JP2011030395A - Device and method for calculating remaining time - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of precisely calculating the remaining time of a secondary battery. <P>SOLUTION: A remaining capacity detection part 212 detects the remaining capacity RC of a battery pack 14. An average voltage information storage part 213 pre-stores the average voltage information showing an average voltage of a battery pack 14 obtained when a constant electric power is discharged from the battery pack 14. In a correction part 214, the average voltage Vave corresponding to a discharge current Idc detected by a current detection resistance 16 and a temperature detected by a temperature sensor 17 are determined by referring to the average voltage information, and the remaining capacity RC is corrected based on the ratio of the average voltage Vave of the battery pack 14 to the voltage V detected by a voltage detection circuit 15. A remaining time calculation part 215 calculates the remaining time T of the battery pack 14 by dividing ImCapa calculated by the correction part 214 by the discharge current Idc detected by the current detection resistance 16, that is, by the arithmetic operation of formula (2). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for calculating the remaining time of a secondary battery that supplies electric power to an electric device driven with constant power.

  Conventionally, the remaining time of a secondary battery that supplies electric power to an electric device driven by constant power, that is, a secondary battery that performs constant power discharge, is obtained by dividing the remaining capacity (mAh) of the secondary battery by the discharge current (mA). It was calculated by.

  However, since the discharge current of the secondary battery gradually increases as the discharge time elapses, the discharge current is lower at the initial stage of discharge than at the end of the discharge, and the conventional remaining time calculation method uses the remaining time calculated at the initial stage of discharge. Was calculated with a value larger than the actual remaining time.

  Therefore, the user is informed that the remaining time is, for example, 1 hour immediately after the start of use of the electric device. If the user believes that notification and is using the electric device, the remaining capacity is considerably long before one hour has passed. Becomes 0, and there is a problem that it becomes impossible to use the electric device earlier than planned.

  Therefore, conventionally, the remaining time of the secondary battery that performs constant power discharge is calculated only as a rough value such as 15 minutes or 30 minutes, and not calculated at a fine time interval such as 1 minute. It was.

  Patent Documents 1 and 2 are known as techniques related to the present invention. In Patent Document 1, for the purpose of accurately detecting the remaining capacity of the battery even if the discharge current changes greatly, a correction coefficient is determined from the average discharge current within a predetermined time, and this correction coefficient is used as the full charge capacity of the battery. A technique for calculating the remaining capacity of a battery by calculating the remaining capacity of the battery by calculating the dischargeable capacity by multiplying by, subtracting the amount of electricity consumed from the dischargeable capacity.

  Further, in Patent Document 2, for the purpose of calculating the remaining capacity in consideration of the temperature characteristics and deterioration of the secondary battery, an approximate expression of the relationship Wh (P) between the power characteristics and the discharge energy is expressed as a temperature correction coefficient (α ), A change in electric capacity (β) and a change in internal resistance (γ) of the battery, and a technique for calculating the remaining capacity using the corrected Wh (P).

Japanese Patent No. 3076192 Japanese Patent No. 3543645

  By the way, in recent years, there is a demand for electric devices such as video cameras to calculate the remaining time of the secondary battery at a minute time interval such as 1 minute.

  However, in the conventional remaining time calculation method, as described above, the remaining time is calculated simply by dividing the remaining capacity by the discharge current. There was a problem that we could not respond.

  The objective of this invention is providing the technique which can calculate the remaining time of a secondary battery accurately.

  (1) A remaining time calculation device according to one aspect of the present invention is a remaining time calculation device that calculates a remaining time of a secondary battery that supplies power to a load device that is driven by constant power, and the voltage of the secondary battery. A voltage detection unit that detects discharge current, a current detection unit that detects a discharge current of the secondary battery, a storage unit that previously stores an average voltage of the secondary battery when the secondary battery is discharged at a constant power, A remaining capacity detector that detects the remaining capacity of the secondary battery, and a correction that corrects the remaining capacity detected by the remaining capacity detector based on the ratio of the average voltage to the voltage detected by the voltage detector. And a remaining time calculating unit that calculates the remaining time of the secondary battery by dividing the remaining capacity corrected by the correcting unit by the discharge current detected by the current detecting unit.

