JP2004031123A - Capacity calculation method and device for battery pack connected in parallel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacity calculation method for a battery pack capable of correctly calculating the capacity of the battery by considering states of cells connected in parallel with one another. <P>SOLUTION: A CPU 102 (not shown) is used for obtaining a curve Wh(P/α) by carrying out temperature correction of an initial characteristic Wh(P) of the battery pack by a temperature correction coefficient α. The characteristic curve after the temperature correction is further corrected by an internal resistance deterioration correction coefficient γ to obtain a curve Wh(P/αγ). The characteristic curve after the internal resistance deterioration correction is further corrected by a capacity deterioration correction coefficient β to obtain a curve βWh(P/αγ). The characteristic curve after the capacity deterioration correction is further corrected by a parallel internal resistance deterioration correction coefficient Γ to obtain a curve βWh(P/αγΓ). The characteristic curve after the parallel internal resistance deterioration correction is further corrected by a parallel capacity deterioration correction coefficient B to obtain a curve βBWh(P/αγΓ). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for calculating the capacity of batteries connected in parallel.
[0002]
[Prior art]
Power-discharge power characteristics are known as one of the characteristics of a rechargeable secondary battery. In general, the battery capacity is calculated using reference characteristics obtained by correcting the basic initial characteristics Wh with a temperature correction coefficient α, a battery capacity deterioration correction coefficient β, and an internal resistance deterioration correction coefficient γ. The temperature correction coefficient α is derived from a change rate at which the internal resistance of the battery changes according to the temperature of the battery. An example of a method of calculating the capacity deterioration correction coefficient β and the internal resistance deterioration correction coefficient γ is described in Japanese Patent Application Laid-Open No. 2000-261901. In the method described in the above publication, the open-circuit voltage of the secondary battery is calculated by one of the following methods when calculating the correction coefficient.
1. Obtain and measure the terminal voltage when there is no load.
2. The estimation is made based on IV characteristics obtained from a plurality of current values and voltage values measured during charging and discharging.
3. The estimation is performed based on the current value and the total voltage value measured during charging and discharging.
As described above, the voltage measurement of the battery is indispensable in any method.
[0003]
[Problems to be solved by the invention]
There is a demand to calculate the battery capacity of a battery in which a plurality of secondary cells are connected in parallel. When batteries are connected in parallel, current flows from the battery with the higher voltage to the battery with the lower voltage. This current is called an adjustment current and flows so as to match the terminal voltage between the batteries. Therefore, it is difficult to calculate the battery capacity in consideration of the state of each unit cell because the actual open-circuit voltage of each unit cell is not known even when the terminal voltage of the unit cells connected in parallel is measured. is there.
[0004]
An object of the present invention is to provide a method and an apparatus for calculating the capacity of a battery pack that correctly calculate the capacity of a battery in consideration of the state of cells connected in parallel.
[0005]
[Means for Solving the Problems]
The present invention relates to a method of calculating the discharge capacity of a battery pack in which a plurality of parallel cells in which a plurality of secondary cells are connected in parallel is connected. The internal resistance is calculated for each of the parallel batteries from the characteristics of the current value of the assembled battery, and the internal resistance is calculated using the maximum value of the calculated internal resistance and the internal resistance values of the parallel batteries other than the parallel battery corresponding to the maximum value. Estimate the maximum value of the internal resistance of the unit cells constituting the parallel battery having the maximum value. Then, the average value of the internal resistance of the cells constituting the parallel battery is calculated using the average value of the internal resistances of the parallel batteries other than the parallel battery having the maximum internal resistance, and the average value of the internal resistance of the cells and The discharge capacity of the parallel battery is corrected by the ratio of the maximum value.
[0006]
Further, the present invention relates to a capacity calculating device for battery packs connected in parallel, wherein a plurality of secondary cells are connected in parallel, and a voltage of each of the parallel batteries is discharged at the time of discharging the battery pack in which a plurality of the parallel batteries are connected in series. And, when the battery pack is discharged, the current flowing through the battery pack is detected, and the internal resistance of each of the parallel batteries is calculated based on the detected voltage and current. By using the extracted internal resistance of the parallel battery and the internal resistance of the parallel battery other than the extracted parallel battery, the maximum value of the internal resistance of the unit cell constituting the extracted parallel battery is calculated. Using the estimated and extracted average value of the internal resistance of the parallel batteries other than the parallel battery, the average value of the internal resistance of the cells constituting the parallel battery is calculated, and the average value of the internal resistance of the cells and the average value of the cells are calculated. Maximum value of battery internal resistance Using a ratio, to calculate the parallel internal resistance deterioration correction factor, in the calculated parallel internal resistance deterioration correction coefficient is obtained so as to correct the discharge capacity of the parallel batteries.
