JP2015081773A - Remaining time calculation device and remaining time calculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately calculate remaining time of a secondary battery.SOLUTION: A remaining time calculation device for calculating remaining time of a secondary battery supplying electric power to a load device at a predetermined discharge rate, includes: a temperature detection unit that detects a temperature of the secondary battery; a remaining-capacity detection unit that detects a remaining capacity of the secondary battery; a discharge-efficiency detection unit detecting discharge efficiency from the discharge rate and the temperature; a correction unit that detects a correction value of the remaining time from the discharge rate, the temperature, and the remaining capacity; and a remaining-time calculation unit that calculates the remaining time of the secondary battery from the discharge rate, the remaining capacity, and the correction value. As a result, it is possible to calculate the remaining time in consideration of a change in the discharge efficiency if discharging continues at the predetermined discharge rate.

Description

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

  Conventionally, the remaining time of a secondary battery that supplies power to an electric device driven by constant power, that is, a secondary battery that performs constant power discharge at a predetermined discharge rate, is the remaining capacity (mAh or mWh) of the secondary battery. It was calculated by dividing by discharge current (mA or mWh) or discharge rate (mA or mWh) / discharge efficiency (%).

  However, as the discharge time elapses after the secondary battery starts discharging, the temperature gradually increases due to heat generated by the discharging. Furthermore, when the secondary battery is discharged at the same discharge rate, the higher the temperature, the higher the discharge efficiency. Therefore, since the temperature is low at the beginning of discharge, the discharge efficiency is lower than at the end of discharge, and in the conventional remaining time calculation method, the remaining time calculated at the beginning of discharge was calculated with a value smaller than the actual remaining time. .

  FIG. 6 shows the temperature change of the secondary battery when discharged from the fully charged state at a constant discharge rate. FIG. 7 is a diagram showing the relationship of the discharge efficiency with respect to the temperature and discharge rate of the secondary battery. As shown in FIG. 6, when the fully charged secondary battery continues to be discharged at a constant discharge rate, the temperature of the secondary battery, which was 5 ° C., gradually increases. In particular, the higher the discharge rate, the higher the temperature of the secondary battery. Moreover, as shown in FIG. 7, at a predetermined discharge rate, the higher the temperature of the secondary battery, the higher the discharge efficiency. From these facts, it can be seen that if the discharge is continued at a constant discharge rate, the temperature and discharge efficiency of the secondary battery gradually increase compared to the initial stage of discharge.

  For example, when discharging is performed at the discharge rate of 48 W until the end of discharge, the temperature of the secondary battery increases from 5 ° C. to 23.5 ° C., and the discharge efficiency increases from 74% to 87%.

  Therefore, when the user is informed that the remaining time is 1 hour, for example, immediately after the start of using the electric device, if the user believes that notification and is using the electric device, the remaining capacity is 0 even after 1 hour has passed. It can be seen that the electric device can be used longer than the scheduled time. If the exact remaining time was known from the start of use, there was no need to reduce the frequency of use, and there was a problem that it was possible to make a plan for using electrical equipment in accordance with the exact remaining time. .

  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).

JP 7-244135 A JP-A-11-218567

  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.

  In order to solve the conventional problem, a remaining time calculation device according to 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 at a predetermined discharge rate. A temperature detector that detects a temperature of the secondary battery, a remaining capacity detector that detects a remaining capacity of the secondary battery, a discharge efficiency detector that detects discharge efficiency from the discharge rate and the temperature, and the discharge rate A correction unit for detecting a correction value of the remaining time from the temperature and the remaining capacity, and a remaining time of the secondary battery is calculated from the discharge rate, the remaining capacity, the discharge efficiency, and the correction value by Equation (1). A remaining time calculating unit.