  A remaining time calculation method according to another aspect of the present invention is a remaining time calculation method for calculating a remaining time of a secondary battery that supplies power to a load device that is driven at a constant power. A voltage detection step for detecting a voltage; a current detection step for detecting a discharge current of the secondary battery; a remaining capacity detection step for detecting a remaining capacity of the secondary battery; and a voltage detected by the voltage detection step. A correction step of correcting the remaining capacity detected by the remaining capacity detection step based on a ratio of the average voltage of the secondary battery obtained in advance by discharging the secondary battery at constant power; and the correction step And a remaining time calculating step of calculating a remaining time of the secondary battery by dividing the remaining capacity corrected by the above by the discharge current detected by the current detecting step.

  According to these configurations, the remaining capacity of the secondary battery is based on the ratio of the average voltage of the secondary battery when the secondary battery is discharged at a constant power with respect to the voltage of the secondary battery detected by the voltage detection unit. Is corrected, the corrected remaining capacity is divided by the discharge current, and the remaining time of the secondary battery is calculated.

  Here, since the discharge current of the secondary battery gradually increases as the discharge time elapses, when the secondary battery in a fully charged state is discharged at a constant power, the voltage of the secondary battery at the initial stage of discharge is higher than the average voltage. The value tends to increase. Therefore, in the initial stage of discharge, the ratio of the average voltage to the voltage of the secondary battery is less than 1 because the denominator is larger than the numerator.

  Therefore, when the remaining capacity of the secondary battery is corrected using the ratio of the average voltage to the voltage of the secondary battery at the initial stage of discharge, the value of the remaining capacity after correction becomes smaller than the remaining capacity before correction. As a result, the remaining time obtained by dividing the corrected remaining capacity by the discharge current at the initial stage of discharge is the conventional remaining time obtained by dividing the remaining capacity before correction by the discharge current at the initial stage of discharge. Smaller than that.

  In other words, in the initial stage of discharge, the remaining capacity of the numerator can be reduced in consideration of the fact that the discharge current of the denominator is reduced, and the remaining time is prevented from being calculated with a value larger than the actual remaining time. be able to. As a result, the remaining time can be accurately calculated, and the remaining time can be calculated at a short time interval such as 1 minute.

  (2) The storage unit stores in advance average voltage information indicating the average voltage according to the discharge current when the secondary battery is discharged at a constant power with a different discharge current, and the correction unit stores the current It is preferable that an average voltage corresponding to the discharge current detected by the detection unit is specified using the average voltage information, and the ratio is calculated using the specified average voltage.

  According to this configuration, the average voltage information indicating the relationship between the discharge current and the average voltage when the secondary battery is discharged at constant power with various discharge currents is stored in advance. And the average voltage according to the actual discharge current at the time of remaining time calculation is specified with reference to average voltage information, and the ratio is calculated using the specified average voltage. Therefore, the remaining time can be calculated in consideration of the actual state of the secondary battery at the time of discharging, and the remaining time can be calculated more accurately.

  (3) It further includes a temperature detection unit that detects the temperature of the secondary battery, and the average voltage information includes the discharge current and the temperature when the secondary battery is discharged at a constant power at a different discharge current and a different temperature. The correction unit specifies the average voltage according to the discharge current detected by the current detection unit and the temperature detected by the temperature detection unit using the average voltage information, and specifies It is preferable to calculate the ratio using the average voltage obtained.

  According to this configuration, the average voltage information indicates the relationship between the discharge current and the average voltage when the secondary battery is discharged at a constant power at various temperatures in addition to various values of the discharge current. And the average voltage according to the actual discharge current and temperature at the time of remaining time calculation is specified with reference to average voltage information, and the ratio is calculated using the specified average voltage. Therefore, the remaining time can be calculated in consideration of the actual state of the secondary battery at the time of discharging, and the remaining time can be calculated more accurately.

(4) When the corrected remaining capacity is ImCapa, the remaining capacity detected by the remaining capacity detecting unit is RC, the average voltage is Vave, and the voltage detected by the voltage detecting unit is V,
ImCapa = (Vave / V) · RC
It is preferable to correct the remaining capacity by the above.

  According to this configuration, since the remaining capacity is corrected using the above formula, the remaining time can be calculated by a relatively simple process.

