JPH09163624A - Secondary battery charging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten charging time without lowering battery performance by storing a voltage value to temperature-compensate for a set voltage into a constant-current constant-voltage charging circuit as the sets of temperature compensation voltage values and selecting an optimal temperature compensation voltage value for the property of matter of a secondary battery to perform constant-current constant-voltage charging. SOLUTION: In a constant-current constant-voltage charging circuit 2, a central control Part 2B is Provided with a memory for storing the sets of optimal temperature compensation voltage values for the property of matter of a battery. The property of matter of a battery is determined on the basis of a signal inputted from a detecting part 7 of the property of matter of a battery or information inputted from a battery to select an optimal temperature compensation value. A charging control part 2A is controlled on the basis of the temperature compensation value and the respective information inputs from a voltage detecting part 3, a current detecting part 4, a temperature detecting part 5 and a timer part 6 to perform constant-current constant-voltage charging. Therefore, various secondary batteries can be fully charged in a short time without lowering the performance.

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 such as a nickel-cadmium battery, a nickel-hydrogen battery and a lithium ion secondary battery.

[0002]

2. Description of the Related Art Nickel-cadmium batteries and nickel-
Hydrogen batteries can be fully charged by constant current charging. When this type of battery is charged with constant current, the battery voltage rises to the peak voltage and then decreases by ΔV.
Fully charged by detecting V drop. However, in the case of a lithium ion secondary battery, the battery voltage increases as it is charged. Since this battery does not have the property of decreasing the battery voltage even when it is fully charged, it is not possible to detect the decrease of the battery voltage by ΔV like a nickel-cadmium battery to detect the full charge. Further, the lithium-ion secondary battery has an adverse effect that the battery performance is significantly deteriorated when the battery voltage is abnormally increased due to overcharge. Therefore, the lithium-ion secondary battery cannot be fully charged by constant current charging, but is fully charged by constant voltage charging.

As described above, the nickel-cadmium battery and the nickel-hydrogen battery are charged with constant current to be fully charged, and the lithium-ion secondary battery is charged with constant voltage to be fully charged. Therefore, the lithium-ion secondary battery cannot be charged by the nickel-cadmium battery charging method in which constant current charging is performed. However, if the charging method is a constant-current constant-voltage charging method that charges the battery by limiting the maximum value of the charging voltage and the maximum value of the charging current, both the nickel-cadmium battery and the lithium-ion secondary battery are fully charged. it can. However, nickel
Cadmium batteries and lithium ion secondary batteries have considerably different battery voltages, so for example, a pack battery in which three nickel-cadmium batteries are connected in series and one lithium ion secondary battery have the same set voltage. Needs to be charged.

A method for charging a battery with a constant current and a constant voltage is described in Japanese Utility Model Laid-Open No. 5-060146. Further, the charging method described in this publication temperature-compensates a set voltage for constant voltage charging. Batteries have a large internal resistance when the ambient temperature is low. In order to compensate for the voltage drop due to the large internal resistance, the battery is charged at a constant voltage with a high set voltage when the ambient temperature is low. When the battery is charged by this charging method, the voltage and current curves change as shown in FIG. In the charging method shown in this figure, as shown in FIG. 2, the set voltage for constant voltage charging at 50 ° C. is set to 4.2 V, and the set voltage at 0 ° C. is 4.4 V, which is increased by 0.2 V. Since the battery at 0 ° C. has a larger internal resistance than the battery at 50 ° C., the set voltage can be increased and the time for constant current charging can be lengthened as shown in the figure. Therefore, when the battery is charged at a low ambient temperature, the time for constant current charging of the battery can be lengthened and the time until full charge can be shortened. 0 to
In the range of 50 ° C., the temperature can be compensated by linearly calculating the set voltage as shown in FIG.

[0005]

However, it is difficult to further shorten the charging time of the battery by this method. This is because if the set voltage is further increased in order to shorten the time for full charge, the charging current of the battery having a high temperature and a small internal resistance does not decrease, and the battery performance is significantly decreased.

The present invention was developed for the purpose of further shortening the charging time without lowering the battery performance.

[0007]

In the secondary battery charging method of the present invention, the constant voltage and constant voltage charging circuit 2 controls the maximum voltage and the maximum charging current of the secondary battery to be charged. Furthermore, the charging method of the present invention performs temperature compensation on the set voltage that limits the maximum voltage of the secondary battery for charging.

Further, in the charging method of the present invention, the voltage value for temperature-compensating the set voltage is stored in the constant-current constant-voltage charging circuit 2 as a plurality of sets of temperature-compensating voltage values, and the constant-current constant-voltage charging circuit 2 stores the voltage value. It is characterized in that the temperature compensation voltage value that is most suitable for the physical properties of the secondary battery is selected and charging is performed with constant current and constant voltage.

