JP2002125327A - Battery charge controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effective prevent misdetection full charge due to memory effect. SOLUTION: In a step S3, full charging is determined, based on the charging voltage. In the full-charge determination, a full-charge determining threshold V' is set using a battery temperature T detected with a temperature sensor and the number of times of intermediate suspension N stored in a memory and this full-charge determining threshold V' is compared with an actual charge voltage V, which is actually detected using a voltage sensor. The full-charge determining threshold V' is defined as V'=V0+αT+Nβ. In the formula, V0 is reference voltage [V], α is temperature compensation coefficient [V/ deg.C], T is battery temperature [ deg.C], N is the number of times of intermediate suspensions [number of times], β is a voltage compensating coefficient [V/ number of times]. When N<20, β=0.04, and when 20<=N<=200, β=0.01.

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 device for detecting full charge from a detection voltage at the time of charging, and more particularly to a technique effective for preventing erroneous full charge detection due to a memory effect.

[0002]

2. Description of the Related Art As is well known, when charging is incompletely stopped halfway through to full charge, a so-called memory effect occurs in the battery, which causes an increase in charging voltage.
If the charging control is performed on the battery in which the memory effect has occurred while monitoring the charging voltage, the charging voltage reaches the full-charge determination threshold value early and becomes insufficiently charged, resulting in a decrease in the dischargeable capacity.

[0003]

Conventionally, in order to eliminate the memory effect and recover the dischargeable capacity, refresh by full charge is performed. However, since refresh by full charge requires a long time, This has reduced convenience. In particular, with regard to the battery for an electric vehicle, full-charging is erroneously detected because the memory effect is likely to occur due to frequent stoppages during charging, such as sudden use during charging or charging just to extend the mileage. If the dischargeable capacity is reduced, the commercial value is impaired.

The present invention has been made in view of the above circumstances, and has as its object to effectively prevent erroneous detection of full charge due to a memory effect.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention employs the following means. According to the invention described in claim 1, the charging voltage (for example, the actual charging voltage V in the embodiment) is equal to or higher than the full-charge determination threshold (for example, the full-charge determination threshold V ′ (= V0 + αT + Nβ) in the embodiment). In a battery charge control device that sometimes detects full charge, the number of halfway stoppages that calculates the number of halfway charge stoppages (for example, the number of halfway stoppages N in the embodiment) in which the battery is not fully charged and stopped halfway is not fully charged. A calculation unit (for example, the control unit 2 in the embodiment) and a full-charge determination threshold setting unit (for example, the control unit 2 in the embodiment) that sets the full-charge determination threshold value according to the number of halfway charging suspensions. It is characterized by having.

According to such a configuration, even if the charging voltage rises due to the memory effect caused by the repetition of the charging halfway stop, the full charge determination threshold value for detecting the full charge according to the number of halfway charging stops. Can be set to be higher than the determination threshold in the battery initial state, so that it is possible to prevent the charging voltage from reaching the full-charge determination threshold in a state of insufficient charging.

According to a second aspect of the present invention, in the battery charge control device according to the first aspect, the full charge determination threshold value setting means increases the full charge determination threshold value in accordance with an increase in the number of halfway charge stoppages. (For example, step S11 in the embodiment), and when a full charge is detected, the full charge determination threshold is lowered (for example, step S7 in the embodiment).

When the battery is fully charged, all or a part of the memory effect is eliminated. For a fully charged battery, if a full charge determination threshold set larger than the initial value is directly used for full charge detection, Although the state of charge may not be detected as being fully charged, according to the above configuration, the full charge determination threshold is lowered after full charge, so the previous full charge determination threshold is used as it is even after the memory effect is eliminated. This can prevent the detection accuracy of the full charge from being lowered.

According to a third aspect of the present invention, in the battery charge control device according to the first or second aspect, the full charge determination threshold value setting means is configured to determine the full charge determination threshold value in accordance with the number of halfway charge stoppages. (For example, the increase amount Nβ in the embodiment).

With this configuration, the full charge determination threshold can be set in accordance with the characteristics of the full charge determination voltage, that is, in accordance with the change in the full charge determination voltage with respect to the number of halfway charge stops. Therefore, the full charge determination becomes more accurate.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of a battery charge control device according to the present invention will be described. This charge control device is used for charging a battery 1 that supplies power to a load such as a motor mounted on an electric vehicle or a hybrid vehicle, for example.
As shown in FIG. 1, a control unit 2, a charger 3, a current sensor 4, a voltage sensor 5, and a temperature sensor 6 are provided.

The control unit 2 includes a current sensor 4 for detecting a discharge current supplied from the battery 1 to a load such as a motor or a generator, and a charging current supplied from the load to the battery 1.
, A signal of a voltage V output from a voltage sensor 5 for detecting a terminal voltage of the battery 1, and a signal of a battery temperature T output from a temperature sensor 6 for detecting the temperature of the battery 1. Is input.

