JPH08289478A - Charging method for secondary battery - Google Patents

Abstract

PURPOSE: To realize quick charging without operating a protective circuit by performing pulse discharging such that the battery voltage does not exceed a protective voltage for longer than a set time after performing pulse charging for shorter than the set time, temporarily stopping the charge/discharge operation in order to detect the voltage and stopping the charging operation when the detected voltage reaches a full-charge voltage. CONSTITUTION: A charge control switch SW1 is turned ON and the charging voltage of a battery B is regulated to a second voltage V2 before the battery is charged with a constant current 1-3C for 80sec. The switch SW1 is then turned OFF and a switch SW1 is turned ON to effect pulse discharge for 10msec. Subsequently, the SW2 is turned OFF and the battery voltage is measured upon elapse of 10msec. It is decided whether the battery voltage thus measured reaches a set voltage V1 and if the set voltage V1 is not reached, pulse charging/ discharging and voltage detection are repeated. With such arrangement, the battery can be charged quickly without causing interruption of charging operating owing to function of a protective circuit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention charges a secondary battery when the battery voltage exceeds a protection voltage higher than a first voltage which is a full charge voltage of the secondary battery for a certain set time or longer. The present invention relates to a charging method for a secondary battery provided with a protection circuit for stopping the charging, and particularly to a charging method effective for rapidly charging a non-aqueous secondary battery.

[0002]

2. Description of the Related Art Among rechargeable secondary batteries,
BACKGROUND ART A lithium ion secondary battery, which is a non-aqueous secondary battery, has a high battery voltage, a high energy density, and excellent cycle characteristics, and has been attracting attention as a power source for portable electric devices. As a method for charging such a non-aqueous secondary battery, generally, there is a constant current / constant voltage charging method as disclosed in JP-A-2-192670.

According to this charging method, when the battery voltage of the secondary battery is lower than the constant voltage of the charging power source, the secondary battery is charged with a constant current. When the battery voltage of the secondary battery reaches the first voltage (for example, 4.1V) which is the full-charge voltage due to the constant current, the secondary battery is thereafter charged with the constant voltage by the first voltage. Then, when the charging current during constant voltage charging decreases to a predetermined value or less, the charging is terminated.

According to such a constant current / constant voltage charging method, the secondary battery can be fully charged without being overcharged, but the secondary battery cannot be rapidly charged.

Therefore, the applicant of the present application has filed Japanese Patent Application Laid-Open No. 6-113.
No. 474, a secondary battery has a second voltage (eg, 4.5 V) higher than the first voltage, which is the full-charge voltage of the secondary battery.
It proposes a rapid charging method in which constant current charging is performed up to, a second voltage is regulated to perform pulse charging, and further pulse charging is performed, followed by constant voltage charging at the first voltage.

[0006]

By the way, a secondary battery such as a non-aqueous secondary battery is disclosed in JP-A-6-105457.
As described in Japanese Patent Publication No. JP-A-2003-264, when the battery voltage exceeds a protection voltage (for example, 4.2 V) higher than a first voltage which is a full-charge voltage of the secondary battery, the secondary battery is usually charged. Equipped with a protection circuit to stop. Therefore, in order to rapidly charge the secondary battery, as described above, even if constant current charging is performed up to the second voltage higher than the protection voltage, before the battery voltage of the secondary battery reaches the second voltage. The protection circuit works and the rechargeable battery stops charging. As a result, the secondary battery is not charged rapidly.

Therefore, an object of the present invention is to charge the secondary battery when the battery voltage of the secondary battery exceeds a protection voltage higher than a first voltage which is a full-charge voltage of the secondary battery for a certain set time or longer. A secondary battery provided with a protection circuit for stopping the charging of the secondary battery enables rapid charging of the secondary battery without stopping charging due to the operation of the protection circuit.

[0008]

According to the present invention, when the battery voltage of the secondary battery exceeds a protection voltage higher than a first voltage which is a full charge voltage of the secondary battery for a set time or more, the secondary battery is A method of charging a secondary battery having a protection circuit for stopping charging of a battery, the step of pulse-charging the secondary battery for a time shorter than the set time, and the step of charging the secondary battery beyond the set time. A step of pulse-discharging the secondary battery so that the battery voltage does not exceed the protection voltage; a step of temporarily suspending charging / discharging of the secondary battery to detect the voltage of the secondary battery; A step of controlling charging of the secondary battery based on the detection result.

