JP2010164322A - Method and device for detecting remaining capacity of battery, and secondary battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting the remaining capacity of a battery which enables accurate compensation of the remaining capacity of the battery. <P>SOLUTION: The remaining capacity of a secondary battery is determined from a discharge current of the secondary battery, while the remaining capacity of the secondary battery is compensated to be a set N% remaining capacity when a period in which the battery voltage of the secondary battery is below N% remaining capacity voltage set according to a discharge current value reaches a determination time set according to the discharge current value. On the occasion, the longest determination time out of the determination time set sequentially according to the discharge current value during a period of measurement of the time when the battery voltage is below the N% remaining capacity voltage, is used for determination of the duration in which the battery voltage is below the N% remaining capacity voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery remaining capacity detection method, a battery remaining capacity detection apparatus, and a secondary battery apparatus that can accurately determine the remaining capacity of a secondary battery that accompanies discharge.

  The remaining capacity of the secondary battery is obtained, for example, by subtracting the discharge capacity obtained by integrating the discharge current from the full charge capacity of the secondary battery. Incidentally, the remaining capacity is displayed as a product [Ah] of current and time, or as a ratio [%] to the full charge capacity. However, as described above, the remaining capacity obtained based on the discharge current is not always accurate. Therefore, when the remaining capacity of the secondary battery is reduced to a certain extent, paying attention to the property that the battery voltage is lowered accordingly, the battery voltage is lowered to a predetermined remaining capacity voltage (for example, 10% remaining capacity voltage). As described above, it has been proposed to forcibly correct the remaining capacity obtained based on the discharge current (see, for example, Patent Documents 1 and 2).

  Incidentally, the change in the battery voltage and the remaining capacity of the secondary battery at the time of discharge differ depending on the magnitude of the discharge current as shown in FIG. 4, for example, and the predetermined remaining capacity voltage (for example, 10% remaining capacity voltage) described above is discharged. The higher the current, the lower. Also, the way in which the battery voltage changes when the remaining capacity decreases depends on the magnitude of the discharge current. The smaller the discharge current, the sharper the change. Therefore, in general, the N% remaining capacity voltage (determination voltage) and the determination time (detection time), which are determination conditions for executing the above-described remaining capacity correction, are determined according to the discharge current value, for example, Is variably set.

  For example, when the discharge current value is [7 A] (= 1.75 C), when the battery voltage continues to be 3.0 V or lower for 1.0 second or longer, this is indicated as the remaining amount of the secondary battery. It is detected that the capacity has decreased to [10%], and the remaining capacity obtained by subtracting the integrated value of the discharge current from the full charge capacity is forcibly corrected to [10%]. Incidentally, when the current value is large, the detection time is set to be long because it takes time until the battery is stabilized.

JP 2006-38747 A JP 2006-170867 A

  However, when performing the above-described determination process, for example, when the discharge current decreases rapidly, determination of battery voltage drop under a determination voltage (N% remaining capacity voltage) determined according to the decreased discharge current, Since the determination of the duration of the decreased battery voltage is performed, the remaining battery capacity may be corrected unintentionally. That is, when the discharge current decreases, a determination voltage (N% remaining capacity voltage) and a determination time are newly set accordingly. However, even if the discharge current decreases, it takes some time to recover the battery voltage. For this reason, the period during which the average voltage during the recovery period of the battery voltage is lower than the newly set determination voltage (N% remaining capacity voltage) continues over the newly set determination time (duration). There are things to do. As a result, even if the battery voltage after recovery becomes higher than the determination voltage (N% remaining capacity voltage), the remaining capacity obtained by subtracting the integrated value of the discharge current from the full charge capacity is forced. [N%] was sometimes corrected.

  The present invention has been made in view of such circumstances, and the object thereof is a battery remaining capacity detection method capable of accurately correcting the remaining battery capacity even when the discharge current is rapidly decreased, It is in providing a battery remaining capacity detection apparatus and a secondary battery apparatus.

The present invention has been made paying attention to the fact that it takes some time to recover the battery voltage even if the discharge current decreases.
In order to achieve the above-described object, the battery remaining capacity detection method according to the present invention detects the discharge capacity by integrating the discharge current value of the secondary battery, and subtracts the discharge capacity from the full charge capacity of the secondary battery. While determining the remaining capacity of the secondary battery, a period during which the battery voltage of the secondary battery is lower than the N% remaining capacity voltage determined according to the discharge current value is determined according to the discharge current value. When the remaining capacity of the secondary battery obtained by subtracting the discharge capacity from the full charge capacity is corrected to a predetermined N% remaining capacity when the determination time is reached,
The longest determination time among the determination times sequentially determined according to the discharge current value during the measurement period of the time when the battery voltage is lower than the N% remaining capacity voltage is the battery voltage is the N% remaining capacity voltage. It is characterized in that it is used for determining the duration of time less than.