  According to the present invention, the remaining time of the secondary battery can be calculated with high accuracy.

It is a block diagram which shows an example of a structure of the battery pack provided with the remaining time calculation apparatus which concerns on one embodiment of this invention, and the load apparatus which carries out constant power discharge of this battery pack. It is the figure which showed an example of average voltage information. It is the graph which showed the time transition of the remaining time calculated using the conventional method when a secondary battery is discharged at constant power until the remaining capacity becomes 0 from a fully charged state. It is the graph which showed the time transition of the remaining time calculated using the method of this Embodiment when a secondary battery is made to discharge constant power until a remaining capacity becomes 0 from a full charge state. It is a flowchart which shows operation | movement of the electric equipment system shown in FIG. It is a flowchart in case a battery pack calculates to the remaining capacity after correction | amendment.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  FIG. 1 is a block diagram showing an example of the configuration of a battery pack 2 provided with a remaining time calculation device 21 according to an embodiment of the present invention and a load device 3 that discharges the battery pack 2 at constant power. And the battery pack 2 and the load apparatus 3 which are shown in FIG. 1 are combined, and the electric equipment system 1 is comprised.

  Here, as the load device 3, various electric devices such as a personal computer driven with constant power can be adopted. In particular, in the present embodiment, an electric device such as a video camera that mainly captures moving images is used. adopt.

  The battery pack 2 includes connection terminals 11, 12, 13, an assembled battery 14 (secondary battery), a voltage detection circuit 15, a current detection resistor 16 (current detection unit), a temperature sensor 17 (temperature detection unit), a control IC 18, and Switching elements Q1 and Q2 are provided. The control IC 18 includes an analog / digital (A / D) converter 201, a control unit 202, and a communication unit 203.

  The battery pack 14, the voltage detection circuit 15, the temperature sensor 17, the current detection resistor 16, and the control IC 18 constitute a remaining time calculation device 21.

  The load device 3 includes connection terminals 31, 32, 33 and a main body 34. The battery pack 2 and the load device 3 are connected to each other by connection terminals 11 and 31 on the DC high side for supplying power, connection terminals 13 and 33 for communication signals, and connection terminals 12 and 32 for power supply and communication signals. Connected.

In the battery pack 2, the connection terminal 11 is connected to the positive electrode of the assembled battery 14 via the switching element Q1 for discharging and the switching element Q2 for charging. As the switching elements Q1 and Q2, for example, p-channel FETs (Field Effect Transistors) are used.
In the switching element Q1, the anode of the parasitic diode is in the direction of the connection terminal 11. The switching element Q2 has a parasitic diode anode in the direction of the assembled battery 14.

  The connection terminal 12 is connected to the negative electrode of the assembled battery 14 via the current detection resistor 16, and the connection terminal 12 is connected from the connection terminal 11 via the switching elements Q 1 and Q 2, the assembled battery 14, and the current detection resistor 16. A current path leading to is configured.

  The current detection resistor 16 converts the charging current and discharging current of the assembled battery 14 into voltage values. The assembled battery 14 is an assembled battery in which a plurality of, for example, three secondary batteries 141, 142, and 143 are connected in series. The secondary batteries 141, 142, and 143 are secondary batteries such as a lithium ion secondary battery and a nickel hydride secondary battery. The assembled battery 14 may be, for example, a single battery, may be, for example, an assembled battery in which a plurality of secondary batteries are connected in parallel, or is an assembled battery connected in combination of series and parallel. May be.

  The temperature sensor 17 is a temperature sensor that detects the temperatures of the secondary batteries 141, 142, and 143. The temperatures of the secondary batteries 141, 142, and 143 are detected by the temperature sensor 17 and input to the analog / digital converter 201 in the control IC 18. Further, the voltage V which is the terminal voltage of the assembled battery 14 and the terminal voltages V1, V2 and V3 of the secondary batteries 141, 142 and 143 are read by the voltage detection circuit 15 respectively, and the analog-digital converter 201 in the control IC 18 is read. Is input. Furthermore, the current value of the current detected by the current detection resistor 16 is also input to the analog-digital converter 201 in the control IC 18. The analog-digital converter 201 converts each input value into a digital value and outputs the digital value to the control unit 202.

