JPH06311663A - Charging method for secondary battery - Google Patents

Abstract

PURPOSE:To allow boosting charge of a secondary battery without sacrifice of the battery performance thereof. CONSTITUTION:In the charging method for secondary battery, constant current charging or quasi-constant current charging is conducted until the battery voltage Vc reaches a first voltage Vt. Subsequently, constant current charging and constant voltage charging with a first voltage Vt (or pause) are repeated. When the charging current Ic decreases below a predetermined level It during the constant voltage charging (or when the battery voltage Vc reaches the set voltage Vt or above), constant voltage charging is conducted with the first voltage Vt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging a secondary battery, and more particularly to a charging method effective for rapidly charging a non-aqueous secondary battery.

[0002]

2. Description of the Related Art Among rechargeable batteries that can be used repeatedly,
The lithium-ion secondary battery, which is a non-aqueous secondary battery, has a high battery voltage (for example, 4.2 V), a high energy density, and excellent cycle characteristics. As a method for charging such a non-aqueous secondary battery, Japanese Patent Laid-Open No. 2-1926
There is a constant current (or quasi-constant current) / constant voltage charging method as disclosed in Japanese Patent Laid-Open No. 70.

According to such a charging method, first, when the battery voltage of the secondary battery is lower than the constant voltage value of the charging power source, the secondary battery is charged with a constant current (or quasi-constant current),
Battery voltage rises gradually. Then, when the battery voltage reaches a predetermined voltage (for example, 4.2 V), constant voltage charging limited by this voltage value is performed thereafter. When the constant voltage charging proceeds, the charging current gradually decreases, and when the charging current decreases to a predetermined value, the charging ends.

In charging such a non-aqueous secondary battery,
When performing rapid charging, it is conceivable to increase the initial constant current (or quasi-constant current) charging current value.

[0005]

However, when the current value is increased to perform the rapid charging, it is necessary to increase the rated output on the charger side as the current value increases.
This leads to an increase in the size and cost of the charger. Further, thermal factors also have an adverse effect such as deterioration in reliability of the charger and the secondary battery. Further, the performance of the secondary battery may be deteriorated by applying a large current.

Therefore, the present invention enables rapid charging of a non-aqueous secondary battery without increasing the size of the charger, increasing the cost and reducing the reliability, and reducing the reliability and the performance of the secondary battery. With the goal.

[0007]

A first rechargeable battery charging method according to the present invention comprises constant current charging or quasi-constant current charging until the battery voltage reaches a first voltage, and then constant current charging and The constant voltage charging with the first voltage is repeatedly performed, and when the charging current during the constant voltage charging becomes a predetermined value or less, the first voltage
It is characterized in that constant voltage charging is performed at the voltage of.

In the second method for charging a secondary battery according to the present invention, constant current charging or quasi constant current charging is performed until the battery voltage reaches the first voltage, and then constant current charging and charging suspension are repeated. When the battery voltage during the charging suspension is equal to or higher than a set voltage, constant voltage charging is performed at the first voltage.

[0009]

In the method of charging the secondary battery according to the present invention, first,
Constant current charging (or quasi-constant current charging) is performed until the battery voltage reaches the first voltage. Then, when the first voltage is reached, constant-current charging and constant-voltage charging (or charging suspension) at the first voltage are repeated.

Here, the first voltage is an optimum voltage for the secondary battery. Therefore, further constant current charging of the secondary battery even after reaching the first voltage means that the secondary battery is charged to a voltage higher than the first voltage, and for the secondary battery,
This is an unfavorable side reaction. Therefore, in the present invention, such a charging operation is performed in the initial stage of charging the secondary battery, and a period during which constant voltage charging is performed at the first voltage (or a period during which charging is suspended) is provided to sufficiently suppress the side reaction. is doing.

Then, when the charging current during constant voltage charging becomes equal to or lower than a predetermined value (or when the battery voltage during charging suspension becomes equal to or higher than a set voltage), the secondary battery is constant voltage charged by the first voltage, Make sure that the battery is fully charged.