The remaining time calculation method 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 at a predetermined discharge rate, the temperature detecting the temperature of the secondary battery. A detection step, a remaining capacity detection step for detecting a remaining capacity of the secondary battery, a discharge efficiency detection step for detecting a discharge efficiency from the discharge rate and the temperature, a remaining capacity from the discharge rate, the temperature and the remaining capacity. A correction step of detecting a correction value of time, and a remaining time calculation step of calculating the remaining time of the secondary battery by the equation (1) from the discharge rate, the remaining capacity, the discharge efficiency, and the correction value. .
(Equation 1)
Remaining time = remaining capacity / discharge rate x discharge efficiency + correction value (1)
According to these configurations, the temperature of the secondary battery is based on the discharge efficiency of the secondary battery when the secondary battery is discharged at a predetermined discharge rate with respect to the temperature of the secondary battery detected by the temperature detection unit. Then, a correction value of the remaining time is extracted from the remaining capacity of the secondary battery detected by the remaining capacity detection unit, the remaining capacity is calculated by the discharge rate, the discharge efficiency is integrated, and the correction value is added. Thus, the remaining time of the secondary battery is calculated.

  Here, since the temperature of the secondary battery gradually increases as the discharge time elapses, when the secondary battery in the fully charged state is discharged at a predetermined rate, the discharge efficiency of the secondary battery in the initial stage of discharge is The value tends to be smaller than that. Therefore, in the initial stage of discharge, it is necessary to consider the amount of change in discharge efficiency that improves the discharge efficiency after continuing the discharge.

  Therefore, the correction value obtained from the discharge rate and the remaining capacity with respect to the temperature of the secondary battery at the initial stage of discharge is added to the remaining time of the secondary battery for correction. As a result, the corrected remaining time becomes larger than the conventional remaining time before correction.

  In other words, the remaining time including the discharge efficiency after the discharge is continued is calculated in consideration of the fact that the discharge efficiency is reduced at the beginning of the discharge, so the remaining time is smaller than the actual remaining time. Can be prevented from being calculated. 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.

  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 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 the corrected amount decided by the temperature and remaining capacity of a secondary battery for every magnitude | size of the discharge rate which concerns on embodiment of this invention. It is the graph which showed the time transition of the remaining time calculated using the conventional method when the secondary battery is discharged at a predetermined rate until the remaining capacity becomes 0 from the fully charged state. A graph showing the time transition of the remaining time calculated using the method of the embodiment of the present invention when the secondary battery is discharged at a predetermined rate from the fully charged state until the remaining capacity becomes 0. is there. It is a flowchart which shows operation | movement of the electric equipment system which concerns on embodiment of this invention. It is the figure which showed the temperature change of the secondary battery at the time of discharging at a fixed discharge rate from the state of full charge. It is a figure which shows the relationship of the discharge efficiency with respect to the temperature and discharge rate of a secondary battery.

  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 and a video camera that are driven with a constant power can be adopted. In particular, in the present embodiment, the electric power source is an electric device such as a laptop computer or a tablet. The state where it is not connected will be described.

  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 also includes an analog / digital 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 DC high-side connection terminals 11 and 31 that perform power supply, 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. For example, N-channel FETs (Field Effect Transistors) are used as the switching elements Q1 and Q2.
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 lithium ion secondary batteries and nickel hydride secondary batteries. 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 temperature 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 V 1, V 2, V 3 of the secondary batteries 141, 142, 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. The control unit 202 functions as a charge / discharge control unit 211, a remaining capacity detection unit 212, a discharge efficiency detection unit 213, a correction unit 214, and a remaining time calculation unit 215 by executing a control program stored in the ROM. To do.

  When a charging device is connected to the battery pack 2, the charging / discharging control unit 211 uses various charging methods such as constant current-constant voltage (CC-CV) charging, trickle charging, pulse charging, and the like. The battery 14 is charged. 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 from 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 an abnormality such as overcurrent or 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 discharge efficiency detection unit 213 stores in advance the discharge efficiency of the assembled battery 14 when the assembled battery 14 is discharged at constant power. Specifically, the discharge efficiency detection unit 213 stores the relationship of the discharge efficiency with respect to the temperature and discharge rate of the secondary battery as shown in FIG.

  The discharge efficiency detection unit 213 inputs the discharge rate set by the charge / discharge control unit 211 or inputs the amount of current flowing through the current detection resistor 16 via the analog-digital converter 201 to calculate the discharge rate. Further, the discharge efficiency detection unit 213 inputs the temperatures of the secondary batteries 141, 142, and 143 detected by the temperature sensor 17 via the analog / digital converter 201. The discharge efficiency detection unit 213 detects the discharge efficiency using the input discharge rate and secondary battery temperature in the relationship between the stored secondary battery temperature and the discharge efficiency relative to the discharge rate.

