JP3347808B2 - Rechargeable battery charging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to, for example, charging method for a secondary battery used as traveling energy source of the electric vehicle.

[0002]

2. Description of the Related Art Conventionally, as a method for efficiently charging a secondary battery such as a lead battery or a nickel cadmium battery while avoiding overcharging, JP-A-1-93071 and JP-A-53-66543. Japanese Patent Laid-Open Publication No. Sho 51-86732 is known.

In the device described in JP-A-1-93071, when it is detected that the terminal voltage of a battery during charging has reached a predetermined set voltage, control is performed so as to reduce the charging current. .

[0004] Japanese Patent Application Laid-Open No. 53-66543 discloses a technique in which the charging current is reduced when it is detected that the time derivative of the terminal voltage of the battery changes from positive to negative during charging. The control is performed as follows.

[0005] Also, those described in JP-A-51-86732, when the state in which the increase rate of the terminal voltage of the batteries during charging is below a predetermined value continues for a predetermined time so as to decrease the charging current Control is performed.

[0006]

The technique disclosed in Japanese Unexamined Patent Publication No. 1-93071 has a problem that if the set voltage is too low, the charging time becomes longer or insufficient charging occurs. If the charge is too high, there is a problem that the battery is overcharged and the life of the battery is shortened.

[0007] Further, in Japanese Unexamined Patent Application Publication No. 53-66543 or Japanese Unexamined Patent Application Publication No. 51-86732, there is a possibility that overcharging has already occurred at the time when the charging current is reduced. There is a problem that shortens the life of the device.

[0008] The present invention has been made in view of the above circumstances, it is to provide a charging method for secondary batteries for efficient charging in a short time while avoiding deterioration of the battery due to overcharging Aim.

[0009]

To achieve the above object , according to the first aspect of the present invention, a battery charger is connected to a charger.
Current and terminal voltage of the battery being charged
The battery is charged based on the charging current and the terminal voltage.
In a method of charging a secondary battery for controlling
Charging with charging current, based on second-order time derivative of terminal voltage
When it is detected that the terminal voltage has reached the inflection point,
A first step of reducing the charging current, and
During charging by the second time derivative of the terminal voltage of the battery.
And it is detected that the terminal voltage has reached the inflection point
A second step of further reducing the charging current, and the second step
Is performed at least once, and then the battery is fully charged.
Third step of stopping charging when the amount of power reaches a predetermined value
A method of charging a secondary battery characterized by including
It is.

According to the above configuration, the terminal voltage during charging of the battery is adjusted.
The terminal voltage reaches the inflection point based on the second-order time derivative of the voltage
Control to decrease the charging current when it is detected that
Is repeated at least twice, so that the charging current
Fine control, no battery damage, faster
Can be charged.

According to the second aspect of the present invention,
In addition to the configuration of claim 1, the terminal is connected during execution of the second step.
After the first derivative of the voltage becomes equal to or less than a predetermined value, the terminal voltage
When the inflection point is reached,
Switch to constant voltage charging to further reduce the charging current.
A method of charging a secondary battery characterized by the following is proposed.

According to the above configuration, the terminal voltage reaches the inflection point.
Control to decrease the charging current when it is detected that
Is repeated at least two times,
After the differential value falls below the predetermined value, the terminal voltage becomes the inflection point.
When it is detected that the battery has reached
To reduce the charging current further,
Set the timing of switching from charging to constant voltage charging appropriately
The battery in less time without damaging the battery.
It works.

According to the third aspect of the present invention,
Charging current and terminals of the battery connected to the charger and charged
Voltage, and based on these charging currents and terminal voltages
In a method of charging a secondary battery for controlling charging of a battery,
Second-order time of terminal voltage while charging the pond with the specified charging current
A first step of calculating a differential value every predetermined time;
When the second derivative of the terminal voltage is 0 or more,
If the rate of increase of the pressure is increasing,
Continue charging with the new charging current with the fixed value added
In the first step, the second-order time differential value of the terminal voltage is less than 0
If the rate of increase of the terminal voltage is decreasing,
Charging with a new charging current obtained by subtracting a predetermined value from the charging current
And the total charge power of the battery
A third step of stopping charging when a predetermined value is reached.
A method for charging a secondary battery characterized by the above is proposed.

