 are performed in the same manner as in the first embodiment. At step 64, it is determined whether the voltage data flag is set. Here, when the voltage data flag is set, a new cell voltage is read during the equalization operation. It may take a considerable time before the equalization process for all cell voltages is completed, and each battery cell voltage may be replaced from the time when it was initially measured due to changes in the temperature distribution during that time. . Therefore, if the voltage data flag is set to continue the equalization process based on the voltage data updated at regular intervals, the process returns to step 60 and the voltage table is read again, and the following is performed. Repeat the process. If the voltage data flag is not set,
Since the data in the voltage table has not been updated, the process returns to step 36 as in the first embodiment, and the following processing is repeated.

According to the present embodiment, each battery cell voltage is measured at regular time intervals during the equalization process to update the voltage data, thereby scheduling the voltage equalization process.
More accurate voltage equalization processing can be performed.

[Third Embodiment] In the second embodiment, the description of the same parts as in the first and second embodiments will be omitted.

The operation according to the present embodiment will be described with reference to FIGS.

Step 3 of the voltage equalization process shown in FIG.
Steps 0 to 34 are performed in the same manner as in the first embodiment. In step 80, a carry-out / receive cell selection process shown in FIG. 7 is performed.

At step 82, higher than target voltage Vobj
Select a battery cell with a higher voltage, and
To V^p1 _k, V^p2 _lRank ‥‥. Step 84
Select a battery cell with a voltage lower than the target voltage Vobj
And V in order from the cell with the lowest voltage.^N1 _i, V^N2 _j‥‥ and ranking
Attach. Here, k, l, ‥‥ i, j are the battery cells.
One of the cell numbers sequentially assigned from the end based on the position of the cell
And battery cells in order from cell 1 located at one end.
Are provided, and a cell N is located at the other end. Stay
In step 86, the battery cell V having the highest cell voltage^p1But,
Whether the cell is located at the edge, ie, k = 1 or
It is determined whether k = N. Battery cell V^p1But at the end
If the cell is not located, the cells at both ends of the cell are charged.
Pressure V_{k + 1}And V_k-1Is greater than the target voltage Vobj
Judge whether or not. Cell k + 1 And the voltage V of k-1_{k + 1}You
And V_k-1Is larger than the target voltage Vobj,
In Step 90, V_{k + 1}> V_k-1Determine whether or not. V
_{k + 1}> V_k-1In the case of, the sum of the voltages of the cell group of k + 1 and k
V_{k + 1}+ V_kIs the sum V of the voltages of the cell group of k and k−1_k-1+ V
_kIn step 98, the cell is taken out.
And select k + 1 and k. V_{k + 1}> V_k-1If not
Is the sum V of the voltages of the cell group of k−1 and k_k-1+ V _kIs k
Sum V of the voltage of the cell group of +1 and k_{k + 1}+ V_kGreater than
In step 100, k−1 and
 Select k. At step 88, cell k + 1 And k−1
Voltage V_{k + 1}And V_k-1At least one of the target voltage
If it is smaller than Vobj, at step 94 the cell k + 1
Voltage V_{k + 1}Is greater than the target voltage Vobj.
Refuse. Voltage V of cell k + 1_{k + 1}Is larger than the target voltage Vobj
If it is, the cell is taken out in step 98 described above.
And select k + 1 and k. Voltage V of cell k + 1_{k + 1}Eyes
If it is smaller than the standard voltage Vobj, at step 96,
Voltage V of cell k-1_k-1Is greater than the target voltage Vobj
To determine Voltage V of cell k-1_k-1Is the target voltage Vobj
If it is greater than
Then, k−1 and k are selected as cells. Cell k−1
Pressure V_k-1Is smaller than the target voltage Vobj, the cell k +
1 And the voltage V of k-1_{k + 1}And V_k-1Both target power
Since it is smaller than the pressure Vobj, select
In step 102, only cell k is selected as the cell to be taken out.
Select. In step 86, the cell V having the highest voltage^p1But
When located at one end of the battery pack, that is, k = 1 or
If it is determined that k = N, at step 92, the cell k becomes k
It is determined whether it is at the position of = 1. Cell k is k = 1
If there is, there is no cell with k = k−1,
Proceeding to step 94 described above, the following processing is performed. Cell k is
If k = 1, k = N, and there is no cell with k = k + 1.
Since there is not, the process proceeds to step 96 described above, and the following processing is performed.
I do. After determining the export cell group as described above
Next, at step 104, the battery cell having the lowest cell voltage is set.
File as the receiving cell. Step 44 and below are the first
The processing is performed in the same manner as in the above embodiment, and this processing ends.