[0007]
【The invention's effect】
According to the present invention, since the capacity calculation is performed in consideration of the state of the unit cells connected in parallel, the capacity of the battery pack connected in parallel can be calculated correctly.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a vehicle equipped with a control unit for calculating the capacity of a battery pack by the method according to the present invention. In the following embodiment, an example in which the assembled battery is applied as a power source of an electric vehicle will be described. In FIG. 1, the vehicle control system includes a vehicle system and a battery control unit. The thick solid line in the figure represents a high-voltage line (high-voltage wiring), and the normal solid line represents a low-voltage line (low-voltage wiring). Dashed lines indicate signal lines transmitted and received between each block.
[0009]
The vehicle system includes a current sensor 201, a voltage sensor 202, a temperature sensor 203, a driving motor 301, an auxiliary system 302, and main relays 303A and 303B. The assembled battery includes secondary cells (cells) C1 to C8. The cells C1 and C2, the cells C3 and C4, the cells C5 and C6, and the cells C7 and C8 are connected in parallel, respectively. In the battery pack, these four parallel batteries (C1, C2), parallel batteries (C3, C4), parallel batteries (C5, C6), and parallel batteries (C7, C8) are connected in series. The battery control unit has a cell voltage detection unit 101, a CPU 102, and a memory 103.
[0010]
The driving motor 301 generates driving power for the vehicle by the electric power supplied from the battery pack, and also generates regenerative power for the battery pack. The auxiliary system 302 drives an air conditioner (A / C) (not shown) mounted on the vehicle with electric power supplied from the battery pack. The main relays 303 </ b> A and 303 </ b> B are controlled to open and close according to a command from the CPU 102, and turn on / off power supply to the drive motor 301 and the auxiliary system 302.
[0011]
The current sensor 201 detects a current flowing through the high-power line, and sends a detection signal to the CPU 102. Voltage sensor 202 detects the voltage (total voltage) of the assembled battery and sends a detection signal to CPU 102. Temperature sensor 203 detects the temperature of the battery pack and sends a temperature detection signal to CPU 102.
[0012]
The cell voltage detection unit 101 includes a terminal voltage of the parallel batteries (C1, C2), a terminal voltage of the parallel batteries (C3, C4), a terminal voltage of the parallel batteries (C5, C6), and a terminal voltage of the parallel batteries (C7, C8). , And sends out four sets of voltage information to the CPU 102. The CPU 102 calculates the maximum charging power during charging (regeneration) and the maximum discharging power during discharging using the voltage information of the four parallel batteries. The calculation of the maximum charge / discharge power is performed when the vehicle is running (when the IGN switch is on) and when the battery pack is charged. The calculation result of the maximum charge / discharge power is transmitted from CPU 102 to vehicle system CPU 304. Further, when the temperature of the battery pack is abnormal, the CPU 102 notifies the vehicle system CPU 304 of the abnormal temperature.
[0013]
The memory 103 stores the voltage information of the four sets of parallel batteries, the information of the current of the high-power line, and the like input to the CPU 102.
[0014]
Vehicle system CPU 304 controls the vehicle system by limiting the power output from the assembled battery so that the power output to drive motor 301 and accessory system 302 is equal to or less than the maximum discharge power received from CPU 102. Further, vehicle system CPU 304 controls the vehicle system by limiting the power for charging the assembled battery so that the power regenerated from drive motor 301 is equal to or less than the maximum charging power received from CPU 102. The vehicle warning light 305 is turned on by a command from the vehicle system CPU 304 to notify the driver of the occurrence of an abnormality in the vehicle system. The auxiliary battery 401 supplies power to the CPU 102 and the vehicle system CPU 304. The switch SW turns on / off power supply from the auxiliary battery 401 in conjunction with turning on / off of an ignition (IGN) switch 402 by the driver.