According to the above configuration, the battery is charged at a predetermined charging current.
The second derivative of the terminal voltage with predetermined time
And the second-order time differential value is 0 or more and
When the rate of increase in pressure is increasing, the charging current
Continue charging with the new charging current to which the predetermined value has been added, and conversely
When the second derivative of the terminal voltage is less than 0 and the terminal voltage
If the rate of increase is decreasing, the charge current is
Since charging is continued with a new charging current that has been subtracted from the fixed value,
Damaging the battery by controlling the charging current more finely
, And can be charged in an extremely short time.

According to the invention described in claim 4,
In addition to the configuration of claim 3, the charging current in the second step is controlled.
When adding or subtracting a constant value, the first-order time
The predetermined value is increased or decreased according to the value of the minute value.
A method of charging a secondary battery is proposed.

According to the above configuration, the first-order time period of the terminal voltage is reduced.
Adds or subtracts a predetermined value from the charging current according to the value of the minute value
Increase or decrease the specified value, so that the charging current can be
Thus, it can be controlled.

According to the invention described in claim 5,
In addition to the configuration of any one of claims 1 to 4,
In the third step, the total charge power of the battery is defined as the terminal voltage.
Calculated by integrating the product with the charging current over the entire charging time
A method of charging a secondary battery characterized by
You.

According to the above configuration, the total charge of the battery
The electric energy is the product of the terminal voltage and the charging current over the entire charging time.
The total charge of the battery is calculated
Competence can be calculated precisely.

[0019]

Embodiments of the present invention will be described below.
A description will be given based on an embodiment of the present invention shown in the attached drawings .

[0020] FIGS. 1 to 3 show a first exemplary embodiment of the present invention, FIG. 1 is a block diagram of a battery charging device, the graph 2 showing the voltage characteristics when the battery was charged at a constant current, Fig. 3 is a graph showing the charging current and the terminal voltage.

In FIG. 1, reference numeral B denotes a secondary battery such as a lead battery, which is connected to a charger C which can control a charging current. The charging current and terminal voltage of battery B during charging are detected by ammeter 1 and voltmeter 2, respectively. The outputs of the ammeter 1 and the voltmeter 2 are input to the control device 3 and subjected to arithmetic processing, and the charging current supplied from the charger C to the battery B is controlled based on the results.

As shown in FIG. 2, when the discharged battery B is charged with a constant current, there is a period in which the terminal voltage V sharply increases immediately after the start of charging (ie, a period until time T ₀ ), and thereafter, the terminal voltage V becomes Increases slowly. Eventually, the terminal voltage V sharply increases, and starts decreasing after reaching the peak.

If the charging is continued until the terminal voltage V reaches the vicinity of the peak, the electrolyte of the battery B is electrolyzed to generate gas, that is, a so-called overcharged state, and the life of the battery B is shortened. Will be. Therefore, in the present embodiment, focusing on the inflection point that appears on the curve of the terminal voltage V before the terminal voltage V of the battery B reaches the peak, the state before the terminal voltage V reaches the inflection point is referred to as the overcharge unreached state. age,
The state after reaching the inflection point is set as an overcharged state, and the charging current is controlled. This, the first participants
A description will be given based on FIG.

FIG. 3 shows a two-stage constant-current charging in which a charging current I ₁ is supplied from a charger C to a battery B at the start of charging, and the charging current I ₁ is detected by an ammeter 1 and is a constant value. Is held. The terminal voltage V of the battery B during charging is detected by the voltmeter 2, and the control device 3 differentiates the terminal voltage V with time to obtain a first-order time differential value V '(= dV /
dt), and the first-order time differential value V ′ is further differentiated with time to obtain a second-order time differential value V ″ (= d ² V / d).
t ² ) is calculated.