Further, in the method for charging a secondary battery according to the second aspect of the present invention, the life of the secondary battery charged by the constant current / constant voltage charging circuit 2 is a new battery or an old battery. Or), the optimum temperature compensation voltage value is selected according to any one of the battery capacity, the battery type, and the battery charging characteristics to fully charge the battery.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify a charging method of a secondary battery for embodying the technical idea of the present invention, and the present invention does not specify the charging method as the following method.

FIG. 3 shows voltage-current characteristics for charging a secondary battery by the method according to the embodiment of the present invention. The charging method in this figure shows voltage characteristics for charging a lithium-ion secondary battery. However, the rechargeable secondary battery is not specified as a lithium ion secondary battery. For example, a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery can be charged in the same manner. However, since the nickel-cadmium battery and the nickel-hydrogen battery have low voltages, they are made into a pack battery in which three batteries are connected in series. The following embodiment shows a method of charging one lithium-ion secondary battery and three nickel-cadmium batteries and a nickel-hydrogen battery, but the conditions of constant current constant voltage charging are as follows: Set the optimum value according to the battery type, number of series connections, and capacity.

The charging method shown in FIG. 3 is a charging method for limiting the maximum values of the charging current and the charging voltage, that is, a method of charging the secondary battery with constant current and constant voltage. The secondary battery, which is charged with a constant current and a constant voltage, compensates the set voltage at the ambient temperature. As shown by the arrow in FIG. 3, the set voltage is corrected to be high when the ambient temperature is low and low when the ambient temperature is high.

The correction value of the set voltage with respect to the ambient temperature is shown in FIG.
Shown in The set voltage is determined as a function of temperature. The set voltage can be compensated not only by the temperature but also by the physical properties of the secondary battery. The physical properties of a battery are the type of battery,
It is the life of the battery, the capacity of the battery, the charging characteristics of the battery, and the like.
A plurality of temperature compensation voltage values as a function of temperature are stored in the charger to change the temperature compensation voltage value according to the physical properties of the secondary battery. FIG. 4 shows A, A1, B, B1, C, C.
The functions of eight types of temperature compensation voltage values of 1, D, and D1 are shown. These functions are stored in the charger of the secondary battery, and the optimum temperature compensation voltage value is selected depending on the secondary battery to be charged. Table 1 shows temperature compensation voltage values of the batteries A to D with respect to the ambient temperature.

[0014]

[Table 1]

In FIG. 4, the functions A to D are selected for the following secondary batteries. A ………… 3HR-AAAU (Sanyo nickel-hydrogen battery) A1 ………… A old battery B ………… 3HR-AAA (Sanyo nickel-hydrogen battery) B1 ………… B old battery C ... US18650 (Lithium-ion secondary battery made by Sony) C1 ......... C old battery D ......... UR18650 (lithium-ion secondary battery manufactured by Sanyo) D1 ......... D battery old What

FIG. 4 is for identifying the optimum temperature compensation voltage value based on the battery type, battery capacity, battery life, and the like. In the charging method of the present invention, the optimum temperature compensation voltage value can be selected, for example, when charging the secondary battery with constant current and constant voltage, with the time of constant current charging as the physical property of the battery. In this method, for example, when the time for constant current charging becomes short, it is determined that the battery is old and the temperature compensation voltage value is compensated high.

In order to select the optimum temperature compensation voltage value depending on the physical properties of the battery to be charged, it is necessary to specify the physical properties of the battery to be charged. The easiest way is
This is a method in which a charger is provided with a battery physical property detection unit such as a changeover switch or a changeover button, and when charging, the physical property of the secondary battery is manually selected by switching over the switch or the changeover button of the battery physical property detection unit. Further, as the battery physical property detection unit, it is possible to provide the mounted battery with unevenness and detect the unevenness to specify the capacity, type, etc. of the battery. This method is suitable for a method in which the battery is used as a battery pack in a case. Furthermore, a storage circuit that stores the physical properties of the battery can be incorporated in the secondary battery. In this secondary battery, the information stored in the memory circuit at the start of charging is read by the charger, the physical properties of the secondary battery are specified by the read information, and the optimum temperature compensation voltage value is selected. In this method, the charger does not need to manually select the physical properties of the battery, but the charger automatically selects the optimum temperature compensation voltage value. further,
It is also possible for the charger to calculate changes in charging current and charging voltage to specify physical properties of the battery, select an optimum temperature compensation voltage value for the specified battery, and charge the battery.

When the set voltage for charging the secondary battery is set high, the chargeable capacity can be increased and the energy capacity can be increased. However, if the set voltage is too high, the battery performance will be degraded. Therefore, the set voltage is adjusted to an optimum value in consideration of the physical properties of the battery and the ambient temperature.

