JP2021058071A - Method and device for setting charging rate - Google Patents

Abstract

To provide a technique which can early estimate the charging rate of a battery and improve the estimation accuracy of the charging rate.SOLUTION: A battery ECU 3 includes a charge control unit 31 and an estimation unit 32. The charge control unit 31 executes constant-voltage charge control when the voltage of a battery B increases to a reference voltage Vc. The estimation unit 32 determines that a predetermined time tc elapses after the completion of the constant-voltage charge control. When it is detected that a secondary battery voltage after the lapse of the predetermined time tc is lower than the reference voltage Vc and is higher than the estimated voltage V2 of the secondary battery after the constant-current charge control is completed, which is estimated only when constant-current charge control is executed to the secondary battery, and the voltage of the battery B after the lapse of the predetermined time tc is lower than the reference voltage Vc and higher than the estimated voltage V2, the charging rate of the battery B is set to 100%.SELECTED DRAWING: Figure 5

Description

The present invention relates to a charging rate setting method and a charging rate setting device.

As a battery pack mounted on a vehicle, a charge rate-open circuit voltage curve (SOC-OCV curve) is used, and after the battery is discharged or charged, the battery open circuit voltage (OCV (Open Circuit Voltage)) is used. Some estimates the battery charge rate (SOC (State Of Charge)).

For example, when the battery voltage exceeds a certain voltage, the charge rate of the battery is determined to be 100%. For example, see Patent Document 1.

JP-A-2017-198455

The battery voltage V is calculated using the open circuit voltage Vocv, the internal resistance r, and the current I. Therefore, if only the voltage V of the battery is considered in the estimation of the charge rate, an error may occur because the internal resistance (rI component) of the battery is included. Further, the open circuit voltage Vocv of the battery acquired after the end of charging is affected by the polarization of the battery, and may not be an accurate value. Therefore, the estimation accuracy of the remaining capacity of the battery may be low until a certain time elapses after the charging is completed. In particular, in a usage such as an industrial vehicle in which recharging is frequently performed, it is required that the accuracy of estimating the remaining capacity can be improved at an early stage.

An object of one aspect of the present invention is to provide a charging rate setting method capable of estimating the charging rate of a battery at an early stage and improving the estimation accuracy of the charging rate.

The charge rate setting method of one aspect according to the present invention is a charge rate setting method in which constant voltage charge control is executed when the voltage of the secondary battery rises to the reference voltage, and the first step and the second step. It has a step and a third step. The first step determines that a predetermined time has elapsed since the constant voltage charging control was completed. The second step is the constant current charge control estimated when the voltage of the secondary battery after the lapse of a predetermined time is lower than the reference voltage and only the constant current charge control is executed for the secondary battery. Detects that the voltage is higher than the estimated voltage of the secondary battery after the end of. The third step sets the charge rate of the secondary battery to 100% when the voltage of the secondary battery after the elapse of a predetermined time is lower than the reference voltage and higher than the estimated voltage.

In the above charge rate setting method, when the voltage of the secondary battery is lower than the reference voltage, it can be determined that the charge control is completed and the polarization is eliminated. Further, when the voltage of the secondary battery is higher than the estimated voltage estimated when only the constant current charge control is executed, it is determined that the constant voltage charge control is executed instead of the constant current charge control. be able to. Therefore, when the voltage of the secondary battery is lower than the reference voltage and higher than the estimated voltage, it is determined that the constant voltage charge control has been executed, and the charge rate of the secondary battery is set (reset) to 100%. .. As a result, the error caused by the influence of the internal resistance (rI component) of the secondary battery can be reset, and the estimation accuracy of the charge rate of the secondary battery can be improved. Further, since the charge rate of the secondary battery can be set to 100% without waiting for the polarization to be eliminated, the charge rate of the secondary battery can be estimated at an early stage.

Further, in the first step, it may be determined that a predetermined time shorter than the polarization elimination time of the secondary battery has elapsed since the constant voltage charging control was completed.