[0012]

1 is a block circuit diagram showing a charging circuit for charging a secondary battery B composed of a lithium ion secondary battery using the charging method of the present invention.

The power supply circuit 1 includes an input filter for removing noise contained in a commercial AC power supply of 100 VAC, a rectifier circuit for converting the input AC into DC, and a switching unit for converting DC of the rectifier into high-frequency AC. And a known DC power supply circuit such as a rectifying / smoothing circuit for rectifying the AC output of the converting transformer to convert it into a smooth DC.

The charging control circuit 2 adjusts the output of the power supply circuit 1 to control the charging voltage and charging current of the secondary battery B, the constant voltage charging circuit 10 and the constant current charging circuit 11, the arithmetic circuit 12, and the current. The detection circuit 13, the voltage detection circuit 14, the charge control switch 15 provided between the power supply circuit 1 and the secondary battery B, and the discharge resistor 1 connected in parallel to the secondary battery B.
6 and a discharge control switch 17.

The differential amplifier 10A constituting the constant voltage charging circuit 10 has a negative side input terminal connected to the secondary battery B via a voltage dividing resistor, and a positive side input terminal connected via a changeover switch SW1. It is connected to the first reference voltage E1 (4.5 V in this embodiment) or the second reference voltage E2 (4.2 V in this embodiment).

The differential amplifier 10A compares the voltage at the-side input terminal, that is, the divided voltage of the secondary battery B, with the reference voltage E1 or E2 at the + side input terminal. Divided voltage (ie
When the battery voltage) becomes higher than the reference voltage E1 or E2, the output of the differential amplifier 10A becomes negative and the base current of the control transistor TR1 is drawn. Therefore, the output supplied via the control transistor TR1 is reduced.

By performing such an operation, the constant voltage charging circuit 10 regulates the charging voltage with a voltage corresponding to the reference voltage E1 or E2, and charges the secondary battery B with a constant voltage.

On the other hand, in the differential amplifier 11A constituting the constant current charging circuit 11, the-side input terminal is connected to the current detecting resistor R connected in series with the secondary battery B, and the + side input terminal is connected to the reference voltage E3. Connected to.

In the differential amplifier 11A, the voltage at the negative input terminal, that is, the voltage generated in the current detection resistor R based on the value of the current flowing in the secondary battery B, and the reference voltage E at the positive input terminal E.
Compare with the voltage of 3. When the voltage generated in the current detection resistor R becomes higher than the reference voltage E3 (in other words, the current value flowing through the secondary battery B becomes larger than a predetermined value), the output of the differential amplifier 11A becomes −, It draws the base current of the control transistor TR1 and reduces the charging current. That is, the constant current charging circuit 11 performs charging by controlling the charging current of the secondary battery B so that it is constant.

The arithmetic circuit 12 comprises a microcomputer. The arithmetic circuit 12 calculates the output of the current detection circuit 13 including an A / D converter and the output of the voltage detection circuit 14 to detect the charge state of the secondary battery B, and the charge control switch 15 and the discharge control switch 17 Also, the opening / closing operation of the changeover switch SW1 is controlled.

First, the first embodiment of the charging method of the present invention will be described.
This will be described with reference to the flowchart of FIG. 2 and the graph of FIG. In step S1, the charge control switch 15 is turned on, the discharge control switch 17 is turned off, and the changeover switch SW1 is set to the reference voltage E1 side. Under the control of the constant current charging circuit 11, a constant charge current IA is set. Charge current.

In step S2, the battery voltage Vc of the secondary battery B is detected, and in step S3 it is determined whether or not the battery voltage Vc has reached a predetermined value Vt. Then, when it is determined that it has arrived, the process proceeds to the next step S4.
The predetermined value Vt is 4.2V, for example.

In step S4, the constant current charging circuit 1
Under the control of 1, a predetermined time Ta (for example, several seconds to several minutes)
The constant current charging is performed, and when the predetermined time Ta has elapsed, the process proceeds to the next step S5.

