JPH11187585A - Charger and charging method for lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the charging capacity accurately during charging operation regardless of fluctuation in the charging characteristics due to battery temperature or C rate of charging current and to notify the detected charging capacity to a user. SOLUTION: A charger for lithium ion secondary battery comprises means 4 for detecting the charging current of a battery being supplied with a charging current from a power supply section 7, means 5 for detecting the charging voltage of the battery, means 8 for detecting the battery temperature, means 6 for controlling constant current charging operation and constant voltage charging operation of battery, means 10 for detecting the charging capacity of the battery based on the charging current and voltage detected by the means 4, 5, and means 11 for indicating the charging capacity detected by the means 10. The charging capacity detecting point of the means 10 is altered depending on the battery temperature detected by the means 8 and indicated on the means 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery charger and a charging method for use in portable equipment such as portable radio equipment.

[0002]

2. Description of the Related Art In recent years, as a power source for a portable device whose size and weight have been rapidly reduced, a lithium ion secondary battery of small size, light weight and high energy density has been actively developed and widely used. .

As a charging method for a battery pack provided with such a lithium ion secondary battery, 4.1 V per cell is used.
Alternatively, a method is generally used in which a 4.2V constant current / constant voltage charge is performed, the charge voltage and the charge current are monitored by a CPU or the like, and the charge is stopped when the charge current decreases to a specified value.

When a battery pack is charged by such a charging method, as a method of detecting a charging capacity during charging, for example, as disclosed in JP-A-6-225466, a constant value is determined by a comparator. There has been known a method of detecting by a charging voltage in a current period and detecting by a charging current in a constant voltage period.

[0005]

However, the charging characteristics of a lithium ion secondary battery vary greatly depending on the battery temperature or the C rate of the charging current during a constant current period. Therefore, the charging capacity displayed by the above method and the actual charging capacity greatly differ depending on the battery temperature during charging and the C rate of the charging current, and there is a possibility that an accurate charging capacity cannot be displayed to the user. .

This point will be described with reference to the drawings. FIG. 5 is a characteristic diagram showing a relationship between a charging capacity detection point due to a difference in battery temperature according to a conventional charging method and a charging capacity at the time of detection.

FIG. 5 shows, as an example, a case where the detection is performed when the charged capacity reaches 50% and 80% of the full charge. However, as shown in FIG. Based on the charging characteristics at a battery temperature of 20 ° C., 50% is detected from a constant voltage value, and 80% is detected from a constant current value. When the battery temperature is 5 ° C., 50% is detected. The actual charge capacity is 13% with respect to the display, and in the case of 5 ° C, the actual charge capacity is about 60% with respect to the 80% display.
It can be seen that the display is different from the actual one.

Further, in portable equipment such as portable radios, large-capacity batteries and small-capacity small batteries may be optionally prepared in addition to standard-sized batteries. May be charged.

In such a case, the charging is performed at a different C rate. However, in the case of a lithium ion secondary battery, even if the C rate changes, the charging time until full charge hardly changes, and the charging time is constant. And the ratio of the constant voltage period changes. For example, the larger the C rate, the greater the voltage rise, so that the constant current period becomes shorter and the constant voltage period becomes longer. Therefore, the change characteristic of the charging capacity also differs depending on the C rate.

This point will be described with reference to FIG. FIG. 6 is a characteristic diagram showing the relationship between the charging capacity detection point due to the difference in the C rate and the charging capacity at the time of detection. As shown in FIG.
When a constant value is set based on the charging characteristic at 0.7 C irrespective of the C rate, as shown in FIG. The actual charging capacity is about 83% against the display of about 35% or 80% of the capacity, and the display and the actual charging capacity differ depending on the C rate of the charging current.

In view of such a conventional technique, the present invention is capable of accurately detecting a charging capacity during charging without being affected by a change in charging characteristics due to a battery temperature or a C rate of a charging current. It is an object of the present invention to provide a battery charger and a charging method for a lithium ion secondary battery to be notified to the public.

[0012]

In order to achieve the above object, the present invention detects a charging current and a charging voltage of a battery to be charged, and detects a battery temperature of the battery or a C of the charging current. A rate is detected, and a detection point of a charge capacity detected by the charge current and the charge voltage is changed according to the battery temperature or the C rate, and is displayed.

According to the present invention, the battery temperature and the charging current C
The charging capacity detection point is changed in accordance with the change in the charging characteristics depending on the rate, so that the user can be accurately notified of the actual charging capacity without being affected by the battery temperature or the C rate of the charging current. It becomes possible.

[0014]

According to the first aspect of the present invention, a current detecting means for detecting a charging current of a battery which is supplied with power by a power supply unit and a voltage detecting means for detecting a charging voltage of the battery. Temperature detecting means for detecting a battery temperature of the battery, charging control means for controlling constant current charging and constant voltage charging of the battery, and a charging current detected by the current detecting means and a voltage detected by the voltage detecting means. A charging capacity detecting unit configured to detect a charging capacity of the battery based on a charging voltage; and a charging capacity displaying unit configured to display a charging capacity detected by the charging capacity detecting unit. It is characterized in that the detection point of the charged capacity detected by the charged capacity detecting means is changed and displayed on the charged capacity display means.