  The correction unit 214 detects a correction value for the remaining time due to a change in discharge efficiency in consideration of a temperature increase when the battery is continuously discharged at the current discharge rate. 6 and 7, it is known that when the discharge is continued at a constant discharge rate, the temperature of the secondary battery increases and the discharge efficiency increases. For this reason, the correction unit 214 detects a correction value for the remaining time in consideration of the amount of change in discharge efficiency resulting from the temperature rise when the discharge is continued until the end of discharge at which the remaining capacity becomes 0 at a predetermined discharge rate.

  The correction unit 214 inputs the remaining capacity from the remaining capacity detection unit 212, and inputs the discharge rate and the temperature of the secondary batteries 141, 142, 143 from the discharge efficiency detection unit 213. Then, when the remaining capacity input at the input discharge rate is continuously discharged until the end of the discharge, the correction unit 214 detects a correction value of the remaining time considering the amount of change in discharge efficiency resulting from the temperature rise from the input temperature. .

  Note that the method of inputting the discharge rate and the temperature of the secondary battery of the correction unit 214 may be the same as that of the discharge efficiency detection unit 213.

  FIG. 2 is a diagram illustrating an example of a correction amount determined by the temperature and remaining capacity of the secondary battery for each discharge rate. As shown in FIG. 2, the correction value has a three-dimensional tabular data structure (look-up table) that includes a secondary battery temperature column and a remaining capacity column for each discharge rate. . The correction unit 214 stores the data structure (lookup table) in a three-dimensional tabular format in advance. Alternatively, the correction unit 214 can use the three-dimensional tabular data structure (lookup table) stored in the control unit 202.

  In the example of FIG. 2, sheets with discharge rates of 12 W, 30 W, and 48 W are shown. These are discharge rate sheets used in the battery pack 2 and the load device 3.

  In the example of FIG. 2, the temperature column of the secondary battery includes three columns of “5 (° C.)”, “25 (° C.)”, and “40 (° C.)”. Here, “5 (° C.)” indicates that the temperature of the assembled battery 14 has a representative value of 5 (° C.) and is less than 15 (° C.). “25 (° C.)” indicates that the temperature of the assembled battery 14 has a representative value of 25 (° C.) and is 15 (° C.) or more and less than 35 (° C.). “40 (° C.)” indicates that the temperature of the assembled battery 14 is 35 (° C.) or more with a representative value of 40 (° C.).

  In the example of FIG. 2, the remaining capacity columns include “100 (%)”, “80 (%)”, “60 (%)”, “40 (%)”, “20 (%)”, “ Six columns of “0 (%)” are provided. Here, “100 (%)” indicates that the remaining capacity is 90 (%) or more and less than 110 (%). The same applies to the other columns, and “x (%)” indicates that the remaining capacity is not less than x−10 (%) and less than x + 10 (%).

  Each box stores a remaining time correction value for temperature and remaining capacity. In other words, the current remaining capacity is zero for each box, with the temperature within the temperature range defined in the corresponding temperature column and the remaining capacity within the capacity range defined in the corresponding remaining capacity column. A correction value for the remaining time when discharging at a predetermined discharge rate until the end of discharge is stored.

  Here, the correction value is set so as to increase when the temperature of the secondary battery is low as shown in FIG. 2 and when the remaining capacity is large.

  It should be noted that the discharge rate shown in FIG. 2, the temperature range of each column of temperature, and the capacity range of each column of remaining capacity are merely examples, and different values may be adopted, and sheets, rows and columns may be adopted. The correction value of the remaining time may be specified with a finer resolution by increasing the number of. Further, the correction value for the remaining time shown in FIG. 2 is a correction value for the described discharge rate, temperature, and remaining capacity value, and the correction value for the discharge rate, temperature, and remaining capacity value not described is described. It is also possible to interpolate with the previous and subsequent values. Further, instead of the table shown in FIG. 2, a function that takes discharge rate, secondary battery temperature and remaining capacity as inputs, and outputs a remaining time correction value is obtained in advance, and this function is used as remaining time correction information. May be adopted.

The remaining time calculation unit 215 receives the correction value for the remaining capacity, the discharge rate, and the remaining time from the correction unit 214, and receives the discharge efficiency from the discharge efficiency detection unit 213. Based on the input data, the remaining time of the assembled battery 14 is calculated by the calculation of Expression (1).
(Equation 1)
Remaining time = remaining capacity / discharge rate × discharge efficiency + correction value (1)
Note that the remaining capacity and discharge rate input method of the remaining time calculation unit 215 may be the same method as that of the correction unit 214.

  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 perform the remaining time correction value and the remaining time correction value at a certain time interval (for example, 1 minute). A process for calculating the remaining time is executed.

  Then, the remaining time calculation unit 215 transmits the calculated remaining time to the load device 3 via the communication unit 203. Then, the load device 3 that has received the remaining time displays the remaining time, for example, on a display unit (not shown). Thereby, the user can recognize the change in the remaining time at a minute time interval such as 1 minute, for example, as compared with the conventional method of calculating the remaining time.

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

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

  FIG. 3 shows the remaining time calculated using the conventional method when a plurality of secondary batteries connected in series are discharged at a constant power from the fully charged state to the end of discharge when the remaining capacity becomes zero. It is the graph which showed transition. 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 20 minutes, whereas on the right vertical axis, one break indicated by a dotted line is set to 5 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 by the discharge rate / discharge efficiency. 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 100 minutes, and the remaining time at the end of discharge is also about 100 minutes. In the graph GR, for example, the remaining time at the point of 20 minutes of discharge is about 80 minutes, and the time from the point of 20 minutes of discharge time to the end of discharge is also about 80 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 88 minutes, which is essentially about 100 minutes, and a value 12 minutes smaller than the actual remaining time is calculated. You can see that. That is, it can be seen that an error of up to 12 minutes occurs between the ideal remaining time and the remaining time calculated by the conventional method.

  Also, at the point of 20 minutes discharge time, 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 time of starting the 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, since the discharge efficiency has a characteristic of gradually increasing as the temperature of the secondary battery rises as the discharge time elapses, the remaining capacity is determined by the discharge rate / discharge efficiency. This is because when the remaining time is obtained by dividing, the value of the discharge efficiency is small at the initial stage of discharge, so that the remaining time is calculated to be smaller than the ideal remaining time.

  FIG. 4 shows the method of the present embodiment (hereinafter referred to as “this method”) when a plurality of secondary batteries connected in series from the fully charged state to the end of discharge when the remaining capacity becomes 0 is discharged at constant power. Is a graph showing the temporal 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 reduces the error in the period from the start of discharge to the discharge time of 40 minutes, which was large in the conventional method. It can be seen that the maximum value was 12 minutes in the conventional method, but significantly reduced to 4.4 minutes in the present method.

  This is nothing but the correction value shown in Equation (1) is set to be large when the remaining capacity is large.

  In other words, since the discharge efficiency of the secondary battery gradually increases as the discharge time elapses, when the secondary battery in the fully charged state is discharged at a predetermined rate, the discharge efficiency of the secondary battery at the initial stage of discharge is The value is smaller than that. Therefore, a large error occurs in the calculation of the remaining time in the early stage of discharge.

  Therefore, using the discharge rate, discharge efficiency, and remaining capacity at the beginning of the discharge, and setting the correction value for the remaining time in consideration of the amount of change in discharge efficiency, the discharge time from the start of discharge when the error in the remaining time was large in the conventional method. The error of the remaining time of the period up to 40 minutes becomes small.

  Therefore, the remaining time is calculated in consideration of the increase in discharge efficiency when the discharge is continued, and the remaining time is prevented from being calculated with a value smaller than the actual remaining time in the initial stage of discharge. .

  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, the control unit 202 determines whether or not the predetermined timing for determining the temperature, voltage, discharge current, and discharge rate of the secondary batteries 141 to 143 has been reached (step S51), and determines that the predetermined timing has been reached. In this case (YES in step S51), the temperature of the secondary batteries 141, 142, 143, the voltage of each of the secondary batteries 141-143, and the discharge current are acquired from the analog-digital converter 201, and the discharge rate is controlled to charge / discharge. Obtained from the unit 211 (step S52). On the other hand, if the predetermined timing has not come (NO in step S51), the process returns to step S51.

  Next, the remaining capacity detection unit 212 calculates the remaining capacity of the assembled battery 14 from the discharge current acquired in step S52 (step S53). And the discharge efficiency detection part 213 detects discharge efficiency from the discharge rate acquired at step S52, and the temperature of the secondary batteries 141, 142, and 143 (step S54).

  Next, when discharging is in progress (YES in step S55), the correction unit 214 shows the temperature and discharge rate of the secondary batteries 141, 142, 143 acquired in step S52 and the remaining capacity acquired in step S53 in FIG. The correction value of the remaining time is specified with reference to the correction value information shown (step S56). On the other hand, if not discharging (NO in step S55), the process returns to step S51.

  Next, the remaining time calculation unit 215 uses the discharge rate acquired in step S52, the remaining capacity calculated in step S53, the discharge efficiency detected in step S54, and the correction value specified in step S56 in equation (1). Substitute and calculate the remaining time after correction (step S57).

  Next, when the discharge is finished (YES in step S58), the process is finished, and when the discharge is not finished (NO in step S58), the process is returned to step S51 and the above process is repeated.

  As described above, according to the remaining time calculation device according to the present embodiment, the correction value of the remaining time is calculated using the equation (1) in consideration of the change in the discharge efficiency when the discharge is continued. Therefore, the remaining time can be calculated with high accuracy.

In this embodiment, the correction unit 214 specifies the correction value of the remaining time from the discharge rate, the temperature of the secondary battery, and the remaining capacity, but the discharge efficiency changes from the discharge rate, the temperature of the secondary battery, and the remaining capacity. The amount may be specified, and the amount of change in discharge efficiency, the remaining time, and the characteristic coefficient of the secondary battery may be calculated as a correction value for the remaining time by calculating Equation (2).
(Equation 2)
Correction value = Remaining capacity x Discharge efficiency change x Characteristic coefficient (2)

  Since the remaining time calculation device and the remaining time calculation method according to the present invention can accurately calculate the remaining time of the secondary battery, the electric device driven with constant power is supplied with electric power at a predetermined discharge rate. This is useful for calculating the remaining time of the secondary battery to be supplied.

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 Discharge Efficiency Detection Unit 214 Correction Unit 215 Remaining Time Calculation Unit

Claims (5)

A remaining time calculating device that calculates the remaining time of a secondary battery that supplies power to a load device at a predetermined discharge rate,
A temperature detector for detecting the temperature of the secondary battery;
A remaining capacity detector for detecting a remaining capacity of the secondary battery;
A discharge efficiency detector for detecting discharge efficiency from the discharge rate and the temperature;
A correction unit that detects a correction value of a remaining time from the discharge rate, the temperature, and the remaining capacity;
A remaining time calculation device comprising: a remaining time calculation unit that calculates the remaining time of the secondary battery using the equation (1) from the discharge rate, the remaining capacity, the discharge efficiency, and the correction value.
(Equation 1)
Remaining time = remaining capacity / discharge rate × discharge efficiency + correction value (1)   The remaining time calculation apparatus according to claim 1, wherein the correction value gradually increases when the temperature decreases and the remaining capacity increases.   The remaining time calculation apparatus according to claim 1, wherein the correction unit has a data structure of correction values for the temperature and the remaining capacity for each magnitude of the discharge rate. The correction unit calculates the correction value from the amount of change in discharge efficiency at the time of discharging until the end of discharge at the discharge rate, the characteristic coefficient of the secondary battery, and the remaining capacity, using Equation (2). The remaining time calculation device according to claim 1 or 2.
(Equation 2)
Correction value = Remaining capacity x Discharge efficiency change x Characteristic coefficient (2) A remaining time calculation method for calculating a remaining time of a secondary battery that supplies power to a load device at a predetermined discharge rate,
A temperature detecting step for detecting a temperature of the secondary battery;
A remaining capacity detecting step for detecting a remaining capacity of the secondary battery;
A discharge efficiency detection step of detecting discharge efficiency from the discharge rate and the temperature;
A correction step of detecting a correction value of a remaining time from the discharge rate, the temperature, and the remaining capacity;
A remaining time calculation method comprising: a remaining time calculation step of calculating a remaining time of the secondary battery by the equation (1) from the discharge rate, the remaining capacity, the discharge efficiency, and the correction value.
(Equation 1)
Remaining time = remaining capacity / discharge rate × discharge efficiency + correction value (1)

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