  The analog-digital converter 201 represents, for example, the current value of the current detected by the current detection resistor 16 as a positive value in the direction in which the assembled battery 14 is charged, and a negative value in the direction in which the assembled battery 14 is discharged. And

  The control unit 202 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And these peripheral circuits and the like. Then, the control unit 202 executes a control program stored in the ROM, so that the charge / discharge control unit 211, the remaining capacity detection unit 212, the average voltage information storage unit 213, the correction unit 214, and the remaining time calculation unit 215 are used. Function.

  When a charging device is connected to the battery pack 2, the charge / discharge control unit 211 charges the assembled battery 14 using various charging methods such as CCCV charging, trickle charging, pulse charging, and the like. Then, for example, when the charging current flowing through the assembled battery 14 becomes equal to or lower than the charging end current value, the charging / discharging control unit 211 determines that the assembled battery 14 is fully charged and ends the charging.

  Further, the charge / discharge control unit 211 detects an abnormality outside the battery pack 2 such as a short circuit between the connection terminals 11 and 12 or an abnormal current from the load device 3 based on each input value from the analog-digital converter 201, or an assembled battery. 14 abnormalities such as an abnormal temperature rise are detected. When such an abnormality is detected, the charge / discharge control unit 211 turns off the switching elements Q1 and Q2, and performs a protective operation for protecting the assembled battery 14 from abnormalities such as overcurrent and overheating.

  The remaining capacity detection unit 212 detects the remaining capacity RC of the assembled battery 14 by, for example, a current integration method. Specifically, the remaining capacity detection unit 212 integrates the current Ic detected by the current detection resistor 16 at a constant time interval (for example, 1 second), thereby calculating the remaining capacity RC charged in the assembled battery 14. calculate. In this case, since the current in the direction of charging the assembled battery 14 is positive and the current in the direction of discharging from the assembled battery 14 is negative, the assembled battery is updated by updating RC with RC ′ = RC + Ic × t. 14 remaining capacity RC is updated. Here, RC ′ represents the remaining capacity after update, and t represents a certain time interval.

  In addition, when the full charge of the assembled battery 14 is detected by the charge / discharge control unit 211, the remaining capacity detection unit 212 sets a predetermined full charge capacity value FCC of the assembled battery 14 as the remaining capacity RC at the present time. To do. Here, the remaining capacity detection unit 212 may calculate the remaining capacity RC using a technique such as a voltage measurement method other than the current integration method.

  The average voltage information storage unit 213 stores in advance the average voltage of the assembled battery 14 when the assembled battery 14 is discharged at a constant power. Specifically, the average voltage information storage unit 213 stores the average voltage information indicating the value of the average voltage with respect to the discharge current and temperature, which is obtained in advance by discharging the battery pack 14 with constant power at different discharge currents and different temperatures. Remember.

  FIG. 2 is a diagram illustrating an example of average voltage information. As shown in FIG. 2, the average voltage information has a two-dimensional tabular data structure including a temperature column and a discharge current column.

  In the example of FIG. 2, the discharge current columns are “0 (A) ˜”, “0.5 (A) ˜”, “1.0 (A) ˜”, “1.5 (A) ˜”. There are four columns. Here, “0 (A) to” indicates that the discharge current is 0 (A) or more and less than 0.5 (A). “0.5 (A) to” indicates that the discharge current is 0.5 (A) or more and less than 1.0 (A). “1.0 (A) to” indicates that the discharge current is 1.0 (A) or more and less than 1.5 (A). “1.5 (A) to” indicates that the discharge current is 1.5 (A) or more.

  In the example of FIG. 2, the temperature column includes four columns of “˜0 (° C.)”, “0 (° C.)”, “10 (° C.)”, and “20 (° C.)”. ing. Here, “˜0 (° C.)” indicates that the temperature of the assembled battery 14 is less than 0 (° C.). “0 (° C.) to” indicates that the temperature of the assembled battery 14 is 0 (° C.) or more and less than 10 (° C.). “10 (° C.) to” indicates that the temperature of the assembled battery 14 is 10 (° C.) or more and less than 20 (° C.). “20 (° C.) to” indicates that the temperature of the assembled battery 14 is 20 (° C.) or higher.

