JP2011172415A - Secondary battery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery device capable of estimating an accurate dischargeable capacity.
SOLUTION: Detection means 30 and 40 for detecting a voltage value, a current value and a temperature value of each of a plurality of secondary battery cells BT, a calculation means 52, a predetermined temperature environment and a predetermined average current. A first table 57 for calculating the remaining capacity from the open circuit voltage of the secondary battery cell BT; and a second table TBL for managing a correction value for correcting the remaining capacity calculated using the first table 57. In the second table TBL, correction values corresponding to the range of the average current value of the secondary battery cell BT and the range of the temperature value of the secondary battery cell BT are recorded. A means for calculating the remaining capacity using the second table TBL corresponding to the remaining capacity is selected, and a correction value corresponding to the average value of the temperature value and the current value obtained from the detecting means 30 and 40 is selected from the second table TBL. From A secondary battery device comprising: correction means for acquiring and correcting the remaining capacity.
[Selection] Figure 1

Description

  The present invention relates to a secondary battery device, and more particularly, to a secondary battery device including a secondary battery module including a plurality of secondary battery cells.

  When various processes are performed in an electronic device supplied with power from a secondary battery device, the power consumption used for each process may differ greatly. Therefore, in electronic devices such as those mentioned above, a secondary battery device is required to be notified of the dischargeable capacity in order to inform the user of the timing when charging is required, the functions that can be used, the time that can be continuously used, etc. To do. Therefore, a secondary battery device mounted on an electronic device that performs various processes as described above is required to accurately estimate the dischargeable capacity.

  In general, in the learning type dischargeable capacity estimation method, the dischargeable capacity including deterioration characteristics is calculated from the internal resistance and the number of charge / discharge cycles, and the discharge end lower limit voltage is also fixed. As a dischargeable capacity estimation method, a method has been proposed in which a dischargeable capacity at a discharge current is obtained from a dischargeable capacity characteristic map stored in advance. In this method, the product of the discharge current and the discharge time is then taken to determine the actual discharged capacity. Then, a technique has been proposed for calculating a percentage of the dischargeable capacity that is actually discharged and subtracting it from the remaining capacity to obtain a new remaining capacity (see, for example, Patent Document 1). ).

  Further, the battery pack capacity is calculated based on the output and time of the current detection means, and the dischargeable capacity of the battery pack is memorized based on the output of the battery identification means, and the discharge capacity until the battery pack reaches a predetermined voltage. And calculating means for lighting the LED below a certain threshold value (see Patent Document 2, for example).

JP-A-8-339835 Japanese Utility Model Publication No. 5-14958

  However, in the above-described learning type dischargeable capacity estimation method, when the remaining battery capacity and discharge (current) rate obtained from the open circuit voltage, temperature, internal resistance, lower limit voltage for use, and deterioration characteristics are varied, battery discharge Since the characteristics greatly fluctuated, it was difficult to accurately measure the remaining capacity.

  In addition, since there are a wide range of parameters for discharge characteristics, there are infinite combinations of parameters, and it is difficult to improve the detection accuracy of all parameters. It is possible to discharge with deterioration characteristics using the above parameters. It was difficult to estimate the capacity accurately.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a secondary battery device capable of estimating an accurate dischargeable capacity.

  A secondary battery device according to an aspect of the present invention includes a plurality of secondary battery cells, voltage detection means for detecting a voltage value of each of the plurality of secondary battery cells, and a current value of the plurality of secondary battery cells. Current detecting means, temperature detecting means for measuring the temperature of each of the plurality of secondary battery cells, voltage value, current value, and temperature value from the voltage detecting means, the current detecting means, and the temperature detecting means. Is calculated using the first table, a first table for calculating the remaining capacity from the open circuit voltage of the secondary battery cell at a predetermined temperature environment and a predetermined average current. A second table for managing a correction value for correcting the remaining capacity, and a recording means for recording, wherein the second table is prepared for each range of the remaining capacity of the secondary battery cell, and the secondary table Average battery cell current And the correction value corresponding to the range of the temperature value of the secondary battery cell is recorded, the calculation means calculates the remaining capacity using the first table, and the remaining capacity The corresponding second table is selected, and the correction value corresponding to the average value of the temperature value obtained from the temperature detecting means and the current value obtained from the current detecting means is obtained from the second table and the remaining table is obtained. And a correction unit that corrects the capacity.

