JPH09182311A - Battery charging controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To charge a battery mounted on an electric vehicle with a device of simple structure. SOLUTION: After detecting full charging (provisional full charging) at the time t4 (the time t4l, t4m and t4h respectively) when the differential value ΔVB/Δt of a battery voltage VB (symbol VB1 denotes a battery voltage when the battery temperature is low, VBm denotes a battery voltage when it is cold and VBh denotes a battery voltage when it is high)becomes a given value, charging continues for a predetermined time Lt (symbols Ltl, Ltm and Lth respectively) in accordance with the battery temperature. This makes it possible to always charge a battery up to the true full-charging irrespective of the battery temperature. Because no data in discharging is required at all in charging, it is possible to simplify the structure of a charging controlling device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charge control apparatus suitable for application to, for example, an electric propulsion vehicle such as an electric vehicle which uses a vehicle-mounted battery as a power source.

[0002]

2. Description of the Related Art A so-called two-stage charging control method is adopted when charging a lead storage battery which is a battery mounted on an electric propulsion vehicle such as an electric vehicle.

FIG. 8 is a change characteristic diagram of the battery voltage VB used for the explanation of the two-stage charging control method. The horizontal axis represents the charging time t and the vertical axis represents the battery voltage VB.

This two-stage charging control method charges at a first stage charging current value, which is a relatively large current value (or power value), until time t1 when the battery capacity reaches about 80%,
After the time point t1, it is a method of performing charging until the full charge time point t4 with the second-stage charging current value which is a relatively small current value. The reason for adopting the two-stage charge control method in this way is that if the battery is fully charged by the first-stage charge current value, the heat generation of the battery becomes excessive, which may deteriorate the battery. This is to prevent it.

In this case, the end time t1 of the first-stage charging is
The battery voltage (battery terminal voltage) VB is a predetermined voltage V1
Is determined at the time when the second stage charging is completed, in other words, the time when the second charge is completed, that is, the time when the battery is fully charged is determined at the time when the amount of change in the battery voltage VB, that is, the differential value ΔVB / Δt becomes equal to or less than the predetermined value K. doing.

The contents of reference numerals t2, t3, VF, VS and the like in FIG. 8 will be described in the embodiment of the present invention.

[0007]

The internal resistance value of the battery changes depending on the ambient temperature of the battery (hereinafter referred to as the battery temperature).

Since the internal resistance value increases at a relatively low temperature, the battery voltage VB reaches the predetermined voltage V1 earlier, and as a result, in the case where the above-mentioned full charge determination is erroneously determined to be full charge, However, there was a problem that charging was terminated even though it was not fully charged.

In order to solve this problem, it is necessary to constantly monitor the capacity of the battery, that is, ampere hour [Ah], and it is necessary to measure and store the discharge current amount, the charge current amount and the time. there were. Therefore, there is a problem that the configuration of the battery charge control device becomes complicated.

It is an object of the present invention to provide a battery charge control device capable of charging a battery to a true full charge with a relatively simple structure.

[0011]

SUMMARY OF THE INVENTION According to the present invention, in a battery charge control device for detecting battery voltage and controlling battery charge, the amount of change in battery voltage is detected during charging of the battery by a charger. Change amount detecting means, charge stopping means for stopping charging by the charger based on the output of the change amount detecting means, battery temperature detecting means for detecting battery temperature, and voltage detected by the change amount detecting means When it is detected that the change amount of is smaller than a predetermined value, an overcharge control unit that stops the charging by the charging stop unit after a time corresponding to the battery temperature is provided.

Further, the present invention is characterized in that the amount of change in the voltage detected by the change amount detecting means is the amount of change in the battery voltage in the second stage of the two-stage charge control.

Further, the present invention is characterized in that trickle charging is performed after the charging by the charging stopping means is stopped after a time corresponding to the battery temperature.

Furthermore, the present invention is characterized in that the battery is a battery mounted on an electric propulsion vehicle.

According to the present invention, full charge (temporary full charge)
After detection, charging is continued (overcharged) only for the time corresponding to the battery temperature, so even if the battery temperature at the time of charging is different, it is possible to always charge up to the true full charge. .

When applied to the two-stage charge control, the charging time until the true full charge can be shortened, and the trickle charge is performed after the true full charge, so that the self-discharge after the true full charge is performed. The decrease in battery capacity can be eliminated.
Further, the configuration relating to the charging control of the electric propulsion vehicle can be simplified.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings referred to below, the same components as those shown in FIG. 8 are designated by the same reference numerals and detailed description thereof will be omitted. Note that description will be made with reference to FIG. 8 as well.

