JP2013156202A - Method for calculating residual capacity of secondary cell and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for calculating a residual capacity of secondary cells capable of appropriately continuing discharge, even when the discharge of the plurality of serially-concatenated secondary cells progresses and the residual capacity (RC) or a relative state of charge (RSOC) becomes a fixed small capacity or less, and to provide a battery pack.SOLUTION: A calculation method includes: while calculating (learning) FCC (Full Charge Capacity) of each of three serially-concatenated battery blocks by a known method, detecting OCV (Open Circuit Voltage) of each battery block; collating the detected OCV with a discharge characteristic of Fig.3 that represents a relationship between OCV and RSOC of the battery block to calculate RSOC of each battery block; multiplying the calculated RSOC by FCC of each battery block to calculate RC of each battery block; and defining a minimum RC of the calculated RCs as a residual capacity of the entire secondary cells.

Description

  The present invention executes a remaining battery capacity calculation method for calculating a remaining capacity based on an open voltage (open terminal voltage, no load voltage) of a plurality of secondary batteries connected in series, and the remaining capacity calculation method. The present invention also relates to a battery pack that generates remaining capacity data.

  Conventionally, the remaining capacity (RC = Remaining Capacity) of a secondary battery mounted on an electronic device such as a personal computer (PC) is the full charge capacity (FCC = Full Charge Capacity), that is, the amount of electricity of the secondary battery in a fully charged state. Calculated by adding / subtracting the charge / discharge current or the integrated value of charge / discharge power (hereinafter referred to as charge / discharge amount) for each of (current value × time) or power amount (power value × time). Yes. The so-called remaining capacity may be expressed as a relative remaining capacity with respect to FCC (RSOC = Relative State Of Charge). In this way, the FCC from which the RC is calculated is reduced in accordance with deterioration due to the use of the secondary battery, but in the actual use state of the secondary battery (hereinafter simply referred to as full charge). In fact, there is little opportunity to calculate an accurate FCC, since there is almost no discharge (or charge from the discharge end state to the fully charged state) until the end of discharge state.

  Therefore, when the battery voltage of the secondary battery falls below a low voltage corresponding to a predetermined RSOC (a known voltage indicating that the RSOC is N%; N is an integer), a technique for correcting the RSOC to N% ( For example, using “Patent Document 1”), the capacity obtained by dividing “discharge amount−charge amount” accumulated from the time of full charge until the above known voltage is detected by “1-N / 100”. Is used as the FCC of the secondary battery.

  In Patent Document 2, an open terminal voltage (hereinafter referred to as an open voltage) detected by interrupting charging during charging of the secondary battery, a charge amount during a period of recharging until full charge, and after full charge A technique for calculating (learning) the FCC of the secondary battery based on the detected open circuit voltage is disclosed. Further, in Patent Document 3, the amount of change in RSOC calculated from the no-load voltage (open voltage) of the secondary battery at the first and second time points, and the amount of change in charge / discharge amount between the first and second time points, Thus, a technique for calculating (learning) the FCC of the secondary battery is disclosed. RC is calculated by multiplying the FCC calculated (learned) in this way by the calculated (or detected) RSOC, and further, a charge / discharge amount from the time of calculating RC is added / subtracted to / from RC to obtain a new value. RC is calculated.

  By the way, for a secondary battery charged by constant current / constant voltage charging, for example, the battery voltage of the battery cell having the maximum voltage is equal to or higher than the detection start voltage of full charge, and the state where the charging current is equal to or lower than a predetermined value continues for a certain time or longer. Is determined to be fully charged. If the battery voltage of the battery cell having the maximum voltage becomes higher than the fully charged detection voltage during this determination, it is determined that the battery is fully charged at that time.

JP-A-5-87896 JP 2011-43460 A JP 2008-261669 A

  However, when a plurality of secondary batteries are connected in series, the battery voltage of any secondary battery is higher than the full-charge determination voltage due to variations in the self-discharge amount of each secondary battery before charging. Even so, it is normal that other secondary batteries are not actually fully charged. And in the case of subsequent discharge, the battery voltage of said other secondary battery with the small charged amount reduces first. For this reason, only when the low voltage of the other secondary battery is detected and the RSOC is corrected, the RC or RSOC value of the entire secondary battery does not hibernate the PC (the sleep state in which the memory contents are stored). ) Has been detected as having been reduced to a value that cannot be transferred to. Even when there is no variation in the amount of self-discharge of each secondary battery, the same problem may occur when there is a difference in the chargeable / dischargeable capacity of each secondary battery due to variations such as deterioration.

  The present invention has been made in view of such circumstances, and the object of the present invention is to increase the remaining capacity (RC) or the relative remaining capacity (RSOC) as the discharge of a plurality of secondary batteries connected in series proceeds. An object of the present invention is to provide a method for calculating the remaining capacity of a secondary battery and a battery pack that can continue discharging appropriately even when the battery capacity becomes a certain small capacity or less.