The first-order time differential value V 'corresponds to the rate of change of the terminal voltage V with time. The larger the value, the larger the slope of the terminal voltage curve in the graph. The second-order time differential value V ″ indicates whether the slope of the terminal voltage curve is increasing or decreasing. When the value is positive, the terminal voltage curve becomes convex downward and increases. In the case of a negative value, the terminal voltage curve becomes convex upward and tends to decrease.
When the second-order time differential value V ″ changes from positive to negative, it corresponds to the inflection point where the direction of the curvature of the terminal voltage curve changes,
At that time, the slope of the terminal voltage curve changes from an increasing tendency to a decreasing tendency.

When the terminal voltage curve reaches the inflection point at the voltage Vc, the control device 3 reduces the charging current from I ₁ to I ₂ to prevent overcharging. Thereafter, charging continues with a charging current I _2, and stops charging when the charged electrical energy of the total has reached a predetermined value determined from the previous discharge electric energy. The total charging power is obtained by integrating the product of the terminal voltage V and the charging current I over the entire charging time. It should be noted that an inflection point may also occur when the terminal voltage V suddenly increases immediately after the start of charging.
The inflection point that occurs when the terminal voltage V is equal to or lower than a predetermined value is ignored.

As described above, the charging current I is reduced when the terminal voltage curve reaches the inflection point and the slope of the terminal voltage curve changes from increasing to decreasing. The timing at which the charging current I is reduced as compared with the charging can be appropriately set, and overcharging can be prevented while prolonging the life of the battery B while performing efficient charging in a short time. There is no possibility of overcharging or insufficient charging due to the temperature of the battery or the individual difference of the battery B.

FIG. 4 shows a second reference example of the present invention.

[0029] The second reference example constant current - performs a constant voltage charging, the charging by constant current charging at a charging current I _1, the slope of the terminal voltage curve terminal voltage curve reaches the inflection point Turning to decrease from increase, it is switched from the constant current charging to the constant voltage charging at the terminal voltage Vc at that time, thereby the charging current gradually decreases from I _1. Then, the charging is stopped when the total charging power reaches a predetermined value.

According to the second embodiment , the switching timing from the constant current charging to the constant voltage charging can be appropriately set, as compared with the conventional constant current-constant voltage charging. The same operation and effect as in the first reference example can be obtained.

Hereinafter, first to fourth embodiments of the present invention will be described.
You. FIGS. 1 and 2 of the first reference example are the first to fourth examples.
The same applies to the embodiment.

FIG. 5 shows a first embodiment of the present invention.

In the first embodiment, the constant current multi-stage charging is performed. _First , the constant current charging is performed with the charging current I ₁ , and when the terminal voltage curve reaches the inflection point, the charging current is reduced to I ₂ and the charging is performed again. Perform constant current charging. Then the charging current the terminal voltage curve reaches inflection point again further reduced to I _3, the charging power amount of total stops charging when it reaches a predetermined value while repeating this.

Thus, according to the first embodiment described above, it is possible to control the charging current I more finely than in the first reference example, and to charge the battery B in a shorter time without damaging the battery B. Becomes possible.

FIG. 6 shows a second embodiment of the present invention.

The second embodiment performs constant current multi-stage constant voltage charging. The charging current is gradually reduced from I ₁ to I ₂ , I ₃ ,... Every time the terminal voltage curve reaches the inflection point. Then, at the inflection point after the rate of increase of the terminal voltage V (that is, the first-order time differential value V 'of the terminal voltage V) becomes equal to or less than a predetermined value, switching to constant voltage charging is performed, and the total amount of charging power reaches the predetermined value. Stop charging when it reaches.

Thus, according to the second embodiment described above, it is possible to control the charging current I more finely than in the second embodiment, and to charge the battery B in a shorter time without damaging the battery B. Becomes possible.

Next, a third embodiment of the present invention will be described with reference to the flowchart of FIG.

First, in step S1, charging of the battery B by the charging current I is started, and in step S3, until the charging of the battery B is completed, in step S3, the second-order time differential value of the terminal voltage V at every minute time t1. It is determined whether or not V ″ is 0 or more.