In the above charge rate setting method, since the predetermined time is shorter than the polarization elimination time of the secondary battery, the charge rate of the secondary battery can be set to 100% without waiting for the polarization elimination. Therefore, the charge rate of the secondary battery can be estimated at an early stage.

Further, the secondary battery is composed of a plurality of cells arranged in series. Further, in the second step, it is detected that the voltage of each cell of the secondary battery after the elapse of a predetermined time is lower than the reference voltage and higher than the estimated voltage. Then, in the third step, the charge rate of the cell of the secondary battery determined that the voltage of the cell of the secondary battery after the elapse of a predetermined time is lower than the reference voltage and higher than the estimated voltage is 100. Set to%. Therefore, since the charge rate of the secondary battery can be set for each cell, the accuracy of estimating the charge rate can be improved.

Further, the secondary battery may be a lithium ion secondary battery in which the positive electrode material is lithium iron phosphate. Lithium-ion batteries using lithium iron phosphate as the positive electrode have a wide range of minute changes in the open circuit voltage due to changes in the charge rate, and when the charge rate is estimated from the open circuit voltage, they are easily affected by measurement errors. However, the charge rate setting method according to the present invention sets (reset) the charge rate of the secondary battery to 100% when it is determined that the constant voltage charge control has been executed. As a result, it is possible to improve the accuracy of estimating the charge rate for the secondary battery, for which it is difficult to estimate the charge rate.

In addition, the secondary battery may supply electric power to an industrial vehicle. Since industrial vehicles are required to be recharged frequently, the accuracy of estimating the charge rate of the secondary battery can be improved more effectively.

Further, the predetermined time may be a parameter that varies depending on the temperature of the secondary battery. Therefore, even if the internal resistance of the secondary battery fluctuates due to a change in the temperature of the secondary battery, the charge rate can be set to 100% according to the temperature, so that the estimation accuracy of the charge rate can be set. Can be improved.

Further, the charge rate setting device of one aspect according to the present invention includes a charge control unit and an estimation unit. The charge control unit executes constant voltage charge control when the voltage of the secondary battery rises to the reference voltage. The estimation unit determines that a predetermined time has elapsed since the constant voltage charging control was completed, and the voltage of the secondary battery after the predetermined time has elapsed is lower than the reference voltage and with respect to the secondary battery. It is detected that the voltage is higher than the estimated voltage of the secondary battery after the constant current charge control is completed, which is estimated when only the constant current charge control is executed, and the voltage of the secondary battery after a predetermined time has elapsed is high. , When the voltage is lower than the reference voltage and higher than the estimated voltage, the charge rate of the secondary battery is set to 100%.

In the charge rate setting device having the above configuration, when the battery voltage is lower than the reference voltage, the estimation unit can determine that the constant voltage charge control has been completed. Further, when the battery voltage is higher than the estimated voltage estimated when only the constant current charging control is executed, the estimation unit indicates that the constant voltage charging control is executed instead of the constant current charging control. Can be determined. Therefore, when the battery voltage is lower than the reference voltage and higher than the estimated voltage, the estimation unit determines that the constant voltage charge control has been executed and sets the charge rate of the secondary battery to 100% (reset). ). As a result, the error caused by the influence of the internal resistance (rI component) of the secondary battery can be reset, and the estimation accuracy of the charge rate of the secondary battery can be improved. Further, since the charge rate of the secondary battery can be set to 100% without waiting for the polarization to be eliminated, the charge rate of the secondary battery can be estimated at an early stage.

According to the present invention, the charge rate of the battery can be estimated at an early stage, and the accuracy of estimating the charge rate can be improved.

It is a figure which shows the use example of the battery pack which concerns on embodiment of this invention. It is a figure for demonstrating CCCV charging. It is a figure for demonstrating the method of estimating the charge rate based on an open circuit voltage. It is a figure for demonstrating the method of setting the charge rate of a battery to 100%. It is a flowchart which shows an example which sets the charge rate of a battery to 100%.