FIG. 1 shows the configuration of an embodiment in which the present invention is applied to an electric vehicle 11 as an electric propulsion vehicle.

In FIG. 1, an electric vehicle 11 includes a battery 12 such as a high voltage lead battery having a nominal voltage value of + 360V.
Is installed. The battery 12 has, for example, a configuration in which 24 single batteries having a nominal voltage value of +15 V are connected in series.

To the battery 12, a voltage sensor 13 for measuring and detecting a terminal voltage (referred to as battery voltage) VB of the battery 12 and an ambient temperature (battery temperature) TB of the battery 12 for measuring and outputting are output. Temperature sensor 1
4 is attached. As described above, the battery 12
Has a configuration in which single batteries are connected in series. Therefore, when measuring the battery temperature TB, the temperature sensor 14
Is, for example, sandwiched between single batteries.

An external charger 17 is provided on the power input side of the battery 12 through a contactor 16 which is an open / close switch.
Is connected. The charger is an external charger 17
However, it may be mounted on the electric vehicle 11.

A three-phase AC power source (not shown) is supplied to the input side of the charger 17 through a plug 18.

The output voltage of the battery 12 is the inverter 2
It is converted into a drive signal of the motor 21 through 0. The PWM (pulse width modulation) control of the inverter 20 is performed by an ECU (electronic controller unit) 23, which is a control unit, and the rotation speed of the motor 21 is controlled by this.
In this case, the ECU 23 is supplied with an electric signal (command signal) according to the depression force of an accelerator pedal as an input means (not shown).

The ECU 23 comprises a microcomputer as a main body, a CPU 24 as a central processing unit,
System program, charge control routine to be described later,
A ROM 25 in which a lead time table and the like are stored, a RAM 26 for work and the like, a timer 27 for timing, and other interfaces are included.

The ECU 23 supplies a battery voltage (also referred to as a voltage value) VB supplied from the voltage sensor 13, a battery temperature (hereinafter referred to as a temperature value) TB supplied from the temperature sensor 14, and a charge supplied from the charger 17. The charging of the battery 12 is controlled based on a current (also referred to as a current value) IB or the like. Although the configuration of the electric vehicle 11 itself becomes a little complicated, the charging current IB may be detected by attaching a current sensor to the power input side of the battery 12 instead of being received from the external charger 17. Needless to say. The low-voltage power supply for the ECU 23 and the like lowers the voltage of the battery 12 through a DC-DC converter and supplies the reduced voltage.

Next, the operation of the above-described embodiment will be described in detail with reference to the flowchart showing the charge control routine of FIG. The control subject is the ECU 23.
Further, this charge control routine is configured to be executed a plurality of times per minute, for example.

Therefore, first, when it is detected that the charger 17 is turned on, the ECU 23 starts a charge control routine and closes the contactor 16. Then, a charging stage display flag (also called a charge control flag) FS, a power reception completion display flag FE, and a differential value flag (also called a full charge flag) FD are FS = 0, FE = 0, respectively.
It is reset to FD = 0 (step S1).

When the charging stage display flag FS is reset, it is in the first-stage charging period TC1 up to the time point t1 (see FIG. 8) described above, and when it is set, that is, when FS = 1. , In the second-stage charging period TC2 between time points t1 and t4. If the power reception completion display flag FE is set (FE = 1), step S8 is performed.
Is satisfied, the charging operation, that is, the charging control routine of the example of FIG. 2 ends. Therefore, when the power reception completion display flag FE is in the reset (FE = 0) state,
Indicates that the charge control routine is being performed. Further, the differential value flag FD is reset (FD = 0) when the time change amount (also referred to as differential value) ΔVB / Δt of the battery voltage VB is larger than a predetermined value K, and is set (FD =) when it is smaller. 1) is done. The differential value flag FD is a flag related to the detection at the time t4 of full charge (see FIG. 8).
Also called a full charge flag.

Next, the charge control flag FS is set (FS
= 1) is determined (step S)
2). In the first determination, this determination does not hold because the reset ((FS = 0) is made in step S1.

Then, it is then determined whether or not the battery voltage VB is higher than a predetermined voltage V1 for determining the end of the first charging (VB> V1) (step S3).

If the voltage is not higher than the predetermined voltage V1, the first-stage charging control is started (first execution processing of the charging control routine) or the first-stage charging control is continued (charging). Execution processing of the control routine after the second time)
The first-stage charging control process is performed (step S4). In addition,
The contents of the first-stage charging control process are omitted since they are not directly related to the present invention, but for example, constant current control with a charging current of 20 [A] is performed.

When the first-stage charge control process of step S4 is completed, that is, when the determination of step S3 is established, the charge control flag FS is set to FS = 1 (step S5).

In order to start the second stage charging, the charging current IB is smaller than the first stage charging current value,
For example, it is set to 8 [A] and the second stage charging control start process is performed (step S6).

After step S6, it is confirmed in step S2 that the charging control flag FS has become FS = 1, and the main flow routine for the second stage charging is started (step S7).

FIG. 3 shows a flow chart of the main flow routine of the second charging in step S7.

In this main flow routine, first, the average current value IB, average voltage value VB, and average temperature value TB for the current one minute are calculated (step S11). The reason for averaging is to eliminate measurement error due to external noise or the like.

Next, the differential value flag FD is set (FD =
1) It is determined whether or not (step S1)
2). In the first processing of the main flow routine, since the differential value flag FD is reset (FD = 0) in step S1 (see FIG. 2), this determination does not hold.

Then, a full charge determination routine (step S
Proceed to 13). FIG. 4 shows a flowchart of the full charge determination routine of step S13.

This full charge determination routine (step S1
In 3), first, it is determined whether or not the current charging current value IB obtained in step S11 exceeds 10 [A] (step S21). In this judgment, the charge control state is 2
This is a process for confirming that it is the second-stage charging period TC2, and when IB> 10 [A], it is the first-stage charging period TC1 and not the second-stage charging period TC2.
There is no possibility that the battery is fully charged, and the fully charged flag FD is reset (FD = 0) (step S22). in this case,
After the processing of step S22, step S8 (see FIG. 2)
Determination, that is, the power reception completion display flag FE is set (F
It is determined whether E = 1). At this time, charging has not been completed yet, and the power reception completion display flag FE described later is in a reset state. Therefore, the determination in step S8 is not established, and then the determination in step S21 is performed again in the order of step S2 → step S7 → step S11 (see FIG. 3) → step S12 → step S13.

Since the process of step S6 is actually completed now, it is the second-stage charging period TC2 and IB =
Since it is 8 [A], the determination in step S21 is not established.

Next, the charging current value IB measured 30 minutes ago
= IBo and the current charging current value IB = IBn (| I
Bo-IBn |) is calculated, and it is determined whether this difference is a value exceeding 1 [A] (step 23). This determination is to make sure that 30 minutes have elapsed since the second-stage charging period TC2 was entered.
That is, when 30 minutes have not elapsed, the difference between the charging current values IB is 12 [A] = (20-8) [A]> 1.
If [A] or more and 30 minutes have passed, 0
[0] = (8-8) [A] <1 [A].

Actually, the start time t1 of the second stage charging (see FIG. 8)
The time from when the battery voltage VB starts to rise rapidly again (refer to FIG. 3) is secured for at least 30 minutes.
Explaining in detail, for example, the depth of discharge DOD (depth)
h of discharge) is 80%, the charging process is started, and the charging current IB of the first-stage charging is, for example, 0.
When the current value corresponds to 2C, the first-stage charging period TC1 until the first-stage charging end time t1 is about 3 hours when the battery capacity up to 80% is charged. In other words, 0.2C is equivalent to the battery 12 at the start of charging.
, The battery capacity becomes 0.8C (0.2C + 0.2C × 3) by the time of charging for about 3 hours.

The time from the end time t1 of the first charging time to the end time t4 of the second charging period TC2 is about 2.5 hours {= 0.2C / 0.08C (0.2C
X8 [A] / 20 [A])}, and the time t2 at which the internal resistance of the battery 12 starts to rise sharply when approaching full charge.
It is known that the time from the end time t4 of the full charge to the end time t4 is within 30 minutes. After all, the time from the end time t1 of the first stage to the start time t2 of the sudden rise of the internal resistance under such a typical condition. The calculated time is about 2 hours, and in the normal case, it can be said that the time of 30 minutes or more is sufficiently secured.

Next, the difference (| VBo-VBn) between the voltage value VBo 30 minutes before (this voltage value was calculated and stored in step S11) and the current voltage value VBn (similar).
|), And it is determined whether or not this difference exceeds a predetermined voltage VS (see FIG. 8) (step S24).
Here, the voltage VS is set in advance to, for example, a half value of the difference between the voltage V2 at the time t2 when the internal resistance suddenly increases and the voltage VF at the time of full charge.

By setting in this way, the time when the determination of step S24 is established is the time after the steep slope time t3 of the battery voltage VB after time t2 in FIG.

Next, after the determination in step S24 is established, that is, after the time t3, the amount of change in the battery voltage VB per minute, that is, the differential value ΔVB / Δt becomes a value equal to or less than the predetermined value K. It is determined whether or not it has become (step S25). The determination in step S25 is for detecting the full charge time t4 shown in FIG.

When the determination in step S25 is established, that is, when (ΔVB / Δt) ≦ K is established, it is determined that the battery is fully charged, and the full charge flag (differential value flag) FD is set to FD = 1 ( Step S26).

When FD = 1, step S1
Since the determination of 2 (see FIG. 3) is established, step S14
Go to the lead time routine. In the present invention, as described below, charging is continued by the next lead time routine (step S14) except when the battery temperature is lower than the specified upper limit value.

FIG. 5 shows a detailed flowchart of the lead time routine (step S14).

Here, first, the temperature value TB calculated in step S11 is read to recognize the current temperature value TB (step S31).

Then, with reference to the necessary overcharge time table (lead time table) LTT (see FIG. 6) stored in the ROM 25, the lead time (overcharge time) Lt is set in accordance with the battery temperature TB ( Step S3
2).

The lead time Lt is set in accordance with the battery temperature TB because the internal resistance value of the battery 12 becomes large when the battery temperature TB is low and becomes small when the battery temperature TB is high. This is because the first-stage charging period TC1 expands and contracts.
That is, as shown in FIG. 7, the battery voltage VBl at a relatively low temperature with a high internal resistance value reaches the predetermined voltage V1 earlier than the battery voltage VBl, and at the time t4l, a required ampere hour, in the above example, , Ampere hour for 0.8C cannot be secured, and at the end t4l
This is because the full charge will not be achieved even if the second-stage charging is performed up to.

Therefore, the lead time Lt until the battery is fully charged is obtained in advance by, for example, an experiment and is stored in the ROM as the lead time table LTT shown in FIG.
It is stored in 25 in advance.

The lead time Lt is set at a relatively low temperature, for example, for a battery 12 having a battery voltage VBl in which the battery temperature TB is about TB = 10 ° C., as shown in FIG. Time Lt is Lt =
It is set to 70 minutes (= Ltl). Further, at room temperature, for example, for the battery 12 having the battery voltage VBm of which the battery temperature TB is about TB = 25 ° C., the lead time Lt is set to Lt = 50 minutes (= Ltm). Further, when the temperature is relatively high, for example, the battery temperature T
For the battery 12 having a battery voltage VBh of B = TB = 50 ° C., the lead time Lt is Lt = 20 minutes (=
Let it be Lth. ) Is set.

After setting the lead time Lt in this way, as shown in FIG. 7, the lead time Lt set from the full charge time t4l related to the battery voltage VB1 at low temperature.
The charging by the second stage charging current corresponding to the time of 1 is started, or the second stage charging current corresponding to the time of the lead time Ltm set from the full charge time t4m related to the battery voltage VBm at room temperature Charging with the battery voltage VBh at high temperature is started or the full charge time t4
The charging by the second-stage charging current corresponding to the lead time Lth set from h is started, and the charging is actually continued.

If the battery temperature TB becomes considerably high during continuous charging, for example, if it exceeds 70 ° C., the charging is temporarily stopped at that time and whether or not it is temporarily stopped. A judgment is made (step S33).

If it is temporarily stopped (step S3)
3: YES), lead time routine (step S1)
4) exits, the second-stage charging main flow routine (step S7) exits, the power reception completion display flag confirmation (step S8) exits (step S8 determines “NO”), step S2 → step S7 → step S11. → Step S
12 → step S14 → step S31 → step S3
The process returns to step S33 again in the order of 2 → step S33.

When the battery temperature TB is within the normal range in the determination in step S33, the cumulative time of overcharge relating to the lead time Lt up to the present time by the timer 27 becomes the set lead time Lt described above. It is determined whether it has reached (step S34).