If the second-order time differential value V ″ is 0 or more in step S3 and the rate of increase of the terminal voltage V tends to increase, it is determined that there is no risk that the battery B will be overcharged, and step S4 I is obtained by adding a predetermined increment p to the charging current I.
+ P is the charging current I. On the other hand, if the second-order time differential value V ″ is less than 0 and the rate of increase of the terminal voltage V tends to decrease in step S3, the battery B may be overcharged with the current charging current I as it is. It is determined that there is, and step S
Ih obtained by subtracting a predetermined reduction amount h from the charging current I at 5
Is the charging current I. In this manner, the charging current I is increased or decreased by the increase amount p or the decrease amount h with reference to the second-order time differential value V ″ of the terminal voltage V at each minute time t1, and when the charging of the battery B is completed in step S2. , The supply of the charging current I is stopped.

According to the third embodiment, the short time t1
Since the second-order time differential value V ″ is referred to each time, it is possible to control the charging current I more finely than in the first and second embodiments described above, and to prevent the battery B from deteriorating in an extremely short time. Charging can be completed.

Next, a fourth embodiment of the present invention will be described with reference to the flowchart of FIG. 8 and the graph of FIG.

First, the charging of the battery B with the charging current I is started in step S11, and until the charging of the battery B is completed in step S12, the second-order time differential value V ″ is set to 0 every minute time t1 in step S13. It is determined whether or not this is the case.

In step S13, the second-order time differential value V "is set to 0.
When the rate of increase of the terminal voltage V has a tendency to increase, it is determined that the battery B is not likely to be overcharged, and the charging current I is increased or set to a constant value in steps S14 to S19 below. The holding control is performed.

That is, in step S14, the first-order time differential value V 'of the terminal voltage V is compared with the constant a, and when the first-order time differential value V' is smaller than a, that is, when the rate of increase of the terminal voltage V is small. In step S15, a large value p (large) is selected as the increase amount p of the charging current I in step S15. If the first-order time differential value V 'is equal to or larger than a in step S14 and the first-order time differential value V' is smaller than a constant b (a <b) larger than a in step S16, S1
At 7, an intermediate value p (medium) is selected as the increase amount p of the charging current I. Further, in step S16, the second-order time differential value V ″
Is greater than or equal to b, the charging current I is determined in step S18.
0 is selected as the increase amount p of. And step S
In step 19, the increment p obtained in each of the steps S15, S17 and S15 is added to the charging current I to obtain a new charging current I.
And

On the other hand, if the second-order time differential value V ″ is less than 0 and the rate of increase of the terminal voltage V tends to decrease in step S13, the battery B may be overcharged with the charging current I as it is. Is determined to exist, and the following step S20
At steps S25 to S25, control for reducing the charging current I is performed.

That is, in step S20, the first-order time differential value V 'of the terminal voltage V is compared with the constant F, and when the first-order time differential value V' exceeds F, that is, when the rate of increase of the terminal voltage V is large. In step S21, the decrease amount h of the charging current I
Is selected as a small value h (small). If the first-order time differential value V 'is equal to or less than F in step S20 and the first-order time differential value V' exceeds a constant G (F> G) smaller than F in step S22, Step S2
At 3, an intermediate value h (medium) is selected as the decrease amount h of the charging current I. Further, in step S22, the second-order time differential value V ″
Is less than or equal to G, the charging current I is determined in step S24.
A large value h (large) is selected as the decrease amount h of. Then, in step S25, each of the above-described steps S21, S2
3. The amount of decrease h determined in S24 is subtracted from the charging current I to obtain a new charging current I.

As described above, when the second-order time differential value V ″ of the terminal voltage V is positive, the magnitude of the first-order time differential value V ′ of the terminal voltage V is referred to. It is determined that there is enough time to reach the inflection point, and the increase amount p of the charging current I is set large. Conversely, if the first-order time differential value V 'is large, it is determined that the inflection point will be reached soon. The increase amount p of the charging current I is set to be small, and when the second-order time differential value V ″ of the terminal voltage V is negative, the magnitude of the first-order time differential value V ′ of the terminal voltage V is referred to, and If the value is large, it is determined that it is just past the inflection point, and the reduction amount h of the charging current I is set to be small. Conversely, if the first-order time differential value V 'is small, it is necessary to pass the inflection point. It is determined that the time has elapsed, and the decrease amount h of the charging current I is set to be large. Thus, according to the fourth embodiment, it is possible to control the charging current I more precisely than in the third embodiment.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various design changes can be made.

