JP5911897B2 - Secondary battery charge control device and secondary battery charge control method - Google Patents

Description

  The present invention relates to a secondary battery charge control device and a secondary battery state detection method.

  In recent years, there has been a technology for converting the kinetic energy of a car into electrical energy (regeneration) and storing it in a battery (secondary battery) by setting the alternator voltage high when the car decelerates in order to improve the fuel efficiency of the car. Widely used.

  In order to perform such regeneration efficiently, it is necessary to control the state of charge of the battery to be a predetermined set value. Therefore, in the technique disclosed in Patent Document 1, the charging current value A after elapse of t seconds from the start of regenerative power generation is compared with upper and lower limit values B1 and B2 of a preset threshold range, and when A> B1, battery charging is performed. Estimating that the state (SOC) is small and making the amount of discharge less than the amount of charge obtained by regenerative power generation. By performing control to increase the amount, the battery can be always charged and the fuel consumption reduction effect by regenerative power generation can be ensured.

JP 2003-52131 A

  By the way, in the technique disclosed in Patent Document 1, there are cases where control is performed in the SOC range where battery acceptability is poor, and in this case, the charging efficiency of the battery is lowered, and thus the fuel consumption reduction effect is suppressed. There is a problem.

  An object of this invention is to provide the secondary battery charge control apparatus and secondary battery charge control method which can improve the charge efficiency of a secondary battery.

In order to solve the above problems, the present invention provides a secondary battery charge control device that controls charging of a secondary battery mounted on a vehicle, an alternator that charges the secondary battery, and a charging rate of the secondary battery. A detecting means for detecting a change point from a constant current charge to a constant voltage charge when charging the secondary battery by the alternator; and the change detected by the detecting means. And a control means for controlling charging of the secondary battery by the alternator so as to obtain a charging rate at a point from the obtaining means and to fall below the charging rate.
According to such a configuration, the charging efficiency of the secondary battery can be increased.

Further, the present invention is characterized in that the alternator performs regenerative charging on the secondary battery during deceleration of the vehicle.
According to such a structure, it becomes possible to improve the charging efficiency at the time of regeneration.

Further, the present invention is characterized in that the control means performs control so as to fall below a predetermined charging rate smaller than the charging rate at the change point.
According to such a configuration, it is possible to prevent the charging rate from exceeding the changing point during regenerative charging.

Further, the present invention is characterized in that the detection of the change point is executed after starting the engine of the vehicle, and the control means performs charge control of the secondary battery based on the detected change point. To do.
According to such a configuration, since control can be performed based on the latest change point, control can be performed more accurately.

Further, the present invention provides a secondary battery charging control method for controlling charging of a secondary battery mounted on a vehicle by an alternator, a obtaining step for obtaining a charging rate of the secondary battery, and the alternator When charging the secondary battery, a detection step for detecting a change point from constant current charging that is charging with a constant current to constant voltage charging that is charging with a constant voltage, and the detection detected by the detection step And a control step of controlling charging of the secondary battery by the alternator so as to obtain a charging rate at a changing point from the obtaining step and to fall below the charging rate.
According to such a method, the charging efficiency of the secondary battery can be increased.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the secondary battery charge control apparatus and secondary battery state detection method which can improve the charging efficiency of a secondary battery.

It is a figure which shows the structural example of the secondary battery charge control apparatus which concerns on embodiment of this invention. It is a block diagram which shows the detailed structural example of the control part of FIG. It is a figure for demonstrating the outline | summary of operation | movement of this embodiment. It is a figure for demonstrating the operation principle of this embodiment. It is a figure for demonstrating the operation principle of this embodiment. It is a figure for demonstrating the operation principle of this embodiment. It is a figure for demonstrating the operation principle of this embodiment. It is a figure for demonstrating the operation principle of this embodiment. It is a flowchart for demonstrating an example of the process performed by embodiment of this invention. It is a flowchart for demonstrating an example of the process performed by embodiment of this invention. It is a flowchart for demonstrating an example of the process performed by embodiment of this invention.