According to the present embodiment, when selecting a cell to be taken out, a battery cell having a voltage lower than the target voltage Vobj is not selected, so that a group of cells to be taken out having a higher voltage is constituted. As a result, the voltage difference between the brought-out cell group and the receiving cell group increases, and the voltage equalization process can be performed more quickly.

[Fourth Embodiment] In the fourth embodiment, the same parts as those in the above-described embodiment will be described.
The same symbols are given and the description is omitted.

As shown in FIG. 11, the battery cells 16
A, 16B, 16C ‥‥ 16N each have a resistor 7
8 and a switch 76 are connected in series (hereinafter referred to as a “discharge circuit”). The discharge circuit 74 turns on the switch 76 and discharges the charge of each battery cell through the resistor 78 to equalize the charge state of each battery cell. The control circuit 20 includes switches 76A, 76B, 76C # 7
6N, and controls ON / OFF of each switch. The charge pump capacitor 24 and the switching connection unit 22 provided in the power storage device according to the above-described embodiment are not provided.

FIG. 12A shows one battery cell 16.
A discharge circuit 74 connected to A is shown. Switch 76A
Is turned on, a current flows in the discharge circuit 74 in the W direction (this current is hereinafter referred to as a “bypass current”). The internal resistance Rin exists inside the battery cell 16A, and the inside of the battery cell 16A can be shown as in FIG.

Here, the resistance values of the resistors 78A, 78B, 78C ‥‥ 78N provided in each discharge circuit 74 are sufficiently larger than the internal resistances of the battery cells 16A, 16B, 16C, # 16N. And Usually 1000-10
It is desirable to make it about 000 times, but it is necessary to make it at least about 100 times.

Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG.

Steps 30 to 34 perform the same processing as in the above-described embodiment. In step 110, the estimated time to reach the target voltage tr to tn is set for each cell. Specifically, it is calculated based on the following concept.

First, in the discharge circuit 74 shown in FIG. 12A, when the switch 76A is turned on, the bypass current I _BP changes the battery cell voltage at time t to Vb.
(t), the discharge circuit resistance value is R _BP ,

[0091]

[Equation 19]

Is obtained.

Battery cell 16 by bypass current I _BP
The amount of change (Δ) from the initial capacity (Qs) of the quantity of electricity (Qb) of A
Q) is

[0094]

(Equation 20)

Is obtained.

The capacity Cb of the battery cell 16A is
It is considered to be constant regardless of changes in the battery cell voltage Vb and the initial voltage Vs of the battery cell 16A. The change in the amount of electricity ΔQ of the battery cell 16A due to the change in the battery cell voltage Vb is ΔQ = Cb · (Vs−Vb (t) ) (3-3)
Becomes

Normally, the quantity of electricity Q of the battery cell and the battery cell voltage (release voltage) V change as shown in FIG. 13 in the case of a lithium ion battery, but change over a narrow range (FIG. 13).
ΔV1, ΔV2), it can be seen that the relationship is almost proportional. Some values of Cb may be prepared depending on the region of V or Q.

From (3-1), (3-2) and (3-3),

[0099]

(Equation 21)

Assuming that 1 / (Cb · R _BP ) = α, the expression (3-
4) is Laplace transformed, provided that the initial value of the integral is 0,

[0101]

(Equation 22)

From equation (3-5), if Vs = Vs / s (unit step input Vs times),

[0103]

(Equation 23)

Is obtained. And inverse Laplace transform of equation (3-6), Vb (t) = Vs · e -α · t (3-7) is obtained, this way, the change of the battery cell voltage after t time prediction it can.

When a target voltage Vr is given, the time tr required to reach the target voltage Vr is given by the following equation (3-7).

[0106]

(Equation 24)

Is obtained.