[0015]
FIG. 2 is a diagram illustrating the power versus discharge power (capacity) characteristics of the battery pack calculated by the method according to the present invention. The power-to-discharge power characteristic is one of the characteristics representing the battery state of the secondary battery. In FIG. 2, the horizontal axis represents the output power P of the battery, and the vertical axis represents the discharge power amount Wh. In general, the curve Wh (P) indicating the initial characteristics of the battery can be approximated by the n-th order expression of the outputable power P. The approximate expression will be described later. The curves Wh (P) indicating the discharge capacities are respectively corrected by the following correction coefficients.
(1) Temperature correction coefficient α
(2) Internal resistance deterioration correction coefficient γ
(3) Capacity deterioration correction coefficient β
(4) Parallel internal resistance deterioration correction coefficient of battery packΓ
(5) Parallel capacity deterioration correction coefficient of battery packΒ
[0016]
The curve Wh (P / α) in FIG. 2 is obtained by correcting the initial characteristic Wh (P) with the temperature correction coefficient α. The curve Wh (P / αγ) is obtained by further correcting the characteristic curve after the temperature correction by the internal resistance deterioration correction coefficient γ. The curve β · Wh (P / αγ) is obtained by further correcting the characteristic curve after the internal resistance deterioration correction by the capacitance deterioration correction coefficient β.
[0017]
The curve β · Wh (P / αγΓ) is obtained by further correcting the characteristic curve after the capacity deterioration correction by the parallel internal resistance deterioration correction coefficient Γ. The curve β · Β · Wh (P / αγΓ) is obtained by further correcting the characteristic curve after the parallel internal resistance deterioration correction by the parallel capacitance deterioration correction coefficient Β. The power-discharge power characteristic β · β · Wh (P / αγΓ) thus obtained is used as a reference characteristic indicating the discharge capacity of the battery pack.
[0018]
The present invention is characterized in that the calculation of the discharge capacity is corrected, in particular, by the above (4) parallel internal resistance deterioration correction coefficient Γ and (5) parallel capacity deterioration correction coefficient Β.
[0019]
The temperature correction coefficient α, the internal resistance deterioration correction coefficient γ, and the capacity deterioration correction coefficient β of the above ( ₁ ) to ( ₃ ) are four sets of parallel batteries C (P ₁ ) (single cells C1 and C2) constituting the assembled battery. ), Parallel battery C (P ₂ ) (comprising cells C3 and C4), parallel battery C (P ₃ ) (comprising cells C5 and C6), and parallel battery C (P ₄ ) (cell C7) And C8) are calculated as coefficients for correcting the average discharge capacity of the parallel batteries.
[0020]
Taking the case of a lithium ion battery as an example, the curve Wh (P) can be approximated by the following equation (1).
(Equation 1)
Wh (P) = aP ³ + bP ² + cP + d (1)
However, the coefficients a, b, c and d are determined from the characteristics of the initial battery.
[0021]
When the temperature correction coefficient α is used to perform temperature correction on the above equation (1), the curve Wh (P / α) equation after the temperature correction is expressed by the following equation (2).
(Equation 2)
Wh (P / α) = a (P / α) ³ + b (P / α) ² + c (P / α) + d (2)
[0022]
The temperature correction coefficient α is a parameter indicating a change in the internal resistance of the battery depending on the temperature. Generally, the internal resistance of a battery decreases with increasing battery temperature. Therefore, the relationship between the temperature and the internal resistance is actually measured in advance and tabulated, and a temperature correction coefficient α is given in the form of a table reference value corresponding to the temperature. The table reference value is stored in the memory 103.
[0023]
When the deterioration correction for the above equation (2) is performed using the internal resistance deterioration correction coefficient γ and the capacity deterioration correction coefficient β, the curve Wh (P / αγ) × β after the deterioration correction is expressed by the following equation (3).
[Equation 3]
Wh (P / αγ) × β
= Β {a (P / αγ) ³ + b (P / αγ) ² + c (P / αγ) + d} (3)
[0024]
The CPU 102 in FIG. 1 calculates the above γ and β in the following procedure.
1. The terminal voltage and current are measured for each parallel battery.
2. The average of the voltage of each parallel battery is calculated.
3. The internal resistance deterioration correction coefficient γ is calculated.
4. The capacity deterioration correction coefficient β is calculated.
[0025]
1. The CPU 102 measures the terminal voltage and current of each parallel battery. The CPU 102 detects four sets of terminals of the parallel batteries C (P ₁ ), C (P ₂ ), C (P ₃ ), and C (P ₄ ) from the cell voltage detection unit 10. The information indicating the voltage is input, and the information indicating the current of the high-power line is input from the current sensor 201. The value of the current flowing through the high voltage line is equal to the value of the current of each parallel battery.
[0026]
2. Calculation of Voltage Average of Parallel Battery The CPU 102 calculates the average value V (Pave) of the voltage values V (P ₁ ) to V (P ₄ ) of each parallel battery indicated by the input voltage information.
[0027]
3. Calculation of Internal Resistance Degradation Correction Coefficient γ The CPU 102 performs a linear regression calculation of the IV characteristics of the parallel battery using the average voltage V (Pave) and the current value of the parallel battery obtained by a plurality of measurements during discharging. FIG. 3 is a diagram for explaining a regression line, which is obtained from the measured data of the current I and the voltage V of a parallel battery being discharged. Lithium-ion batteries, nickel-metal hydride batteries, and the like have good linearity of IV characteristics at the time of discharge, so that the regression line can be extended based on measured data. The crosses in the figure represent measurement data. The regression line in this case can be expressed by the following equation (4).
(Equation 4)
V (Pave) = E ₀ (Pave) −I × R (Pave) (4)
Here, V (Pave) is the average terminal voltage of the parallel batteries, the V-axis intercept E ₀ (Pave) is the average open-circuit voltage of the parallel batteries, and the slope R (Pave) of the regression line is the average internal resistance of the parallel batteries.
[0028]
The CPU 102 sets the reciprocal of the rate of increase of the internal resistance average R (Pave) as the internal resistance deterioration correction coefficient γ. Specifically, the ratio of the internal resistance average R0 (Pave) obtained in the initial state of the battery to the internal resistance average R1 (Pave) obtained in the deteriorated state of the battery is calculated, and the internal resistance is calculated by the following equation (5). The deterioration correction coefficient γ is calculated.
(Equation 5)
γ = R0 (Pave) / R1 (Pave) (5)
[0029]
4. Calculation of Capacity Deterioration Correction Coefficient β FIG. 4 is a diagram showing the relationship between the discharge capacity (Ah) actually measured in the initial state of the parallel battery and the open circuit voltage. As the map data according to FIG. 4, data actually measured in advance is stored in the memory 103. The CPU 102 compares the amount of electricity measured during the discharge with the capacity based on the map data. Specifically, the electric current value at a predetermined time during the discharge is integrated to calculate the amount of discharged electricity Ahd, the open-circuit voltage average value E ₁ (Pave) at the start of the integration of the current value, and the integration of the current value The open-circuit voltage average value E ₂ (Pave) at the end is obtained by the regression calculation. CPU102 calculates a capacity difference ΔAh corresponding to the difference between _{E 1} and _{E 2} (Pave) in FIG. 4, to calculate the capacity deterioration correction factor β according to the following equation (6).
(Equation 6)
β = Ahd / ΔAh (Pave) (6)
As described above, the temperature correction coefficient α, the average internal resistance deterioration correction coefficient γ of the parallel batteries constituting the assembled battery, and the average capacity deterioration correction coefficient β of the parallel batteries are obtained.
[0030]
When the deterioration correction for the above equation (3) is performed using the parallel internal resistance deterioration correction coefficient Γ and the parallel capacity deterioration correction coefficient Β of the entire assembled battery, the curve Wh (P / αγΓ) × β × Β after deterioration correction is expressed by the following equation ( 7).
(Equation 7)
Wh (P / αγ) × β × Β
= ΒΒ ｛{a (P / αγΓ) ³ + b (P / αγΓ) ² + c (P / αγΓ) + d｝ (7)
[0031]
CPU calculates parallel internal resistance deterioration correction coefficient で in the following procedure.
1. The terminal voltage and current are measured for each parallel battery.
2. Calculate the maximum discharge power for each parallel battery.
3. The one with the smallest maximum discharge power is extracted.
4. The largest internal resistance R _C max among the cells constituting the extracted parallel battery is estimated.
5. The ratio between the internal resistance R _C max and the internal resistance R _C ave of another unit cell is calculated, and is set as a parallel internal resistance deterioration correction coefficient Γ.
[0032]
1. Measurement of Terminal Voltage and Current for Each Parallel Battery The measurement is the same as that described in the calculation of the internal resistance deterioration correction coefficient γ and the capacity deterioration correction coefficient β, and thus the description is omitted. The data measured when calculating γ and β may be used as is, or newly measured data may be used.
[0033]
2. Calculation of maximum discharge power for each parallel battery CPU 102 performs a linear regression operation on the IV characteristics of each parallel battery using the voltage value indicated by the input voltage information and the current value indicated by the current information. The regression line in this case can be expressed by the following equation (8).
(Equation 8)
V (P) = E ₀ (P) −I × R (P) (8)
Here, V (P) is the terminal voltage of the parallel battery, the V-axis intercept E ₀ (P) is the open voltage of the parallel battery, and the slope R (P) of the regression line is the internal resistance of the parallel battery.
[0034]
FIG. 5 is a diagram for explaining the regression line of the above equation (8), which is obtained from measurement data of the current I and the voltage V of the parallel battery being discharged. Lithium-ion batteries and nickel-metal hydride batteries have almost the same internal resistance during charging and discharging, and have good linearity of IV characteristics during charging and discharging. The regression line can be extended to the charging side. The crosses in the figure represent measurement data.
[0035]
In FIG. 5, the current Imax (P) at the intersection B of the regression line and the discharge stop voltage Vmin (P) during discharge gives the maximum discharge current of the parallel battery. The maximum discharge power Pmax (P) of the parallel battery is calculated by the following equation (9) using the above equation (8).
(Equation 9)
Pmax (P) = Vmin (P) × Imax (P)
= Vmin (P) × (E ₀ (P) −Vmin (P)) / R (P) (9)
[0036]
3. The CPU 102 extracts the parallel battery with the minimum maximum discharge power. The CPU 102 calculates the maximum discharge power Pmax (P ₁ ), Pmax (P ₂ ) of the four parallel batteries C (P ₁ ) to C (P ₄ ) calculated as described above. , Pmax (P ₃ ) and Pmax (P ₄ ) are extracted. Hereinafter, the extracted minimum value is referred to as Pmax (Pmin). The parallel battery corresponding to Pmax (Pmin) is denoted by C (Pmin), and the internal resistance of this parallel battery C (Pmin) is denoted by R (Pmin).
[0037]
4. The CPU 102 estimates the largest internal resistance R _C max among the cells constituting the parallel battery C (Pmin). The CPU 102 determines that only one cell among the extracted cells constituting the parallel battery C (Pmin) is the other. Assume that the internal resistance is higher than that of a single cell. That is, in the case where the battery pack is composed of eight cells C1 to C8 as an example, one cell deteriorates, its internal resistance R _C max increases, and the cells of the other seven cells _{C1 to} C8 increase. It is assumed that the internal resistance takes the same normal value. The internal resistance R (Pmin) of the parallel battery C (Pmin) is given by the following equation (10).
(Equation 10)
R (Pmin) = ( _RC max × _RC cave ⁽ⁿ⁻¹⁾ ) / ( _RC max + (n−1) × _RC cave) (10)
However, R C _ave is the average value of the internal resistance of the normal unit cells. n is the number of cells constituting the parallel battery. In the example of FIG. 1, n = 2.
[0038]
Mean value _R C ave of the internal resistance of each cell is given by the following equation (11).
[Equation 11]
_{R (P) ave = R C} ave n / (n × R C ave) (11)
Here, R (P) ave is the average value of the internal resistance R (P) of the parallel batteries C (P) other than the parallel battery C (Pmin). n is the number of cells constituting the parallel battery.
[0039]
The CPU 102 calculates the internal resistances R (P) of the parallel batteries C (P) other than the parallel battery C (Pmin), calculates the average value of these internal resistances R (P), and calculates Then, the average value R _C ave of the internal resistance of the cell is calculated. The calculated average value R _C ave is further substituted into the above equation (10) to calculate the internal resistance R _C max.
[0040]
5. Calculation of ratio of internal resistance R _C max to internal resistance R _C ave of another unit cell CPU 102 calculates R _C max / R _C ave. R _C max / R _C ave is called an internal resistance maximum cell ratio (R (Pmin) ratio), and the reciprocal R _C ave / R _C max is set as a parallel internal resistance deterioration correction coefficient Γ of the assembled battery (Equation 12).
(Equation 12)
_{Γ = R C ave / R C} max (12)
[0041]
The CPU 102 calculates the parallel capacity deterioration correction coefficient Β as follows. The CPU 102 compares the capacity of each parallel battery obtained from the map data with the amount of electricity measured during discharging. When calculating the capacity deterioration correction coefficient β described above, the actually measured amount of electricity was compared with the average discharge capacity of the parallel batteries, but here, instead of the average capacity of the parallel batteries, the actually measured amount of electricity and each parallel battery were used. In comparison with the discharge capacity. More specifically, the electric current value at a predetermined time during the discharge is integrated to calculate the discharge electricity amount capAh, and the open-circuit voltage value E ₁ (P) at the start of the current value integration and the end of the current value integration are calculated. The open-circuit voltage value E ₂ (P) at the time is obtained for each parallel battery by the regression calculation. CPU102 calculates a capacity difference corresponding to the difference between _{E 1} and _{E 2} of each parallel battery .DELTA.Ah (P) in FIG. 4, is calculated by the following equation (13) the capacity deterioration factor (Ahratio).
(Equation 13)
Ahratio = capAh / ΔAh (P) (13)
[0042]
The CPU 102 sets the minimum value among the capacity deterioration coefficients (Ahratio) of the respective parallel batteries to Ahratiomin. The CPU 102 further calculates an average value Ahratioave of the capacity deterioration coefficient (Ahratio) of each parallel battery, and calculates a parallel battery capacity deterioration correction coefficient の of the entire assembled battery using the following equation (14).
[Equation 14]
Β = (Ahratioave- (Ahratioave-Ahratiomin) × n) / Ahratioave (14)
Here, n is the number of cells constituting the parallel battery.
[0043]
The embodiments described above are summarized.
(1) connected to the single batteries C1 and C2 parallel cell C connected in parallel _{(P 1),} and unit cell C3 and C4 the parallel battery C connected in parallel _{(P 2),} the unit cells C5 and C6 in parallel The assembled parallel battery C (P ₃ ) and the parallel battery C (P ₄ ) in which the unit cells C7 and C8 are connected in parallel are connected in series to form an assembled battery. The CPU 102 measures the relationship between the temperature and the internal resistance in advance and forms a table, and refers to the table data as a temperature correction coefficient α.
(2) The current flowing through the battery pack is detected by the current sensor 201, and the terminal voltage of each parallel battery constituting the battery pack is detected by the cell voltage detection unit 101. The CPU 102 performs a linear regression calculation on the IV characteristics of the parallel battery using the average voltage V (Pave) and the current value of the parallel battery obtained by a plurality of measurements during discharging, and calculates the average internal resistance R (Pave) of the parallel battery. The reciprocal of the rate of increase is taken as the internal resistance deterioration correction coefficient γ.
(3) The CPU 102 integrates the current value during a predetermined time during the discharge to calculate the amount of discharged electricity Ahd, and calculates the open-circuit voltage average value E ₁ (Pave) at the start of the integration of the current value and the current value. The open-circuit voltage average value E ₂ (Pave) at the end of the integration is obtained by regression calculation. CPU102 is capacitance difference .DELTA.Ah corresponding to the difference between _{E 1} and _{E 2} a (Pave) calculated from the map data of FIG. 4, the capacity deterioration correction coefficient β taking the ratio of the Ahd and .DELTA.Ah (Pave).
[0044]
(4) The CPU 102 pays attention to the parallel battery C (Pmin) in which the internal resistance R (P) of the parallel battery C (Pmin) has the maximum value, and the inside of one of the cells constituting the parallel battery. Assuming that the resistance rises as compared with the internal resistance of the other cells and has a maximum value R _C max, and the internal resistance of the other cells takes the same normal value, the internal resistance maximum cell ratio R _C max / Calculate R _C ave. CPU102 was the reciprocal _R C ave _{/ R} C max of the internal resistance maximum cell ratio as a parallel internal resistance deterioration correction coefficient Γ of the battery pack. R _C ave is an internal resistance of the other unit cell which is calculated from the internal resistance R (P) in parallel batteries other than parallel cell C (Pmin). Since the parallel internal resistance deterioration correction coefficient Γ is calculated using the internal resistance maximum cell ratio, it is possible to obtain a correction coefficient corresponding to the battery having the lower capacity of the unit cells constituting the parallel battery. Furthermore, since it is assumed that the internal resistance of one of the cells constituting the parallel battery C (Pmin) increases and takes the maximum value R _C max, the correction coefficient is calculated by assuming the worst value of the internal resistance. Can be calculated. As a result, the battery can be used in an appropriate region so that the used battery voltage does not deviate from the upper and lower limit values in any of the cells constituting the assembled battery, and the battery can be prevented from being deteriorated.