Further, in the charging method of the present invention, the set voltage can be switched during charging. It is possible to set a high voltage first to lengthen the time for constant current charging to shorten the entire charging time, and then lower the set voltage to fully charge the battery without degrading the battery performance. In this charging method, first, the maximum voltage of the battery is set to the first set voltage, the secondary battery is charged with a constant current and constant voltage, and when the battery voltage reaches the first set voltage, the battery is switched to the second set voltage and set to the constant voltage. Charge with constant current. This charging method uses the second set voltage
Fully charged as the optimum temperature compensation voltage value depending on the ambient temperature and the physical properties of the battery.

In this charging method, as shown in FIG. 5, the battery voltage is initially equal to or lower than the first set voltage, so that constant current charging is performed. The battery voltage rises as the charging progresses, and when the battery voltage reaches the first set voltage, the maximum voltage of the battery is changed to the second voltage.
Since the voltage is switched to the set voltage, the constant current charging can be switched to the constant voltage charging.

In the charging method of this figure, the switching timing for switching the set voltage from the first set voltage to the second set voltage is
It is assumed that the battery voltage rises to the first set voltage. The switching timing can be determined not only by the battery voltage but also by detecting the charging current or by detecting the battery temperature. The method of detecting the charging current and determining the switching timing is such that when the charging current becomes equal to or less than the setting current, the setting voltage is set to the first value.
The set voltage is switched to the second set voltage. The set current for specifying the switching timing is preferably smaller than the charging current for constant current charging the secondary battery, but is set to a current value substantially equal to the current value for constant current charging.

If the maximum voltage of the secondary battery is set to the first set voltage and the battery is charged with constant current and constant voltage, the battery voltage is limited to the first set voltage when the battery voltage rises to the first set voltage. The charging current gradually decreases. Therefore, the charging current can be detected and the first set voltage can be switched to the second set voltage. Furthermore, when the secondary battery is charged, the battery temperature also rises. Therefore, it is possible to detect the battery temperature and switch the set voltage from the first set voltage to the second set voltage.

In the charging method shown in FIG. 5, the first set voltage is fixed and the second set voltage is changed to a temperature compensation voltage value which is optimum for the ambient temperature and physical properties of the battery. Since this method does not change the first set voltage, it has a feature that the secondary battery can be fully charged with a simple circuit. However, in this charging method, the first set voltage can also be changed depending on the ambient temperature of the battery. For example, the first
The set voltage can be set to be 0.3 to 1.0 V higher than the second set voltage.

FIG. 6 shows a circuit for charging the secondary battery as described above. The charging circuit shown in this figure includes a power supply 1 for converting an input alternating current into a voltage capable of charging a secondary battery,
A constant current constant voltage charging circuit 2 that adjusts the output of the power source 1 to charge the secondary battery with a constant current constant voltage, and a voltage detection unit 3 that inputs the battery voltage of the secondary battery to the constant current constant voltage charging circuit 2.
A current detection unit 4 for detecting the charging current of the secondary battery and inputting it to the constant current / constant voltage charging circuit 2, a temperature detection unit 5 for detecting the ambient temperature, and a timer unit for controlling the charging time of the secondary battery. 6 and 6.

Although not shown, the power supply 1 includes a diode bridge that rectifies an input alternating current and converts it into a direct current, and a smoothing circuit of an electrolytic capacitor that smoothes an output of the diode bridge. The power supply 1 is a DC-DC that converts input AC into DC, converts DC into AC, and steps down the voltage.
A converter can also be used.

The constant current / constant voltage charging circuit 2 includes a charging control section 2A for controlling the charging state of the secondary battery, and this charging control section 2
A central control unit 2B that controls A and a battery physical property detection unit 7 that detects physical properties of the battery are provided. The central control unit 2B has a built-in microprocessor. Further, the central control unit 2B includes a memory (not shown) that stores a plurality of sets of temperature compensation voltage values that are optimal for the physical properties of the battery. The central control unit 2B calculates a battery voltage and a charging current input from the voltage detection unit 3 and the current detection unit 4 and a signal input from the battery physical property detection unit 7 to control the charging control unit 2A and charge control. The output voltage and the output current are adjusted by the unit 2A, the secondary battery is set to the optimum temperature compensation voltage value, and the constant current and constant voltage are charged.

The constant current / constant voltage charging circuit 2 determines the physical properties of the battery by the signal input from the battery physical property detection unit 7 or the information input from the battery, and the central control unit 2B determines the optimum physical property of the battery. The temperature compensation voltage value is selected to control the charging control unit 2A to fully charge the secondary battery. Further, the constant current / constant voltage charging circuit 2 sets the maximum voltage of the battery to the first set voltage and performs constant current / constant voltage charging, and when the battery is charged to a predetermined capacity, sets the set voltage to the first set voltage. Can also be switched to the second set voltage for constant current constant voltage charging.
This charging method specifies the physical properties of the battery from the charging time by limiting the maximum value of the battery voltage to the first set voltage, selects the temperature compensation voltage value that is optimal for the specified physical properties of the battery, and 2 Fully charged as a set voltage.