  Next, an embodiment of the present invention will be described.

(A) Description of Configuration of Embodiment FIG. 1 is a diagram showing a power supply system of a vehicle having a secondary battery charge control device according to an embodiment of the present invention. In this figure, the secondary battery charge control device 1 includes a control unit 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, and a discharge circuit 15 as main components, and detects the state of the secondary battery 14. To do. Here, the control unit 10 refers to outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 to detect the state of the secondary battery 14. The voltage sensor 11 detects the terminal voltage of the secondary battery 14 and notifies the control unit 10 of it. The current sensor 12 detects the current flowing through the secondary battery 14 and notifies the control unit 10 of the current. The temperature sensor 13 detects the secondary battery 14 itself or the surrounding environmental temperature, and notifies the control unit 10 of it. The discharge circuit 15 is configured by, for example, a semiconductor switch and a resistance element connected in series, and the secondary battery 14 is intermittently discharged when the control unit 10 performs on / off control of the semiconductor switch.

  The secondary battery 14 is composed of, for example, a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, or a lithium ion battery, and is charged by the alternator 16 to drive the starter motor 18 to start the engine and load 19 To supply power. The alternator 16 is driven by the engine 17 to generate AC power, convert it into DC power by a rectifier circuit, and charge the secondary battery 14.

  The engine 17 is composed of, for example, a reciprocating engine such as a gasoline engine and a diesel engine, a rotary engine, or the like, and is started by a starter motor 18 to drive driving wheels through a transmission to provide propulsive force to the vehicle. Drive to generate power. The starter motor 18 is constituted by, for example, a DC motor, generates a rotational force by the electric power supplied from the secondary battery 14, and starts the engine 17. The load 19 is configured by, for example, an electric steering motor, a defogger, an ignition coil, a car audio, a car navigation, and the like, and operates with electric power from the secondary battery 14.

  FIG. 2 is a diagram illustrating a detailed configuration example of the control unit 10 illustrated in FIG. 1. As shown in this figure, the control unit 10 includes a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication unit 10d, and an I / F (Interface) 10e. ing. Here, the CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The ROM 10b is configured by a semiconductor memory or the like, and stores a program 10ba or the like. The RAM 10c is configured by a semiconductor memory or the like, and stores data generated when the program ba is executed, and a parameter 10ca such as a table or a mathematical expression described later. The communication unit 10d communicates with an ECU (Electronic Control Unit) that is a host device and notifies the host device of the detected information. The I / F 10e converts the signal supplied from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 into a digital signal and takes it in, and supplies a driving current to the discharge circuit 15 to control it.

(B) Description of Operation Principle of Embodiment Next, the operation principle of the embodiment will be described with reference to the drawings. FIG. 3 is a diagram showing the relationship between the SOC of the secondary battery 14 and the charge acceptance. As shown in FIG. 3, the range in which the SOC of the secondary battery 14 is 0 to A1% is an SOC range in which the charge acceptance is good but the engine 17 may not be restarted. Moreover, the range where the SOC is A1 to A2% is an SOC range where the charge acceptability is good and the engine 17 cannot be restarted. Furthermore, when the SOC is in the range of A2 to 100%, the charge acceptance is poor, but there is no possibility that the engine cannot be restarted. In this embodiment, it is possible to efficiently charge the secondary battery 14 with the electric power generated by the alternator 16 during regenerative power generation by controlling the SOC of FIG. 3 to be in the range of A1 to A2%. As a result, fuel efficiency can be improved.