  Each basket stores an average voltage with respect to temperature and current. That is, each battery pack 14 is fully charged with a temperature within the temperature range defined in the corresponding temperature column and a discharge current within the current range defined in the corresponding discharge current column. Is stored as an average voltage when constant power is discharged until the remaining capacity RC becomes zero. Here, the average voltage is obtained by, for example, averaging the voltage V measured at a constant time interval from the start of discharge to the end of discharge.

  Note that the temperature range in each column of temperature and the range of current in each column of discharge current shown in FIG. 2 are merely examples, and different values may be adopted, or the number of rows and columns may be increased to make more detailed. The average voltage may be specified with resolution. Further, instead of the table shown in FIG. 2, a function having discharge current and temperature as inputs and an average voltage as outputs may be obtained in advance, and this function may be adopted as the average voltage information.

  In the example of FIG. 2, a two-dimensional table in which an average voltage corresponding to the discharge current and the temperature is determined is adopted, but the present invention is not limited to this, and either the discharge current or the temperature and the average A one-dimensional table in which the voltage is determined may be adopted. In this case, the correction unit 214 specifies the average voltage from the discharge current or temperature.

  Returning to FIG. 1, the correction unit 214 specifies the average voltage Vave corresponding to the discharge current Idc detected by the current detection resistor 16 and the temperature detected by the temperature sensor 17 by referring to the average voltage information, The remaining capacity RC is corrected based on the ratio of the average voltage Vave of the assembled battery 14 to the voltage V detected by the voltage detection circuit 15.

  Here, when the corrected remaining capacity is ImCapa, the average voltage is Vave, and the voltage detected by the voltage detection circuit 15 is V, the correcting unit 214 corrects the remaining capacity RC by Expression (1).

ImCapa = (Vave / V) · RC (1)
The remaining time calculation unit 215 divides the remaining time T of the assembled battery 14 by dividing the ImCapa calculated by the correction unit 214 by the discharge current Idc detected by the current detection resistor 16, that is, by the calculation of Expression (2). calculate.

T = ImCapa / Idc (2)
When the charge / discharge control unit 211 detects that the assembled battery 14 is in a discharged state, the correction unit 214 and the remaining time calculation unit 215 calculate the ImCapa and the remaining time T at regular time intervals (for example, 1 minute). Execute the calculation process.

  Then, the remaining time calculation unit 215 transmits the calculated remaining time T to the load device 3 via the communication unit 203. And the load apparatus 3 which received the remaining time T displays the remaining time T on a display part which is not illustrated, for example. As a result, the user can recognize the change in the remaining time T at a minute time interval such as 1 minute, for example, as compared with the conventional remaining time calculation method.

  The remaining time calculation unit 215 calculates the remaining time T at a time interval such as 1 second, which is smaller than 1 minute, for example, and the calculated remaining time T is 1 minute on the basis of the remaining time T at the start of discharge. Each time it decreases, the calculated remaining time T may be transmitted to the load device 3.

  As a result, the load device 3 receives the remaining time T only when the remaining time T is reliably reduced by 1 minute, thereby reducing communication traffic between the battery pack 2 and the load device 3 and the load device 3. The processing load for displaying the remaining time T can be reduced.

  FIG. 3 shows the time transition of the remaining time calculated using the conventional method when a plurality of secondary batteries connected in series from the fully charged state until the remaining capacity becomes zero is discharged at constant power. It is the shown graph. In FIG. 3, the left vertical axis represents the remaining time, and the right vertical axis represents the error between the remaining time calculated by the conventional method and the ideal remaining time. The horizontal axis indicates the discharge time.

  The unit of the left and right vertical and horizontal axes is in minutes. However, on the left vertical axis, one break indicated by a dotted line is set to 50 minutes, while on the right vertical axis, one break indicated by a dotted line is set to 10 minutes. It is assumed that the secondary battery is in a fully charged state at the start of discharge.

  The conventional method is a method of calculating the remaining time by dividing the remaining capacity RC by the discharge current Idc. Also, in FIG. 3, a graph G10 shows a temporal transition of the remaining time calculated by the conventional method, a graph GR shows a temporal transition of the ideal remaining time, and a graph GD10 includes the graph G10 and the graph GR. The error is shown.