  A method for calculating a remaining capacity of a secondary battery according to the present invention calculates a full charge capacity of a plurality of secondary batteries connected in series, and calculates a remaining capacity of the plurality of secondary batteries based on the calculated full charge capacity. In the method, the full charge capacity is calculated for each secondary battery, the open circuit voltage of each secondary battery is detected, and the discharge characteristics indicating the relationship between the open voltage of the secondary battery and the relative remaining capacity with respect to the full charge capacity, And calculating the relative remaining capacity of each secondary battery based on the detected open circuit voltage, and multiplying the calculated relative remaining capacity by the full charge capacity of each secondary battery, the remaining capacity of each secondary battery is calculated. The smallest remaining capacity of the calculated remaining capacity is calculated as the remaining capacity of the plurality of secondary batteries.

  The method for calculating the remaining capacity of a secondary battery according to the present invention determines whether or not the charging current and discharging current of the secondary battery are smaller than a predetermined current in a time series, and the state of determining that it is small continues for a predetermined time or more It is characterized by determining whether to continue, and when it is determined to continue, the open circuit voltage of each secondary battery is detected.

  The method for calculating the remaining capacity of a secondary battery according to the present invention specifies a secondary battery having the smallest remaining capacity among the calculated remaining capacity, stores information for identifying the identified secondary battery, and stores the stored information The remaining capacity of the secondary battery identified by is the remaining capacity of the plurality of secondary batteries.

  The secondary battery remaining capacity calculation method according to the present invention determines whether or not the secondary battery is in a fully charged state, and after determining that the secondary battery is in a fully charged state, information for identifying the secondary battery. It is characterized by updating.

  The battery pack according to the present invention includes a plurality of secondary batteries connected in series, first calculation means for calculating a full charge capacity of the secondary battery, and the plurality of secondary batteries based on the calculated full charge capacity. In the battery pack comprising the generating means for generating the remaining capacity data, the first calculating means detects the full charge capacity for each secondary battery, and detects the open voltage of each secondary battery. Based on the detection means, the discharge characteristics indicating the relationship between the open voltage of the secondary battery and the relative remaining capacity with respect to the full charge capacity, and the open voltage detected by the detection means, the relative remaining capacity of each secondary battery is calculated. Second calculating means for calculating, and third calculating means for calculating the remaining capacity of each secondary battery by multiplying the relative remaining capacity calculated by the second calculating means by the full charge capacity of each secondary battery. The generating means includes the third calculating means. Of the remaining capacity out, characterized in that you have to produce data of the smallest remaining capacity.

  In the battery pack according to the present invention, means for determining in time series whether or not the charging current and discharging current of the secondary battery are smaller than a predetermined current, and the state of determining that the means are small continue for a predetermined time or more. First detection means for determining whether or not the detection means detects the open circuit voltage of each secondary battery when it is determined that the first determination means continues. .

  The battery pack according to the present invention stores means for specifying the secondary battery having the smallest remaining capacity among the remaining capacity calculated by the third calculating means, and information for identifying the secondary battery specified by the means. Storage means, and the generation means generates data of the remaining capacity of the secondary battery identified by the information stored in the storage means.

  The battery pack according to the present invention includes second determination means for determining whether or not the secondary battery is in a fully charged state, and the storage means determines that the second determination means is in a fully charged state. In this case, the information for identifying the secondary battery is updated.

In the present invention, the full charge capacity (FCC) of each of a plurality of secondary batteries connected in series is determined by a method known per se (for example, the amount of change in RSOC at any two time points and the time between the two time points). Based on the amount of change in the amount of charge and discharge in the battery, it is calculated by a technique for learning FCC of the secondary battery (detailed in Patent Document 2), while detecting the open circuit voltage (OCV) of each secondary battery and detecting it The RSOC of each secondary battery is calculated based on the discharge characteristics indicating the relationship between the OCV of the secondary battery and the RSOC. Then, the RC of each secondary battery is calculated by multiplying the calculated RSOC by the FCC of each secondary battery, and the minimum RC among the calculated RCs is set as the remaining capacity of the plurality of secondary batteries as a whole.
Thereby, RC of the some secondary battery connected in series is calculated separately, and the remaining capacity of the whole some secondary battery is represented by the minimum RC of calculated RC. For this reason, before a secondary battery whose self-discharge amount is larger than other secondary batteries (or chargeable / dischargeable capacity is smaller than other secondary batteries) is in a low voltage state higher than the discharge end voltage, An adequately small remaining capacity is calculated for the entire secondary battery after securing an appropriate amount of discharge until the discharge is actually stopped.