  Next, the detailed operation principle of the present invention will be described with reference to FIG. FIG. 4 is a diagram showing the relationship between the SOC of the secondary battery 14 and the charging current of the secondary battery 14. In FIG. 4, broken lines with long intervals indicate the maximum current that can be charged by the secondary battery 14, and broken lines with short intervals indicate the maximum current that can be supplied to the secondary battery 14. More specifically, since the maximum current that can be supplied to the secondary battery 14 shown by the short dashed line is determined by the capacity of the alternator 16 and the load current, it is constant when the SOC of the secondary battery 14 is smaller than B3. Value (Ic in the example of FIG. 4). On the other hand, the maximum chargeable current of the secondary battery 14 indicated by the long dashed line decreases as the SOC increases. For this reason, the SOC is larger than B3, which is a point where the maximum current that can be supplied to the secondary battery 14 indicated by the short dashed line and the maximum current that can be charged by the secondary battery 14 indicated by the long dashed line intersect. In this case, as the SOC increases, the current supplied from the alternator 16 is not charged.

  Therefore, in the embodiment of the present invention, the short dashed line indicating the maximum current that can be supplied to the secondary battery 14 and the long dashed line indicating the maximum current that can be charged by the secondary battery 14 cross B3. B2 that is smaller than the margin is set as the upper limit value of SOC, SOC that is lower by a predetermined amount than B2 is defined as B1, and regenerative power generation is performed by controlling so that the SOC of the secondary battery 14 is in the range of B1 to B2. In this case, the acceptability of the secondary battery 14 can be improved, and fuel consumption can be improved. The SOC may be controlled so that the SOC of the secondary battery 14 is in the range of B1 to B2 with B1 being a predetermined amount higher than the SOC that can ensure the restart of the engine 17. Further, when B1 shown in FIG. 4 is lower than A1 shown in FIG. 3, the control of the SOC may be stopped and the replacement of the secondary battery 14 may be prompted.

  Incidentally, the point B3 shown in FIG. 4 differs depending on the state of the secondary battery 14, aging, ambient temperature, and the like. For this reason, in the embodiment of the present invention, for example, when the engine 17 is started, this point B3 is detected, and B2 is obtained from the detected B3. Then, charge control is performed based on the obtained B2. This will be described with reference to FIGS.

  FIG. 5 shows the relationship between the current and voltage during regenerative power generation when the SOC of the secondary battery 14 changes from a state slightly smaller than B3 shown in FIG. 4 to a state exceeding B3. As shown in the uppermost part of FIG. 5, in this example, the vehicle repeatedly executes traveling and regeneration. In the state before time t3, the SOC of the secondary battery 14 is smaller than B3, so that the secondary battery 14 is charged by a constant current by the alternator 16. That is, a constant current Ic flows from the alternator 16 to the secondary battery 14, and the voltage of the secondary battery 14 increases as the charging progresses. Then, after time t3, the current flowing from the alternator 16 to the secondary battery 14 becomes smaller than Ic, and the terminal voltage of the secondary battery 14 becomes constant, so that the operation shifts to constant voltage charging. To do.

  FIG. 6 shows temporal changes in voltage and current when changing from constant current charging to constant voltage charging. As shown in FIG. 6, in the constant current charging state, the current flowing from the alternator 16 to the secondary battery 14 is constant, so the time change ΔI≈0, and the voltage applied to the secondary battery 14 Temporal change ΔV> 0. Then, when changing from constant current charging to constant voltage charging, the voltage applied to the secondary battery 14 is constant, so the time change of voltage ΔV≈0, and the time of the current flowing from the alternator 16 to the secondary battery 14 Change ΔI <0.

  In the present embodiment, when the engine 17 is started, first, control is performed so that the SOC of the secondary battery 14 increases. As a result, when the SOC of the secondary battery 14 increases and exceeds B3 shown in FIG. 4, it changes from constant current charging to constant voltage charging, so this change point is detected and set to B3. Here, as a method of detecting the change point, for example, the voltage V and the current I are measured at a predetermined interval (for example, an interval of several milliseconds to several tens of milliseconds). Then, when the time series data of the measured voltage V and current I are V3, V2, V1, V0 and I3, I2, I1, I0 in order from the oldest, as shown in FIG. At the same time, the SOC at the timing when the current changes from constant to monotonously decreases is set to B3. After the change point is specified, a value obtained by subtracting several% (for example, 1%) from B3 is set as B2 and the upper limit of the SOC is set, and an SOC lower than B2 by a predetermined amount is set as B1. Charging control is performed so that the SOC of the secondary battery 14 is within the range of B1 to B2. As described above, the SOC may be controlled so that the SOC that is higher than the SOC that can ensure the restart of the engine 17 is B1, and the SOC of the secondary battery 14 is in the range of B1 to B2. .

  According to such control, since the secondary battery 14 is maintained in a state where the SOC is lower than B2 shown in FIG. 4, when regenerative power generation is performed, the current supplied from the alternator 16 is reduced. All are received and stored in the secondary battery 14. As a result, by increasing the charging efficiency during regenerative charging, the kinetic energy of the automobile can be converted into electric energy and efficiently stored. Moreover, by using B2 having a margin as an upper limit instead of B3 which is the SOC of the change point, for example, it is prevented that power is not wasted without being charged by exceeding B3 during regenerative charging. it can. As the margin value, the increase in SOC in one regenerative charge depends on the type of vehicle and the type of secondary battery 14, but is generally within 1%, so 1% is used as the margin value. be able to. Of course, it may be set to several percent for a margin.

  Next, the operation of the embodiment of the present invention will be described more specifically with reference to FIG. In FIG. 8, the solid line shows the temporal change of the vehicle speed. In the example of this figure, the vehicle starts to accelerate at time T1, shifts to constant speed travel at time T2, decelerates from time T3, and stops at time T4. On the other hand, a two-dot chain line indicates a charging current flowing through the secondary battery 14 according to the conventional technique, and a one-dot chain line indicates a charging current flowing through the secondary battery 14 according to the present embodiment. When comparing these, in the prior art, the SOC of the secondary battery 14 may be operated in a state exceeding B3 shown in FIG. 4, and in that case, it is not possible to accept all the current supplied from the alternator 16, As indicated by the two-dot chain line, the current decreases with time. On the other hand, in this embodiment, since the SOC of the secondary battery 14 is operated in a state that does not exceed B2 shown in FIG. 4, the maximum current is not clipped as shown by the alternate long and short dash line. It flows from the alternator 16 to the secondary battery 14. For this reason, the charge by regeneration can be performed efficiently. According to the present embodiment, by efficiently charging the secondary battery 14 during deceleration, the frequency of charging during idling, acceleration, constant speed traveling, etc. can be reduced, and fuel efficiency can be improved.

  Next, an example of processing executed in the present embodiment will be described with reference to FIGS. 9 and 10. First, FIG. 9 is a flowchart for explaining an example of processing executed from the start to the stop of the engine 17. When the processing of this flowchart is started, the following steps are executed.

  In step S10, the CPU 10a determines whether or not a predetermined time or more has elapsed since the last calculation of SOCmax. If it is determined that the predetermined time or more has elapsed (step S10: Yes), the process proceeds to step S13. In other cases (step S10: No), the process proceeds to step S11. For example, when one day or more has elapsed since the previous calculation, it is determined that a predetermined time or more has elapsed, and the process proceeds to step S13. In this process, when the predetermined time or more has not elapsed since the previous calculation, the state of the battery does not change significantly, so that the SOCmax measured last time can be reused.

  In step S11, the CPU 10a determines that the previously calculated SOCmax is used. As a result, the previous SOCmax is used by the processing of FIG. 10, and charging is controlled.

  In step S12, the CPU 10a obtains B2 by B2 = SOCmax−mrg1, and obtains B1 by B1 = B2−mrg2. This B2 corresponds to B2 shown in FIG. 4, and mrg1 is a value corresponding to the difference (= B3-B2) between B3 and B2 shown in FIG. For example, mrg1 can be about several percent (preferably 1%). Note that the reason for setting the margin in this way is to prevent the shift to constant voltage charging due to exceeding B3 during regenerative charging when no margin is provided. The specific value of mrg1 is generally set to 1% because the SOC that increases with one regenerative charge is within 1%. Of course, it may be set to several percent for a margin. Further, as B1, an SOC lower than B2 by a predetermined amount (= mrg2) is set to B1. As this mrg2, it can be about several percent, for example. Instead of obtaining B1 from B2, an SOC that is a predetermined amount higher than the SOC that can ensure restart of the engine 17 may be used as B1.

  In step S13, the CPU 10a moves the voltage values stored in the variables V0 to V3 one by one. That is, the voltage value measured in the previous process and stored in the variable V2 is moved to the variable V3, and the voltage value measured in the previous process and stored in the variable V1 is moved to the variable V2. Then, the voltage value measured in the previous process and stored in the variable V0 is moved to the variable V1.

  In step S14, the CPU 10a moves the current values stored in the variables I0 to I3 one by one. That is, the voltage value measured in the previous process and stored in the variable I2 is moved to the variable I3, and the current value measured in the previous process and stored in the variable I1 is moved to the variable I2. Then, the current value measured in the previous process and stored in the variable I0 is moved to the variable I1.

  In step S15, the CPU 10a moves the SOC values stored in the variables SOC0 to SOC3 one by one. That is, the SOC value calculated in the previous process and stored in the variable SOC2 is moved to the variable SOC3, and the SOC value calculated in the second process and stored in the SOC1 is stored in the variable SOC2. The SOC value calculated in the previous processing and stored in the variable SOC0 is moved to the variable SOC1.

  In step S16, the CPU 10a obtains the latest voltage value and current value by referring to the outputs of the voltage sensor 11 and the current sensor 12 and stores them in V0 and I0, respectively. The SOC value is stored in SOC0. As a method of calculating the SOC, for example, when the engine 17 is stopped and the state of the secondary battery 14 is stable, the secondary battery 14 is pulse-discharged using the discharge circuit 15, The SOC can be obtained using the internal resistance calculated from the voltage and current at that time. Alternatively, the SOC can be obtained from the voltage value (open circuit voltage) when it is determined that the voltage fluctuation of the secondary battery 14 is stable. Then, after starting the engine 17, the SOC at that time can be obtained by integrating the current flowing through the secondary battery 14 with respect to this SOC. Note that the SOC may be calculated by other methods.

  Through the processes in steps S13 to S16, the time series voltage values shown in FIG. 7 are stored in the variables V0 to V3, the time series current values shown in FIG. 7 are stored in the variables I0 to I3, and the variables SOC0 to SOC3. 7 stores time-series SOC values corresponding to the voltage and current shown in FIG.

  In step S17, the CPU 10a determines whether or not the latest voltage V0 is larger than Vchg. If the latest voltage V0 is larger (step S17: Yes), the process proceeds to step S18, and otherwise (step S17: No). finish. Here, Vchg is a threshold voltage for determining whether or not regenerative charging is being performed. When the detected voltage exceeds Vchg, it is determined that regenerative charging is being performed. As Vchg, for example, 14V can be used.

  In step S18, the CPU 10a determines whether or not | V0−V1 | <Vth1 and V2−V3> Vth2 is satisfied. If both of these conditions are satisfied (step S18: Yes), the process proceeds to step S19. In other cases (step S18: No), the process ends. Here, | V0−V1 | <Vth1 as the first condition indicates that V0≈V1 as shown in FIG. 7, and V2−V3> Vth2 as the second condition is shown in FIG. Thus, in order to show that V2> V3, both of these two conditions are satisfied at the timing of t3 shown in FIG. Regarding the threshold values Vth1 and Vth2, for example, 0.01V can be used as Vth1, and 0.05V can be used as Vth2. Since these threshold values Vth1 and Vth2 vary depending on the sampling period, it is desirable to use appropriate values according to the sampling period and the environment.