In step S5, the changeover switch SW
With 1 as the reference voltage E2, under the control of the constant voltage charging circuit 10, constant voltage charging with the reference voltage E2 (that is, 4.2 V) is performed. At this time, the battery voltage of the secondary battery B is Ta for a predetermined time.
Due to the constant current charging in, the predetermined value Vt (that is, the reference voltage E2 = 4.2V) is exceeded. Therefore, the discharge control switch 17 is turned on and the secondary battery B is discharged to 4.2V to perform constant voltage charging, thereby reliably preventing the secondary battery B from being overcharged.

In step S6, it is determined whether or not a predetermined time Tb (for example, several seconds to several minutes) has elapsed from the start of constant voltage charging in step S5. When it is determined that the predetermined time Tb has elapsed, the charging current Ic of the secondary battery B is detected in step S7.

In step S8, it is determined whether or not the charging current Ic detected in step S7 is less than or equal to a predetermined value It (a value sufficiently smaller than the constant current value IA). If it is not equal to or less than the predetermined value It, the process returns to step S1 and thereafter, the operations from step S1 to step S8, that is, the predetermined time T
The constant current charging of a and the constant voltage charging of the predetermined time Tb are repeatedly performed.

Then, when the charging current Ic becomes less than or equal to the predetermined value It in step S8, in step S9
Until the predetermined time Tc elapses from the start of charging, the reference voltage E
Constant voltage charging at 2 (ie 4.2V) is continuously performed,
Then, in step S10, the charging control switch 1
5 and the discharge control switch 17 are turned off to finish the charging of the secondary battery B.

Next, a second embodiment of the charging method of the present invention will be described.
This will be described with reference to the flowchart of FIG. 4 and the graph of FIG. The embodiment is the same as step S of the first embodiment shown in FIG.
It differs from the first embodiment in that step S21 is performed instead of step 3 and step S4.

That is, in the first embodiment, in step S3, the battery voltage Vc of the secondary battery B is the predetermined value Vt (4.2).
V) is reached, in the next step S4, under the control of the constant current charging circuit 11, a predetermined time Ta
Constant-current charging (for example, several seconds to several minutes) is performed. Therefore, the secondary battery B is always exposed to a voltage equal to or higher than the predetermined value Vt (that is, 4.2 V), which is appropriate for the predetermined time Ta, and may be slightly deteriorated.

Therefore, in the second embodiment, in order to minimize the time during which the secondary battery B is exposed to a voltage equal to or higher than an appropriate predetermined value Vt (that is, 4.2V), in step S21, The battery voltage of the secondary battery B is the specified value VT
(In this embodiment, it is determined whether or not it has reached 4.4V). Then, when it is determined that it has arrived, the next step S
5, the changeover switch SW1 is set to the reference voltage E2,
Under the control of the constant voltage charging circuit 10, constant voltage charging with the reference voltage E2 (that is, 4.2 V) is performed.

As a result, the secondary battery B is charged rapidly by exceeding the predetermined value Vt so that the secondary battery B can be charged rapidly while the deterioration of the secondary battery B is prevented more reliably. I have to.

Furthermore, a third embodiment of the charging method of the present invention is
Description will be made with reference to the flowchart of FIG. 6 and the graph of FIG. 7. In step S31, the discharge control switch 17
Is turned off and the changeover switch SW1 is set to the reference voltage E1 side. Then, in step S32, the charging control switch 15 is turned on, and constant current charging with the charging current IA is performed under the control of the constant current charging circuit 11. To do.

In step S33, the battery voltage Vc of the secondary battery B is detected, and in step S34 it is determined whether or not the battery voltage Vc has reached a predetermined value Vt. To step S35. The predetermined value Vt is 4.2V, for example.

In step S35, under the control of the constant current charging circuit 11, constant current charging is performed for a predetermined time Ta (for example, several seconds to several minutes), and when the predetermined time Ta elapses,
Then, the process proceeds to step S36.