As a result, the charging capacity detection point is changed in accordance with the change in the charging characteristics due to the battery temperature, and it is possible to accurately inform the user of the actual charging capacity without being affected by the battery temperature. It becomes possible.

According to a second aspect of the present invention, there is provided a current detecting means for detecting a charging current of a battery which is supplied with power from a power supply and charged, a voltage detecting means for detecting a charging voltage of the battery, and the battery. C rate detecting means for detecting the C rate of the charging current, charging control means for controlling the constant current charging and constant voltage charging of the battery, and the charging current detected by the current detecting means and the voltage detected by the voltage detecting means. A charging capacity detecting means for detecting a charging capacity of the battery based on a charging voltage; and a charging capacity displaying means for displaying a charging capacity detected by the charging capacity detecting means. The present invention is characterized in that a threshold value of the charged capacity detected by the charged capacity detecting means is changed according to a rate and is displayed on the charged capacity displaying means.

As a result, the charging capacity detection point is changed in accordance with the change in the charging characteristics due to the charging current C rate, and the actual charging capacity is accurately used without being affected by the charging current C rate. It is possible to notify the person.

According to a third aspect of the present invention, a charging current and a charging voltage of a battery to be charged are detected, a battery temperature of the battery is detected, and the charging current and the charging voltage are determined according to the battery temperature. The detection point of the charge capacity to be calculated is changed and displayed.

As a result, the charging capacity detection point is changed in accordance with the change in the charging characteristics due to the battery temperature.
It is possible to accurately inform the user of the actual charge capacity without being affected by the battery temperature.

According to a fourth aspect of the present invention, a charging current and a charging voltage of a battery to be charged are detected, a C rate of the charging current is detected, and the charging current and the charging voltage are determined according to the C rate. The threshold value of the charge capacity calculated according to the above is changed and displayed.

As a result, the charging capacity detection point is changed in accordance with the change in the charging characteristics due to the C rate of the charging current, and the actual charging capacity can be accurately determined without being affected by the C rate of the charging current. It is possible to notify the user.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a block configuration of a charger for a lithium ion secondary battery according to Embodiment 1 of the present invention, where P is a battery pack connected to a charging circuit C. , A battery cell 1, a protection circuit 2, a thermistor 3 for detecting the battery temperature of the battery, a plus terminal A, a minus terminal B, and a temperature detection terminal T.

The charging circuit C includes a current detecting means 4 for detecting a charging current of the battery, a voltage detecting means 5 for detecting a voltage between terminals AB of the battery pack P, and a charging for performing constant current and constant voltage charging. Control means 6, power supply section 7 for supplying power to battery pack P via charge control means 6, thermistor 3
Temperature detecting means 8 for detecting the temperature of the battery from the resistance value of
The D converter 9 is built in the CPU for controlling the entire charger, and stores a charge capacity detection point according to each battery temperature. Is provided.

Next, Embodiment 1 configured as described above
Will be described. The charging control means 6
In accordance with the output signals of the current detecting means 4 and the voltage detecting means 5, constant-current and constant-voltage charging of 4.1 V / cell or 4.2 V / cell is performed. Further, the current detecting means 4 and the voltage detecting means 5
The output signal of the temperature detecting means 8 is input to the charge capacity detecting means 10 built in the CPU via the AD converter 9. Then, the charge capacity detection means 10 determines an optimum detection point according to the battery temperature detected by the temperature detection means 8, and detects the charge capacity based on the battery voltage or the charge current.

FIG. 2 is a characteristic diagram showing the relationship between the charging capacity (%) and the charging time (H) when the charging capacity detection point is changed due to the difference in the battery temperature. In FIG. 2, when a discharged lithium ion secondary battery is charged at 20 ° C., the constant current period is reached when the charge capacity is up to about 70% of the full charge, and the constant voltage period is reached when the charge capacity is about 70% or more. Is shown.

Therefore, the charging capacity is detected by the charging voltage during the constant current period of 0 to about 70%, and is detected by the charging current during the constant voltage period of about 70% to 100%. For example, when the user is notified by the charge capacity display means 11 that the battery has been charged to 50% and 80%,
As shown in FIG. 2, at 50%, the charging voltage is detected, and
At 0%, it is detected by the charging current.

However, when a discharged lithium ion secondary battery is charged at 5 ° C., the charging reaction of the battery becomes slow, and therefore, the constant current period is reached up to about 30% of the charged capacity, and the constant current period is reached above about 30%. The voltage period is reached. Therefore, when the charging capacity is 50% and 80%, both are detected by the charging current.

Since the current decreasing characteristic in the constant voltage period also changes depending on the temperature, the current value for detecting the charge capacity of 80% is different from the case of 20 ° C.