Here, in (3-7), e ^−α · ^t = 1−
By approximating α · t, when a target voltage Vbr is given, the time tr required to reach the target voltage Vbr is:

[0109]

(Equation 25)

And can be predicted by a simple formula not using logarithm. If the discharge circuit is turned on for this time, it can be brought to the initially set target voltage.

Here, if α is small (Cb is large and 78A is large) or t is small, the degree of approximation is high, so care must be taken when approximating.

As described above, the time (expected arrival time) tr1 to trn for each battery cell required to reach the target voltage Vr can be set by the equation (3-9). It should be noted that the time calculated by Expression (3-8) before approximation may be used as the estimated arrival times tr1 to trn.

In step 112, switches 76A, 76B, 76C provided in the discharge circuit 74 of each battery cell
$ 76N is turned on for the expected arrival time calculated as described above. When the switch of the discharge circuit is turned on, a bypass current flows through the discharge circuit, and the resistors 78A, 78B, 7
Discharge starts from 8C ‥‥ 78N. By performing this discharge for the expected arrival time, the voltage of each battery cell becomes equal to the target voltage.

Here, when the main current flows, the main cell flows and the battery cell voltage fluctuates. Therefore, the influence thereof is taken into consideration.

As shown in FIG. 12 (B), assuming that the internal resistance of the battery is R _IN and the main current is I _M , at this time, the current I _MBP of the main current I _M flowing through the discharge circuit 74 is

[0116]

(Equation 26)

Is obtained. Therefore, if the battery internal resistance R _IN is sufficiently small or the resistance value R _BP of the resistor 78A is sufficiently large, the current I _MBP flowing through the discharge circuit 74 is sufficiently small, and even if the main current I _M flows, the bypass current is reduced. _IBP will not be affected.

Normal battery internal resistance R_INIs about 3-5mΩ
Therefore, the resistance value R of the resistor 78A_BPTo about 30-50Ω
If you choose, the main current I_MFlows to the discharge circuit 74 when
Current I_MBPIs about 5 mA (I_M1/1000)
Is originally the bypass current I _BPIs 1 at battery voltage 3.6V
20 to 72 mA, the current I
_MBPIs about 7%. The main current I_MIs special
In the case of a hybrid car, it always flows in the same direction
Not necessarily, on average, plus and minus
Because it is considered, the current component flowing through the discharge circuit 74 is actually
I_MBPImpact both positive and negative, and
It is considered to be a storm. Therefore, even in this case, the main current is
It is not necessary to consider the fluctuation due to the flow.
Call Note that the resistance value R of the resistor 78 is_BPIs at least a battery
Internal resistance R_INShould be about 100 times the
It is desirable to make it about 000 to 10000 times.

At step 114, it is determined whether or not the estimated arrival time has elapsed for all the battery cells.
If the estimated arrival times have not elapsed for all the battery cells, the process waits until the estimated arrival times have elapsed. If the estimated arrival times have elapsed, the process ends.

According to the present embodiment, a simpler circuit (discharge circuit) can be provided, and voltage equalization can be performed at low cost. In addition, since the resistance value of the resistor in the discharge circuit is set to a sufficiently large value compared to the resistance value inside the battery cell, even if the main current flows, the influence on the current value flowing in the discharge circuit is small, and Irrespective of whether or not the current flows, the absolute value of the current flowing in the discharge circuit also becomes small, and the effect of eliminating the need for heat generation can be obtained. Furthermore, according to the present embodiment, the calculation of the expected time to reach the target voltage, that is, the time to discharge from the resistor, is performed in consideration of the fact that the battery cell voltage changes during discharge and the bypass current value also changes. Therefore, more accurate discharge can be performed, and discharge can be performed more appropriately.

[0121]

As described above, according to the present invention, each voltage of the power storage means detected when no current flows from the power storage means, that is, the power storage means is influenced by its internal resistance and the like. Since the power storage means is equalized based on an accurate voltage in a state where the power storage means is not received, there is an advantageous effect that accurate and appropriate equalization can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power storage device according to first, second, and third embodiments.

FIG. 2 is a flowchart illustrating a voltage equalization process according to the first embodiment.

FIG. 3 is a flowchart illustrating a part of a voltage equalization process according to the first embodiment.

FIG. 4 is a flowchart illustrating a voltage equalization process according to a second embodiment.