In the present invention, a state in which the charging current and discharging current (hereinafter also referred to as charging / discharging current) of the secondary battery detected in time series is smaller than the predetermined current, that is, the state in which charging / discharging is not performed is the predetermined time. When the operation is continued, the open circuit voltage of each secondary battery is detected.
Thereby, the open circuit voltage is detected more accurately in a state where the influence of charging and discharging on the secondary battery is removed.

In the present invention, since the secondary battery once identified as having the smallest RC has a high probability of continuing the smallest RC, the secondary battery having the smallest RC among the RCs of the secondary batteries calculated separately. Is stored, and the RC of the secondary battery identified by the stored information is defined as the remaining capacity of the plurality of secondary batteries as a whole.
Accordingly, since the secondary battery that determines the remaining capacity of the entire plurality of secondary batteries is fixed until the information is updated, the remaining capacity is prevented from changing discontinuously. Further, while the information is updated, a new remaining capacity can be calculated in a timely manner by adding / subtracting the charge / discharge amount from the RC of the secondary battery specified by the previously updated information.

In the present invention, after the secondary battery with the highest battery voltage is fully charged, the information specifying the secondary battery with the smallest RC is updated.
Thereby, the secondary battery with the smallest RC is appropriately identified in the voltage state where the difference in RC is most prominent. Further, a point where the remaining capacity may change discontinuously is specified after detection of the full charge state.

According to the present invention, the RC of the secondary batteries connected in series is calculated separately, and the remaining capacity of all the secondary batteries is represented by the smallest RC among the calculated RCs. Before the battery goes into a low voltage state higher than the discharge end voltage, an adequate amount of discharge until the end of discharge is actually secured, and an adequately small remaining capacity is calculated for the entire secondary battery. The
Therefore, even when the discharge of secondary batteries connected in series progresses and the remaining capacity (RC) or the relative remaining capacity (RSOC) falls below a certain small capacity, the discharge should be continued as appropriate. Is possible.
Also, when the battery voltage of the secondary battery decreases and approaches a low voltage corresponding to the predetermined RSOC, the RSOC larger than the predetermined RSOC is suddenly corrected, and the value is decreased to a predetermined RSOC having a significantly different numerical value. Can be prevented.

It is a block diagram which shows the structural example of the battery pack which concerns on this invention. It is a graph of the discharge characteristic which illustrates the relationship between the open circuit voltage (OCV) of a battery block, and a relative remaining capacity (RSOC). It is explanatory drawing for demonstrating the change of RSOC accompanying the discharge of a battery block. It is a flowchart which shows the process sequence of CPU which calculates the remaining capacity of a secondary battery. It is a flowchart which shows the process sequence of CPU which calculates the remaining capacity of a secondary battery.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram showing a configuration example of a battery pack according to the present invention. In the figure, reference numeral 10 denotes a battery pack. The battery pack 10 is detachably attached to an electric device 20 such as a personal computer (PC) or a portable terminal. The battery pack 10 includes, for example, battery blocks 11, 12, and 13 that are formed by connecting three battery cells 111, 112, 113, 121, 122, 123, 131, 132, and 133, which are made of, for example, lithium ion batteries. A secondary battery 1 that is connected in series in order is provided. The secondary battery 1 is configured such that the positive electrode of the battery block 13 and the negative electrode of the battery block 11 become a positive electrode terminal and a negative electrode terminal, respectively.

  The voltages of the battery blocks 11, 12, and 13 are each independently applied to the analog input terminal of the A / D conversion unit 4, converted into a digital voltage value, and from the digital output terminal of the A / D conversion unit 4 It is given to the control unit 5 comprising a computer. The analog input terminal of the A / D conversion unit 4 is arranged in close contact with the secondary battery 1, and the detection output of the temperature detector 3 that detects the battery temperature of the secondary battery 1 by a circuit including a thermistor, A detection output of a current detector 2, which is interposed in a charging / discharging path on the negative electrode terminal side of the secondary battery 1 and includes a resistor for detecting a charging current and a discharging current of the secondary battery 1, is given. These detection outputs are converted into digital detection values and given to the control unit 5 from the digital output terminal of the A / D conversion unit 4.

  The charge / discharge path on the positive electrode terminal side of the secondary battery 1 is provided with a circuit breaker 7 composed of P-channel type MOSFETs 71 and 72 that block the charge current and the discharge current, respectively. The MOSFETs 71 and 72 are connected in series with their drain electrodes butted together. A diode connected in parallel between the drain electrode and the source electrode of each of the MOSFETs 71 and 72 is a parasitic diode (body diode). MOSFETs 71 and 72 may be N-channel type.