The control section 2 determines whether or not the battery 1 has been charged until it is fully charged and stopped halfway, and every time the charging is stopped halfway, the number of halfway stops (number of halfway charging stops) N , A process of reducing the number of halfway stops N when full charge is detected, and
Battery temperature T, reference voltage V0 and number of stops N on the way
A full charge determination threshold value V ′ is set based on the above, a process of comparing the full charge determination threshold value V ′ with the voltage V input from the voltage sensor 5 to perform a full charge determination, and a temperature rise dT of the battery temperature T. / Dt and a predetermined temperature control threshold value to perform a charging stop determination process. In addition, the number of stops N
Is stored (stored) in a memory in the control unit 2, and is read from the memory as needed.

Next, a charging control flow of the battery 1 executed by the control unit 2 will be described with reference to a flowchart of FIG. First, in step S1 of FIG.
Rapid charging is started with a charging current of 5 [C].

This rapid charging is usually performed when there is a request from the user to use the battery 1 or the electric vehicle equipped with the battery 1 quickly. For this reason, the user considers that it is sufficient that the battery is charged to the extent that it can be used for the time being, and sometimes stops charging halfway without charging until the battery is fully charged. Therefore, in step S2, it is determined whether or not the charging is stopped halfway.

If the result of the determination in step S2 is "YES", that is, if the charging is not performed until full charge and stopped halfway due to the user's intention, the process proceeds to step S11, and if "NO", that is, the charging is not performed. If it is continuing, the process proceeds to step S3. In step S11, the number N of halfway stops is incremented by "1", and the result is stored in the memory.

On the other hand, in step S3, a full charge determination is made based on the charging voltage. Specifically, the temperature sensor 6
A full charge determination threshold value V 'is set using the battery temperature T detected in step (1) and the number of halfway stops N stored in the memory, and the full charge determination threshold value V' and the actual charge actually detected by the voltage sensor 5 are set. Compare with the voltage V. The full charge determination threshold V ′ is
V '= V0 + αT + Nβ.

In this equation, V0 is a reference voltage [V], α is a temperature correction coefficient [V / ° C.], T is a battery temperature [° C.], N is the number of stoppages [times], and β is a voltage correction coefficient [V / Times], and the voltage correction coefficient β is switched, for example, as follows according to the number of halfway stops N. N <20; β = 0.04 20 ≦ N ≦ 200; β = 0.01

Here, the reason why the voltage correction coefficient β is set as described above will be described with reference to FIG. 2 showing the characteristics of the full charge determination voltage (change with respect to the number of halfway stops N). FIG.
As shown by the solid line, the measured voltage at the time of full charge tends to increase with an increase in the number of halfway stops N, and further, in a section where the number of halfway stops N is small (N <20 section), the voltage rising gradient Is steep, while the other sections (20 ≦
(N section), the rising gradient of the voltage is gentle.

In the present embodiment, the measured voltage shown by the solid line in FIG. 2 is approximated by two straight lines having different slopes, and the full charge determination threshold V 'is defined by these two straight lines. That is, in the section of “the number of halfway stops N <20”, the measured voltage is linearly approximated by a broken line A, and in the section of “20 ≦ the number of halfway stops N ≦ 200”, the measured voltage is linearly approximated by a broken line B, These broken lines A and B are used as the full charge determination threshold value V '.

It should be noted that a fixed limit value is set for the increase amount Nβ of the full charge determination threshold value V ′. For example, as shown in FIG. 4, in a section in which the number of halfway stops N is 200 or more, the increase amount Nβ is held at a predetermined limit value.

In step S3, "V <V0 + αT
+ Nβ ”, that is, when the actual charge voltage V is less than the full charge determination threshold V ′, steps S2 and S3
The rapid charging is continued while repeating the processing of “V ≧ V0
+ ΑT + Nβ ”, that is, when the actual charge voltage V is equal to or higher than the full charge determination threshold V ′ and full charge is detected,
Proceed to step S4.

In the full charge determination in step S3, as shown in FIG. 4, the full charge determination threshold V 'gradually increases as the number of stoppages N in the middle increases, and the full charge determination threshold V' changes to the initial battery state. Determination threshold (= V0 + αT)
Since the charging voltage is set higher than the above, even if the charging voltage is increased due to the effect of the memory effect, it is not determined that the battery is fully charged in a state of insufficient charging, and a decrease in the dischargeable capacity is effectively avoided.

In step S3, in the section where the number of stoppages N is small (N <20), the voltage rise d
The voltage correction coefficient β is set to be large in accordance with the large V / dt, and the number N of intermediate stops is large (20 ≦ N ≦ 20).
0), the voltage correction coefficient β is set small in accordance with the small voltage rise dV / dt, so that the degree of coincidence between the full charge determination threshold V ′ and the characteristic of the full charge determination voltage (FIG. 2) is high. , And an accurate full charge determination can be made.

