JP2903954B2 - Rechargeable battery charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for a sealed secondary battery such as a nickel-cadmium battery and a nickel-hydrogen battery.

[0002]

2. Description of the Related Art Conventionally, in charging a secondary battery, a constant current method in which charging is performed at about 0.1 to 1.0 C with a constant current or a constant voltage is generally performed. In this charging method, a long time is required for charging. Therefore, in recent years, rapid charging with a constant current of 1.0 C or more has become mainstream. There was a disadvantage that the electrode active material was quickly deteriorated due to liquid leakage and heat generation.

Further, as disclosed in Japanese Patent Application Laid-Open No. 64-81628, there is a charging method in which charging is performed with a constant current having a pulse waveform, gas generation due to charging is reduced, and charging efficiency is improved.

[0004]

However, when a secondary battery is charged by rapid charging in an environment with a high ambient temperature, a large current is supplied to the battery in order to increase the charging speed. And the temperature of the secondary battery rises to a dangerous temperature, and a dangerous state occurs such as leakage of the secondary battery. Conversely, in an environment where the ambient temperature is low, the internal pressure of the secondary battery tends to increase, and the terminal voltage tends to increase. If charging is performed with a charging current similar to that at normal temperature in such a state, normal charging may not be performed and battery leakage may occur, or the life of the secondary battery may be shortened.

In the charging of the pulse waveform disclosed in Japanese Patent Application Laid-Open No. 64-81628, the ambient temperature and the secondary battery temperature are not taken into consideration. Since the calorific value is very large, there is a risk that the battery may generate heat so that it cannot be held by hand. Therefore, in the case of a secondary battery that generates a large amount of heat, such as a nickel-metal hydride battery,
It is necessary to monitor temperature detection information with a temperature detecting element such as a thermistor attached to the battery.

SUMMARY OF THE INVENTION An object of the present invention is to provide a charging device for a secondary battery which does not cause a dangerous state or shorten the life of the secondary battery even when the ambient temperature is high or low. To provide.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a charging device for charging a chargeable / dischargeable secondary battery with a current having a pulse waveform, which measures the temperature of the secondary battery. In accordance with the battery temperature measured by the measuring means, the charging is performed by changing the duty ratio and the current value of the pulse, and the charging is performed with the charging current and the duty ratio according to the battery temperature. Thus, the battery can be safely and optimally charged according to the state of the battery without putting the battery in a dangerous state during charging.

[0008]

According to the above-mentioned measures, it is possible to always provide optimal charging regardless of the change of the ambient temperature and the state of the battery, and to provide a charging device which can suppress the rise in the battery internal pressure and the battery temperature.

[0009]

An embodiment of the present invention will be described. FIG. 1 is a block diagram of the present invention. In the figure, 1 is a DC power supply,
2 is a secondary battery to be charged, 3 is a battery temperature measuring unit, 4 is a switch means inserted in series in a constant current circuit, and 5 is a control device. The temperature measuring unit 3 is a temperature detecting element such as a thermistor, and measures the battery temperature of the secondary battery.
Based on the detection, the microcomputer of the control device 5 turns on the switch means 4 (for example, a transistor).
/ OFF control to control the DC power supply 1. The change in pulse width due to battery temperature (or battery temperature change)
ON / OF from microcomputer to transistor
This is performed by outputting the F signal. The change in the current value due to the battery temperature change (or the battery temperature) changes the current value by controlling the transistor and changing the resistance value, for example, as shown in FIG.

FIG. 3 is a characteristic diagram showing a pulse waveform current, has a positive pulse waveform as shown in the figure, and repeats charging ON / OFF at predetermined time intervals. These charging ON and O
The relationship of the FF, the duty ratio _{Q = t on / (t on} + t
_off ), 0 <Q <1, and for the purpose of shortening the charging time, it is preferable to set the value as close to 1 as possible.

