JP2017225225A - Charging rate estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging rate estimation device which can estimate a battery charging rate if the reliability of a current integration value is low.SOLUTION: The charging rate estimation device includes: a charge control unit 31 which performs constant current and constant voltage charge control; and an estimation unit 32 which, in constant voltage charge control, acquires a constant voltage charge start charging rate when the voltage of a battery B reaches a target voltage to obtain, from the constant voltage charge start charging rate, an estimated time until reaching a charging rate at full charge, and to obtain, from the constant voltage charge start time, a ratio of the estimated time to a continuation time during which constant voltage charging continues, and obtain a difference between the charging rate at the full charge and the constant voltage charge start charging rate and add a value, obtained by multiplying the ratio by the difference, to the constant voltage charge start charging rate, so as to obtain an estimated charging rate.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a charging rate estimation device that estimates a charging rate of a battery.

  As an existing charging rate estimation device, for example, a technology for estimating a charging rate of a battery (a ratio (percentage) of a remaining capacity to a full charging capacity of a battery) based on an integrated value of a current flowing through a battery being charged is known. ing.

As another existing charging rate estimation device, for example, there is a device that sets the charging rate of a battery to 100 [%] at the time when the voltage of the battery being charged reaches a target voltage.
As related technologies, there are, for example, Patent Document 1 and Patent Document 2.

JP 2015-1118060 A JP 2013-011590 A

  However, in the charging rate estimation device that estimates the charging rate based on the integrated current value, the current detection unit becomes abnormal (for example, the failure of the current detection unit or the disconnection of the measurement wiring), and the current flowing through the battery cannot be detected. When the accumulated value cannot be obtained or when the reliability of the estimated charge rate obtained based on the current accumulated value decreases due to the long current accumulation time, there is a large difference between the estimated charge rate and the actual charge rate. May occur.

  An object of one aspect of the present invention is to provide a charging rate estimation device that can estimate the charging rate of a battery even when the reliability of the current integrated value is low.

The charging rate estimation apparatus which is one form which concerns on this invention is provided with a control part and an estimation part.
The charge control unit performs constant current constant voltage charge control. In the constant voltage charge control, the estimation unit obtains a constant voltage charge start charge rate when the battery voltage reaches the target voltage, and estimates the time from the constant voltage charge start charge rate until the charge rate at full charge is reached. Determine the ratio between the duration of constant voltage charging from the constant voltage charge start time and the estimated time, and determine the difference between the charge rate at full charge and the constant voltage charge start charge rate. Is added to the constant voltage charging start charging rate to obtain the estimated charging rate.

  According to the present invention, it is possible to estimate the charging rate of the battery even when the reliability of the current integrated value is low.

It is a figure which shows an example of the battery pack containing the charging rate estimation apparatus of embodiment. It is a flowchart for demonstrating operation | movement of a control part. It is a figure for demonstrating charge control. It is a figure which shows an example of internal resistance-constant voltage charge start charge rate information and current-constant voltage charge start charge rate information. It is a figure which shows an example of electric current-internal resistance-constant voltage charge start charge rate information. It is a figure which shows an example of electric current-internal resistance-estimated time information.

Hereinafter, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating an example of a battery pack including the charging rate estimation apparatus according to the embodiment.
The battery pack 1 shown in FIG. 1 is mounted on a vehicle such as an electric forklift, for example, and supplies power to a load such as an inverter that drives a travel motor.

  In addition, the battery pack 1 includes a plurality of battery modules 2, a control unit 3, and a storage unit 4. The storage unit 4 is configured by, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), or the like.

  Each battery module 2 includes a battery stack S, a switch SW, a current detection unit 21, a temperature detection unit 22, and a monitoring unit 23. The battery stacks S of the battery modules 2 are connected in parallel to each other to form an assembled battery. The battery module 2 may be one instead of plural.

  The battery stack S is composed of a plurality of batteries B (for example, lithium ion batteries, nickel metal hydride batteries, or electric double layer capacitors) connected in series. Each of the battery stacks S may be composed of one battery B.