Moreover, the battery remaining capacity detection device according to the present invention includes:
<a> current detection means for detecting the discharge current value of the secondary battery;
<b> The discharge current value detected by the current detection means is integrated to detect the discharge capacity, and the remaining capacity of the secondary battery is obtained by subtracting the discharge capacity from the full charge capacity of the secondary battery. A remaining capacity calculating means;
<c> Voltage detection means for detecting a terminal voltage of the secondary battery;
<d> The N% remaining capacity voltage set according to the discharge current value is compared with the battery voltage detected by the voltage detecting means, and the battery voltage continuously falls below the N% remaining capacity voltage. A measuring means for measuring time;
<e> When the time measured by the measuring means exceeds the determination time determined in accordance with the discharge current value, the remaining capacity obtained by the remaining capacity calculating means is set to a predetermined N% remaining amount. A remaining capacity correcting means for correcting the capacity;
<f> A determination time in which the longest determination time among the determination times sequentially determined according to the discharge current value during the measurement period of the duration by the measurement unit is used for determination of the duration in the remaining capacity correction unit And a control means.

  Preferably, the N% remaining capacity voltage and the determination time of the secondary battery are set for each current region in which the magnitude of the discharge current is divided into a plurality of stages, and the N% remaining capacity voltage is the discharge voltage. The larger the current value is, the lower the setting time is. The larger the discharge current value is, the longer the setting time is. The determination time used for the determination of the duration is such that the battery voltage is the N% remaining capacity. It is desirable to determine the longest time among the determination times sequentially obtained according to the discharge current value during the measurement period of the time below the voltage.

Specifically, in the determination time control means, after the measurement of the time during which the battery voltage falls below the N% remaining capacity voltage is started, the determination times sequentially obtained according to the discharge current value are compared with each other. The longest of the determination times may be determined as the determination time used for determining the duration time.
The battery voltage is compared with the N% remaining capacity voltage determined according to the discharge current value every predetermined period, and the determination time is set as a multiple of the comparison period. desirable.

  The secondary battery device according to the present invention includes a secondary battery and a battery remaining capacity detection device having the above-described configuration.

  According to the present invention, even when the N% remaining capacity voltage is newly set as the discharge current decreases, the time delay required for the recovery of the battery voltage is absorbed by increasing the determination time. Thus, unintentional N% remaining capacity correction can be prevented. In other words, the voltage determination time (duration) set according to the decreased discharge current is used to recover the battery voltage by adopting the voltage determination time (duration) at the time of large current before the discharge current decreases. The battery voltage is determined by absorbing the required time delay, and thus N% remaining capacity correction can be performed accurately.

The schematic block diagram of the pack battery for demonstrating the battery remaining capacity detection method and battery remaining capacity detection apparatus which concern on one Embodiment of this invention. The figure which shows an example of the control procedure of the battery remaining charge detection which concerns on this invention. The figure for demonstrating the effect | action of the battery remaining charge detection which concerns on this invention. The figure which shows the relationship between the change of a battery voltage at the time of discharge of a secondary battery, and remaining capacity.

Hereinafter, a battery remaining capacity detection method and a battery remaining capacity detection apparatus according to an embodiment of the present invention will be described with reference to the drawings. Further, the secondary battery device according to the present invention is realized as a so-called pack battery including a secondary battery and a battery remaining capacity detection device.
FIG. 1 is a schematic configuration diagram of a battery pack, in which 10 is a secondary battery and 20 is a battery remaining capacity detection device. The secondary battery 10 is, for example, a lithium ion battery that secures a required battery voltage and battery capacity by connecting a plurality of battery cells in series and parallel. The secondary battery 10 is connected to a charger (not shown) to be charged, and is connected to an electronic device (load) (not shown) via the battery remaining capacity detection device 20 to be used as a power source for the electronic device. .

  The battery remaining capacity detection device 20 basically includes a current detection unit (current detection means) 21 that detects a discharge current value of the secondary battery 10, and the discharge current detected by the current detection unit 21. A remaining capacity calculating section (remaining capacity calculating means) 22 for determining the remaining capacity of the secondary battery 10; and a voltage detecting section (voltage detecting means) 23 for detecting a terminal voltage (battery voltage) of the secondary battery 10. Composed.

  Incidentally, the remaining capacity calculation unit 22 is realized by using, for example, a microprocessor, and sequentially accumulates the discharge current values detected by the current detection unit 21 to obtain the discharge capacity of the secondary battery 10. It plays the role of calculating the remaining capacity by subtracting the discharge capacity from the full charge capacity of the secondary battery 10 that is calculated and determined in advance. Further, the remaining capacity calculation unit 22 is configured such that the remaining capacity of the secondary battery 10 is set in advance from the battery voltage detected by the voltage detection unit 23 (for example, 10% remaining capacity; If a low remaining capacity as a value in the range of 12% is available), and it is detected that the N% remaining capacity has been reached as will be described later, the remaining capacity determined as described above is used. A remaining capacity correction unit (remaining capacity correction means) 24 for forcibly correcting the capacity to N% remaining capacity is provided.

  The determination as to whether or not the N% remaining capacity has been reached is made by determining whether or not the battery voltage falls below a preset N% remaining capacity voltage in the measuring unit (measurement means) 25, and whether or not the battery voltage is N% remaining. This is performed by determining whether or not the period below the capacity voltage continues for a preset determination time. Incidentally, the N% remaining capacity voltage and the determination time are set in advance for each current region in which the magnitude of the discharge current is divided into a plurality of stages as shown in Table 1, for example, according to the magnitude of the discharge current. Are registered in the memory 26. The N% remaining capacity voltage and the determination time used for the remaining capacity determination are selectively obtained from the memory 25 according to the discharge current value detected by the current detection unit 21 and given to the measurement unit 25. . The above-described remaining capacity correction unit 24 is activated when the measurement unit 25 detects that the remaining capacity of the secondary battery 10 has reached N% remaining capacity, and performs remaining capacity correction. Further, the remaining capacity of the secondary battery 10 obtained as described above is appropriately notified to the above-described electronic device via the communication processing unit 28.

  Here, the battery remaining capacity detection device 20 according to the present invention is characterized in that the remaining capacity calculation unit 22 includes a determination time control unit (determination time control means) 27 in addition to the basic functions described above. is there. When the measurement unit 25 detects that the battery voltage is lower than the N% remaining capacity voltage, the determination time control unit 27 sequentially obtains according to the change in the discharge current value during the measurement period of the duration. It plays the role which employ | adopts the longest determination time in the determination time to be used for determination of the continuation time in this measurement part 25.

  Specifically, the measurement unit 25 determines the battery voltage under the N% remaining capacity voltage set according to the discharge current value, and the state is continued after the battery voltage falls below the N% remaining capacity voltage. When the discharge current decreases during the period of time measurement, and the N% remaining capacity voltage (determination voltage) and the determination time are newly obtained along with this, the determination time control unit 27 determines the discharge current. It takes the role of adopting the longest determination time among a plurality of determination times determined in accordance with the change and setting this as a determination condition (determination time) to be given to the measurement unit 25. Therefore, even when the discharge current rapidly decreases and the determination time newly obtained from the memory 26 is shortened accordingly, the long determination time at the time of a large current set before the discharge current is reduced is maintained. This is used for determining the remaining capacity in the measurement unit 25. As a result, the measuring unit 25 is only secondary when the period in which the battery voltage falls below the newly set N% remaining capacity voltage (determination voltage) continues for the long determination time at the time of the large current described above. It is detected that the remaining capacity of the battery 10 has reached N% remaining capacity.

  FIG. 2 shows an example of the processing procedure of the above-described N% remaining capacity determination in the battery remaining capacity detection device 20. This determination process is executed, for example, every predetermined cycle (for example, 250 milliseconds). Specifically, first, the battery voltage of the secondary battery 10 (average battery voltage in one cycle; the average battery voltage is calculated as an average value of battery voltages obtained every cycle shorter than the predetermined cycle, for example, every 20 milliseconds. ) And the N% remaining capacity voltage (determination voltage) obtained from the memory 26 in accordance with the discharge current value at that time (step S1). Incidentally, when the battery voltage of the secondary battery 10 is sufficiently high as in the initial stage of discharge and does not decrease to the N% remaining capacity voltage (judgment voltage), the remaining capacity correction is unnecessary, so the previous judgment time. (Count value) is reset to [0] and <Step S2>, and the duration counter is reset to [0] <Step S3>. Further, the remaining capacity detection flag indicating that the N% remaining capacity determination process is being executed is reset to [0] (step S4).

  The duration time counter and the determination time (count value) are determined so that the N% remaining capacity determination process is repeatedly executed at a predetermined cycle (for example, 250 msec). It is set as the number of periods in which the state below the voltage (determination voltage) continues. Specifically, when the detection time (determination time) is set as 1.0 seconds as shown in Table 1 above, the determination time (count value) is [1.0 seconds ÷ 250 milliseconds = 4. Times]. Conversely, when the count value by the duration counter is 6 times, the duration time is obtained as [250 msec × 4 times = 1.5 seconds].