It should be noted that the timer 27 sets the full charge time t4, in other words, the start time t4l, t4m, t4 of the continuous charging.
Timing of the set lead time Lt is started from h (step S35).

When the timer 27 has finished measuring the set lead time Lt (step S34: "YE").
S ”), it is determined that the battery has reached the true full charge, the charging by the charger 17 is stopped, the contactor 16 is opened, and the power reception completion display flag FE is set to FE = 1.

As a result, the determination at step S8 (see FIG. 2) is established and the charging control routine is ended (step S9).

As described above, according to the above-described embodiment, the battery temperature TB is detected after the full charge (temporary full charge) is detected at the time t4 when the differential value ΔVB / Δt of the battery voltage VB reaches the predetermined value. A corresponding lead time Lt is set to overcharge. Therefore, the battery temperature TB
Regardless of, the effect of always being able to charge to a true full charge is achieved.

In this charge control routine,
Since the data at the time of discharging, for example, the data such as the discharging current amount is not required at all and the charging can be controlled by the so-called charging system alone, there is an advantage that the configuration of the charging control device can be simplified. Since the configuration can be simplified, the probability of failure of the charging system is reduced, and the derivative effect of being able to construct a highly reliable system can be obtained. Note that, when the overcharge time Lt elapses, the charger 17 It is also possible to automatically switch to so-called trickle charge control using a current value that is small enough to compensate for self-discharge, without stopping the charging by. In this case, since it is considered that the battery 12 of the electric vehicle 11 is often charged by using the midnight power, for example, when the electric vehicle 11 is reused in the next morning, the true full charge state is always maintained. The advantage of being retained is obtained. In addition, by automatically switching to trickle charging, if the electric vehicle 11 is not used during so-called consecutive holidays, even when the electric vehicle 11 is used after the consecutive holidays, the electric vehicle 11 is always fully charged in a fully charged state. The advantage is that the vehicle 11 can be used.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0065]

As described above, according to the present invention, after detecting the full charge (temporary full charge), the charging is further continued for the time corresponding to the battery temperature to perform the overcharge. . Therefore, even when the battery temperature at the time of charging is different, the effect of always being able to charge up to the true full charge is achieved.

In this case, since it is not necessary to constantly monitor the capacity of the battery at the time of discharging and charging, that is, the ampere hour, the effect of relatively simplifying the configuration of the battery charge control device is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electric vehicle to which an embodiment of the present invention is applied.

FIG. 2 is a flowchart of a charge control routine used to explain the operation of FIG.

FIG. 3 is a flowchart of a second-stage charging main flow routine in the charging control routine.

FIG. 4 is a flowchart of a full charge determination routine in a second stage charging main flow routine.

FIG. 5 is a flowchart of a lead time routine in a second stage charging main flow routine.

FIG. 6 is a diagram showing the contents of a lead time table.

FIG. 7 is a diagram for explaining a lead time setting.

FIG. 8 is a diagram provided for explaining two-step charging control.

[Explanation of symbols]

11 ... Electric vehicle 12 ... Battery 13 ... Voltage sensor 14 ... Temperature sensor 17 ... Charger 23 ... ECU IB ... Charging current TB ... Battery temperature VB ... Battery voltage Lt ... Overcharge time (lead time) ΔVB / Δt ... Differential value

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H02J 7/04 H02J 7/04 C

Claims (4)

[Claims] 1. A battery charge control device for detecting a battery voltage to control charging of a battery, comprising: a change amount detecting means for detecting a change amount of a battery voltage during charging of a battery by a charger; A charge stopping unit that stops charging by the charger based on the output of the amount detecting unit, a battery temperature detecting unit that detects a battery temperature, and a change amount of the voltage detected by the change amount detecting unit is smaller than a predetermined value. A charge control device for a battery, comprising: an overcharge time control means for stopping the charge by the charge stop means after a time corresponding to the battery temperature is detected when the value is detected. 2. The battery charge control according to claim 1, wherein the change amount of the voltage detected by the change amount detecting means is a change amount of the battery voltage in the second stage of the two-stage charge control. apparatus. 3. The battery charge control device according to claim 1, wherein trickle charging is performed after the charging by the charging stopping means is stopped after a time corresponding to the battery temperature. 4. The battery charge control device according to claim 1, wherein the battery is a battery mounted on an electric propulsion vehicle.