  ADVANTAGE OF THE INVENTION According to this invention, the secondary battery apparatus which can estimate exact dischargeable capacity can be provided.

It is a figure which shows roughly the example of 1 structure of the secondary battery apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the relationship between the voltage of a secondary battery cell, and discharge capacity at the time of changing a temperature environment and a discharge (current) rate. FIG. 2 is a diagram for describing an example of a table for managing a correction value of a remaining capacity of a secondary battery cell in the secondary battery device shown in FIG. 1. It is a figure for demonstrating an example of the several table with which the remaining capacity is prepared for every remaining capacity (SOC) range of a secondary battery cell. In the secondary battery apparatus shown in FIG. 1, it is a figure for demonstrating an example of the correction method of the table which correct | amends the remaining capacity of a secondary battery cell after completion of discharge. FIG. 2 is a diagram for explaining an example of a table correction method for correcting the remaining capacity of secondary battery cells in the secondary battery device shown in FIG. 1. It is a flowchart for demonstrating an example of the correction method of the correction value of the table which manages the correction value of the remaining capacity of a secondary battery cell.

  Hereinafter, a secondary battery device according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the secondary battery device according to this embodiment includes a battery module 20, a battery monitoring unit 30, a current detection unit 40, and a battery management unit 50. The battery module 20 includes a plurality of assembled batteries 10. The assembled battery 10 includes a plurality of secondary battery cells BT. The secondary battery cell BT is, for example, a nickel metal hydride battery or a lithium ion battery.

  The battery monitoring unit 30 includes a voltage sensor 32 that detects a voltage between the positive terminal and the negative terminal of each of the plurality of secondary battery cells BT, and a temperature sensor 34 that detects the temperature of each of the plurality of secondary battery cells BT. I have. The temperature sensor 34 includes a thermistor that measures the temperature of the secondary battery cell BT. The voltage value detected by the voltage sensor 32 and the temperature value detected by the temperature sensor 34 are transmitted to the communication interface 54 of the battery management unit 50 via communication means (not shown). In FIG. 1, a load (use device) 60 is connected to the battery module 20.

  The current detection unit 40 includes a shunt resistor (not shown) that can detect a current output from the battery module 20. The current value detected by the current detection unit 40 is supplied to an MPU (micro processing unit) 52 of the battery management unit 50.

  The battery management unit 50 includes an MPU 52 that performs arithmetic processing, a communication interface 54 that communicates with the battery monitoring unit 30 and higher-level control means (not shown), a memory 56, and a time management means 58.

  The MPU 52 periodically obtains, from the battery monitoring unit 30 and the current detection unit 40, A / D converted values of the voltage values, temperature values, and current values of the plurality of secondary battery cells BT. The period in which the MPU 52 acquires these values is managed by the time management means 58.

  The MPU 52 calculates a remaining capacity (SOC: state of charge) of the secondary battery cell BT based on the open circuit voltage (OCV) value of the secondary battery cell BT, the acquired temperature value, And a means (not shown) for calculating the dischargeable capacity by correcting the value of the remaining capacity (SOC) from the current value.

  FIG. 2 shows an example of a characteristic curve (hereinafter referred to as a discharge characteristic curve) between voltage and discharge capacity when the secondary battery cell BT is discharged at a constant discharge (current) rate. A discharge characteristic curve (OCV table curve) when a new secondary battery cell BT is discharged at a low discharge (current) rate in a normal temperature environment (for example, an environment of 25 ° C.) has a characteristic as shown in graph 1, for example. Graph 1 shows the characteristics of the open-circuit voltage and the discharge capacity of the secondary battery cell BT in a room temperature environment. In FIG. 2, the vertical axis of the graph represents voltage [V] and the horizontal axis represents discharge capacity [% or A]. In the memory 56, for example, an OCV table 57 for calculating the remaining capacity of the secondary battery cell BT from the open circuit voltage of the secondary battery cell BT in a normal temperature environment is recorded.