Hereinafter, embodiments will be described in detail based on the drawings.
FIG. 1 is a diagram showing an example of a battery pack including the charge rate setting device of the embodiment.

The battery pack 1 shown in FIG. 1 is mounted on, for example, an industrial vehicle Ve such as an electric forklift, and supplies electric power to a load such as an inverter that drives a drive motor.

Further, the battery pack 1 includes a plurality of battery modules 2, a battery ECU (charge rate setting device) 3, and a storage unit 4. The storage unit 4 is composed of, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory).

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 ECU 23, respectively. The battery stacks S of each battery module 2 are connected in parallel to each other to form an assembled battery.

The battery stack S is composed of a plurality of battery cells B (for example, a rechargeable secondary battery such as a lithium ion battery or a nickel hydrogen battery) connected in series. In the following description, each battery module 2 or each battery cell B may be simply referred to as "battery B". Each battery stack S may be composed of one battery cell B, respectively. Further, the number of each of the battery B and the switch SW is not limited to three.

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

The current detection unit 21 is composed of, for example, a Hall element and a shunt resistor, and detects the current flowing through each battery B.

The temperature detection unit 22 is composed of, for example, a thermistor, and detects the temperature of each battery B in units of battery cells B.

The monitoring ECU 23 is composed of, 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 of each battery cell B. Further, the monitoring ECU 23 controls the on / off of the switch SW according to the instruction sent from the battery ECU 3. Further, the monitoring ECU 23 sends the battery state information indicating the voltage of each battery B, the current detected by the current detection unit 21, and the temperature detected by the temperature detection unit 22 to the battery ECU 3.

The battery ECU 3 includes a charge control unit 31 that charges each battery B by performing predetermined charge control, and an estimation unit 32 that sets the charge rate of each battery B. As predetermined charge control, the charge control unit 31 includes, for example, constant current constant voltage charge control (hereinafter, also referred to as “CCCV (Constant Current Constant Voltage) charge”) and constant current charge control (hereinafter, “CC (Constant Current)). (Also referred to as "charging"), constant voltage charging control (hereinafter, also referred to as "CV (Constant Voltage) charging") and the like are executed. The battery ECU 3 is composed of, for example, a CPU or a programmable device (FPGA or PLD). In the battery ECU 3, the charge control unit 31 and the estimation unit 32 are realized when the CPU or the programmable device executes a predetermined program. Further, the charge rate setting device is configured to include, for example, at least a charge control unit 31 and an estimation unit 32.

FIG. 2 is a diagram for explaining CCCV charging. The horizontal axis of the graph shown in FIG. 2A shows time, and the vertical axis shows the voltage V of the battery B. The horizontal axis of the graph shown in FIG. 2B shows time, and the vertical axis shows the current I flowing through the battery B.

First, the charge control unit 31 gradually increases the voltage V of the battery B to the reference voltage Vc while maintaining the current I at a constant current Ic from the start of charging until the voltage V rises to the reference voltage Vc (t0 to t1). CC charging is performed to charge the battery B by sending the current command value to the charger Ch so that the voltage rises to.

Next, the charge control unit 31 keeps the voltage V at the reference voltage Vc or higher and the current from the time when the voltage V rises to the reference voltage Vc until the current I decreases to the end current If (t1 to t2). CV charging is performed to charge the battery B by sending a current command value to the charger Ch so that I gradually decreases to the end current If. Further, the charger Ch sends information such as the voltage of the power supply to the charge control unit 31.

Then, when the voltage V of at least one battery B of each battery B of the assembled battery is equal to or higher than the reference voltage Vc and the current I flowing through the battery B becomes equal to or lower than the end current If. It is determined that the battery B satisfies the full charge determination condition, and CV charging is terminated.