(Embodiment 2) FIG. 3 shows a block configuration of a battery charger for a lithium ion secondary battery according to Embodiment 2 of the present invention. The difference is that the identification resistor 12 is built in and the C rate detection means 13 is connected to the capacitance detection means 10, and the other configuration is the same.

In the thus configured charger for a lithium ion secondary battery according to Embodiment 2, the C rate detecting means 13 identifies the rated capacity of the battery to be charged according to the size of the rated capacity identification resistor 12, The C rate of the charging current is detected. Then, the capacity detecting means 10 determines an optimum detection point in accordance with the output signal of the C rate detecting means 13, and detects the charging capacity based on the charging voltage or the charging current.

FIG. 4 is a characteristic diagram showing the relationship between the charging capacity (%) and the charging time (H) when the charging capacity detection point is changed depending on the difference in the C rate of the charging current.

A lithium ion secondary battery having a rated capacity corresponding to a C rate of 0.7 C in a constant current period was charged at 20 ° C. As an example, the user was charged to 50% and 80%. Is detected by the charging voltage at 50% and by the charging current at 80%.

However, in a lithium ion secondary battery having a rated capacity corresponding to a C rate of 1 C in a constant current period, a voltage increasing characteristic and a current decreasing characteristic are different from those of 0.7 C. Therefore, the capacity detection point is changed depending on the rated capacity of the lithium ion secondary battery. When the temperature naturally changes, the charge capacity detecting means 10 changes the detection point according to the temperature change, as in the first embodiment.

[0035]

As described above, according to the present invention, the battery capacity during charging can be accurately detected without being affected by the change in the charging characteristics due to the battery temperature or the C rate of the charging current of the lithium ion secondary battery. Then, it is possible to notify the user.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a charger for a lithium ion secondary battery according to Embodiment 1 of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a charging capacity (%) and a charging time (H) at the time of detection according to a battery temperature.

FIG. 3 is a block diagram showing a configuration of a lithium ion secondary battery charger according to Embodiment 2 of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a charging capacity (%) and a charging time (H) at the time of detection, based on a C rate.

FIG. 5 is a characteristic diagram showing a relationship between a charging capacity (%) and a charging time (H) at the time of detection related to a battery temperature in a conventional charger for a lithium ion secondary battery.

FIG. 6 is a characteristic diagram showing a relationship between a charging capacity (%) and a charging time (H) at the time of detection related to a C rate in a conventional charger for a lithium ion secondary battery.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 battery cell 2 protection circuit 3 thermistor P battery pack 4 current detection means 5 voltage detection means 6 charge control means 7 power supply unit 8 temperature detection means 9 AD converter 10 charge capacity detection means 11 charge capacity display means 12 rated capacity identification resistance 13 C Rate detection means A plus terminal B minus terminal C charging circuit T temperature detection terminal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02J 7/10 H02J 7/10 L // H01M 10/40 H01M 10/40 Z

Claims (4)

[Claims] 1. A current detecting means for detecting a charging current of a battery supplied and charged by a power supply unit, a voltage detecting means for detecting a charging voltage of the battery, and a temperature for detecting a battery temperature of the battery. Detecting means; charging control means for controlling constant current charging and constant voltage charging of the battery; and detecting the charge capacity of the battery based on the charging current detected by the current detecting means and the charging voltage detected by the voltage detecting means. Charging capacity detecting means, and charging capacity displaying means for displaying the charging capacity detected by the charging capacity detecting means, wherein the charging capacity detected by the charging capacity detecting means according to the battery temperature detected by the temperature detecting means. A lithium ion secondary battery charger characterized in that a detection point is changed and displayed on the charge capacity display means. 2. A current detecting means for detecting a charging current of a battery supplied and charged by a power supply unit, a voltage detecting means for detecting a charging voltage of the battery, and a C rate of the charging current of the battery. C-rate detecting means for detecting, charging control means for controlling constant-current charging and constant-voltage charging of the battery, and charging of the battery by charging current detected by the current detecting means and charging voltage detected by the voltage detecting means A charging capacity detecting means for detecting a capacity; and a charging capacity displaying means for displaying a charging capacity detected by the charging capacity detecting means, wherein the charging capacity is determined according to a C rate of the charging current detected by the C rate detecting means. A lithium ion secondary battery charger characterized in that a threshold value of the charge capacity detected by the detection means is changed and displayed on the charge capacity display means. Detecting a charging current and a charging voltage of a battery to be charged, and detecting a battery temperature of the battery;
A charging method in a lithium ion secondary battery charger, wherein a detection point of a charging capacity calculated by the charging current and the charging voltage is changed according to the battery temperature and displayed. 4. A charge capacity threshold calculated by detecting a charge current and a charge voltage of a battery to be charged, detecting a C rate of the charge current, and calculating the charge current and the charge voltage in accordance with the C rate. Is changed and displayed. A charging method in a lithium ion secondary battery charger, characterized in that: