JP2002325365A - Detection method of battery residual capacity balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect residual capacity balance to know precisely battery life time, and to control output of power source unit. SOLUTION: A detecting method of battery residual capacity balance detects charge current of a plural of battery units charged, detects the voltage balance of a plural of battery units when charge current is in a specified range, and integrates detected voltage balance. It detects the Residual capacity balance of a plural of battery units is detected by the integrated value of this voltage balance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for detecting a remaining capacity difference between a plurality of batteries.

[0002]

2. Description of the Related Art A power supply device having a plurality of batteries has a difference in the remaining capacity of the batteries as it is used. This is because the electric characteristics of the batteries are not the same. The remaining capacity of the battery is calculated by integrating the charging current and the discharging current. Therefore, if the charge current and the discharge current flowing through a plurality of batteries are the same,
The calculated remaining capacity is also the same. In a plurality of batteries connected in series, the charging current and the discharging current have the same current value. Therefore, the remaining capacity of a plurality of batteries connected in series is calculated as the same value. However, the actual remaining capacity of a plurality of batteries connected in series to be charged and discharged is not always the same. When a plurality of series-connected batteries having a difference in remaining capacity are charged and discharged, a battery having a small remaining capacity may be overdischarged. Further, when a plurality of batteries are charged and discharged with the remaining capacity being a predetermined setting range, the remaining capacity of a battery having a low remaining capacity may deviate from the setting range. This causes the life of the battery to be shortened. In addition, it also causes a limitation on the output of the power supply device.

In order to avoid the above-mentioned problems, a difference in remaining capacity between a plurality of batteries is detected. If the remaining capacity difference is accurately detected, the remaining capacity of the battery having the smallest remaining capacity can be accurately detected. Therefore, the battery can be charged and discharged while preventing overdischarge. Further, by detecting that the remaining capacity difference increases, it is possible to accurately determine the replacement time of the deteriorated battery because the remaining capacity becomes small.

[0004] The remaining capacity difference of a battery can be determined from the voltage difference of the battery. When a plurality of batteries are connected in series and charged, the remaining capacity difference can be calculated from the difference between the battery voltages. FIG. 1 shows a difference in battery voltage when batteries having different remaining capacities are connected in series and charged. This figure shows that for the first 12 minutes
The graph shows the change in the battery voltage when the battery is charged at a constant current at 3 A and then the battery is charged at a constant current at 6.5 A for 18 minutes, and the voltage difference between the batteries having a remaining capacity difference. As shown in this figure, the voltage of a battery with a small remaining capacity is lower than the voltage of a battery with a large remaining capacity. Therefore, the remaining capacity difference can be calculated from the battery voltage difference.

[0005]

However, as shown in the figure, the voltage difference between batteries having a difference in remaining capacity is extremely small. Further, the voltage difference changes depending on the state of charging.
This makes it extremely difficult to accurately calculate the remaining capacity difference between a plurality of batteries. This figure shows the voltage difference of the battery having the remaining capacity difference of 5%.
It is extremely small at 60 mV. Further, since the voltage difference fluctuates as much as 6 times at the minimum and at the maximum, the remaining capacity difference cannot be accurately calculated from the voltage difference.

The present invention has been developed to solve this drawback. An important object of the present invention is to provide a method for detecting a remaining capacity difference of a battery, which can detect the remaining capacity difference very accurately.

[0007]

According to the method for detecting a remaining capacity difference of a battery according to the present invention, a voltage difference between a plurality of charged battery units is detected, and the detected voltage differences are integrated. The remaining capacity difference between the plurality of battery units is detected based on the integrated value of the voltage difference.

Preferably, the detection method of the present invention detects charging currents of a plurality of charged battery units, and detects a voltage difference between the plurality of battery units when the charging current is within a set range. This method can more accurately detect the remaining capacity difference. This is because it is possible to detect the remaining capacity difference while preventing the adverse effect that the charging current fluctuates and the voltage difference fluctuates.

The voltage difference between the plurality of battery units can be detected at a predetermined sampling cycle, for example, a sampling cycle of 10 msec to 1 sec. Shortening the sampling cycle is effective in accurately detecting the remaining capacity difference. However, if the sampling period is shortened, a high-speed A / D converter or the like is required, and the circuit and arithmetic processing become complicated because the voltage difference is frequently integrated.

The present invention detects a difference in remaining capacity of a battery unit, and the battery unit is a battery module having a plurality of batteries or a single battery. The method of detecting a remaining capacity difference by using a battery module in which a plurality of batteries are connected in series as a battery unit is advantageous when an extremely large number of batteries are connected in series as in a hybrid car.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate a method for detecting a remaining capacity difference of a battery for embodying the technical idea of the present invention, and the present invention uses the following method for detecting a remaining capacity difference. Do not specify.

The method for detecting a remaining capacity difference of a battery according to the present invention does not directly detect a remaining capacity difference of a battery unit based on a voltage difference of a charged battery. The battery voltage difference is integrated, and the remaining capacity difference is detected based on the integrated value. When a plurality of battery units having a difference in remaining capacity are connected in series and charged, as shown in FIG.
A voltage difference occurs in the battery unit. However, the voltage difference between the battery units is extremely small. This figure shows six nickel-
The voltage difference between the battery modules in which the hydrogen batteries are connected in series is shown, and the voltage difference is only 60 mV at the maximum. That is, the voltage difference is extremely small even though the battery unit has six batteries connected in series.
The small voltage difference makes it difficult to accurately detect the remaining capacity difference. To further complicate matters, the voltage difference between a plurality of battery units having the same remaining capacity difference fluctuates greatly as charging progresses. This further makes it difficult to detect the remaining capacity difference. According to the present invention, in order to solve this problem and accurately detect the remaining capacity difference, the voltage difference of the battery unit is integrated, and the remaining capacity difference is detected based on the integrated value.

The voltage difference between the battery units having the remaining capacity difference is
When integrated, the difference gradually increases. FIG. 2 shows the integrated value of the voltage difference. Since the integrated value of the voltage is the integrated value of the voltage difference and the time, it is the area between the curve of the voltage difference in FIG. 1 and the x-axis (the area indicated by hatching). As shown in this figure, in a battery unit having a remaining capacity difference, the integrated value of the voltage increases as charging progresses. The integrated value of the voltage difference increases with time. Even if the voltage difference of the battery unit fluctuates during charging, the integrated value is not affected by this and accurately corresponds to the remaining capacity difference of the battery unit. In other words, the integrated value is an accurate parameter for detecting the remaining capacity difference of the battery unit.

In order to integrate the voltage differences between the plurality of battery units, the voltage differences between the battery units are detected at a predetermined sampling cycle. The sampling period is, for example, 100 m
sec. However, the sampling period is 10
msec to 1 sec. The sampling cycle is set to a time during which the voltage fluctuation of the charged battery unit can be accurately detected. Since the voltage fluctuation of the battery unit is relatively slow, it can be detected sufficiently accurately with a sampling period of 10 msec. If the accuracy of detecting the remaining capacity difference can be reduced, the sampling cycle can be made longer than 1 sec.

The time for integrating the detected voltage differences is made longer so that the remaining capacity difference can be accurately detected. The integration time is set to, for example, 1 to 30 minutes, preferably 3 to 20 minutes, and more preferably 5 to 20 minutes. FIG. 3 shows a remaining capacity difference with respect to a value obtained by integrating a voltage difference detected in a sampling cycle of 100 msec for 12 minutes. This figure is a graph that specifies the remaining capacity difference of the battery unit using the integrated value as a parameter. This figure shows that the integrated value of the voltage difference of the battery unit can detect the remaining capacity difference of the battery unit almost linearly. In other words, the remaining capacity difference of the battery unit increases in proportion to the integrated value of the voltage difference. Therefore, the remaining capacity difference of the battery unit can be detected very accurately and easily from the integrated value of the voltage difference.

FIG. 3 shows characteristics when the battery unit is charged under the following conditions. (1) The battery unit is a battery unit in which six nickel-hydrogen batteries are connected in series. (2) The battery unit is charged at a constant current of 13 A for 12 minutes, the voltage difference of the battery unit is integrated over 12 minutes, and the remaining capacity difference of the battery unit with respect to this integrated value is shown. (3) When charging is started, the remaining capacity of the battery unit having a large remaining capacity is 50%. (4) When charging is completed, the remaining capacity of the battery unit having the larger remaining capacity is 90%. (5) The outside air temperature during charging is 25 ° C.

FIG. 4 shows a charging circuit for a hybrid car using the method for detecting a remaining capacity difference according to the present invention. The hybrid car shown in FIG. 1 includes a driving battery 1 for driving a motor for driving the car, a control circuit 2 for controlling the charging and discharging of the driving battery 1, a power supply to the control circuit 2, and an electric device for the car. The battery 3 for supplying electric power also includes a cooling fan 4 for forcibly cooling the driving battery 1.

The driving battery 1 is connected to a motor / generator 6 via an inverter 5. The driving battery 1 is discharged by supplying power to the motor via the inverter 5. The inverter 5 is controlled by the control circuit 2 to adjust the power supplied from the driving battery 1 to the motor. The driving battery 1
It is charged by the generator of the motor / generator 6. The generator is
When the vehicle is driven by the engine 7 or when the vehicle is decelerated, the vehicle is driven by the wheels of the vehicle to perform regenerative braking to charge the drive battery 1. The motor / generator 6 includes one motor used in combination with the generator, or separately includes the motor and the generator.

The driving battery 1 has a plurality of battery units connected in series. The battery unit is a battery module in which a plurality of nickel-hydrogen batteries are connected in series. The battery unit can be one battery. In addition, the battery of the battery module may be a nickel-cadmium battery or a lithium ion secondary battery.

The illustrated control circuit 2 includes a battery control circuit 8 for controlling the charging and discharging of the driving battery 1 and a vehicle control circuit 9 for controlling the running state of the vehicle. The battery control circuit 8
The charging and discharging are controlled by detecting the temperature, the voltage and the flowing current of the driving battery 1. The battery control circuit 8 detects the remaining capacity difference of the battery unit of the driving battery 1 and charges and discharges the battery unit so as not to be overcharged and overdischarged. The battery control circuit 8 detects a difference between the remaining capacity of the driving battery 1 and the remaining capacity of the battery unit, and controls charging and discharging so that the remaining capacity becomes the set capacity. When a signal for driving the motor is input from the vehicle control circuit 9 when the remaining capacity of the driving battery 1 is at the set capacity, the battery control circuit 8 supplies power from the driving battery 1 to the motor via the inverter 5. I do. When the remaining capacity of the driving battery 1 becomes smaller than the set capacity, the battery control circuit 8 outputs a signal for driving the motor / generator 6 to the vehicle control circuit 9. The vehicle control circuit 9 to which this signal is input drives the motor / generator 6 with the engine 7 to charge the drive battery 1. Furthermore, when the brake is depressed to decelerate the automobile, the automobile control circuit 9 outputs a regenerative braking signal for charging the driving battery 1 to the battery control circuit 8. The battery control circuit 8 to which the regenerative braking signal is input determines whether or not the drive battery 1 can be charged from the calculated remaining capacity. The battery 1 is charged.

As the operating time of the drive battery 1 increases, a difference in remaining capacity occurs in the battery unit. The hybrid car of FIG. 4 detects the remaining capacity difference of the battery unit according to the flowchart of FIG.

[Step S = 1, 2] The charging current of the driving battery 1 is detected, and it is determined whether or not the charging current is an average current. The reason why the charging current is detected is to confirm that the driving battery 1 is charged with the average current and to detect the voltage difference. The magnitude of the charging current fluctuates the voltage difference between the battery units and causes an error in detecting the remaining capacity difference. For example, when a battery unit having the same remaining capacity difference is charged with a large current and a small current, the voltage difference between the battery units is
When charging with a large current, the charge is larger than when charging with a small current. According to the present invention, since the remaining capacity difference is detected from the voltage difference, an error increases if the voltage difference fluctuates due to another factor. In order to minimize the detection error of the remaining capacity difference, the remaining capacity difference is detected from the voltage difference at the average current. If the charging current is not the average current, loop this step.

[Step S = 3] If the charging current is an average current, the battery control circuit 8 detects the voltages of all (m) battery units. The voltage is detected for each battery unit. [Step S = 4] From the voltage of the highest voltage battery unit (Vmax), the voltage of the lowest voltage battery unit (Vm)
in) is subtracted to calculate a voltage difference (ΔV). [Step S = 5] The detected voltage difference (ΔV) is integrated and integrated. [Step S = 6] In this step, 1 is added to n. [Step S = 7] In this step, it is determined whether or not n exceeds 6000. Battery unit voltage is 100
When detection is performed at a sampling cycle of msec, the number of times of integration of the voltage difference becomes 6000 times, which is 6000 × 0.1 s
ec is 10 minutes. Therefore, in this step, it is determined whether or not the integration time has passed 10 minutes. Until the integration time reaches 10 minutes, the process jumps to the step of S = 1 and loops the steps of S = 1 to 7. [Step S = 8] From the integrated value of the integrated voltage difference,
The remaining capacity difference of the battery unit is detected. The remaining capacity difference is the difference between the battery unit having the maximum remaining capacity and the battery unit having the minimum remaining capacity. The battery control circuit 8 stores the characteristic for detecting the remaining capacity difference from the integrated value of the voltage difference, for example, the characteristic of FIG. 3 in the nonvolatile memory, and detects the remaining capacity difference from the stored characteristics.

[0024]

The method for detecting the remaining capacity difference of a battery according to the present invention comprises:
There is a feature that the remaining capacity difference between a plurality of battery units can be detected very accurately. This is because the remaining capacity difference detection method of the present invention detects the remaining capacity difference based on the integrated value of the voltage differences of the plurality of charged battery units. The detection method of the present invention does not directly detect the remaining capacity difference based on the voltage difference of the charged battery unit. This is because the voltage difference between the plurality of battery units is extremely small, and the voltage difference varies depending on the state of charge, so that the remaining capacity difference cannot be accurately detected using only the voltage difference as a parameter. According to the detection method of the present invention, the remaining capacity difference is detected by an integrated value obtained by integrating the voltage difference between the battery units. The integrated value of the voltage difference increases with time. For this reason, even if the voltage difference fluctuates during charging, the battery capacity accurately responds to the remaining capacity difference of the battery unit without being affected by this. Thus, the detection method of the present invention can accurately detect the remaining capacity difference of the battery unit by using the integrated value of the voltage difference as a parameter.

[Brief description of the drawings]

FIG. 1 is a graph showing voltage characteristics when a battery unit having a remaining capacity difference is charged.

FIG. 2 is a graph showing an integrated value of a voltage difference in FIG. 1;

FIG. 3 is a graph showing a remaining capacity difference characteristic with respect to a voltage difference integrated value.

FIG. 4 is a block diagram showing a charging circuit of a hybrid car using the method for detecting a remaining capacity difference according to the present invention;

FIG. 5 is a flowchart showing a method for detecting a remaining capacity difference according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Drive battery 2 ... Control circuit 3 ... Battery for electric equipment 4 ... Cooling fan 5 ... Inverter 6 ... Motor / generator 7 ... Engine 8 ... Battery control circuit 9 ... Car control circuit

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2G016 CA03 CB12 CB31 CC01 CC04 CC07 CC16 CC23 CC24 CD02 CF06 5G003 AA07 BA03 CA01 CA11 DA04 EA05 FA06 GC05 5H030 AS06 AS08 FF42 FF43 FF52

Claims (5)

[Claims] 1. A battery comprising: detecting a voltage difference between a plurality of charged battery units; integrating the detected voltage differences; and detecting a remaining capacity difference between the plurality of battery units based on the integrated value. Method for detecting the remaining capacity difference. 2. The remaining capacity of a battery according to claim 1, wherein a charge current of the plurality of battery units being charged is detected, and a voltage difference between the plurality of battery units is detected when the charge current is within a set range. Difference detection method. 3. The method according to claim 1, wherein a voltage difference between the plurality of battery units is detected at a predetermined sampling cycle. 4. The method according to claim 1, wherein the battery unit is a battery module having a plurality of batteries. 5. The method according to claim 1, wherein the battery unit is a single battery.