  On the other hand, when the battery voltage of the secondary battery 10 is lower than the N% remaining capacity voltage (determination voltage) <step S1>, the determination time obtained from the memory 26 according to the current discharge current magnitude The larger one of (count value) and the determination time (count value) obtained last time (one cycle before) is selected, and this is set as the determination time used for the current remaining capacity determination (step S5). Then, the determination time set as described above is updated as the previous (one cycle before) determination time (count value) <Step S6>, and the value of the duration counter is incremented (incremented by +1) by [1]. <Step S7>.

  The time during which the battery voltage continuously falls below the N% remaining capacity voltage (determination voltage) by this processing is measured by the duration counter, and the determination time used for remaining capacity determination is determined during the determination time detection period. It is set as the longest judgment time. If the determination time (count value) is set as described above, and the time (count value) during which the battery voltage is continuously lower than the N% remaining capacity voltage (determination voltage) is obtained by the continuous time counter. Then, it is determined whether or not the value of the duration counter (duration) exceeds the determination time (count value) <step S8>. If the value of the continuous time counter (continuous time) exceeds the determination time (count value), the remaining capacity detection flag is set to indicate that the remaining capacity of the secondary battery 10 has reached N% remaining capacity [ 1] <Step S9>. On the contrary, when the value of the duration counter (duration) is less than the determination time (count value), it is assumed that the remaining capacity of the secondary battery 10 has not decreased to the N% remaining capacity and the remaining capacity. The detection flag is reset to [0] <Step S4>. Then, the remaining capacity correction unit 24 described above receives such a remaining capacity detection flag, and when the remaining capacity detection flag is [1], the remaining capacity of the secondary battery 10 reaches N% remaining capacity. The remaining capacity correction is executed.

  Thus, according to the battery remaining capacity detection device (battery remaining capacity detection method) 20 that performs N% remaining capacity determination from the battery voltage of the secondary battery 10 and corrects the remaining capacity of the secondary battery 10 as described above. While measuring the time when the battery voltage is lower than the N% remaining capacity voltage (judgment voltage), the amount of discharge changes, and in particular, the discharge current decreases rapidly, and the N% remaining capacity voltage (judgment voltage) has been reduced. Even if it is newly set as a higher voltage value, the determination time remains as the longest determination time in the duration determination period, that is, the long determination time at the time of large current. Therefore, even if there is a delay in the change in the battery voltage accompanying the decrease in the discharge current, it is not determined that the N% remaining capacity has been accidentally reached from the battery voltage.

  Specifically, as illustrated in FIG. 3, when the discharge current of the secondary battery 10 (capacity 4000 mAH) is 18 A (= 4.5 C), the 10% remaining capacity voltage is 2 based on the determination conditions shown in Table 1. .8V is set, and the determination time is set as 2.0 seconds (8 cycles). Under this condition, the measurement of the duration of the state starts when the battery voltage of the secondary battery 10 falls below the 10% remaining capacity voltage [2.8V], and the 10% remaining capacity voltage becomes 2. Assuming that 8V suddenly decreases to 1.5A, at the next remaining amount judgment timing after a certain period, the 10% remaining capacity voltage from the memory 26 is 3.1V according to the magnitude of the changed discharge current. The determination time is determined as 0.5 seconds (2 periods).

  When the remaining capacity determination is performed using the determination condition obtained from the memory 26 as it is in this way, for example, in a determination process after 0.25 seconds and a determination process after 0.5 seconds as shown in FIG. Since the 10% remaining capacity determination condition is satisfied twice consecutively, this is erroneously assumed that the remaining battery capacity has dropped to 10% remaining capacity even though the recovery of the battery voltage is delayed. It will be judged.

  In this respect, in the present apparatus (method), as described above, the determination time is set as the longest determination time in the duration determination period, and in this example, the determination time when the discharge current is 18A. It is left as it is for 2.0 seconds (8 cycles). As a result, also in the determination process in the transition after 0.5 seconds, it is determined whether or not the battery voltage of the secondary battery 10 is lower than the newly set 10% remaining capacity voltage. Accordingly, since the determination condition is not satisfied with the recovery of the battery voltage, specifically, the battery voltage becomes higher than the 10% remaining capacity voltage, so the remaining capacity of the secondary battery 10 is reduced to 10% remaining capacity. As a result, it is not erroneously determined. As a result, it is possible to forcibly correct the remaining capacity determined according to the discharge current to 10% remaining capacity only when the remaining capacity of the secondary battery 10 has truly decreased to 10% remaining capacity. In other words, even if the change in the battery voltage of the secondary battery 10 due to the change in the discharge current is delayed, it is ensured that the battery voltage of the secondary battery 10 has dropped to the N% remaining capacity voltage (exactly). ) And the remaining capacity can be corrected.