When the CV charging is completed, the charge control unit 31 ends the CCCV charging, sends a charging stop instruction to the charger Ch, and switches all the switches SW from on to off. Upon receiving the charge stop instruction, the charger Ch stops the power supply to the battery pack 1.

FIG. 3 is a diagram for explaining a method of estimating the charge rate based on the open circuit voltage. The horizontal axis of the graph shown in FIG. 3 indicates the charge rate (SOC), and the vertical axis of the graph shown in FIG. 3 indicates the open circuit voltage (OCV). The alternate long and short dash line shown in FIG. 3 shows the curve V1, and the alternate long and short dash line shows the curve C2.

Curve V1 shows a charge rate-open circuit voltage curve of a lithium ion battery (hereinafter referred to as "LFP-based battery") using LFP (lithium iron phosphate: LiFePO _{4) as a positive electrode material.} Curve V2, NMC _{(ternary: LiNi x Mn y Co z O} 2) and lithium-ion batteries are used as a positive electrode material (hereinafter, referred to as "NMC based battery") charging rate of - the open circuit voltage curve Shown.

As shown in FIG. 3, the LFP battery has a wider range (hereinafter referred to as “flat region”) in which the change in the open circuit voltage due to the change in the charging rate is wider than that of the NMC battery, and the open circuit voltage. If the charge rate is estimated from, it is easily affected by measurement error. Therefore, in particular, the LFP-based battery tends to accumulate measurement errors as compared with the NMC-based battery and the like.

Further, the voltage V of the battery is calculated by using the open circuit voltage Vocv, the internal resistance r, and the current I. See Equation 1.
V = Vocv + rI ... Equation 1

Therefore, if only the voltage V of the battery B is considered in the estimation of the charge rate, an error may occur because the internal resistance (rI component) of the battery B is included. Further, the open circuit voltage Vocv of the battery acquired after the end of charging is affected by the polarization of the battery B, and may not be an accurate value. Therefore, the estimation accuracy of the remaining capacity of the battery B may be low until a certain time elapses from the end of charging until the polarization disappears.

Further, since the LFP-based battery has a longer polarization elimination time than the NMC-based battery and the like, there is a problem that it takes time to measure the voltage of the battery B. In particular, industrial vehicles such as electric forklifts are used from morning till night without a break, so additional charging is required frequently. Therefore, the charging rate can be increased early without waiting for polarization to be eliminated after charging is completed. It is desirable to estimate. Therefore, in the present embodiment, the control unit 31 sets (reset) the charge rate of the battery B to 100% when it is determined that the CCCV charge has been executed.

FIG. 4 is a diagram for explaining a method of setting the charge rate of the battery to 100%. The horizontal axis of the graph shown in FIG. 4 indicates time, and the vertical axis indicates the voltage V of the battery B. The time ta indicates the time when the charge control unit 31 has finished charging. The dotted line shown in FIG. 4 shows the voltage waveform C1, and the alternate long and short dash line shows the voltage waveform C2.

The voltage waveform C1 shows an example of the waveform of the measured voltage of the battery B after the CCCV charging is completed, which is measured when the CV charging of the CCCV charging is executed for the battery B. In CCCV charging, CV charging is executed after CV charging is executed. Therefore, the voltage waveform C1 shows the waveform of the CCCV charge after the CV charge is completed.

The voltage waveform C2 shown in FIG. 4 shows an example of the waveform of the estimated voltage of the battery B after the CC charging, which is estimated when only the CC charging is executed for the battery B, is completed. The information of the voltage waveform C2 is information calculated based on the actually measured values accumulated by the experiment, and is stored in the storage unit 4 in advance. The information of the voltage waveform C2 is a parameter that depends on the temperature of the battery B. The storage unit 4 may store information on different voltage waveforms C2 based on a plurality of temperatures. Therefore, for example, a four lift used outdoors is strongly affected by the outside air. In such a case, even if the temperature of the battery B changes and the internal resistance of the battery B fluctuates, the charge rate can be set to 100% according to the temperature, so that the estimation accuracy of the charge rate can be set. Can be improved.