  The switch SW is configured by, for example, a semiconductor relay such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an electromagnetic relay. When electric power is supplied from the charger Ch to the battery pack 1, the battery B included in the battery module 2 in which the switch SW is turned on (conductive) is charged, and the voltage of the battery B increases.

The current detection unit 21 includes, for example, a Hall element or a shunt resistor, and detects the current I flowing through each battery B.
The temperature detection part 22 is comprised by the thermistor, for example, and detects the temperature T of each battery B.

  The monitoring unit 23 is a circuit configured by, for example, a CPU (Central Processing Unit) or a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.), and detects the voltage V of each battery B. In addition, the monitoring unit 23 controls on / off (shut-off) of the switch SW according to an instruction sent from the control unit 3. Further, the monitoring unit 23 sends battery state information indicating the voltage V of each battery B, the current I detected by the current detection unit 21, and the temperature T detected by the temperature detection unit 22 to the control unit 3.

  The control unit 3 includes a charge control unit 31 that charges each battery B by performing constant current and constant voltage charge control, and an estimation unit 32 that estimates a charge rate (SOC: State Of Charge) of each battery B. Further, the control unit 3 sends the estimated charging rate estimated by the estimation unit 32 to the vehicle-side control unit 5 after the charging is stopped. The vehicle-side control unit 5 causes the output unit 6 (for example, a display, a monitor, and a printer) to output (display or print) the charging rate sent from the control unit 3. In addition, the control part 3 is a circuit comprised by CPU or a programmable device, for example, and the charge control part 31 and the estimation part 32 are implement | achieved when CPU or a programmable device runs a predetermined | prescribed program. In addition, the charging rate estimation device includes, for example, at least a charging control unit 31 and an estimation unit 32.

The operation of the control unit 3 will be described.
FIG. 2 is a flowchart for explaining the operation of the control unit 3. FIG. 3 is a diagram for explaining the charging control. 3A is a diagram showing a variation example of the voltage V of the battery B, FIG. 3B is a diagram showing a variation example of the current I flowing through the battery B, and FIG. 3C is an actual charge of the battery B. It is a figure which shows the example of a fluctuation | variation of a rate (one-dot chain line: 301) and an estimated charging rate (solid line: 302). Note that the horizontal axis of the graph shown in FIG. 3A represents time, and the vertical axis represents the voltage V of the battery B. Also, the horizontal axis of the graph shown in FIG. 3B indicates time, and the vertical axis indicates the current I flowing through the battery B. Further, the horizontal axis of the graph shown in FIG. 3C indicates time, and the vertical axis indicates the charging rate of the battery B. The horizontal axes of the graphs A to C in FIG. 3 are the same time axis.

  In step S1, the charging control unit 31 of the control unit 3 starts constant current charging control. First, when the constant current charging control is started, the charging control unit 31 gradually increases the voltage V to the target voltage Vt while maintaining the current I at a constant current Ic from time t0 to time t1 shown in FIG. The current command value is transmitted to the charger Ch, and each battery B is charged based on the transmitted current command value. Moreover, the estimation part 32 calculates | requires estimated charging rate SOC1 based on the integrated value of the electric current I from the time t0 to the time t1. For example, the estimation unit 32 calculates the estimated charging rate SOC1 by calculating the estimated charging rate SOC1 (= integrated value of current I / full charge capacity × 100) from time t0 to time t1. In addition, the estimation part 32 memorize | stores the charging rate of the battery B estimated before the start of charge in the memory | storage part 4, and let the memorize | stored charging rate be the estimated charging rate SOC1 from the time t0 to the time t1. Good. The target voltage Vt is, for example, a full charge voltage, but is not limited to a full charge voltage and may be an arbitrary voltage.

  In step S2, the charging control unit 31 determines whether or not the voltage V is equal to or higher than the target voltage Vt. If the voltage V is smaller than the target voltage Vt (No), the process proceeds to step S2, and the voltage V is If the charge control unit 31 detects that the reliability of the integrated current value is low at the target voltage Vt or higher (Yes), the process proceeds to step S3. Here, when the reliability of the current integration value is low, the current detection unit is in an abnormal state (for example, failure of the current detection unit or disconnection of the measurement wiring), the current flowing through the battery cannot be detected, and the current integration value is obtained. Or the reliability of the estimated charging rate obtained based on the current integrated value is reduced due to the long current integration time. An abnormal state of the current detection unit is detected by the control unit 3 based on the current I, voltage V, temperature T, and the like. Whether or not the current integration time is long is determined based on whether the current integration time measured by the control unit 3 is added to the current integration time and a predetermined time (a time in which the reliability of the current integration is reduced). ) And the controller 3 determines that the reliability of the current integrated value has decreased if the current integrated time is equal to or longer than a predetermined time.