  In the graph GR, the remaining time at the start of discharge is about 285 minutes, and the remaining time at the end of discharge is also about 285 minutes. In the graph GR, for example, the remaining time at the point P1 after 100 minutes from the start of discharge is about 185 minutes, and the time from the time of the point P1 to the end of discharge is also about 185 minutes. That is, it can be seen that the graph indicating the transition of the ideal remaining time is a straight line having a slope of -1.

  On the other hand, as shown in the graph G10, the remaining time at the start of discharge is calculated to be about 340 minutes, which is essentially about 285 minutes, and is 55 minutes (more precisely 53 minutes) than the actual remaining time. It can be seen that a large value is also calculated. In other words, it can be seen that there is a maximum error of 53.4 minutes between the ideal remaining time and the remaining time calculated by the conventional method.

  In addition, even at point P2 after 100 minutes from the start of discharge, the remaining time calculated by the conventional method is considerably larger than the ideal remaining time, although the error is reduced as compared with the start of discharge.

  As can be seen from the graph GD10, the error between the graph G10 and the graph GR decreases as the discharge time elapses. That is, it can be seen that the remaining time calculated by the conventional method greatly deviates from the ideal remaining time in the early stage of discharge.

  As explained in the background art, the discharge current has a characteristic of gradually increasing as the remaining capacity decreases as the discharge time elapses, so the remaining time is obtained by dividing the remaining capacity by the discharge current. In this case, since the value of the discharge current of the denominator is small at the beginning of discharge, the remaining time is calculated to be larger than the ideal remaining time.

  FIG. 4 shows the method of the present embodiment (hereinafter referred to as “the present method”) when a plurality of secondary batteries connected in series from the fully charged state until the remaining capacity becomes zero is discharged at a constant power. It is the graph which showed the time transition of the remaining time calculated using. 4, the units and scales of the vertical and horizontal axes are the same as those in FIG.

  Also, in FIG. 4, a graph G1 shows the temporal transition of the remaining time calculated using this method, the graph GR is the same as the graph GR of FIG. 3, and the graph GD1 is an error between the graph G1 and the graph GR. Is shown.

  As can be seen by comparing the graph G1 and the graph GR, it can be seen that the remaining time calculated by this method is very close to the ideal remaining time. In particular, it can be seen that the error at the initial stage of discharge is significantly smaller than the conventional method.

  Specifically, as shown in the graph GD1, the error between the graph G1 and the graph GR changes in a convex curve with a peak near the middle of the discharge period, and the maximum value of the error is It can be seen that the conventional method is 53.4 minutes, but this method is significantly reduced to 10.9 minutes.

  This is because the RC shown in the equation (1) is corrected by Vave / V to obtain ImCapa, and the remaining time T is obtained by dividing the ImCapa by the discharge current Idc as shown in the equation (2). There is nothing else.

  That is, since the discharge current of the secondary battery gradually increases as the discharge time elapses, when the secondary battery in the fully charged state is discharged at constant power, the voltage V of the secondary battery at the initial stage of discharge is higher than the average voltage Vave. Increases the value. Therefore, Vave / V is less than 1 at the beginning of discharge.

  Therefore, when the remaining capacity RC is corrected using Vave / V at the initial stage of discharge, ImCapa has a smaller value than the remaining capacity RC before correction. Accordingly, the remaining time T obtained by dividing ImCapa by the discharge current Idc at the initial stage of discharge becomes smaller than the remaining time obtained by dividing the remaining capacity RC by the discharge current Idc at the initial stage of discharge.

  Therefore, in ImCapa / Idc, ImCapa is reduced in consideration of the fact that the discharge current Idc of the denominator is small, and the remaining time is prevented from being calculated at a value larger than the actual remaining time at the beginning of discharge. It is.

  FIG. 5 is a flowchart showing the operation of the electrical equipment system 1 shown in FIG. It is assumed that the assembled battery 14 is in a fully charged state before starting this flowchart. First, in step S1, the charge / discharge control unit 211 determines whether or not discharge has started. Here, the charge / discharge control unit 211 may determine that the discharge of the assembled battery 14 has started when the analog-digital converter 201 outputs a negative current.

  When the charge / discharge control unit 211 determines that the discharge has started (YES in step S1), the remaining time calculation unit 215 determines whether or not the calculation timing of the remaining time T has been reached (step S1). S2). On the other hand, if the discharge has not started (NO in step S1), the process returns to step S1.