[0009]

According to the present invention, first, after the secondary battery is pulse-charged for a time shorter than the set time during which the protection circuit operates, the battery voltage of the secondary battery exceeds the protection voltage over the set time. The secondary battery is pulse-discharged so that it does not exist. As a result, the battery voltage of the secondary battery drops below the protection voltage within the set time by the subsequent pulse discharge even if the voltage once exceeds the protection voltage by pulse charging,
Therefore, the protection circuit does not work.

Thereafter, the charging / discharging of the secondary battery is temporarily stopped to detect the voltage of the secondary battery (that is, the open circuit voltage of the secondary battery is detected), and this voltage becomes the first voltage. When it reaches, the rapid charging of the secondary battery is stopped.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a battery pack P charged according to the present invention.
Is shown. The battery voltage of the battery pack P is higher than the first voltage V1 (for example, 4.1V) which is the full charge voltage of the secondary battery B for a certain set time or longer for a certain period of time or more. Protective voltage E (eg 4.2
Protection circuit 1 which stops the charging of the secondary battery B when V) is exceeded.
It has. The protection circuit 1 compares the battery voltage of the secondary battery B with the protection voltage E, and outputs “High” and “Low”.
The Schmitt trigger circuit 2 for inverting the output, the inverting amplifier circuit 3 for inverting the output of the Schmitt trigger circuit 2, and the switching circuit 4 which is on / off controlled by the output of the inverting amplifier circuit 3. The switching circuit 4 includes a transistor 5 and a MOSFET including a parasitic diode 7.
It is composed of T6. The protection circuit 1 is a secondary battery B
If the battery voltage exceeds the protection voltage for 100 msec or longer, the MOSFET 6 is turned off and the charging of the secondary battery B is stopped.

On the other hand, FIG. 2 shows a charging circuit for charging the above-mentioned battery pack P. The power supply circuit 21 is AC100.
An input filter that removes noise included in a commercial AC power supply of V, a rectifier circuit that converts the input AC into DC, a switching unit that converts the DC of the rectifier into high-frequency AC, and a high-frequency AC specified. It is composed of a conversion transformer for converting to a voltage and a known DC power supply circuit such as a rectifying / smoothing circuit for rectifying the AC output of the conversion transformer to convert it into a smooth DC.

This charging circuit detects the charging current, a constant voltage / constant current charging circuit 22 that controls the charging voltage and charging current of the secondary battery B by adjusting the output of the power supply circuit 21, and the arithmetic circuit 23. A current detection circuit 24, a voltage detection circuit 25 for detecting the battery voltage, a charge control switch SW1 connected between the power supply circuit 21 and the secondary battery B, and a discharge resistor connected in parallel to the secondary battery B. 26 and discharge control switch S
And a discharge circuit of W2.

The constant voltage / constant current charging circuit 22 has two transistors 29 and 30 forming a constant current circuit, a differential amplifier 31 connected to the base of the transistor 29, and a + input terminal of the differential amplifier 31. Second voltage V2 connected
(For example, 4.5 V). The differential amplifier 31 is
The base voltage of the current control transistor 29 is controlled to limit the charging voltage so that the charging voltage does not exceed the second voltage V2.

The arithmetic circuit 23 comprises a microcomputer. The arithmetic circuit 23 calculates the outputs of the current detection circuit 24 and the voltage detection circuit 25, which are A / D converters, detects the state of charge of the secondary battery B, and performs on / off control of the charge control switch SW1 and the discharge control switch SW2. Then, the secondary battery B is subjected to pulse charging and pulse discharging. In order to control the time of these pulse charge and pulse discharge, the arithmetic circuit 2
3 includes a timer circuit (not shown).

An embodiment of the charging method of the present invention will be described below.
This will be described with reference to the flowchart of FIG. 3 and the graph of FIG.