  Note that when the reliability of the current integrated value is high, the process does not proceed to step S3, and the charging control unit 31 obtains the charging rate using the integrated current value. Further, the charge control unit 31 uses the measured voltage V (= closed circuit voltage), refers to the information associated with the charge rate and the closed circuit voltage stored in the storage unit 4, and corresponds to the voltage V. You may ask for a charge rate.

  In step S2, the charging control unit 31 does not detect that the reliability of the current integrated value is low and may only determine whether the voltage V is equal to or higher than the target voltage Vt. In the case where low is detected, it is possible to improve reliability by implementing the present invention.

In step S3, when the reliability of the current integrated value is low, the charge control unit 31 executes the process (1), and the estimation unit 32 executes the processes (2) to (4).
(1) When the voltage V is equal to or higher than the target voltage Vt, the charging control unit 31 ends the constant current charging control and starts constant voltage charging control.

In the constant voltage charge control, the charge control unit 31 gradually decreases the current command value transmitted to the charger Ch in order to gradually decrease the current I while maintaining the voltage V at the target voltage Vt.
(2) The estimation unit 32 acquires the constant voltage charge start charge rate SOC0. In the example of FIG. 3, the constant voltage charge start charge rate SOC0 (for example, 80 [%]) is acquired at time t1.

  Here, the constant voltage charging start charging rate SOC0 is obtained by experiment or simulation, for example, with a value close to the actual charging rate of the battery B when the voltage V becomes equal to or higher than the target voltage Vt. It is remembered.

  The constant voltage charging start charging rate SOC0 may be calculated based on the current command value or current Ich when the constant current charging control is performed and the internal resistance of the battery B. The actual open circuit voltage of the battery B when the voltage V becomes the target voltage Vt and changes from the constant current charge control to the constant voltage charge control is determined from the target voltage Vt (the current command value when the constant current charge control is performed or Since it is close to the voltage obtained by subtracting the voltage determined by (current Ich) × (internal resistance of battery B), the charge rate calculated by the open circuit voltage-charge rate characteristic curve is determined using the obtained open circuit voltage. The voltage charging start charging rate SOC0 can be set. In addition, since the internal resistance of the battery B changes depending on the temperature and the degree of deterioration, the predetermined charging rate may be obtained in consideration of the temperature and the degree of deterioration.

  Further, the constant voltage charge start charge rate SOC0 may be acquired using the information of the internal resistance-constant voltage charge start charge rate information 401 or the current-constant voltage charge start charge rate information 402 shown in FIG. FIG. 4 is a diagram illustrating an example of internal resistance-constant voltage charge start charge rate information 401 and current-constant voltage charge start charge rate information 402.

  The internal resistance-constant voltage charging start charging rate information 401 shown in FIG. 4A indicates information “r1”, “r2”, “r3”, etc. indicating the range of the internal resistance R, and the range of the constant voltage charging starting charging rate SOC0. This is a table in which information “SOCr1”, “SOCr2”, “SOCr3”, and the like are associated with each other. The relationship between the internal resistance R and the constant voltage charge start charge rate SOC0 is that the larger the internal resistance R of the battery B, the lower the constant voltage charge start charge rate SOC0 and the smaller the internal resistance R, the constant voltage charge start charge rate SOC0. Is set high. This is because the difference between the closed circuit voltage of the battery B and the actual open circuit voltage increases as the internal resistance R of the battery B increases.

  For example, when using the internal resistance-constant voltage charge start charge rate information 401, the control unit 3 obtains the internal resistance R, and refers to the internal resistance-constant voltage charge start charge rate information 401 using the obtained internal resistance R. The constant voltage charging start charging rate SOC0 corresponding to the internal resistance R is acquired. For example, if the internal resistance R is in the range of “r1”, “SOCr1” is acquired as the constant voltage charge start charge rate SOC0. The internal resistance R may be set as the degree of deterioration.