[0050] For example, the state of the second-order time differential value V "= 0 in the terminal voltage V in the embodiment (i.e., inflection point) charged relative to the
Although the current I is controlled, V ″ = 0 in the present invention.
Is assumed to include the case where V ″ is a value near 0.

When calculating the second-order time differential value V ″ of the terminal voltage V, it is not always necessary to directly calculate the second-order time differential value V ″, and the terminal voltage V and its first-order time differential value V ′ are used. It is possible to estimate the second-order time differential value V ″. For example, in FIG. 2, while the terminal voltage V changes from “small” to “maximum”, the first-order time differential value V ′ changes from “small”. Although it increases to "large" and then decreases and then decreases to "0", the position of "large" where the first-order time differential value V 'changes from increasing to decreasing is the second-order time differential value V "= Corresponds to zero inflection point.

In the third embodiment, the determination of the degree of overcharge state and the determination of the degree of overcharge unreached state are performed based on the magnitude of the first-order time differential value V '. The value V ′ can be estimated from the terminal voltage V and the second-order time differential value V ″ without directly calculating. For example, in FIG. 2, overcharging has not been reached until the second-order time differential value V ″ = 0. In the state, the first-order time differential value V ′ is small until the second-order time differential value V ″ reaches “large” from “small”, and the first-order time differential value V ′ until it reaches “0” from “large”. Can be estimated to be large, and further, in an overcharged state exceeding the second-order time differential value V ″ = 0, the first-order time differential value until the second-order time differential value V ″ reaches “−large” from “0”. V 'is large and the first floor until it reaches "-large" to "-small" It can be estimated that between differential value V 'is small. Since the second-order time differential value V "also eventually is a value obtained from the terminal voltage V, to determine the degree and extent of overcharge unreached status of the overcharged state based on the terminal voltage V of the batteries B Becomes possible.

In the present invention, the first-order time differential value V '
And the second-order time differential value V ″ need not be an exact differential value in a mathematical sense, and the first-order time differential value V ′ is obtained by dividing the amount of change in the terminal voltage V during a minute predetermined time by the predetermined time. Value, and the second-order time differential value V ″
Can be substituted by a value obtained by dividing the amount of change of the first-order time differential value V 'in a minute predetermined time by the predetermined time.

[0054]

As described above, according to the first aspect of the present invention, the second-order time differential value of the terminal voltage during charging of the battery is provided.
It is detected that the terminal voltage has reached the inflection point based on
Control to reduce the charging current at least twice
Since the charging is performed repeatedly, the charging current is
It is possible to charge in a shorter time without damaging the pond.
You.

According to the second aspect of the present invention,
Charge when terminal voltage reaches inflection point
Repeat the control to reduce the current at least twice
In the meantime, after the first derivative of the terminal voltage becomes
When it is detected that the terminal voltage has reached the inflection point,
Since the charging current is further reduced by the voltage control,
Set the timing of switching from charging to constant voltage charging appropriately
The battery in less time without damaging the battery.
It works.

According to the third aspect of the present invention,
While charging the battery with the specified charging current, when the terminal voltage is on the second floor
Is calculated every predetermined time, and the second-order time differential value is calculated.
0 or more and the rate of increase in terminal voltage is increasing
Is a new charging current obtained by adding a predetermined value to the charging current.
To continue charging, and conversely, the terminal time
Full and the rate of increase in terminal voltage is decreasing
Is a new charging current obtained by subtracting a predetermined value from the charging current.
, So that charging current can be controlled more finely
Battery in a very short time without damaging the battery.
It becomes possible.

According to the fourth aspect of the present invention,
Depending on the value of the first derivative of the terminal voltage,
Add or subtract a fixed value Increase or decrease the specified value, so charge
The current can be more finely controlled.