When the CV charging of the CCCV charging to the battery B is completed, the voltage after the CC charging is executed gradually decreases from the reference voltage Vc as shown in the voltage waveform C1 of FIG. 4, and when the polarization elimination time tb elapses. It converges to the voltage Vx. The voltage drop of the voltage waveform C1 is mainly due to the voltage drop accompanying the elimination of the polarization of the battery B. The characteristics of polarization are known in advance, and the estimated amount of the value of the voltage Vx associated with the elimination of polarization is stored in the storage unit 4 in advance.

On the other hand, as shown in the voltage waveform C2 of FIG. 4, the estimated voltage estimated after only CC charging is executed sharply drops from the reference voltage Vc in a short time as compared with the voltage of the voltage waveform C1. .. The sharp drop in the voltage of the voltage waveform C2 is mainly due to the influence of the voltage drop caused by the decrease in the internal resistance (rI component) of the battery B. After that, the voltage waveform of the voltage waveform C2 gradually decreases. The subsequent gradual decrease in the voltage waveform of the voltage waveform C2 is mainly due to the voltage drop accompanying the elimination of the polarization of the battery B.

Therefore, as shown in FIG. 4, the voltage V1 of the voltage waveform C1 at a predetermined time tk after the completion of CV charging is lower than the reference voltage Vc and higher than the estimated voltage V2 of the voltage waveform C2. The predetermined time tc is set to be shorter than the polarization elimination time tb of the battery B.

Therefore, when the voltage of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc and higher than the estimated voltage V2 shown in the voltage waveform C2, that is, the range Vd of the reference voltage Vc and the estimated voltage V2. If it is, the estimation unit 32 determines that the CCCV charge has been executed by the charge control unit 31. Further, in the estimation unit 32, when the voltage of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc by a predetermined voltage and higher than the estimated voltage V2 shown in the voltage waveform C2 by a predetermined voltage. In addition, the charge control unit 31 may determine that the CCCV charge has been executed. Since there are innumerable CC charging conditions, the estimated voltage used for the determination may be set to a value higher than the estimated voltage V2 of the voltage waveform C2. In that case, it is preferable to derive how high the value should be set by using statistical processing or the like based on the result of the voltage waveform C2.

When it is determined that the CCCV charge has been executed, the estimation unit 32 sets (reset) the charge rate of the battery B to 100%. Specifically, the estimation unit 32 extracts information on the voltage width (V1-Vx) of the battery B, which fluctuates from the predetermined time tc to the polarization elimination time tb, from the storage unit 4, and refers to the extracted information. The voltage Vx of the battery B after the polarization at the polarization elimination time tb is eliminated is set to 100%. Information on the voltage width (V1-Vx) of the battery B, which fluctuates from the predetermined time tc to the polarization elimination time tb, is stored in the storage unit 4 in advance.

FIG. 5 is a flowchart showing an example of setting the charge rate of the battery to 100%. First, the charge control unit 31 of the battery ECU 3 starts CC charging (S101). The charge control unit 31 waits for processing until the voltage V of the battery B rises to the reference voltage Vc (see FIG. 2A) (S102: NO), and CC when the voltage V of the battery B rises to the reference voltage Vc. Charging is completed (S103). When the CC charging is completed, the charge control unit 31 starts CV charging (S104).

The charge control unit 31 waits for processing after the voltage V of the battery B rises to the reference voltage Vc until the current I decreases to the end current If (S105: NO), and when the current I decreases to the end current If (S105: NO). S105: YES), CV charging is terminated (S106).