[0045]
The above (4) will be supplementarily described. FIG. 6 is a diagram illustrating a parallel battery in which two unit cells V1 and V2 are connected in parallel. When a load is connected to the parallel battery, the parallel battery passes a current I to the load. The cell voltage detection unit 101 detects a terminal voltage V under load. In a state where the SOC (charging state) of the cell V1 is higher than the SOC of the cell V2 and a capacity adjustment current flows from the cell V1 to the cell V2, a part of the current I1 of the cell V1 flows to the cell V2. Flows. When the adjustment current flows from the battery with the higher voltage to the battery with the lower voltage due to the variation in the voltage of the cells in the parallel cells, the open voltages of the two cells take different values. FIG. 7 is a diagram illustrating the terminal voltage detected by the cell voltage detection unit 101 over time, and the open-circuit voltage of each cell. In FIG. 7, the horizontal axis represents time, and the vertical axis represents voltage. The curve V indicates the terminal voltage of the parallel battery, the curve _E01 indicates the open voltage of the cell V1, and the curve _E02 indicates the open voltage of the cell V2. FIG. 7 shows that even when the terminal voltage V of the parallel battery does not fall below the lower voltage limit when the battery is used, the open voltage of the cell V2 may be lower than the lower voltage limit. The calculation method according to the present invention calculates the discharge capacity of the assembled battery such that the battery voltage of the unit cell having the lower battery voltage among the parallel batteries does not fall below the lower limit.
[0046]
(5) When calculating the parallel capacity deterioration correction coefficient Β as a battery pack, a parallel battery having a minimum capacity deterioration coefficient (Ahratio) is extracted, and the capacity deterioration coefficient of this parallel battery and the capacity deterioration coefficient of the parallel battery are extracted. It is possible to use the battery in an appropriate area so that the battery voltage of all the parallel batteries does not exceed the upper and lower limits, and prevent the battery from deteriorating. can do. Note that the capacity deterioration coefficient (Ahratio) is a coefficient indicating the capacity of each parallel battery, and a parallel battery with the smallest capacity deterioration coefficient can be regarded as a parallel battery whose capacity deterioration has progressed compared to other parallel batteries.
[0047]
The number n of unit cells constituting the parallel battery and the number m of parallel batteries connected in series used in the above description are not limited to the above-described example, and may be set as appropriate.
[0048]
In the above description, the open-circuit voltage of the parallel battery is estimated by a regression line. The reason for this is that the estimated open-circuit voltage and the actual open-circuit voltage of a battery having good linearity of the charge-discharge IV characteristics are well matched.
[0049]
As a method of obtaining the open-circuit voltage of the parallel battery, the open-circuit voltage may be obtained by measuring the voltage at no load instead of the above estimation.
[0050]
Correspondence between each component in the claims and each component in the embodiment of the invention will be described. The assembled battery includes, for example, the cells C1 to C8. Parallel connection cells, for example, parallel cell C _(P 1) connected single cells C1 and C2 in parallel, the parallel batteries C _(P 2) of the unit cells C3 and C4 are connected in parallel, parallel single cells C5 and C6 It constituted by connecting in parallel cell C _(P 3), and parallel battery C _{(P 4)} of the unit cell C7 and C8 are connected in parallel to the. Further, the voltage sensor 202 is a voltage detecting unit, the current sensor 201 is a current detecting unit, and the CPU 102 is an internal resistance calculating unit, an extracting unit, an estimating unit, an average value calculating unit, a correction coefficient calculating unit, and a discharge capacity correcting unit. Configure each. Note that each component is not limited to the above configuration as long as the characteristic functions of the present invention are not impaired.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a vehicle equipped with a control unit for calculating a discharge capacity of a battery pack by a method according to the present invention.