  A discharge characteristic curve when the secondary battery cell BT deteriorated by use is discharged at a constant rate in a low-temperature environment is, for example, a discharge characteristic as shown in graph 2. When the secondary battery cell BT is a lithium ion battery, the internal impedance increases when the secondary battery cell BT is used in a low temperature environment or when deterioration has progressed. Therefore, the dischargeable capacity of the secondary battery cell BT having the discharge characteristic of graph 2 is smaller than that of the secondary battery cell BT having the discharge characteristic of graph 1.

  Furthermore, when the deteriorated secondary battery cell BT is discharged in a low temperature environment, the discharge characteristic curve when the discharge (current) rate is changed in the middle is the discharge characteristic as shown in graph 3, for example. When the discharge (current) rate of the secondary battery cell BT increases, the electromotive voltage of the secondary battery cell BT decreases due to the characteristic of I (current) × R (resistance). Therefore, even when the voltage of the secondary battery cell BT is the same, the dischargeable capacity is further reduced in the case of the discharge characteristic of the graph 3 than in the case of the discharge characteristic of the graphs 1 and 2.

  As described above, the dischargeable capacity of the secondary battery cell BT changes with the temperature change of the secondary battery cell BT and the discharge (current) rate change of the battery module 20. Therefore, in the dischargeable capacity calculation process that requires accuracy, it is necessary to calculate the dischargeable capacity by correcting the remaining capacity calculated from the open circuit voltage of the secondary battery cell BT using, for example, the OCV table 57.

  Therefore, in the secondary battery device according to the present embodiment, a plurality of tables TBL for correcting the remaining capacity corresponding to temperature changes and discharge (current) rate changes are recorded in the memory 56. FIG. 3 shows an example of the table TBL. The table TBL stores correction values based on previously measured values.

  In each region of the table TBL shown in FIG. 3, correction values corresponding to the temperature range of the secondary battery cell BT and the range of the discharge (current) rate are stored. For example, when the temperature of the secondary battery cell BT is A2 [° C.] or higher and lower than A3 [° C.] and the discharge (current) rate of the battery module 20 is B2 [A] or higher and lower than B3 [A], The MPU 52 acquires a value stored in the area A as a correction value.

  A plurality of tables TBL are prepared for each range of the remaining capacity of the secondary battery cell BT. In the example shown in FIG. 4, X tables TBL are recorded in the memory 56 for each range of the remaining capacity of the secondary battery cell BT.

  When the remaining capacity calculated using the OCV table 57 is corrected, the correction amount also changes according to the range of the remaining capacity of the secondary battery cell BT. Therefore, if all the remaining capacity is corrected by one table TBL and the dischargeable capacity of the secondary battery cell is calculated, it becomes difficult to calculate the dischargeable capacity with high accuracy. Therefore, in the secondary battery device according to the present embodiment, the table TBL is prepared for each range of the remaining capacity of the secondary battery cell BT, and the accuracy of calculating the dischargeable capacity is further improved.

  Here, the MPU 52 opens the open voltage value in the temperature value obtained from the temperature sensor 34 from the open voltage value of the secondary battery cell BT in each temperature environment measured in advance, and opens in the temperature environment in which the OCV table 57 is acquired. Means (not shown) for correcting the voltage value, means (not shown) for calculating an average value (current rate) of current values when the current of the secondary battery cell BT is not stable, and a discharge (current) rate Is provided with means (not shown) for averaging the discharge (current) rate when the current is not stable.