  The control unit 5 includes a CPU 51, which includes a ROM 52 that stores information such as programs, a RAM 53 that stores temporarily generated information, a timer 54 that measures various times in parallel, and a battery pack 10. The I / O port 55 for inputting / outputting each unit is connected to each other by a bus. The I / O port 55 is connected to the digital output terminal of the A / D conversion unit 4, the gate electrodes of the MOSFETs 71 and 72, and the communication unit 9. The communication unit 9 communicates with a control / power supply unit (charging unit) 21 included in the electrical device 20. The ROM 52 is a non-volatile memory composed of a flash memory. In addition to the program, the ROM 52 stores, for example, a learning value for the full charge capacity (learning capacity) and an initial value for the charging current (that is, a set current).

  The CPU 51 executes processing such as calculation and input / output according to a control program stored in advance in the ROM 52. For example, the CPU 51 captures the voltage values of the battery blocks 11, 12, and 13 and the detection value of the charging / discharging current of the secondary battery 1 at a cycle of 250 ms, and the secondary battery 1 of the secondary battery 1 based on the captured voltage value and detection value. Charge current or charge power or discharge current or discharge power is integrated, and the charge amount or discharge amount calculated by the integration is stored in the RAM 53. The unit of charge / discharge amount when charge / discharge current and charge / discharge power are integrated is Ah, Wh. The fetch period of the voltage value and the detected value of the charge / discharge current is not limited to 250 ms. The CPU 51 also generates data such as remaining capacity, relative remaining capacity, and charging current, and transmits the generated data to the electrical device 20 via the communication unit 9.

  The breaker 7 is electrically connected between the drain electrode and the source electrode of each of the MOSFETs 71 and 72 when an ON signal of L (low) level is given from the I / O port 55 to the gate electrodes of the MOSFETs 71 and 72 during normal charge / discharge. It is supposed to be. When the charging current of the secondary battery 1 is cut off, the conduction between the drain electrode and the source electrode of the MOSFET 71 is cut off by applying an H (high) level off signal from the I / O port 55 to the gate electrode of the MOSFET 71. The Similarly, when the discharge current of the secondary battery 1 is cut off, an H (high) level off signal is applied from the I / O port 55 to the gate electrode of the MOSFET 72, thereby causing conduction between the drain electrode and the source electrode of the MOSFET 72. Blocked. When the MOSFETs 71 and 72 are N-channel type, an on / off signal of H / L level obtained by inverting the above L / H level may be given to the gate electrode. When the secondary battery 1 is in a properly charged state, the MOSFETs 71 and 72 of the circuit breaker 7 are both turned on, and the secondary battery 1 is in a state where it can be discharged and charged.

  The electric device 20 includes a terminal unit 22 connected to a control / power supply unit 21. The control / power supply unit 21 is supplied with power from a commercial power source (not shown) to drive the terminal unit 22 and supplies a charging current to the charging / discharging path of the secondary battery 1. The control / power supply unit 21 also drives the terminal unit 22 by the discharge current supplied from the charge / discharge path of the secondary battery 1 when the supply of power from the commercial power supply is cut off. When the secondary battery 1 charged by the control / power supply unit 21 is a lithium ion battery, for example, a constant current (MAX current of about 0.5 to 1 C) and a constant voltage (MAX 4.2 to 4.4 V / battery cell) Is charged. When the battery voltage of the battery block with the maximum voltage is not less than the full charge detection start voltage and the state where the charging current is not more than a predetermined value continues for a certain period of time or longer, the CPU 51 is in the fully charged state (hereinafter referred to as the secondary battery 1). , Also referred to as full charge). Further, for example, in the battery block with the maximum voltage, when the battery voltage becomes a certain voltage or more, the MOSFET 71 is turned off for a certain period (for example, 60 minutes or 15 minutes to 90 minutes), and the open circuit voltage (OCV = Open Circuit Voltage) is detected, and when the detected open circuit voltage is equal to or higher than a certain voltage, it may be determined that the battery is fully charged. Instead of determining full charge by the open-circuit voltage, it may be determined that the battery is fully charged when the battery voltage being charged is the maximum and the battery voltage is equal to or higher than a predetermined voltage.

  Communication between the control / power supply unit 21 and the communication unit 9 is performed by a communication method such as an SMBus (System Management Bus) method using the control / power supply unit 21 as a master and the control unit 5 including the communication unit 9 as a slave. In the case of the SMBus system, the serial clock (SCL) is supplied from the control / power supply unit 21, and the serial data (SDA) is transferred between the control / power supply unit 21 and the communication unit 9 in both directions. In the present embodiment, the control / power supply unit 21 polls the communication unit 9 at a cycle of 2 seconds and reads the content of data to be transmitted by the communication unit 9. The polling cycle of 2 seconds depends on the setting on the control / power supply unit 21 side.