FIG. 5 is a flowchart illustrating a cell voltage reading process according to a second embodiment.

FIG. 6 is a flowchart illustrating a voltage equalization process according to a third embodiment.

FIG. 7 is a flowchart illustrating part of a voltage equalization process according to a third embodiment.

FIG. 8 is a graph showing a relationship between a cell voltage distribution and an average voltage after voltage equalization.

FIG. 9 is a block diagram showing a cell voltage change during an equalizing operation.

FIG. 10 is a graph showing a relationship between f (t) = e ^−at and f (t) = 1−at.

FIG. 11 is a circuit diagram of a power storage device according to a fourth embodiment.

FIG. 12 is a discharge circuit diagram of one battery cell according to a fourth embodiment.

FIG. 13 is a graph showing a relationship between a battery voltage and a battery capacity in the fourth embodiment.

FIG. 14 is a flowchart illustrating a voltage equalization process according to a fourth embodiment.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 power storage device 14 ammeter (detection means) 16A, 16B, 16C セ ル 16N battery cell (power storage means) 18A, 18B, 18C ‥‥ 18N voltage measuring instrument (voltage detection means) 20 control circuit (control means) 22 switching connection Unit 24 Battery 76A, 76B, 76C @ 76N Switch 78A, 78B, 78C @ 78N Resistor (discharge means)

Claims (6)

[Claims] A plurality of power storage means connected in series; a voltage detection means for detecting a voltage of each of the power storage means; a detection means for detecting whether or not a current flows from the power storage means; Based on each voltage of the power storage means detected by the voltage detection means when it is detected that no current is flowing by the detection means, equalization means for equalizing the amount of power stored in the plurality of power storage means, Power storage device provided with. 2. The equalizing means, comprising: a power storage device connectable to each of the power storage means; and a moving means for moving a charge from at least one power storage means to at least one other power storage means via the power storage device. Based on the voltage of each of the power storage means, for equalizing the amount of power stored in the plurality of power storage means, a discharge power storage means for discharging electric charge, a receiving power storage means for receiving the discharged electric charge, and Determining means for determining the amount of charge transfer from the means to the receiving and storing means; and controlling the moving means such that the amount of charge transfer determined by the determining means moves from the discharging and storing means to the receiving and storing means. The power storage device according to claim 1, further comprising: control means. 3. The method according to claim 2, wherein the number of the discharged power storage means is N, the n-th voltage of the discharged power storage means is Vns, and the n-th voltage of the discharged power storage means after equalization is equal to n.
Vn (t), the mth voltage of the receiving and storing means is Vrms, the mth target voltage of the receiving and storing means after equalization is Vrm (t), and the electric capacity of the storing means. Is Cb, the electric capacity of the capacitor is Cc, the cycle in which the charge is transferred from the release storage unit to the reception storage unit via the storage unit is Ti, and the period when the charge is transferred from the release storage unit to the storage unit is Ti. Η is a coefficient in consideration of the charge loss, and λ is a coefficient in consideration of the charge loss when the charge is transferred from the battery to the receiving and storing means. The power storage device according to claim 2, wherein a charge that moves by moving the charge by the moving unit for a short time is determined as the charge transfer amount. (Equation 1) Where: 4. The equalizing unit includes: a discharging unit configured to discharge an amount of electricity from the power storage unit; and an electric power unit configured to equalize the storage amounts of the plurality of power storage units based on respective voltages of the power storage unit. Discharge storage means for discharging an amount, determining means for determining a charge discharge amount discharged from the discharge storage means, and the discharging so that the charge discharge amount determined by the determining means is discharged from the discharge storage means. The power storage device according to claim 1, further comprising control means for controlling the means. 5. The discharge means has a resistance value for consuming electric charge from the power storage means, the resistance being 100 times or more the resistance value inside the power storage means. 4. The power storage device according to 4. Wherein said determining means, Vr target voltage after equalization, the capacitance of the accumulator unit Cb, the next a voltage of the storage means the resistance value of V _S the resistor R _BP, as 2 Time tr1 or t calculated from the formula
The power storage device according to claim 5, wherein the amount of electricity discharged during any one of r2 is determined as the amount of charge discharged by the discharging unit. (Equation 3) (Equation 4) Where α = 1 / (Cb · R _BP )