  In step S2, if the remaining time calculation unit 215 has reached the calculation timing of the remaining time T (YES in step S2), the process proceeds to step S5. On the other hand, if the remaining time calculation unit 215 has not reached the calculation timing of the remaining time T (NO in step S2), the process proceeds to step S3.

  Here, as the calculation timing of the remaining time T, it is possible to employ the time when discharge starts and the time when a certain time interval (for example, 1 minute) has elapsed since the start of discharge.

  In step S3, the remaining capacity detector 212 determines whether or not the remaining capacity RC detection timing has been reached. If the remaining capacity RC detection timing has been reached (YES in step S3), RC ′ = The remaining capacity RC is updated by RC + I × t (step S4), and the process returns to step S2. In addition, what is necessary is just to employ | adopt the remaining capacity of the assembled battery 14 at the time of a discharge start as FCC, when discharge is started when the remaining capacity RC is not a full charge state.

  On the other hand, if the remaining capacity detection unit 212 determines that the remaining capacity detection timing has not been reached (NO in step S3), the process returns to step S2.

  Here, as the detection timing of the remaining capacity RC, it is possible to employ a discharge start time and a time when a certain time interval (for example, 1 second) has elapsed since the discharge start time.

  In step S5, the remaining capacity detector 212 detects the remaining capacity in the same manner as in step S4.

  Next, the correction unit 214 specifies the average voltage Vave corresponding to the discharge current Idc detected by the current detection resistor 16 and the temperature of the assembled battery 14 detected by the temperature sensor 17 by referring to the average voltage information. (Step S6).

  Specifically, for example, when the discharge current Idc = 1.2 (A) and the temperature = 15 (° C.) are detected, the correction unit 214 sets “1.0 (A) ˜” in the table shown in FIG. 6.90 (V) at which the column and the column of “10 (° C.) ˜” cross is specified as the average voltage.

  Next, the correction unit 214 substitutes the voltage V of the assembled battery 14 detected by the voltage detection circuit 15, the average voltage Vave specified in step S6, and the remaining capacity RC detected in step S5 into the equation (1). Then, ImCapa is calculated and the remaining capacity RC is corrected (step S7).

  Next, the remaining time calculation unit 215 divides ImCapa calculated in step S7 by the discharge current Idc detected in step S6 to calculate the remaining time T (step S8).

  Next, the remaining time calculation unit 215 transmits the remaining time T calculated in step S8 to the load device 3 via the communication unit 203 (step S9).

  Next, when the discharge is finished (YES in step S10), the process is finished, and when the discharge is not finished (NO in step S10), the process is returned to step S2 and the above process is repeated.

  As described above, according to the remaining capacity calculation device according to the present embodiment, the remaining capacity RC is corrected using the equation (1), the ImCapa is calculated, and the remaining time T is calculated using this ImCapa. The remaining time T can be calculated with high accuracy.

  In the above flowchart, the battery pack 2 calculates up to the remaining time T, but is not limited to this, and the battery pack 2 calculates up to the corrected remaining capacity (ImCapa), and the corrected remaining capacity (ImCapa). And the discharge current Idc may be transmitted to the load device 3, and the load device 3 may calculate the remaining time based on ImCapa / Idc.

  In this case, the following flowchart can be adopted. FIG. 6 shows a flowchart when the battery pack 2 calculates up to the remaining capacity after correction.

  First, the control unit 202 determines whether or not the predetermined timing for determining the temperature, voltage, and discharge current Idc of the secondary batteries 141 to 143 has been reached (step S21), and if it is determined that the predetermined timing has been reached (YES in step S21), the temperature of the assembled battery 14, the voltages of the secondary batteries 141 to 143, and the discharge current Idc are acquired from the A / D converter 201 (step S22). On the other hand, if the predetermined timing has not been reached (NO in step S21), the process returns to step S21.

  Next, the remaining capacity detection unit 212 calculates the remaining capacity RC of the assembled battery 14 from the discharge current Idc acquired in step S22 (step S23).

  Next, when discharging is in progress (YES in step S24), the correction unit 214 refers to the average voltage information shown in FIG. 2 from the discharge current Idc acquired in step S22 and the temperature of the assembled battery 14, and determines the average voltage. Vave is specified (step S25). On the other hand, if not discharging (NO in step S24), the process returns to step S21.