  In step S19, the CPU 10a determines whether or not I0-I1 <Ith1 and | I2-I3 | <Ith2, and if both of these conditions are satisfied (step S19: Yes), the process proceeds to step S20. Otherwise (step S19: No), the process ends. Here, the first condition I0-I1 <Ith1 indicates that I0 <I1 as shown in FIG. 7, and the second condition | I2-I3 | <Ith2 is shown in FIG. Thus, in order to show that I2≈I3, both of these two conditions are satisfied at the timing of t3 shown in FIG. Regarding the threshold values Ith1 and Ith2, for example, -0.05A can be used as Ith1, and 0.01A can be used as Ith2. Note that these threshold values Ith1 and Ith2 vary depending on the sampling period as described above, and therefore it is desirable to use appropriate values according to the sampling period and the environment.

  In step S20, the CPU 10a obtains SOCmax by SOCmax = (SOC1 + SOC2) / 2. Note that SOCmax is a value corresponding to B3 in FIG. Further, SOC1 is the SOC calculated at the timing when V1 and I1 shown in FIG. 7 are measured, and SOC2 is the SOC calculated at the timing when V2 and I2 shown in FIG. 7 are measured. Therefore, a value corresponding to the SOC at time t3 can be obtained by obtaining the average SOC of SOC1 and SOC2. Instead of obtaining the average value, SOCmax = SOC1 or SOCmax = SOC2 may be used. According to such a method, calculation can be simplified.

  In step S21, the CPU 10a obtains B2 by B2 = SOCmax-mrg1 and B1 by B1 = B2-mrg2 as in step S12. The method for obtaining the values of mrg1 and mrg2 is the same as in step S12 described above.

  With the above processing, after engine 17 is started, t3 which is a change point from constant current charging to constant voltage charging is detected, SOCmax is obtained from SOC2 and SOC1 before and after the detected t3, and B2 is based on this SOCmax. Can be calculated.

  Next, an example of processing executed while the vehicle is traveling will be described with reference to FIG. When the process shown in FIG. 10 is executed, the following steps are executed.

  In step S30, the CPU 10a calculates the SOC of the secondary battery 14 at that time. As a method for obtaining the SOC, the same method as that described in step S16 described above can be used.

  In step S31, the CPU 10a determines whether or not SOC> B1 calculated in step S30, and if this condition is satisfied (step S31: Yes), the process proceeds to step S32, and otherwise (step S31: In No), it progresses to step S33. Here, the value obtained in step S12 or step S21 in FIG. 9 can be used as B1.

  In step S32, the CPU 10a determines whether or not SOC <B2 calculated in step S30, and if this condition is satisfied (step S32: Yes), the process proceeds to step S33, and otherwise (step S32: In No), it progresses to step S34. Here, as B2, the value obtained in step S12 or step S21 in FIG. 9 can be used.

  In step S33, the CPU 10a controls the alternator 16 to start power generation, or continues power generation when power generation is in progress. Thereby, when the SOC of the secondary battery 14 is larger than B1 and smaller than B2 (when B1 <SOC <B2), or when the SOC is equal to or less than B1 (when B1 ≦ SOC), Charging of the next battery 14 is started or continued.

  In step S34, the CPU 10a controls the alternator 16 to stop power generation. Thereby, when the SOC of the secondary battery 14 is B2 or more (when B2 ≧ SOC), the charging of the secondary battery 14 is stopped.

  According to the above processing, charging by the alternator 16 is started or continued when the SOC is less than B2, and power generation of the alternator 16 is stopped when the SOC is B2 or more.

(D) Description of Modified Embodiment The above embodiment is an example, and it is needless to say that the present invention is not limited to the case described above. For example, in the above embodiment, as shown in FIG. 4, control is performed based on B2 obtained by subtracting a predetermined margin mrg1 from B3, which is the SOC at the transition point from constant current charging to constant voltage charging. However, of course, the case where mrg1 = 0 is also included in the present invention.

  In the above embodiment, the lower limit value B1 of the SOC is obtained by subtracting the margin mrg2 from B2, but B1 may be a fixed value (for example, 60%). Or you may make it change according to the temperature detected by the temperature sensor 13. FIG. For example, when the temperature at which the engine 17 is difficult to start is low, the value of B1 may be temporarily increased.