  By this polling, for example, the remaining capacity and relative remaining capacity data of the secondary battery 1 are transferred to the control / power supply section 21 via the communication section 9 in a cycle of 2 seconds, and the display device (not shown) included in the electric device 20 Is displayed as a value (%) of the relative remaining capacity. Further, the initial value of the charging current set by the control unit 5, that is, the charging current data is transmitted to the control / power supply unit 21 via the communication unit 9 in the same manner as the remaining capacity data. The control / power supply unit 21 charges the secondary battery 1 with a constant current / constant voltage based on the charging current transmitted from the control unit 5.

Next, a method for calculating (learning) the full charge capacity (FCC) of one battery block constituting the secondary battery 1 will be described.
FIG. 2 is a graph of discharge characteristics illustrating the relationship between the open circuit voltage (OCV) and the relative remaining capacity (RSOC) of the battery blocks 11, 12, and 13. In the figure, the horizontal axis represents the relative remaining capacity (%) defined as the ratio of the remaining capacity (RC) to the full charge capacity (FCC), and the vertical axis represents the open circuit voltage (V). In the present embodiment, the voltage at which the battery blocks 11, 12, 13 are fully charged is 4.2V, and the end-of-discharge voltage is 3V.

  The FCC is calculated by, for example, a known method detailed in Patent Document 2. In other words, the graph shown in FIG. 2 is stored as a function or table in the ROM 52 or RAM 53, and the OCV of one battery block detected at any two points in time is applied to the stored function or table, and the RSOC is separately set. The FCC is calculated by applying the calculated RSOC difference (ΔRSOC) and the change amount (ΔRC) of the remaining capacity between the time points to the following equation (1). The FCC can be learned by repeating the calculation according to the equation (1) in a timely manner.

FCC = ΔRC / (ΔRSOC / 100) (1)
Here, when the OCV of one battery block detected at time 1 and time 2 is OCV1 and OCV2, ΔRSOC is calculated as “RSOC1−RSOC2” from FIG. Further, ΔRC between the time point 1 and the time point 2 is calculated by integrating the charging / discharging current between the time points. However, the charging current and the discharging current here are detected as values having different signs.

Next, the method according to the present invention for calculating the remaining capacity based on the FCC calculated (learned) for each of the battery blocks 11, 12, and 13 will be described.
Prior to calculating the remaining capacity, first, OCVs of the battery blocks 11, 12, and 13 of the secondary battery 1 are detected separately. In this case, in order to detect each OCV more accurately, the OCV is detected when a period in which the secondary battery 1 is not charged or discharged continues for a predetermined time (for example, 1 hour) or more. In order to confirm that the secondary battery 1 is not charged or discharged, it is only necessary to confirm that the charge / discharge current (absolute value thereof) is smaller than a predetermined current.

  By applying the OCV of the battery blocks 11, 12, 13 detected as described above to the function or table stored in the ROM 52 or RAM 53 as described above, the RSOC of the battery blocks 11, 12, 13 can be determined separately. Calculated. By applying each calculated RSOC to the following formula (2), RC of the battery blocks 11, 12, 13 is calculated separately.

RC = RSOC x FCC (2)
Here, the FCC is calculated (learned) for each of the battery blocks 11, 12, and 13 by the equation (1).

Of the RCs calculated by the equation (2), there is a problem of which RC is used as the remaining capacity of the secondary battery 1, but in the present embodiment, the RC having the smallest value is set to two. The remaining capacity of the secondary battery 1 is assumed. The reason for doing so will be described with reference to FIG.
FIG. 3 is an explanatory diagram for explaining a change in RSOC associated with the discharge of the battery blocks 11, 12, and 13. In the figure, the horizontal axis represents the relative remaining capacity (%), and the vertical axis represents the open circuit voltage (V). The solid line in FIG. 3 exemplifies the relationship between the OCV and the RSOC of the battery blocks 11, 12, and 13, similarly to the solid line shown in FIG. 2.

  Now, even if the battery blocks 11, 12, 13 have almost the same chargeable / dischargeable capacity, there may be a difference in the self-discharge amount between the battery blocks 11, 12, 13. For example, when the self-discharge amounts of the battery blocks 11 and 13 are minimum and maximum, the battery block 12 even when the battery voltage of the battery block 11 is 4.2 V as shown by the point A1 in FIG. , 13 remains at a level lower than 4.2 V as indicated by points B1 and C1. Even in such a case, it is determined that the secondary battery 1 is in a fully charged state.

  On the other hand, the FCC of each of the battery blocks 11, 12, and 13 calculated by the equation (1) is independent of the amount of self-discharge as long as the capacity that can be charged and discharged in the battery blocks 11, 12, and 13 is substantially the same. It becomes almost constant. The remaining capacity when the secondary battery 1 is fully charged is set as the FCC, and the remaining capacity of the secondary battery 1 is calculated in a timely manner by adding / subtracting the charge / discharge amount from the FCC to the FCC. Is the conventional method.