In steps S1 to S4, the charge control switch SW1 is turned on, and the charge voltage of the secondary battery B is regulated to the second voltage V2 (4.5V). In other words,
Make sure that the battery voltage of the secondary battery B does not exceed the second voltage V2, and set the secondary battery B to 1 for the set time T1 (80 msec).
Pulse charging is performed with a constant current of C to 3C.

In step S5, when the set time T1 has elapsed, the charge control switch SW1 is turned off to interrupt the pulse charging of the secondary battery B.

In steps S6 to S8, the discharge control switch SW2 is turned on, and during the set time T2 (10
msec), the secondary battery B is pulse-discharged. Therefore, even if the battery voltage of the secondary battery B exceeds the protection voltage of the protection circuit 1 due to the above-mentioned pulse charging, the battery voltage of the secondary battery B rapidly rises to the protection voltage due to the pulse discharge. Fall below. That is, the battery voltage of the secondary battery B does not exceed the protection voltage for more than 100 msec in which the protection circuit 1 operates.

In steps S9 to S12, the discharge control switch SW2 is turned off to interrupt the pulse discharge of the secondary battery B, and after the set time T3 (10 msec) has elapsed, the battery voltage of the secondary battery B is measured. This battery voltage indicates an open circuit voltage, and it is possible to measure the battery voltage of the secondary battery that is not affected by the internal resistance of the secondary battery B, the contact resistance of the mounting portion of the battery pack P, and the like.

In step S13, it is determined whether or not the measured battery voltage of the secondary battery B has reached the set voltage V1 (that is, 4.1V which is the full charge voltage).
If the set voltage V1 has not been reached yet, the process returns to step S2, and thereafter, the processes of pulse charging, pulse discharging, and battery voltage detection are repeated.

When the battery voltage reaches the set voltage V1, full charge detection is performed in step S14, and the charging operation of the secondary battery B ends. After the full charge is detected,
Instead of immediately ending the charging of the secondary battery B, the constant voltage charging may be performed at the set voltage V1, and the charging may be ended after the elapse of a predetermined time or after the charging current becomes a predetermined value or less.

[0023]

According to the present invention, when the battery voltage of the secondary battery exceeds a protection voltage higher than a first voltage which is a full charge voltage of the secondary battery for a certain set time or longer, the secondary battery is charged. A method of charging a secondary battery having a protection circuit for stopping, wherein the step of pulse-charging the secondary battery for a time shorter than the set time, and the battery voltage of the secondary battery exceeding the set time is A step of pulse-discharging the secondary battery so as not to exceed a protection voltage; a step of temporarily suspending charging / discharging of the secondary battery to detect the voltage of the secondary battery;
Since it comprises a step of controlling the charging of the secondary battery based on the detection result, a secondary battery having a protection circuit for stopping the charging of the secondary battery when the battery voltage exceeds a protection voltage, Rapid charging can be performed without stopping the charging due to the operation of the protection circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a battery pack to be charged according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing an embodiment of the present invention.

FIG. 4 is a graph partially showing a battery voltage and a charging current of a secondary battery charged according to an embodiment of the present invention.

[Explanation of symbols]

 P pack battery B secondary battery 1 protection circuit 21 DC power supply 22 constant voltage / constant current charging circuit 23 arithmetic circuit 26 discharge resistance SW1 charge control switch SW2 discharge control switch

Claims (2)

[Claims] 1. A protection circuit for stopping the charging of the secondary battery when the battery voltage of the secondary battery exceeds a protection voltage higher than a first voltage which is a full charge voltage of the secondary battery for a certain set time or more. A method of charging a secondary battery comprising: a step of pulse-charging the secondary battery for a time shorter than the set time, and the battery voltage of the secondary battery exceeds the protection voltage over the set time. So that the secondary battery is pulse-discharged, a step of temporarily suspending charging / discharging of the secondary battery to detect the voltage of the secondary battery, and the secondary battery based on the detection result. And a step of controlling charging of the battery. 2. The secondary battery according to claim 1, wherein the pulse charging is performed by constant current charging such that the battery voltage of the secondary battery does not exceed a second voltage higher than the protection voltage. Charging method.