  When calculating the dischargeable capacity, the MPU 52 sets the open-circuit voltage of the secondary battery cell BT to a value corresponding to the temperature when the OCV table 57 is acquired based on the temperature value obtained from the temperature sensor 34. The remaining capacity corresponding to the corrected open circuit voltage is calculated from the OCV table 57. Then, the table TBL corresponding to the calculated remaining capacity is selected and stored in the area corresponding to the discharge (current) rate based on the temperature value obtained from the temperature sensor 34 and the current value obtained from the current detection unit 40. Acquire a correction value and correct the remaining capacity.

  When the correction value acquired from the table TBL is stored as the capacity value of the secondary battery cell BT, the dischargeable capacity is calculated from the remaining capacity obtained from the open circuit voltage using the OCV table 57. The value is obtained by adding or subtracting (dischargeable capacity = remaining capacity−correction value, or dischargeable capacity = remaining capacity + correction value).

  When the correction value obtained from the table TBL is stored as a ratio value [%] to the remaining capacity calculated from the OCV table 57, the dischargeable capacity is corrected with the remaining capacity obtained from the OCV table 57. The product of the value is divided by 100 (dischargeable capacity = remaining capacity × correction value / 100).

  Furthermore, in the secondary battery device according to the present embodiment, the MPU 52 includes a correction unit (not shown) that corrects the correction value stored in the table TBL. A graph 4 shown in FIG. 5 shows an example of a discharge characteristic curve of the secondary battery cell BT obtained based on the OCV table 57 and the table TBL when discharged at a predetermined temperature and a predetermined discharge (current) rate. ing. A graph 5 shown in FIG. 5 shows an example of a change in voltage value when the secondary battery cell BT having a predetermined remaining capacity is actually discharged at a predetermined temperature and a predetermined current rate.

  For example, as shown in FIG. 5A, when the discharge characteristic curve based on the OCV table 57 and the table TBL is different from the actual discharge characteristic curve, the MPU 52 corrects the correction value stored in the table TBL. It is configured.

  Hereinafter, the operation of the MPU 52 during and after the battery module 20 is discharged will be described with reference to FIG. First, the MPU 52 performs integration processing of the current value detected by the current detection unit 40 (step ST1). Next, it is determined whether or not the current of the battery module 20 is stable (step ST2). The MPU 52 determines that the current is stable when various conditions for determining whether or not the current value and the current integrated value supplied from the current detection unit 40 are stable are satisfied.

  When it is determined that the current is stable, the MPU 52 corrects the open-circuit voltage value of the secondary battery cell BT in accordance with the temperature value obtained from the temperature sensor 34, and calculates the calculated open-circuit voltage value. Using this, the remaining capacity is calculated from the OCV table 57 (step ST3).

  Subsequently, the MPU 52 selects a table TBL corresponding to the calculated remaining capacity. For example, the MPU 52 refers to the table TBL corresponding to the secondary battery cell BT whose remaining capacity is the minimum value, the discharge (current) rate calculated from the current value obtained from the current detection unit 40, and the temperature sensor 34. Based on the obtained temperature value, a correction value is acquired from the selected table TBL, the remaining capacity obtained from the OCV table 57 is corrected, and the dischargeable capacity is calculated (step ST4). The MPU 52 communicates the calculated dischargeable capacity to the upper control means via the communication interface 54 as necessary.

  Subsequently, when the battery module 20 is discharged, the MPU 52 performs current integration processing (step ST5), and records the current integration value in the memory 56 as an internal variable. Next, the MPU 52 determines whether or not the voltage value of the secondary battery cell BT obtained from the voltage sensor 32 has reached the lower limit voltage value (step ST6). When the voltage value of the secondary battery cell BT reaches the lower limit voltage value, the discharge of the secondary battery cell BT is completed. The discharge is continued until the discharge of the secondary battery cell BT having the minimum remaining capacity is completed. In addition, the value of the lower limit voltage of the secondary battery cell BT can be appropriately changed within a range where the secondary battery cell BT can be safely used.

  When the voltage value of the secondary battery cell BT reaches the lower limit voltage value, the MPU 52 determines whether the voltage value of the secondary battery cell BT reaches the lower limit voltage value based on the recorded current integrated value. It is determined whether or not the discharge (current) rate has continued for a certain period (step ST7).