  Next, the correction unit 214 obtains the voltage V of the assembled battery 14 from the respective voltages of the secondary batteries 141 to 143 acquired in step S22, the average voltage Vave specified in step S25, and the remaining capacity RC calculated in step S23. Are substituted into the equation (1) to calculate the corrected remaining capacity (ImCapa) (step S26).

  Next, the communication unit 203 transmits the remaining capacity after correction (ImCapa) calculated by the correction unit 214 and the discharge current Idc acquired in step S22 to the main body unit 34 via the connection terminals 13 and 33 ( Step S27).

  Then, the main body 34 divides the corrected remaining capacity (ImCapa) transmitted from the battery pack 2 by the discharge current Idc, and calculates the remaining time T.

  When the flowchart shown in FIG. 6 is adopted, the remaining time calculation unit 215 of the battery pack 2 may be provided in the main body 34 of the load device 3. In this case, the remaining time calculation device according to the present invention includes the remaining time calculation unit 215 provided in the load device 3 and the remaining time calculation device 21 shown in FIG.

DESCRIPTION OF SYMBOLS 1 Electric equipment system 2 Battery pack 3 Load apparatus 14 Battery 15 Voltage detection circuit 16 Current detection resistance 17 Temperature sensor 21 Remaining time calculation apparatus 141,142,143 Secondary battery 201 Analog-digital converter 202 Control part 211 Charge / discharge control part 212 Remaining Capacity Detection Unit 213 Average Voltage Information Storage Unit 214 Correction Unit 215 Remaining Time Calculation Unit

Claims (5)

A remaining time calculation device that calculates the remaining time of a secondary battery that supplies power to a load device that is driven with constant power,
A voltage detector for detecting the voltage of the secondary battery;
A current detection unit for detecting a discharge current of the secondary battery;
A storage unit that stores in advance an average voltage of the secondary battery when the secondary battery is discharged at a constant power;
A remaining capacity detector for detecting a remaining capacity of the secondary battery;
A correction unit that corrects the remaining capacity detected by the remaining capacity detection unit based on the ratio of the average voltage to the voltage detected by the voltage detection unit;
A remaining time calculation unit that calculates a remaining time of the secondary battery by dividing the remaining capacity corrected by the correction unit by the discharge current detected by the current detection unit. apparatus. The storage unit stores in advance average voltage information indicating the average voltage according to the discharge current when the secondary battery is discharged at a constant power with a different discharge current,
The correction unit specifies an average voltage corresponding to a discharge current detected by the current detection unit using the average voltage information, and calculates the ratio using the specified average voltage. Item 3. A remaining time calculation apparatus according to Item 1. A temperature detection unit for detecting the temperature of the secondary battery;
The average voltage information indicates the average voltage with respect to the discharge current and the temperature when the secondary battery is discharged at a constant power at different discharge currents and different temperatures,
The correction unit specifies an average voltage corresponding to the discharge current detected by the current detection unit and the temperature detected by the temperature detection unit using the average voltage information, and uses the specified average voltage The remaining time calculating apparatus according to claim 2, wherein the ratio is calculated. The correction unit is ImCapa, the remaining capacity after correction, RC is the remaining capacity detected by the remaining capacity detection unit, Vave is the average voltage, and V is the voltage detected by the voltage detection unit.
ImCapa = (Vave / V) · RC
The remaining time calculation apparatus according to claim 1, wherein the remaining capacity is corrected by the following. A remaining time calculation method for calculating a remaining time of a secondary battery that supplies power to a load device that is driven by constant power,
A voltage detection step of detecting a voltage of the secondary battery;
A current detection step of detecting a discharge current of the secondary battery;
A remaining capacity detecting step for detecting a remaining capacity of the secondary battery;
The remaining capacity detected by the remaining capacity detection step based on the ratio of the average voltage of the secondary battery obtained in advance by discharging the secondary battery with constant power to the voltage detected by the voltage detection step. A correction step for correcting
A remaining time calculation step of calculating a remaining time of the secondary battery by dividing the remaining capacity corrected by the correction step by the discharge current detected by the current detection step. Method.

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