  The current-constant voltage charging start charging rate information 402 shown in FIG. 4B includes information “i1”, “i2”, “i3”, and the like indicating the range of the current I, and information “showing the range of the constant voltage charging starting charging rate SOC0”. This is a table in which SOCi1, “SOCi2,” “SOCi3” and the like are associated with each other. The relationship between the current I and the constant voltage charge start charge rate SOC0 is that the constant current charge start charge rate SOC0 is lower as the current I flowing through the battery B is larger, and the constant voltage charge start charge rate SOC0 is higher as the current I is smaller. Is set. This is because the difference between the closed circuit voltage of battery B and the actual open circuit voltage increases as current I flowing through battery B increases.

  For example, when the estimation unit 32 uses the current-constant voltage charging start charging rate information 402, the control unit 3 obtains the current I and refers to the current-constant voltage charging start charging rate information 402 using the obtained current I. Then, the constant voltage charging start charging rate SOC0 corresponding to the current I is acquired. If the current I is in the range of “i1”, “SOCi1” is acquired as the constant voltage charge start charge rate SOC0. The current I may include a current command value and a constant current Ic during constant current charging control.

  Further, since the internal resistance R and the current I cannot be measured when the current detection unit 21 is in an abnormal state, the constant voltage charge start charge rate SOC0 is obtained even if the constant voltage charge start charge rate SOC0 is acquired based on the temperature T. Good. In that case, based on the information indicating the temperature T acquired from the temperature detection unit 22, the estimation unit 32 lowers the constant voltage charge start charging rate SOC <b> 0 as the temperature T of the battery B is lower, and the temperature T of the battery B becomes lower. The higher the constant voltage charging start charging rate SOC0 is, the higher it is. This is because the internal resistance R increases as the temperature T of the battery B decreases, and the difference between the closed circuit voltage of the battery B and the actual open circuit voltage increases as the internal resistance R increases.

  Further, the constant voltage charge start charge rate SOC0 may be obtained using information of current-temperature-internal resistance-constant voltage charge start charge rate information 501 shown in FIG. FIG. 5 is a diagram illustrating an example of current-internal resistance-constant voltage charge start charge rate information.

The current-internal resistance-constant voltage charging start charging rate information 501 shown in FIG. 5 includes information “i1”, “i2”, “i3”, etc. indicating the range of the current I, and information “r1”, “ “r2”, “r3”, etc., and information “SOC11”, “SOC12”, “SOC13”, “SOC21”, “SOC22”, “SOC23”, “SOC31”, “SOC32”, “SOC33”, etc. indicating the value of the constant voltage charging start charging rate SOC0. Associated table. For example, when using the current-internal resistance-constant voltage charge start charge rate information 501, the estimation unit 32 uses the measured current I and the obtained internal resistance R to charge current-internal resistance-constant voltage charge start charge. Referring to rate information 501, constant voltage charge start charge rate SOC0 corresponding to current I and internal resistance R is acquired. For example, if the current I is “i1” and the internal resistance R is “r1”, “SOC11” is acquired as the constant voltage charge start charge rate SOC0. The current I may include a current command value and a constant current Ic during constant current charging control.
(3) The estimation unit 32 obtains the estimated time t (from time t1 to time t2 in FIG. 3). The time estimated to take from the constant voltage charge start charge rate SOC0 to the full charge rate (= 100 [%]) is obtained by experiments and simulations and stored in the storage unit 4 or the like. That is, from the time t1 when the constant voltage charging control is started, the time t2 when the battery B reaches the full charge rate is estimated, and the time from the time t1 to the time t2 is set as the estimated time t. The time may include date / time or year / month / date / time.

  The estimated time t may be changed according to the internal resistance R or current I. Regarding the relationship between the internal resistance R and the estimated time t, the estimated time t is set shorter as the internal resistance R of the battery B is lower, and the estimated time t is set longer as the internal resistance R is higher. The internal resistance R may be set as the degree of deterioration. The relationship between the current I and the estimated time t is set such that the larger the current I flowing through the battery B, the shorter the estimated time t, and the smaller the current I, the longer the estimated time t. The current I may include a current command value and a constant current Ic during constant current charging control.