The estimation unit 32 determines whether or not a predetermined time ct (see FIG. 4) has elapsed since the CV charging was completed (S107). The process of S107 corresponds to the first step of this embodiment. When the predetermined time ct (see FIG. 4) has not elapsed since the CV charging is completed (S107: NO), the estimation unit 32 waits for the process until the predetermined time tk elapses. When a predetermined time tc has elapsed since the end of CV charging (S107: YES), the estimation unit 32 determines whether or not the voltage of the battery B is lower than the reference voltage Vc (S108). In this case, the estimation unit 32 determines whether or not the voltage of the battery B is lower than the reference voltage Vc in units of the battery cells B.

When the voltage of the battery B is higher than the reference voltage Vc (S108: NO), the estimation unit 32 determines that the battery B has an abnormality and ends the process. Therefore, since the estimation unit 32 can set the battery charge rate for each battery cell B, the estimation accuracy of the charge rate can be improved. Further, the estimation unit 32 may determine the abnormality of the battery B in units of the battery cells B. When the estimation unit 32 determines that the battery B has an abnormality, the estimation unit 32 may notify the mechanic or the user of the abnormality through a lamp connected to the vehicle ECU 5. Further, even when the individual battery cells B are connected in series, the abnormal battery cell B can be specifically identified by determining the voltage in units of the battery cells B. As a result, only the abnormal battery cell B can be replaced, and the cost can be reduced as compared with the case where the battery B is replaced in units of the battery pack 1 or the battery stack S. As a result, the financial burden on the user can be reduced.

When the voltage of the battery B is lower than the reference voltage Vc (S108: YES), the estimation unit 32 determines whether or not the voltage of the battery B is higher than the estimated voltage (S109). When the voltage of the battery B is lower than the estimated voltage (S109: NO), the estimation unit 32 determines that CC charging has been executed, and ends the process. The processing of S108 and S109 corresponds to the second step of this embodiment. When the voltage of the battery B is higher than the estimated voltage (S109: YES), the estimation unit 32 determines that the CCCV charge has been executed (S110), and sets (reset) the charge rate of the battery B to 100%. (S111). The process of S111 corresponds to the third step of this embodiment. When this process is completed, the process is completed.

From the above configuration, the estimation unit 32 determines that a predetermined time tc has elapsed since the CV charging was completed. Then, the estimation unit 32 completes the estimated CV charging when the voltage of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc and only CC charging is executed for the battery B. It is detected that the voltage is higher than the estimated voltage V2 of the battery B later. Then, the estimation unit 32 sets the charge rate of the battery B to 100% when the voltage of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc and higher than the estimated voltage V2.

When the voltage of the battery B is lower than the reference voltage Vc, the estimation unit 32 can determine that the CV charging is completed. Further, when the voltage of the battery B is higher than the estimated voltage V2 estimated when only CC charging is executed, it can be determined that CV charging is executed instead of CC charging. Therefore, when the voltage of the battery B is lower than the reference voltage Vc and higher than the estimated voltage V2, it is determined that the CV charging has been executed, and the charging rate of the battery B is set (reset) to 100%. As a result, the error caused by the influence of the internal resistance (rI component) of the battery B can be reset, and the estimation accuracy of the battery B can be improved. Further, since the charge rate of the battery B can be set to 100% without waiting for the polarization to be eliminated, the charge rate of the battery B can be estimated at an early stage.

Further, the battery B is composed of a plurality of battery cells B arranged in series. Further, the estimation unit 32 detects that the voltage of each battery cell B of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc and higher than the estimated voltage V2, respectively. Then, the estimation unit 32 determines that the voltage of the battery cell B of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc and higher than the estimated voltage V2. Set the charge rate to 100%. Therefore, since the charge rate of the battery B can be set for each battery cell B, the estimation accuracy of the charge rate can be improved.

Further, the estimation unit 32 determines that the battery B has been charged by CCCV charging when the voltage of the battery B after the elapse of the predetermined time tc is lower than the reference voltage Vc and higher than the estimated voltage V2. Then, the charge rate of the battery B is set to 100%. As a result, the error caused by the influence of the internal resistance (rI component) of the battery B can be reset, and the estimation accuracy of the battery B can be improved.