However, when a nickel cadmium battery or a nickel hydride battery is charged, gas generation and a rise in battery temperature occur. These lower the charging efficiency. In particular, at low temperatures, the internal pressure of the battery becomes higher than at high temperatures. Therefore, it is preferable to provide a gas absorption time by extending the charge OFF time, and as shown in FIG. It is preferable to reduce the ratio Q and conversely, at high temperatures, shorten the charge OFF time and increase the duty ratio Q. However, increasing the duty ratio Q increases the temperature rise because charging OFF time is shortened. Therefore, the duty ratio Q needs to be set in accordance with the battery in consideration of charging efficiency.
FIG. 4 shows the relationship between the duty ratio Q and the discharge capacity when the charge amount is constant. When the temperature exceeds 0.65 at a low temperature of 10 ° C. or less, gas diffusion is insufficient and the discharge capacity decreases. Also, when the charge is ON at 0.50 or less, the charge is turned OFF
It is not appropriate because the time is long. FIG. 5 shows the relationship between the discharge capacity, the duty ratio Q, and the temperature rise when the charge amount at a high temperature of 40 ° C. or higher is kept constant. At 40 ° C. or higher, gas generation is smaller than at lower temperatures, and the value of the duty ratio Q can be close to 1. However, if it exceeds 0.95, the battery temperature becomes too high in the fully charged state, so that the battery temperature is not more than 0.15.
Although it is necessary to set the temperature to 95 or less, it is not necessary to set the temperature to 0.85 or less because the temperature rise is small.
5 <Q ≦ 0.95 is appropriate. Battery temperature is 10-40
At the time of ° C., the duty ratio Q is 0.65 <Q ≦ 0.85. The duty ratio Q is increased or decreased within this range depending on conditions such as the type and history of the secondary battery and the charging current.

As the secondary battery is charged, the battery temperature rises at the end of charging. This is because when near full charge, oxygen is generated at the anode of the battery and the oxygen undergoes a recombination reaction at the cathode, generating reaction heat and adding to the heat generated by the specific resistance of the battery, causing the battery temperature to rise rapidly. It is. Therefore, at the end of charging, the charging current is reduced according to this temperature change. FIG. 6 is a diagram showing a rise in battery temperature when charged from an ambient temperature of 20 ° C. When charging is performed at a constant charge current, the battery temperature changes by 40 ° C. or more at the end of charging, and the battery becomes high temperature, A problem occurs with the life. Therefore, the charging current is reduced as the battery temperature rises. FIG. 7 is a diagram showing a temperature rise when the charging current is reduced along with charging. When the battery temperature rises from 10 to 20 ° C., the charging current is increased to 100% (1%). 0.0 to 5.0 CmA)
%, The temperature rise can be halved. If the temperature rise exceeds 20 ° C.
By setting it to 90%, the temperature rise can be suppressed to less than half. As a result, a sharp rise in the battery temperature and the battery internal pressure can be suppressed. The charging current also increases and decreases within this range depending on conditions such as the type and history of the secondary battery and the charging current.

FIG. 8 shows that as the temperature rises due to charging,
FIG. 5 is a diagram illustrating a rise in battery temperature when a duty ratio Q is changed. When the change in the battery temperature is in the range of 10 to 20 ° C., the temperature rise can be suppressed to に よ り by setting the duty ratio Q to 0.80, and the change in the battery temperature becomes 2%.
In the range of 0 to 40 ° C., the temperature rise can be reduced to ℃ or less by setting the duty ratio Q to 0.80 or less. When the change in the battery temperature exceeds 40 ° C., the duty ratio Q is set to 0.40 and the charge OFF time is lengthened, so that the battery temperature can be suppressed from increasing and charging can be performed.

FIG. 9 is a diagram showing the battery temperature associated with charging. At the end of charging, the battery temperature rises sharply. In particular, when the battery is charged at a high temperature of 40 ° C., the temperature immediately exceeds 70 ° C., which affects the performance of the battery. Therefore, when the battery temperature is 5
When the temperature exceeds 0 ° C, the charging current is set to 100% at the start of charging.
By setting it to 50% of (1 to 5 CmA), charging can be performed while suppressing a temperature rise. However, when the temperature exceeds 70 ° C., charging is performed with a small current of 5% or less to prevent deterioration of battery performance. The result of charging a 1100 mAh nickel-metal hydride battery by changing the ambient temperature using the charging device according to the present invention will be described.