FIG. 2 is a diagram illustrating power versus discharge power characteristics of a battery pack.
FIG. 3 is a diagram illustrating a regression line.
FIG. 4 is a diagram illustrating a relationship between a measured discharge capacity and an open circuit voltage in an initial state of a parallel battery.
FIG. 5 is a diagram illustrating a regression line.
FIG. 6 is a diagram showing a parallel battery in which two unit cells are connected in parallel.
FIG. 7 is a diagram showing a terminal voltage of a parallel battery and an open voltage of each cell.
[Explanation of symbols]
101: cell voltage detection unit, 102: CPU,
103: memory, 201: current sensor,
304: vehicle system CPU, C1 to C8: single cells

Claims (4)

A method for calculating the discharge capacity of a battery pack in which a plurality of secondary cells are connected in parallel and the plurality of parallel batteries are connected in series,
Detecting the voltage of each of the parallel batteries at the time of discharging the battery pack,
Detecting the current flowing through the battery pack during the discharging,
The internal resistance is calculated for each of the parallel batteries from the characteristics based on the detected current value and voltage value,
The calculated internal resistance extracts the parallel battery having the maximum value,
The extracted internal resistance value of the parallel battery, and the maximum value of the internal resistance of the unit cell constituting the extracted parallel battery using the average value of the internal resistance of the parallel battery other than the extracted parallel battery,
Using the average value of the internal resistance of the parallel battery other than the extracted parallel battery, calculate the average value of the internal resistance of the cells constituting the parallel battery,
A parallel internal resistance deterioration correction coefficient is calculated using a ratio of the average value of the internal resistance of the unit cells and the maximum value of the internal resistance of the unit cells,
A capacity calculation method for battery packs connected in parallel, wherein the discharge capacity of the parallel batteries is corrected by the parallel internal resistance deterioration correction coefficient. The method of claim 1, wherein the capacity of the battery packs connected in parallel is calculated.
The detected current value, the detected voltage value, and a coefficient indicating the capacity of each parallel battery are calculated from the initial characteristics of the parallel battery, respectively.
Calculate a parallel capacity deterioration correction coefficient using the minimum value and the average value of the coefficient indicating the capacity,
A capacity calculation method for battery packs connected in parallel, further comprising correcting the discharge capacity of the parallel batteries with the parallel capacity deterioration correction coefficient. 3. The method for calculating the capacity of battery packs connected in parallel according to claim 1 or 2,
Calculating (1) a temperature correction coefficient, (2) an internal resistance deterioration correction coefficient, and (3) a capacity deterioration correction coefficient for correcting the average discharge capacity of the parallel battery,
The discharge capacity of the parallel battery is further corrected by the (1) temperature correction coefficient, (2) internal resistance deterioration correction coefficient, and (3) capacity deterioration correction coefficient. Method. A battery pack in which a plurality of secondary cells are connected in parallel, and a plurality of the parallel batteries are connected in series,
At the time of discharging the battery pack, voltage detecting means for detecting a voltage of each of the parallel batteries,
When the battery pack is discharged, current detection means for detecting a current flowing through the battery pack,
Based on the voltage and current detected by the voltage detecting means and the current detecting means, an internal resistance calculating means for calculating an internal resistance for each of the parallel batteries;
Extraction means for extracting a parallel battery having the maximum internal resistance calculated by the internal resistance calculation means,
Using the internal resistance of the parallel battery extracted by the extracting means and the internal resistance of the parallel battery other than the extracted parallel battery, the maximum value of the internal resistance of the unit cells constituting the extracted parallel battery is calculated. Estimating means for estimating,
Using the average value of the internal resistance of the parallel batteries other than the parallel battery extracted by the extraction means, average value calculation means for calculating the average value of the internal resistance of the unit cells constituting the parallel battery,
A correction coefficient for calculating a parallel internal resistance deterioration correction coefficient using a ratio between the average value of the internal resistance of the cell calculated by the average value calculation means and the maximum value of the internal resistance of the cell estimated by the estimation means Calculating means;
A discharge capacity correction means for correcting the discharge capacity of the parallel battery with the parallel internal resistance deterioration correction coefficient calculated by the correction coefficient calculation means,
A capacity calculating device for assembled batteries connected in parallel, characterized by comprising:

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