  If the constant discharge (current) rate does not continue for a certain period, the MPU 52 ends the process. When it is determined that the constant discharge (current) rate has continued for a certain period, the MPU 52 calculates a capacity error (step ST8).

  In the example shown in FIG. 5, in the characteristics shown in the graph 5, a constant discharge (current) rate is continued in the period 22 before the voltage of the secondary battery cell BT reaches the lower limit voltage. Comparing graph 4 and graph 5 shown in FIG. 5A, the time required for the voltage of the secondary battery cell BT to reach the lower limit voltage is different. Since graphs 4 and 5 are discharged at a common constant discharge (current) rate, the capacity actually discharged this time (current integrated value), the dischargeable capacity calculated from the OCV table 57 and the table TBL, and There is an error in. The MPU 52 calculates the difference 23 by subtracting (or adding) the current integrated value from the dischargeable capacity calculated in step 4 to obtain a capacity error.

  Subsequently, after the voltage of the secondary battery cell BT reaches the lower limit voltage, the MPU 52 determines whether or not a certain period 24 in which the current of the battery module 20 is in a stable state again has elapsed as shown in FIG. (Step ST9).

  If the certain period has not elapsed, the MPU 52 ends the process. At this time, the MPU 52 may be configured to end the process after correcting the correction value stored in the area of the corresponding table TBL using the capacity error calculated in step ST8.

  When the fixed period 24 has elapsed, the MPU 52 uses the open circuit voltage to discharge the remaining capacity of the secondary battery cell BT from the OCV table at a constant discharge (current) and constant temperature, and the dischargeable capacity when the discharge is completed. Is calculated (step 10).

  The MPU 52 corrects the correction value stored in the corresponding temperature and discharge (current) rate area of the table TBL based on the error calculated in Step 10 and the capacity error calculated in Step 8 ( Step 11). The capacity error calculated in step 8 may include an integration error of the current integration value, but the error calculated in step 10 is a value that does not include the current integration error. Therefore, by calculating the error in step 10, it is possible to calculate a more accurate error.

  When correcting the correction value stored in the area of the table TBL, the MPU 52 adds or subtracts a value smaller than the correction value to the correction value of the table TBL (correction is performed via a low-pass filter). For example, the correction value is corrected by a value smaller than the calculated correction value by multiplying the correction value by a coefficient less than 1. For example, the coefficient less than 1 may be a constant value, a value that changes linearly according to the magnitude of the correction value, or a value that changes nonlinearly.

  By correcting the correction value in this way, for example, even when noise is included in the values obtained from the voltage sensor 32 and the temperature sensor 34, the correction value of the table TBL is prevented from being largely corrected. Thus, the correction value of the table TBL can be gradually brought close to an accurate value. Therefore, it is possible to reduce the influence of noise included in the voltage value, the temperature value, and the current value, and the correction value including the integration error of the current value.

  For example, as illustrated in FIG. 6, the MPU 52 corrects the correction value stored in the table TBL. That is, when correcting the correction value stored in the area A as the area corresponding to the predetermined discharge (current) rate and the predetermined temperature in the table TBL of the predetermined remaining capacity (SOC) range, for example, Correction values stored in other areas are also corrected. The correction of the correction value is likely to be accompanied by the deterioration of the secondary battery cell BT. The deterioration of the secondary battery cell BT was discharged in the range of other discharge (current) rate and in another temperature range. This is because the dischargeable capacity in this case is also affected. At this time, the correction value of the area other than the area A is determined based on the correction value of the correction value of the area A.

  Note that, as information stored in each area of the table TBL at this time, the corrected correction value, the time information of the correction, and the correction frequency information are recorded. At this time, the MPU 52 acquires time information from the time management means 58 and records it in the table TBL.

  Thus, the correction state of each area of the table TBL can be determined from the time information of the correction and the number of corrections. The MPU 52 can determine the reliability of the correction value of the table TBL based on such information. The MPU 52 can select an area for correcting the correction value of the table TBL according to the reliability.