FIG. 10 shows the secondary battery temperature and the
FIG. 11 shows the duty ratio of the secondary battery according to the present embodiment.
It shows the change in temperature and the charging current value. For secondary battery temperature
The duty ratio Q is between 0 and 80 ° C as shown in the figure.
Change to 0.50 ≦ Q ≦ 0.95. Also, with charging
The temperature change and current value of the secondary battery
When the change is 10 to 20 ° C., the charging current is the current at the start of charging.
2.7 CmA when を is 3.0 CmA (100%)
(90%) when the battery temperature change is 20-40 ° C
2.25 CmA (75%), battery temperature change is 40 ~
1.5C at 50 ° C mA (50%) above 50 ° C
0%. If the temperature of the secondary battery at the start of charging is 20 ° C
For example, start charging at a duty ratio of 0.70 and start charging.
After that, if the battery temperature rises by 10 ° C to reach 30 ° C,
The electric current is 90% at the start of charging, and the duty ratio Q is 0.5.
80.

Table 1 shows a comparison of the battery temperature, battery internal pressure, and discharge capacity of a 1100 mAh nickel-metal hydride battery which was charged by the charging device according to the present invention while changing the ambient temperature, and which was charged at a constant current. After charging with constant current,
While the battery internal pressure is 10 kg / cm ² or more and the battery temperature rises up to 47 ° C., the charging method according to this charging method has a battery internal pressure of 10 kg / cm ² or less and a maximum battery temperature rise of 18 ° C. There is little increase in battery temperature and battery internal pressure, and 803 in constant current charging even at high temperatures.
mAh and 73% of nominal capacity versus 1035m
Ah and a discharge capacity of 94% of the nominal capacity are obtained, which means that charging efficiency is good and proper charging can be performed.

[0017]

[Table 1]

[0018]

As described above, the secondary battery charging apparatus according to the present invention is configured to charge the secondary battery by changing the duty ratio and the charging current according to the temperature of the secondary battery or the temperature change. The secondary battery can be charged without increasing the internal pressure and battery temperature of the battery, and the industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a circuit diagram of a DC power supply unit.

FIG. 3 is a characteristic diagram showing a pulse waveform current.

FIG. 4 is a diagram showing a relationship between a duty ratio and a discharge capacity when a charge amount is fixed.

FIG. 5 is a diagram showing a relationship between a discharge capacity, a duty ratio, and a temperature rise when a charge amount at a high temperature is fixed.

FIG. 6 is a diagram showing an increase in battery temperature.

FIG. 7 is a diagram showing a temperature rise when a charging current is reduced with charging.

FIG. 8 is a diagram showing a rise in battery temperature when the duty ratio is changed with a rise in temperature due to charging.

FIG. 9 is a diagram showing a battery temperature accompanying charging.

FIG. 10 is a diagram illustrating a duty ratio and a battery temperature according to an embodiment of the present invention.

FIG. 11 is a diagram showing a charging current and a battery temperature in an example according to the present invention.

[Explanation of symbols]

1 is a DC power supply, 2 is a secondary battery, 3 is a temperature measuring unit,
Is a switch means, 5 is a control device, 6 is a DC power supply, and 7 is a microcomputer.

Claims (2)

(57) [Claims] 1. A charging device for charging a secondary battery with a current having a pulse waveform, comprising a temperature measuring means for measuring the temperature of the secondary battery, wherein the battery temperature measured by the temperature measuring means is 10 ° C. or less. At time, the duty ratio Q is set to 0.
50 ≦ Q <0.65, 0.65 ≦ Q <0.85 when the battery temperature is 10 to 40 ° C., and 0.85 when the battery temperature is 40 ° C. or higher.
<Q ≦ 0.95, and when the change in the battery temperature measured by the temperature measuring means is 10 to 20 ° C., the charging current is increased by 100% (1.0 to 1.0%).
5.0% when the battery temperature change is 20 to 40 ° C, and 50% or less when the battery temperature change is 40 ° C or higher. Charging device for a secondary battery. 2. When the change in battery temperature measured by the temperature measuring means is 10 ° C. to 20 ° C., the duty ratio Q
To 0.80, 0.80>Q> 0.40 when the battery temperature change is 20 to 40 ° C., to 0.40 when the battery temperature change is 40 ° C. or more, and When the battery temperature measured by the measuring means is 50 to 70 ° C., the current value of the pulse is set to 100% (1.0 to 5.
5% when the temperature is 70 ° C. or more.
The charging device for a secondary battery according to claim 1, wherein the charging device is changed as follows.