  As a more specific example, the RSOC of the battery blocks 11, 12, 13 when the secondary battery 1 is fully charged is 100%, 96%, 92%, and then the RSOC of the battery block 11 is 11 Assume that the secondary battery 1 is discharged until it decreases to%. The capacity | capacitance which can be charged / discharged by the battery blocks 11, 12, and 13 shall be substantially the same. In such a case, while the battery block 11 moves on the solid line shown in FIG. 3 from the point A1 to the point A2, the battery blocks 12 and 13 move from the points B1 and C1 to the points B2 and C2, respectively. The RSOC at points B2 and C2 is 7% and 3%.

  In general, when the battery voltage of the battery block having the smallest voltage among the battery blocks 11, 12, and 13 decreases to a voltage corresponding to the point B2 (or the point C2), the remaining capacity of the secondary battery 1 is 7 % (Or 3%) is corrected. That is, according to the conventional method, when the battery voltage of the battery block 13 reaches a low voltage corresponding to 7% (or 3%) of the RSOC, the RSOC of the battery block 11 having the maximum voltage is in a fully charged state. The amount of discharge current (or discharge power) is subtracted from 100% to 11%, but the RSOC of the secondary battery 1 as a whole is 7% (or 3%), which suddenly differs greatly from this 11%. ) Is corrected. Thereby, when the low voltage by the battery block 13 is detected, it is shown that only 7% (or 3%) of the remaining capacity of the secondary battery 1 is already left.

  On the other hand, in this embodiment, since the remaining capacity of the secondary battery 1 is calculated based on the RC of the battery block 13 from when the secondary battery 1 is fully charged, as described above, The remaining capacity that has been 11% or more until that time is prevented from suddenly becoming 7% (or 3%). Further, since the FCC is calculated for each of the battery blocks 11, 12, and 13, even if there is a difference in the capacity that can be charged and discharged in the battery blocks 11, 12, and 13, the remaining capacity is newly added. When calculated, the remaining capacity of the secondary battery 1 is calculated based on the RC of the battery block having the smallest RC.

  In the present embodiment, the remaining capacity of the secondary battery 1 is newly calculated when the period in which neither charging nor discharging is continued for one hour or longer, the secondary battery 1 is in a fully charged state. The remaining capacity of the secondary battery 1 may be newly calculated only after the detection.

Below, operation | movement of the control part 5 of the battery pack mentioned above is demonstrated using the flowchart which shows it. The following processing is executed by the CPU 51 according to a control program stored in advance in the ROM 52.
4 and 5 are flowcharts showing the processing procedure of the CPU 51 for calculating the remaining capacity of the secondary battery 1. The period at which the process of FIG. 4 is started is, for example, 250 milliseconds, but is not limited thereto.

  The time keeping flag and the full charge flag used in the processes of FIGS. 4 and 5 are stored in the RAM 53 and cleared to 0 by a predetermined initialization process. The timekeeping flag is a flag indicating that timekeeping has already started, and the full charge flag indicates that the fully charged state of the secondary battery 1 has been detected by a process (not shown) different from FIGS. It is a flag which shows. Other calculation process data is also stored in the RAM 53 as appropriate. In addition, the table values corresponding to the graph shown in FIG. 2 and the FCCs of the battery blocks 11, 12, 13 calculated by other processing (not shown) are stored in the ROM 52 or the RAM 53.

  When the process of FIG. 4 is activated, the CPU 51 captures the voltage of the current detector 2 via the A / D converter 4, converts the captured voltage into a current, and detects the charge / discharge current (S11). Actually, the charge / discharge current may be detected based on the voltage taken a plurality of times. Thereafter, the CPU 51 determines whether or not the detected charging / discharging current is larger than, for example, −5 mA (discharging current region) and smaller than 20 mA (charging current region) (S12). (S12: NO), after that, nothing is executed and the process of FIG. 4 is terminated.

  Here, in consideration of the fact that there is a conversion error in the A / D converter 4 and the fact that there is a current that becomes an apparent charging current inside the battery pack 10, the charging current smaller than 20 mA and the absolute value are A discharge current smaller than 5 mA is not detected as a charge / discharge current. However, the current value to be compared with the charge / discharge current in step S12 is not limited to 20 mA and −5 mA.

  When the detected charging / discharging current is larger than −5 mA and smaller than 20 mA (S12: YES), it may be determined that charging / discharging is not performed, so the CPU 51 confirms whether or not the timing is already being performed. Therefore, it is determined whether or not the time keeping flag is set to 1 (S13). If it is not set to 1 (S13: NO), the CPU 51 starts measuring time using the timer 54 (S14), sets a counting flag to 1 (S15), and ends the processing of FIG.