In step S4, normal charging is started with a charging current of, for example, 0.2 [C]. Even during the normal charging, the charging may be stopped halfway due to the user's intention or the like. Therefore, in the subsequent step S5, it is determined whether or not the charging is stopped halfway. If the determination result of step S5 is "YES",
That is, when charging is stopped halfway, step S11
If “NO”, that is, if charging is continuing, the process proceeds to step S6.

In step S6, a charge stop determination is made using the battery temperature T. Specifically, the temperature rise dT / dt of the battery temperature T detected by the temperature sensor 6 is compared with a predetermined temperature control threshold (for example, 1.5 [° C.] / 7 [min]). If the result of the comparison is “temperature rise dT / dt <predetermined temperature control threshold”, steps S5 and S5
The normal charging is continued while repeating the determination of 6.

On the other hand, the comparison result is “temperature rise dT
If / dt ≧ predetermined temperature control threshold ”, that is, if the charging stop condition is satisfied, the process proceeds to step S7. In step S7, the number of halfway stops N is decremented by "10", and the result is held in the memory.

Accordingly, in the next step S3,
Since the full charge determination is performed using the number of halfway stops N corrected in the downward direction, the full charge determination using the appropriate full charge determination threshold V ′ is performed for the battery 1 in which all or a part of the memory effect has been eliminated. As a result, an adverse effect on the battery 1 due to overcharging can be effectively avoided. Thereafter, in step S8, normal charging is stopped.

Note that the present invention is not limited to the above-described embodiment, and the specific numerical values described above are only examples, and the present invention is not limited to these. For example, in the above embodiment, the rising gradient of the full charge determination threshold value V 'is set large in a section where the number of halfway stops N is small and small in a section where it is large (dashed line X in FIG. 5). (Solid line Y in FIG. 5).

[0030]

As is apparent from the above description, according to the present invention, the following effects can be obtained. (1) According to the first aspect of the present invention, even if the charging voltage rises due to the effect of the memory effect caused by the repetition of the charging halfway stop, the full charge for detecting the full charge according to the number of halfway charging stops. Since the determination threshold can be set higher than the determination threshold in the battery initial state, it is possible to prevent the charging voltage from reaching the full charge determination threshold in a state of insufficient charging, and to effectively reduce the dischargeable capacity. Can be prevented.

(2) According to the second aspect of the present invention, the full charge determination threshold gradually increased as the number of halfway charge stops increases is temporarily reduced after full charge, so that the full charge determination threshold up to that time is stored in the memory. It is possible to effectively avoid a decrease in the accuracy of full charge detection that may be caused by using the battery as it is even after the effect is eliminated, and to effectively prevent an adverse effect on the battery due to overcharging.

(3) According to the third aspect of the present invention, the full charge determination threshold value is large when the change of the full charge determination voltage with respect to the number of halfway charge stoppages starts (when the number of halfway charge stoppages is small). Since the setting is made along the way (as the number of charging stops on the way increases), the amount of increase is reduced, accurate full charge can be performed.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a battery charge control device according to the present invention.

FIG. 2 is a characteristic diagram illustrating a change in a full charge determination voltage with respect to the number of halfway charging stops.

FIG. 3 is a flowchart showing a charge control flow executed by a control unit in FIG. 1;

FIG. 4 is a diagram illustrating a setting example of an increase amount of a full charge determination threshold value with respect to the number of halfway charging stops.

FIG. 5 is a diagram illustrating another example of setting the increase amount of the full charge determination threshold with respect to the number of halfway charge stoppages.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Battery 2 Control part (means for stopping the number of stops, means for setting a full charge determination threshold value) 3 Charger 4 Current sensor 5 Voltage sensor 6 Temperature sensor

Continued on the front page F term (reference) 2G016 CA03 CB12 CB31 CC01 CC03 CC04 CC13 CC27 CC28 5G003 AA01 BA01 CA01 CA14 CB01 CC02 FA06 GC05 5H030 AA01 AS08 BB01 FF43 FF51

Claims (3)

[Claims] 1. A battery charge control device that detects full charge when a charge voltage becomes equal to or higher than a full charge determination threshold, calculates a number of halfway charge stoppages in which the battery is not charged until full charge and stopped halfway. And a full charge determination threshold value setting unit that sets the full charge determination threshold value according to the number of halfway charge stop times. 2. The full charge determination threshold setting means increases the full charge determination threshold in accordance with an increase in the number of halfway charge suspensions, and decreases the full charge determination threshold when a full charge is detected. The battery charge control device according to claim 1. 3. The charge control of a battery according to claim 1, wherein the full charge determination threshold value setting means switches an increase amount of the full charge determination threshold value in accordance with the number of halfway charge suspensions. apparatus.