In step S36, the charging control switch 15 is turned off to stop the charging of the secondary battery B. Then, in step S37, step S36
A predetermined time Tb (for example,
Judge whether or not several seconds to several minutes) have elapsed. When it is determined that the predetermined time Tb has elapsed, the battery voltage Vc of the secondary battery B is detected in step S38.

In step S39, step S3
The battery voltage Vc detected at 8 is a predetermined value Vt (that is, 4.
2V) or higher. If it is not equal to or more than the predetermined value Vt, the process returns to step S32, and thereafter step S3.
The operation from 2 to step S39, that is, the constant current charging for the predetermined time Ta and the charging suspension for the predetermined time Tb are repeated.

Then, in step S39, when the pressure Vc of the battery becomes equal to or higher than the predetermined value Vt, in step S40, the charge control switch 15 is turned on, the discharge control switch 17 is turned on, and the changeover switch SW1 is set to the reference voltage. It is set to the E2 side, and the secondary battery B can be discharged to 4.2V. Then, in step S41, under the control of the constant voltage charging circuit 10, a predetermined time Tc has elapsed from the start of charging.
Constant voltage charging is performed at the reference voltage E2 (that is, 4.2 V) until the time elapses, and then in step S42,
The charge control switch 15 and the discharge control switch 17 are turned off, and the charging of the secondary battery B is completed.

The present invention is not limited to the above three embodiments. For example, in the third embodiment, instead of the constant current charging for the predetermined time Ta, constant current charging until reaching the predetermined value Vt may be performed.

[0039]

The method of charging the secondary battery according to the present invention comprises:
Constant-current charging or quasi-constant-current charging is performed until the battery voltage reaches a first voltage, and then constant-current charging and constant-voltage charging (or charging suspension) at the first voltage are repeatedly performed, and the constant-voltage charging is performed. When the charging current at the time becomes less than or equal to a predetermined value (or the battery voltage at the time of charging suspension becomes more than the set voltage), constant voltage charging is performed at the first voltage, so the battery performance of the secondary battery is improved by overcharging. The secondary battery can be rapidly charged without lowering it.

[Brief description of drawings]

FIG. 1 is a circuit diagram for implementing the present invention.

FIG. 2 is a flowchart showing a first embodiment of the present invention.

FIG. 3 is a graph showing a battery voltage and a charging current according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a second embodiment of the present invention.

FIG. 5 is a graph showing a battery voltage and a charging current in the second embodiment of the present invention.

FIG. 6 is a flowchart showing a third embodiment of the present invention.

FIG. 7 is a graph showing a battery voltage and a charging current in the third embodiment of the present invention.

[Explanation of symbols]

 2 charge control circuit 10 constant voltage charge circuit 11 constant current charge circuit 12 arithmetic circuit 15 charge control switch 16 discharge resistance 17 discharge control switch

Claims (6)

[Claims] 1. Constant-current charging or quasi-constant-current charging until the battery voltage reaches a first voltage, and then constant-current charging and constant-voltage charging at the first voltage are repeated to perform the constant-voltage charging. When the charging current at the time becomes less than a predetermined value, the first
A method of charging a secondary battery, which is characterized in that constant voltage charging is performed at the voltage of. 2. The secondary battery according to claim 1, wherein the constant current charging after reaching the first voltage is regulated by a second voltage higher than the first voltage. How to charge. 3. The charging method for a secondary battery according to claim 1, wherein the constant voltage charging is performed by discharging the battery voltage to the first voltage. 4. Constant-current charging or quasi-constant-current charging is performed until the battery voltage reaches a first voltage, and then constant-current charging and charge suspension are repeatedly performed, and the battery voltage during the suspension of charging is equal to or higher than a set voltage. Then, a constant voltage charging is performed at the first voltage, wherein the secondary battery is charged. 5. The secondary battery according to claim 4, wherein the constant current charging after reaching the first voltage is regulated by a second voltage higher than the first voltage. How to charge. 6. The method of charging a secondary battery according to claim 4, wherein the constant voltage charging is performed by discharging the battery voltage to the first voltage.