  When the timekeeping flag is set to 1 in step S13 (S13: YES), that is, when timekeeping has already started, the CPU 51 determines whether or not one hour has elapsed since the time measurement was started. (S16) If the time has not elapsed (S16: NO), the processing of FIG. 4 is once terminated. When one hour has elapsed (S16: YES), the CPU 51 clears the timekeeping flag to 0 for the next timekeeping (S17), and then each battery block 11, 12, 13 OCVs are detected (S18).

  Thereafter, the CPU 51 calculates the RSOC of each of the battery blocks 11, 12, and 13 by applying the detected OCV to a table stored in the ROM 52 or the RAM 53 (S19). As described above, when the OCV of each battery block 11, 12, 13 detected at two points in time is obtained, the FCC of each battery block 11, 12, 13 is obtained by using the equation (1). calculate. Further, the CPU 51 calculates the RC of each battery block 11, 12, 13 by applying the calculated RSOC and the FCC of each battery block 11, 12, 13 stored in the ROM 52 or RAM 53 to Equation (2). Then, each calculated RC is temporarily stored in the RAM 53 (S21).

  Next, moving to FIG. 5, the CPU 51 determines whether or not the full charge flag is set to 1 (S <b> 22), and if it is not set (S <b> 22: NO), the process proceeds to step S <b> 26 described later. When the full charge flag is set to 1 (S22: YES), that is, when it is detected by other processing (not shown) that the secondary battery 1 is in the full charge state, the CPU 51 performs the next full charge. The full charge flag is cleared to 0 in preparation for the state detection (S23).

  Thereafter, the CPU 51 identifies the battery block having the smallest RC among the RCs of the battery blocks 11, 12, and 13 stored in the RAM 53 (S 24), and stores the serial number (eg, 1, 2, 3) of the identified battery block in the RAM 53. (S25). The serial numbers here are information for identifying the battery blocks 11, 12, and 13. The battery blocks 11, 12, and 13 may be identified using information other than the serial numbers.

  Next, the CPU 51 reads the serial number of the battery block stored in the RAM 53 (S26), and reads the RC of the battery block identified by the read serial number from the RAM 53 (S27). Further, the CPU 51 generates communication data from the read RC (S28), and transmits the generated communication data to the control / power supply unit 21 via the communication unit 9 (S29), and then ends the process of FIG. .

  In the above flowchart, a known means for calculating the FCC for each battery block by a process not shown corresponds to the “first calculation means” recited in the claims, and step S28 corresponds to the “generation means” recited in the claims. Step S18 corresponds to the “detection means” described in the claims, step S19 corresponds to the “second calculation means” described in the claims, and step S20 corresponds to the “third calculation means” described in the claims. Corresponding to Further, step S12 corresponds to “means for determining in time series” described in the claims, step S16 corresponds to “first determination means” described in the claims, and step S24 corresponds to “ Step S25 and RAM 53 correspond to the “storage means” recited in the claims, and step S22 corresponds to the “second determination means” recited in the claims.

  In this embodiment, it is determined whether or not the full charge flag is set to 1 in step S22 shown in FIG. 5, but steps S24 and S25 are executed each time without making this determination. You may do it. In this case, the remaining capacity is calculated regardless of whether or not the secondary battery 1 is fully charged.

Further, in the present embodiment, the remaining capacity is calculated while the secondary battery 1 is not being charged / discharged. The subsequent charge / discharge amount is added to the remaining capacity thus calculated. The remaining capacity may be calculated at any time by subtracting.
Further, although only the remaining capacity communication data is generated, the calculated remaining capacity may be divided by FCC to calculate the RSOC, and RSOC communication data may be generated from the calculated RSOC and transmitted.

As described above, according to the present embodiment, the FCC of each of the three battery blocks connected in series is calculated (learned) by a method known per se, while the OCV of each battery block is detected and detected. The OCV is calculated based on the discharge characteristics indicating the relationship between the OCV of the battery block and the RSOC, and the RSOC of each battery block is calculated. Then, the RC of each battery block is calculated by multiplying the calculated RSOC by the FCC of each battery block, and the smallest RC among the calculated RCs is set as the remaining capacity of the entire secondary battery.
Thereby, RC of the some battery block connected in series is calculated separately, and the remaining capacity of the whole secondary battery is represented by the minimum RC of the calculated RC. For this reason, one battery block whose self-discharge amount is larger than other battery blocks (or the chargeable / dischargeable capacity is smaller than other battery blocks) is in a low voltage state corresponding to 7% or 3% of RSOC. Before, for example, the RSOC of the entire secondary battery is calculated to be 11% or more, and an appropriate amount of discharge is secured until the discharge is stopped at 3V.
Therefore, even when the discharge of a plurality of battery blocks connected in series progresses and the remaining capacity (RC) or the relative remaining capacity (RSOC) falls below a certain small capacity, it is possible to continue discharging appropriately. It becomes possible.