  Further, when the difference between B1 and B2 becomes small, it is determined that the deterioration of the secondary battery 14 has progressed, and in order to give priority to restart of the engine 17, the battery may be charged to B2 or more. .

  In the process shown in FIG. 9, the process proceeds to step S20 to obtain the SOCmax at the timing of time t3 shown in FIG. 7, but it may be assumed that the detection of time t3 is missed. In such a case, for example, the SOCmax can be obtained by the process shown in FIG. In FIG. 11, parts corresponding to those in FIG. In FIG. 11, compared with FIG. 7, the processes of step S50 and step S51 are added. Since other than this is the same as in FIG. 7, the following description will focus on steps S50 and S51. In step S18, the CPU 10a determines whether or not | V0−V1 | <Vth1 and V2−V3> Vth2 is satisfied. If both of these conditions are satisfied (step S18: Yes), the process proceeds to step S19. In other cases (step S18: No), the process proceeds to step S50. In step S50, the CPU 10a determines whether or not | V0−V1 | <Vth1 and | V2−V3 | <Vth1. If both of these conditions are satisfied (step S50: Yes), the process proceeds to step S51. In other cases (step S50: No), the process ends. For example, when the timing of time t3 is missed, V1 to V3 are arranged on a straight line with a slope of the CV charging period shown in FIG. 7 being almost zero, in which case | V0−V1 | <Vth1 and | V2 Since −V3 | <Vth1 is satisfied, the process proceeds to step S51. In step S51, the CPU 10a determines whether or not I0-I1 <Ith1 and I2-I3 <Ith1. If both of these conditions are satisfied (step S51: Yes), the process proceeds to step S20 and SOCmax is calculated. In other cases (step S51: No), the process ends. For example, when the timing of time t3 is missed, I1 to I3 are arranged on a straight line with a negative slope of the CV charging period shown in FIG. 7, and in this case, I0-I1 <Ith1 and I2-I3 <Ith1 Since the above is established, the routine proceeds to step S20, where SOCmax is calculated. As described above, according to the flowchart shown in FIG. 11, even when the detection of the timing at time t3 is missed, SOCmax can be calculated appropriately.

DESCRIPTION OF SYMBOLS 1 Secondary battery charge control apparatus 10 Control part (sending means, control means)
10a CPU
10b ROM
10c RAM
10d Communication unit 10e I / F
11 Voltage sensor (detection means)
12 Current sensor (detection means)
13 Temperature Sensor 14 Secondary Battery 15 Discharge Circuit 16 Alternator 17 Engine 18 Starter Motor 19 Load

Claims (5)

In a secondary battery charging control device that controls charging of a secondary battery mounted on a vehicle,
An alternator for charging the secondary battery;
Obtaining means for obtaining a charging rate of the secondary battery;
When charging the secondary battery by the alternator, detecting means for detecting a change point changing from constant current charging to constant voltage charging;
Control means for controlling charging of the secondary battery by the alternator so as to obtain a charging rate at the change point detected by the detecting means from the finding means and to be lower than the charging rate;
A secondary battery charge control device comprising:   The secondary battery charge control device according to claim 1, wherein the alternator performs regenerative charging on the secondary battery when the vehicle is decelerated.   The secondary battery charging control device according to claim 1, wherein the control unit performs control so as to be lower than a predetermined charging rate smaller than a charging rate at the change point. The change point is detected after the vehicle engine is started,
4. The secondary battery charge control device according to claim 1, wherein the control unit performs charge control of the secondary battery based on the detected change point. 5. In a secondary battery charging control method for controlling charging by an alternator of a secondary battery mounted on a vehicle,
A requesting step for determining a charging rate of the secondary battery;
When charging the secondary battery by the alternator, a detection step of detecting a change point that changes from constant current charging that is charging by a constant current to constant voltage charging that is charging by a constant voltage;
A control step of acquiring the charging rate at the change point detected by the detecting step from the obtaining step and controlling charging of the secondary battery by the alternator so as to be lower than the charging rate;
A secondary battery charge control method comprising:

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