  Further, the estimated time t may be obtained using the current-internal resistance-estimated time information 601 shown in FIG. That is, the estimated time t may be obtained by determining according to the current I and the internal resistance R. FIG. 6 is a diagram illustrating an example of current-internal resistance-estimated time information.

  The current-internal resistance-estimated time information 601 shown in FIG. 6 includes information “i1”, “i2”, “i3” indicating the range of the current I, and information “r1” “r2” “r3” indicating the value of the internal resistance R. , Etc., and information “t11”, “t12”, “t13”, “t21”, “t22”, “t23”, “t31”, “t32”, “t33”, and the like indicating the value of the estimated time t. For example, when using the current-internal resistance-estimated time information 601, the estimating unit 32 refers to the current-internal resistance-estimated time information 601 using the measured current I and the obtained internal resistance R, and determines the current I And an estimated time t corresponding to the internal resistance R is obtained. For example, if the current I is “i1” and the internal resistance R is “r1”, “t11” is obtained as the estimated time t. The current I may include a current command value and a constant current Ic during constant current charging control.

Further, the estimated time t may be acquired based on the temperature T because the internal resistance R and the current I cannot be measured when the current detector 21 is in an abnormal state. In that case, based on the information indicating the temperature T acquired from the temperature detection unit 22, the estimation unit 32 shortens the estimation time t as the temperature T of the battery B is low, and estimates as the temperature T of the battery B is high. Increase the time t.
(4) The estimation unit 32 starts measuring the duration tc. The duration tc is the time from the constant voltage charge control start time t1 to the current time when the constant voltage charge control is continued.

  In step S4, the estimation part 32 calculates | requires estimated charging rate SOC1. The estimation unit 32 obtains a ratio D (= tc / t) between the duration tc in which constant voltage charge control has been continued from the constant voltage charge control start time t1 and the estimated time t, and a charge rate at full charge (= 100 [%]) and the constant voltage charge start charge rate SOC0, a difference Sub (= 100−SOC0) is obtained, and a value obtained by multiplying the ratio D and the difference Sub (= D × Sub) is obtained as the constant voltage charge start charge rate SOC0. To obtain an estimated charging rate SOC1 (= SOC0 + D × Sub). See Equation 1.

SOC1 = SOC0 + (tc / t) × (100−SOC0) (Formula 1)
In step S5, the charge control unit 31 determines whether or not the duration tc is the time when the estimated time t has elapsed, and if the duration tc is not the time when the estimated time t has elapsed (No), the constant voltage In order to continue charge control, it transfers to step S4, and when the continuation time tc is the time when the estimated time t passed (Yes), it transfers to step S6.

  In step S6, when the duration tc has passed the estimated time t, the charging control unit 31 ends the constant voltage charging control. When the constant voltage charging control is finished, the charging control unit 31 transmits a charging stop instruction to the charger Ch, and switches all the switches SW from on to off to stop charging of each battery B. In addition, when the current command value becomes equal to or less than the predetermined current command value, the charge control unit 31 transmits a charge stop instruction to the charger Ch and switches all the switches SW from on to off to charge each battery B. You may comprise so that it may stop. The charger Ch stops the power supply to the battery pack 1 when receiving the charge stop instruction.

  Moreover, the estimation part 32 will set the estimated charge rate of the fully charged battery with the highest voltage V among each battery B to 100 [%], when the continuation time tc becomes the time which passed the estimated time t. Moreover, you may estimate the estimated charge rate of less charge batteries other than a full charge battery among each battery B based on the voltage V of the less charge battery when charge stops. Therefore, the estimation accuracy of the charging rate of each battery B after stopping charging can be improved. For example, when the estimated charging rate of at least one battery B is 100 [%], 100 [%] is output to the user as the charging rate of the assembled battery, and the estimated charging rate of at least one battery B is 0 [%]. ], If 0 [%] is output to the user as the charging rate of the assembled battery, the difference between the actual charging rate of each battery B and the charging rate of the assembled battery output to the user is Since it can suppress, it can prevent a user from feeling uncomfortable.

  According to the embodiment, during the constant current and constant voltage charging of each battery B, when the voltage V becomes equal to or higher than the target voltage Vt, the current detection unit 21 is abnormal by obtaining the estimated charging rate SOC1 using Equation 1. Even when the current flowing through the battery B cannot be detected due to a state, etc., and the current integrated value cannot be obtained, or when the reliability of the estimated charging rate obtained based on the current integrated value is reduced due to a long current integrating time The charging rate of the battery B can be estimated.

Further, an estimated charging rate SOC1 close to the actual charging rate of the battery B can be obtained.
Conventionally, when the integrated current value cannot be obtained, the estimated charging rate SOC1 of the battery B is set to 100 [%] when the voltage V of the battery B being charged reaches the target voltage Vt at time t1.

  However, in the present embodiment, the constant voltage charge start charge rate SOC0 is acquired at the constant voltage charge control start time t1, and the estimated charge rate SOC1 is obtained based on Equation 1, so that the time t1 to the time t2 (estimated time t2 ), The estimated charging rate SOC1 is as shown by a primary straight line 302 (solid line) shown in FIG. Accordingly, the linear line 302 obtained using Equation 1 is shown in FIG. 3C from the case where the estimated charging rate SOC1 is set to 100 [%] from time t1 to time t2 (estimated time t) as in the prior art. It can be approximated to a curve 301 (one-dot chain line) indicating the actual charging rate of the battery B. Further, since the primary straight line 302 is close to the curve 301, even when the charging is stopped during the constant voltage charging control, the charging rate of the battery B is made closer to the actual charging rate than the conventional estimated charging rate SOC1 set to 100 [%]. Can do.

  Further, as shown in the processes of (2) and (3) of step S3, the constant voltage charge start charging rate SOC0 and the estimated time t are changed according to the internal resistance R, current I, deterioration degree, and temperature T, The primary straight line 302 can be made closer to the curve 301 by obtaining the estimated charging rate SOC1 using Equation 1.

  In the process of step S3 (2), the charge control unit 31 obtains the constant voltage charge start charge rate SOC0 and obtains the estimated charge rate SOC1 using equation 1 in step S4. In the process (2), the constant voltage charging start charging rate SOC0 may be set to the estimated charging rate SOC1, and then the estimated charging rate SOC1 may be obtained using Equation 1 in step S4.

  Further, the present invention is not limited to the above-described embodiment, and various improvements and changes can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Battery module 3 Control part 4 Memory | storage part 5 Vehicle side control part 6 Output part 21 Current detection part 22 Temperature detection part 23 Monitoring part 31 Charge control part 32 Estimation part Ch Charger S Battery stack B Battery SW switch

Claims (4)

A charge control unit for controlling constant current and constant voltage charge;
In constant voltage charge control, when the voltage of the battery reaches the target voltage, obtain a constant voltage charge start charge rate, obtain an estimated time from the constant voltage charge start charge rate until reaching the full charge rate, Obtain the ratio between the duration of constant voltage charging from the constant voltage charge start time and the estimated time, determine the difference between the charge rate at the time of full charge and the constant voltage charge start charge rate, and An estimation unit for obtaining an estimated charging rate by adding a value obtained by multiplying the difference to the constant voltage charging start charging rate;
A charging rate estimation device comprising: The charging rate estimation device according to claim 1,
The estimation unit includes
The larger the internal resistance of the battery, the lower the constant voltage charge start charging rate, and the smaller the internal resistance of the battery, the higher the constant voltage charge start charging rate,
The charge rate estimation apparatus characterized by the above-mentioned. The charging rate estimation device according to claim 1 or 2,
The estimation unit includes
The larger the current flowing through the battery, the lower the constant voltage charging start charging rate, and the smaller the current flowing through the battery, the higher the constant voltage charging starting charging rate.
The charge rate estimation apparatus characterized by the above-mentioned. The charging rate estimation device according to claim 1,
The charging rate estimation apparatus characterized by changing the said estimation time according to the electric current which flows through the said battery, and the internal resistance of the said battery.

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