In addition, when the state in which the charging / discharging current of the secondary battery detected every 250 milliseconds is smaller than 20 mA and larger than −5 mA, that is, the state where charging / discharging is not performed continues for one hour or more, the OCV of each battery block Is detected.
Therefore, the OCV can be detected more accurately in a state where the influence of charging and discharging on the battery block is removed.

Further, since the battery block once identified as having the smallest RC is likely to remain at the smallest RC, the serial number for identifying the battery block having the smallest RC among the RCs of the battery blocks calculated separately is stored in the RAM. The RC of the battery block identified by the stored serial number is set as the remaining capacity of the entire secondary battery.
Therefore, since the battery block that determines the remaining capacity of the entire secondary battery is fixed until the serial number is updated, it is possible to prevent the remaining capacity from changing discontinuously. Further, by adding / subtracting the charge / discharge amount from the RC of the battery block specified by the previously updated sequence number while the sequence number is updated, a new remaining capacity can be calculated in a timely manner.

Furthermore, after the battery block with the highest battery voltage is fully charged, the serial number for specifying the battery block with the smallest RC is updated.
Therefore, it is possible to appropriately specify the battery block having the smallest RC in the voltage state where the difference in RC is most prominent. In addition, it is possible to identify a point where the remaining capacity may change discontinuously after detection of the fully charged state.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Secondary battery 11, 12, 13 Battery block 10 Pack battery 2 Current detector 4 A / D conversion part 5 Control part 51 CPU
52 ROM
53 RAM
54 Timer 71, 72 MOSFET
9 Communication Department 20 Electrical Equipment 21 Control / Power Supply

Claims (8)

In the method of calculating the full charge capacity of a plurality of secondary batteries connected in series, and calculating the remaining capacity of the plurality of secondary batteries based on the calculated full charge capacity,
Calculate the full charge capacity for each secondary battery,
Detect the open voltage of each secondary battery,
Based on the discharge characteristics indicating the relationship between the open voltage of the secondary battery and the relative remaining capacity relative to the full charge capacity, and the detected open voltage, the relative remaining capacity of each secondary battery is calculated,
Calculate the remaining capacity of each secondary battery by multiplying the calculated relative remaining capacity by the full charge capacity of each secondary battery,
Of the calculated remaining capacities, the smallest remaining capacity is set as the remaining capacity of the plurality of secondary batteries. It is determined in time series whether the charging current and discharging current of the secondary battery are smaller than a predetermined current,
Determine whether the state that is determined to be small continues for a predetermined time or more,
The method for calculating the remaining capacity of the secondary battery according to claim 1, wherein when it is determined to continue, an open circuit voltage of each secondary battery is detected. Of the calculated remaining capacity, identify the secondary battery with the smallest remaining capacity,
Stores information that identifies the specified secondary battery,
The method for calculating the remaining capacity of the secondary battery according to claim 1 or 2, wherein the remaining capacity of the secondary battery identified by the stored information is used as the remaining capacity of the plurality of secondary batteries. Determining whether the secondary battery is fully charged,
The method for calculating the remaining capacity of the secondary battery according to claim 3, wherein information for identifying the secondary battery is updated after it is determined that the battery is in a fully charged state. A plurality of secondary batteries connected in series, a first calculation means for calculating a full charge capacity of the secondary battery, and data of remaining capacity of the plurality of secondary batteries based on the calculated full charge capacity In the battery pack comprising the generating means,
The first calculating means detects a full charge capacity for each secondary battery;
Detecting means for detecting an open voltage of each secondary battery;
A second calculating the relative remaining capacity of each secondary battery based on the discharge characteristics indicating the relationship between the open voltage of the secondary battery and the relative remaining capacity with respect to the full charge capacity, and the open voltage detected by the detecting means. A calculation means;
Third calculation means for calculating the remaining capacity of each secondary battery by multiplying the relative remaining capacity calculated by the second calculation means by the full charge capacity of each secondary battery,
The battery pack is characterized in that the generation means generates data of the smallest remaining capacity among the remaining capacity calculated by the third calculation means. Means for chronologically determining whether the charging current and discharging current of the secondary battery are smaller than a predetermined current;
First determination means for determining whether or not the state for determining that the means is small continues for a predetermined time or more,
6. The battery pack according to claim 5, wherein when the first determination unit determines that the first determination unit continues, the detection unit detects an open circuit voltage of each secondary battery. Means for specifying a secondary battery having the smallest remaining capacity among the remaining capacity calculated by the third calculating means;
Storage means for storing information for identifying the secondary battery specified by the means;
7. The battery pack according to claim 5, wherein the generation unit generates data of a remaining capacity of the secondary battery identified by the information stored in the storage unit. A second determination means for determining whether or not the secondary battery is in a fully charged state;
8. The battery pack according to claim 7, wherein the storage unit is configured to update information for identifying the secondary battery when the second determination unit determines that the battery is in a fully charged state.

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