  For example, the correction value of the table can be determined to have higher reliability as the correction time is newer, and can be determined to have higher reliability as the number of corrections increases. The reliability determined in this way may be recorded in each area of the table TBL, or may be referred to by being communicated from the MPU 52 to the upper control means through the communication interface 54 as appropriate.

  As described above, the MPU 52 is configured to calculate the remaining capacity of the secondary battery cell BT and the dischargeable capacity corrected for the remaining capacity, and further to correct the correction value for correcting the remaining capacity, thereby The table TBL is always corrected so that the dischargeable capacity corresponding to the deterioration state of the secondary battery cell BT is calculated. Therefore, according to the secondary battery device according to the present embodiment, it is possible to provide a secondary battery device capable of improving the calculation accuracy of the dischargeable capacity and estimating the accurate dischargeable capacity.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, in the above-described embodiment, the operation of the MPU 52 at the time of discharging has been described, but the chargeable capacity can be estimated using the OCV table 57 and the table TBL also at the time of charging.

  In the above-described embodiment, the OCV table 57 corresponds to the discharge characteristics when discharged at a constant discharge (current) rate in a room temperature environment, but there are a plurality of OCV tables corresponding to a plurality of temperature environments. It may be prepared and recorded in the memory 56. Even in these cases, the same effects as those of the above-described embodiment can be obtained.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  BT ... secondary battery cell, TBL ... table (second table), 30 ... battery monitoring unit, 32 ... voltage sensor, 34 ... temperature sensor, 40 ... current detection unit, 50 ... battery management unit, 52 ... MPU (calculation means) ), 54 ... Communication interface, 56 ... Memory (recording means), 57 ... OCV table (first table), 58 ... Time management means, 60 ... Load.

Claims (5)

A plurality of secondary battery cells;
Voltage detection means for detecting the voltage value of each of the plurality of secondary battery cells;
Current detection means for detecting current values of the plurality of secondary battery cells;
Temperature detecting means for measuring the temperature of each of the plurality of secondary battery cells;
A calculation means for supplying a voltage value, a current value, and a temperature value from the voltage detection means, the current detection means, and the temperature detection means;
A first table for calculating a remaining capacity from an open circuit voltage of the secondary battery cell at a predetermined temperature environment and a predetermined average current, and a correction value for correcting the remaining capacity calculated using the first table A second table for managing
The second table is prepared for each range of remaining capacity of the secondary battery cell, and the correction value corresponding to the range of the average current value of the secondary battery cell and the range of the temperature value of the secondary battery cell. Is recorded,
The calculating means selects the remaining capacity using the first table and the second table corresponding to the remaining capacity, and the temperature value obtained from the temperature detecting means and the current detecting means And a correction unit that corrects the remaining capacity by acquiring the correction value corresponding to the average value of the current values obtained from the second table.   The said calculating means is further provided with the voltage correction means which correct | amends the voltage value obtained from the said voltage detection part in the temperature environment obtained from the said temperature detection part to the said open circuit voltage value in the said predetermined temperature environment. The secondary battery device described.   The calculation means includes a current integration means for integrating the current value obtained from the current detection means, a means for determining whether or not the voltage value of the secondary battery cell has reached a lower limit voltage, and the secondary battery cell An error calculating means for calculating a capacity error between the current integrated value integrated by the current integrating means when the voltage value of the current value reaches the lower limit voltage and the capacity value calculated by the correcting means, and based on the capacity error The secondary battery device according to claim 1, further comprising correction means for correcting a correction value corresponding to the temperature value and the average current value when the lower limit voltage value is reached. A time management means,
When the correction means corrects the correction value by the correction means, the calculation means obtains correction time information of the correction value from the time management means, and the correction time information and the correction frequency of the correction value are obtained. The secondary battery device according to claim 3, wherein the secondary battery device is configured to record the correction means together with the correction value.   The correction means is configured to correct another correction value when correcting the correction value corresponding to the temperature value and the average current value when the lower limit voltage value is reached. Secondary battery device.

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