Further, the battery B is a lithium ion secondary battery in which the positive electrode material is lithium iron phosphate. Lithium-ion batteries using lithium iron phosphate as the positive electrode have a wide range of minute changes in the open circuit voltage due to changes in the charge rate, and when the charge rate is estimated from the open circuit voltage, they are easily affected by measurement errors. This point The estimation unit 32 of the present embodiment sets (reset) the charge rate of the battery B to 100% when it is determined that the CV charge has been executed. As a result, the accuracy of estimating the charge rate can be improved regardless of the type of battery.

Further, the predetermined time tc is a parameter that varies depending on the temperature of the battery B. Therefore, even if the internal resistance of the battery B fluctuates due to a change in the temperature of the battery B, the charge rate can be set to 100% according to the temperature, so that the estimation accuracy of the charge rate is improved. can do.

Further, although the battery pack 1 shows an example of supplying electric power to a load such as an inverter for driving a drive motor, it may be a cargo handling motor or the like for driving a hydraulic pump.

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

1 Battery pack 2 Battery module 3 Battery ECU (charge rate estimation device)
4 Storage unit 5 Vehicle ECU
21 Current detection unit 22 Temperature detection unit 23 Monitoring ECU
31 Charge control unit 32 Estimator unit S Battery stack B Battery cell SW switch Ch Charger Ve Vehicle

Claims (7)

It is a method of setting the charge rate of a secondary battery in which constant voltage charge control is executed when the voltage of the secondary battery rises to the reference voltage.
The first step of determining that a predetermined time has elapsed since the constant voltage charging control was completed, and
The constant current charge control estimated when the voltage of the secondary battery after the lapse of the predetermined time is lower than the reference voltage and only the constant current charge control is executed for the secondary battery. The second step of detecting that the voltage is higher than the estimated voltage of the secondary battery after the completion of
The third step of setting the charge rate of the secondary battery to 100% when the voltage of the secondary battery after the elapse of the predetermined time is lower than the reference voltage and higher than the estimated voltage. When,
A charging rate setting method characterized by having. The charging rate according to claim 1, wherein the first step determines that a predetermined time shorter than the polarization elimination time of the secondary battery has elapsed since the constant voltage charging control was completed. Setting method. The secondary battery is composed of a plurality of cells arranged in series.
In the second step, it is detected that the voltage of each cell of the secondary battery after the elapse of the predetermined time is lower than the reference voltage and higher than the estimated voltage, respectively.
In the third step, the voltage of the cell of the secondary battery after the elapse of the predetermined time is determined to be lower than the reference voltage and higher than the estimated voltage of the secondary battery. The charging rate setting method according to claim 1 or 2, wherein the charging rate is set to 100%. The charging rate setting method according to any one of claims 1 to 3, wherein the secondary battery is a lithium ion secondary battery in which the positive electrode material is lithium iron phosphate. The charging rate setting method according to any one of claims 1 to 4, wherein the secondary battery supplies electric power to an industrial vehicle. The charging rate setting method according to any one of claims 1 to 5, wherein the predetermined time is a parameter that varies depending on the temperature of the secondary battery. A charge control unit that executes constant voltage charge control when the voltage of the secondary battery rises to the reference voltage,
It is determined that a predetermined time has elapsed since the constant voltage charging control is completed, and the voltage of the secondary battery after the predetermined time has elapsed is lower than the reference voltage and the secondary battery has On the other hand, it is detected that the voltage is higher than the estimated voltage of the secondary battery after the constant current charging control, which is estimated when only the constant current charging control is executed, is completed, and the second after the predetermined time has elapsed. An estimation unit that sets the charge rate of the secondary battery to 100% when the voltage of the secondary battery is lower than the reference voltage and higher than the estimated voltage.
A charging rate setting device characterized by being provided with.

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