The voltage detector 3 detects the battery voltage, converts the detected battery voltage into a digital value, and inputs it to the central controller 2B. The current detector 4 detects the charging current of the battery,
It is converted into a digital value and input to the central controller 2B. The temperature detector 5 detects the ambient temperature of the secondary battery, converts the detected temperature into a digital value, and inputs it to the central controller 2B. The temperature detector 5 can also detect both the ambient temperature and the battery temperature and input them to the central controller 2B. The voltage detection unit 3, the current detection unit 4, and the temperature detection unit 5 detect the detected voltage and current,
An A / D converter for converting an analog temperature signal into a digital signal is incorporated (not shown).

The timer section 6 stores the total time for charging the secondary battery. The timer unit 6 starts counting when charging is started. When the timer unit 6 finishes counting, the central control unit 2B controls the charging control unit 2A to finish charging the secondary battery. The timer unit 6 can also store the switching timing for switching the set voltage from the first set voltage to the second set voltage. The timer unit 6 is the first
The charging method that determines the timing of switching from the set voltage to the second set voltage is suitable for, for example, a method of detecting whether or not the secondary battery has been sufficiently discharged and fully charging it.
This is because it takes a certain amount of time for the battery voltage of the fully discharged secondary battery to rise to the first set voltage. The switching timing stored in the timer unit 6 is set to a time that does not have a bad influence when the set voltage of the secondary battery is set to the first set voltage, for example, 10 minutes to 1 hour.

[0030]

The secondary battery charging method of the present invention is characterized in that it can prevent the performance of various secondary batteries from deteriorating and can be fully charged in a short time. This is because the charging method of the present invention not only compensates the set voltage for constant current / constant voltage charging with temperature, but also compensates this set voltage to a voltage value optimal for the physical properties of the battery. According to the charging method of the present invention, the temperature compensation voltage value most suitable for the physical properties of the battery is stored in the constant current / constant voltage charging circuit.
The constant current constant voltage charging circuit selects a temperature compensation voltage value that is most suitable for the battery to be charged and charges the battery. This method is for batteries with different manufacturing methods and electrode materials, lithium-ion secondary batteries, nickel-hydrogen batteries, nickel-cadmium batteries, or new batteries and old batteries to be fully charged in near ideal conditions in a short time. It is possible to realize extremely excellent features. Furthermore, the charging method of the present invention, like a lithium ion secondary battery, requires a high battery voltage in order to increase energy efficiency, but even in a battery in which a bad effect occurs when the battery voltage is set high, Each battery can be charged by setting the optimum temperature compensation voltage value. Therefore, it has a feature that it can be used in a high energy efficiency state without deteriorating the battery performance.

[Brief description of the drawings]

FIG. 1 is a voltage when a secondary battery is charged by a conventional method,
Graph showing time variation of current characteristics

FIG. 2 is a graph showing changes in set voltage for constant current constant voltage charging.

FIG. 3 is a graph showing voltage-current characteristics for charging a secondary battery with a constant current and a constant voltage by the method according to the embodiment of the present invention.

FIG. 4 is a graph showing changes in set voltage for charging a secondary battery by the method according to the embodiment of the present invention.

FIG. 5 is a graph showing voltage-current characteristics for charging a secondary battery with a constant current and a constant voltage by a method according to another embodiment of the present invention.

FIG. 6 is a block circuit diagram of a charging circuit used in the method according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power supply 2 ... Constant current constant voltage charging circuit 2A ... Charge control part 2B ... Central control part 3 ... Voltage detection part 4 ... Current detection part 5 ... Temperature detection part 6 ... Timer part 7 ... Battery physical property detection part

Claims (2)

[Claims] 1. A set voltage (2) for limiting the maximum voltage of the secondary battery while controlling the maximum voltage and the maximum charging current of the secondary battery to be charged by the constant current / constant voltage charging circuit (2) for charging. In the method of charging with temperature compensation, the voltage value for temperature compensation of the set voltage is stored in the constant-current constant-voltage charging circuit (2) as multiple sets of temperature-compensated voltage values, and is optimized depending on the physical properties of the secondary battery to be charged. A method for charging a secondary battery, comprising: selecting a temperature-compensated voltage value according to 1 above, and performing constant-current constant-voltage charging. 2. The secondary battery according to claim 1, wherein the physical property of the battery for selecting the optimum temperature compensation voltage value is any one of battery life, battery capacity, battery type, and battery charging characteristics. How to charge the battery.