  The present invention is not limited to the embodiment described above. Although the lithium ion battery has been described as an example of the secondary battery 10 here, the present invention can be similarly applied to a nickel cadmium battery or a nickel hydrogen battery. Needless to say, the N% remaining capacity is not limited to the exemplified 10% remaining capacity. Furthermore, as shown in Patent Documents 1 and 2 described above, the present invention can be similarly applied to a case where a function of detecting the battery temperature of the secondary battery 10 and correcting the remaining capacity is provided. In addition, it is sufficient to realize the current detection unit 21 and the like by using a known method. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 10 Secondary battery 20 Remaining capacity detection apparatus 21 Current detection part 22 Remaining capacity calculation part 23 Voltage detection part 24 Remaining capacity correction | amendment part 25 Measurement part 26 Memory 27 Determination time control part 28 Communication processing part

Claims (7)

While integrating the discharge current value of the secondary battery to detect the discharge capacity and subtracting the discharge capacity from the full charge capacity of the secondary battery to obtain the remaining capacity of the secondary battery, the battery of the secondary battery When the period during which the voltage falls below the N% remaining capacity voltage determined according to the discharge current value reaches the determination time determined according to the discharge current value, the discharge capacity is subtracted from the full charge capacity. When correcting the remaining capacity of the secondary battery determined in this way to a predetermined N% remaining capacity,
The longest determination time among the determination times sequentially determined according to the discharge current value during the measurement period of the time when the battery voltage is lower than the N% remaining capacity voltage is the battery voltage is the N% remaining capacity voltage. The remaining battery capacity detection method characterized by using it for determination of the continuation time less than this. The N% remaining capacity voltage and the determination time of the secondary battery are set for each current region in which the magnitude of the discharge current is divided into a plurality of stages, and the N% remaining capacity voltage is the discharge current value. Is set to be lower, the determination time is set to be longer as the discharge current value is increased,
The determination time used for the determination of the duration is determined as the longest time among the determination times sequentially obtained according to the discharge current value during the measurement period of the time when the battery voltage falls below the N% remaining capacity voltage. The method for detecting a remaining battery capacity according to claim 1.   The battery voltage is compared with an N% remaining capacity voltage determined according to the discharge current value every predetermined period, and the determination time is set as a multiple of the comparison period. The battery remaining capacity detection method according to claim 1. Current detection means for detecting the discharge current value of the secondary battery;
Calculating the remaining capacity of the secondary battery by integrating the discharge current value detected by the current detection means to detect the discharge capacity and subtracting the discharge capacity from the full charge capacity of the secondary battery Means,
Voltage detecting means for detecting a terminal voltage of the secondary battery;
The N% remaining capacity voltage set according to the discharge current value is compared with the battery voltage detected by the voltage detecting means, and the time during which the battery voltage continuously falls below the N% remaining capacity voltage is measured. Measuring means to perform,
When the time measured by the measuring means exceeds a determination time determined according to the discharge current value, the remaining capacity obtained by the remaining capacity calculating means is corrected to a predetermined N% remaining capacity. Remaining capacity correction means for
A determination time control unit that uses the longest determination time among the determination times sequentially determined according to the discharge current value during the measurement period of the duration by the measurement unit to determine the duration in the measurement unit. What is claimed is: A battery remaining capacity detection device. The N% remaining capacity voltage and determination time of the secondary battery are set for each current region in which the magnitude of the discharge current is divided into a plurality of stages, and the N% remaining capacity voltage of the secondary battery is The discharge current value is set larger as the discharge current value is larger, and the determination time is set longer as the discharge current value is larger.
The determination time control means compares the determination times sequentially obtained according to the discharge current value after starting the measurement of the time when the battery voltage falls below the N% remaining capacity voltage, The battery remaining capacity detection device according to claim 4, wherein the longest time is determined as a determination time used for determining the duration. The measuring means compares the battery voltage with a N% remaining capacity voltage determined according to the discharge current value at predetermined intervals,
The battery remaining capacity detection device according to claim 4, wherein the determination time determined according to the discharge current value is set as a multiple of the comparison period.   A secondary battery device comprising a secondary battery and the battery remaining capacity detection device according to any one of claims 4 to 6.

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