According to the invention described in claim 5,
The total charge power of the battery is calculated by comparing the terminal voltage and the charge current.
The product is calculated by integrating over the entire charging time.
Accurate calculation of the total charging power of the pond
You.

[Brief description of the drawings]

FIG. 1 is a block diagram of a battery charger.

FIG. 2 is a graph showing voltage characteristics when a battery is charged with a constant current.

FIG. 3 is a graph showing a charging current and a terminal voltage according to a first reference example ;

FIG. 4 is a graph showing a charging current and a terminal voltage according to a second reference example ;

FIG. 5 is a graph showing a charging current and a terminal voltage according to the first embodiment.

FIG. 6 is a graph showing the charging current and the terminal voltage of the second embodiment.

FIG. 7 is a flowchart illustrating a charging method according to a third embodiment.

FIG. 8 is a flowchart illustrating a charging method according to a fourth embodiment.

FIG. 9 is a graph showing the charging current and the terminal voltage of the fourth embodiment.

[Explanation of symbols]

B Battery C Charger I Charging current V Terminal voltage V 'First-order time differential value V "Second-order time differential value p Increase (predetermined value) h Decrease (predetermined value) t1 minute time (predetermined time)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koyo Sekine 1-4-1, Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-4-217826 (JP, A) JP-A Heisei 5-83876 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/42-10/48 H02J ⁷ /00-7/12

Claims (5)

(57) [Claims] 1. An electric power source connected to a charger (C) and charged.
Detection of charging current (I) and terminal voltage (V) of pond (B)
Then, based on the charging current (I) and the terminal voltage (V),
Battery (B) charging method to control the rechargeable battery
There are, to charge the battery (B) is at a predetermined charging current (I), the terminal voltage
(V) based on the second-order time differential value (V ″)
(V) is charged when it is detected that the inflection point has been reached.
A first step of reducing the current (I) and during charging with the reduced charging current (I),
Based on the second-order time differential value (V ″) of the terminal voltage (V),
When it is detected that the terminal voltage (V) has reached the inflection point
A second step of further reducing the charging current (I); and performing the second step at least once.
(B) when the total charging power reaches a predetermined value
And a third step of stopping charging. 2. The method according to claim 1, wherein a terminal voltage (V) is applied during execution of said second step.
After the first-order differential value (V ') becomes equal to or less than a predetermined value,
When it is detected that the voltage (V) has reached the inflection point,
Switching from current charging to constant voltage charging and charging current (I)
2. The method according to claim 1, further comprising:
How to charge the next battery. 3. An electric power source connected to a charger (C) and charged.
Detection of charging current (I) and terminal voltage (V) of pond (B)
Then, based on the charging current (I) and the terminal voltage (V),
Battery (B) charging method to control the rechargeable battery
Terminal while charging the battery (B) with a predetermined charging current (I).
A second-order time differential value (V ″) of the voltage (V) is calculated for a predetermined time (t
1) a first step of calculating each time, and a second-order time differential value of the terminal voltage (V) in the first step
(V ″) is 0 or more, and the rate of increase of the terminal voltage (V) increases.
When the charging current (I) is increasing,
Continue charging with new charging current (I) to which (p) is added
And the second order time of the terminal voltage (V) in the first step.
When the differential value (V ″) is less than 0 and the terminal voltage (V) increases
When the charging rate is decreasing, the charging current (I) is
Charging is continued with a new charging current (I) from which the constant value (h) is subtracted.
A second step that follows, and that the total charging power of the battery (B) has reached a predetermined value;
And a third step of stopping charging when the battery is charged. 4. The method according to claim 2, wherein the charging current (I) is set to a predetermined value in the second step.
When adding or subtracting (p, h), the terminal voltage (V)
The predetermined value according to the value of the first-order time differential value (V ′)
4. The method according to claim 3, wherein (p, h) is increased or decreased.
How to charge the above secondary battery. 5. The method according to claim 3, wherein in the third step, the total of the battery (B) is
Is the product of the terminal voltage (V) and the charging current (I).
Is calculated by integrating over the entire charging time.
The secondary according to any one of claims 1 to 4,
How to charge the battery.