JPH06339234A - Charge controller - Google Patents

Abstract

PURPOSE:To realize optimum charging by deciding a charging pattern at the time of intermittent charging according to a battery voltage, a battery temperature and a charging time when a full charging, the intermittent charging and trickle charging are controlled by a pulse waveform current. CONSTITUTION:A sealed secondary cell 5 is charged by a pulse waveform power source 1 through a switch 2. When charging is started, the cell is fully charged until a battery voltage becomes a predetermined voltage V, and shifted to an intermittent charging. In the intermittent charging, when a pulse output is OFF, a battery voltage V is measured, when it is a set voltage or less, next pulse is turned ON, and when it is the set voltage or higher, next pulse is turned OFF. When a mean charging current is reduced and a variation becomes smaller than a set value, the intermittent charging is finished, and it is shifted to a trickle charging. These controls are conducted by A/D-converting a battery voltage T by an A/D converter 4, and switching the switch 2 by its output by a microcomputer 3. Thus, overcharging due to heat dissipation is prevented, and suitable charging is realized.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a method of charging a secondary battery, a voltage detection method of detecting the battery voltage of the secondary battery and controlling charging has been the mainstream from the past.

In general, the charging current is efficiently and almost fully charged (at a state where the rated charging voltage is reached) during the full charging period by the current, and during the subsequent trickle charging period, the self-discharging amount of the secondary battery is supplemented. From the various viewpoints such as the life of the secondary battery and the charging efficiency, it is considered that the characteristics are ideal. Here, trickle charging refers to a charging method in which a battery is charged with a minute current for the purpose of supplementing the self-discharged portion. Further, there is also one that supplies an intermittent charging current between them.

[0004]

However, depending on the history of the battery and the like, the charging current may gradually increase at the end of charging as shown in FIG. 2, and in such a case, overcharging may occur. is there. An object of the present invention is to provide a charge control device capable of preventing heat runaway in an intermittent charging unit and performing proper charging.

[0005]

In order to solve the above-mentioned problems, the present invention determines the charging in the intermittent charging section by the battery voltage, the battery temperature and the charging time, and performs the optimum charging.

Conventionally, in Japanese Patent Publication No. 59-3105,
A battery voltage detection circuit that detects the battery voltage and intermittent charging is performed when the battery voltage reaches a certain set voltage due to the correlation between the battery voltages, and a pulse is generated by generating a pulse each time the intermittent charging is stopped or restarted. There is proposed a device which counts and when a set number of counts is reached, a timer is activated to completely stop charging after a set time.

The purpose of this device is generally 12 for secondary batteries.
Although the discharge amount of 100 (%) can be obtained by obtaining the charge amount of 0 (%), the charge amount obtained by full charge is 90 to 100%, and the remaining charge of 20 to 30%. The amount is secured, and at the end of charging the secondary battery, 10
In order to secure a discharge amount of 0 (%), overcharge is prevented even in a battery having the characteristics shown in FIG. 2, so that a malfunction does not occur even in a battery having an increased internal resistance. .

However, the battery temperature and the ambient temperature are not taken into consideration, and there is a risk of overcharging or insufficient charging due to heat dissipation. The present invention is a device that monitors a battery voltage, a battery temperature, and a charging time, and controls an amount of charge in an intermittent charging unit to charge a secondary battery. It won't happen.

[0009]

According to the above device, optimum charging can always be performed regardless of changes in the ambient temperature and the state of the battery.

[0010]

EXAMPLES Examples of the present invention will be described. FIG. 1 is a block diagram of the present invention, in which a pulsed power supply 1 for supplying a charging current to a sealed secondary battery 5, a digital-analog converter 4,
Receiving signals of battery temperature and battery voltage of the secondary battery, microcomputer 3 for controlling charging, receiving signals from the microcomputer to turn charging current ON and O
It is composed of a switch 2 for FF.

FIG. 3 is a flowchart of one embodiment.
When charging is started, full charging is performed until the battery voltage reaches the set value V, and intermittent charging is switched. For intermittent charging, the battery voltage when the pulse output is OFF is measured, and if the voltage is below the set voltage, the next pulse output is turned on, and if it is above the set voltage, the next pulse output is turned off. This causes the average charging current to decrease. This current is measured, and when the amount of change in the current becomes smaller than the set value I, the intermittent charging is terminated and trickle charging is started. As a result, the charging current does not gradually increase due to heat escape and overcharging does not occur. The charging current is measured by counting the number of times the pulse current is output. Since V and I have different charging characteristics depending on the type of battery, they are set according to the battery.

FIG. 4 is a flowchart of another embodiment, in which the intermittent charging pattern is 4 depending on the charging time and the battery temperature.
The type is stored in memory. When charging starts, the timer starts, the battery temperature is measured, and the battery voltage starts to be measured. When the battery voltage reaches the set voltage V after starting charging, the battery temperature is measured. Then, the charging pattern for intermittent charging is determined by the charging time from the start of charging to the set voltage and the difference T between the temperature at the start of charging and the temperature at the set voltage, and charging is performed, and after completion, switching to trickle. In the intermittent charging pattern, the time to reach the set voltage is longer than the comparison time, and when the temperature rise of the battery is higher than the set temperature (Pattern 1), the time to reach the set voltage is longer than the comparison time. When the battery temperature rise is lower than the set temperature (Pattern 2), the time to reach the set voltage is shorter than the comparison time, and when the battery temperature rise is higher than the set temperature (Pattern 3), the set voltage is reached. Is shorter than the comparison time and the temperature rise of the battery is lower than the set temperature (pattern 4). Then, the charging current is exponentially reduced by the following equation (1). I = I ₀ e ~ at (1) This is approximated by the following equation (2) and controlled by the microcomputer. I = I ₀ (1-at + 1/2! At ² ) (2) By changing the value of a here, the charge amount can be changed according to the pattern. FIG. 5 shows an example of the intermittent charging pattern. For example, in Expression (2), the value of a is 5 for pattern 1, 1 for pattern 2, 10 for pattern 3, and 0.1 for pattern 4. Further, in the case of patterns 1 and 3 in which the battery temperature is high, the charging current is linearly reduced only by the first-order term of the equation (2) in order to reduce the adverse effect on the battery. As a result, in the case of the pattern 3 in the overcharged state, a short intermittent charge is required, and conversely, in the case of the pattern 4 having a sufficient charge, the intermittent charge can be performed for a long time to compensate for the insufficient charge. By performing intermittent charging according to the state of the battery in this manner, there is no overcharging or insufficient charging, and optimal charging can be performed without adversely affecting the battery. The set voltage V is set according to the type of battery, and the intermittent charging pattern is a straight line, an index,
It can be reduced by two steps.

FIG. 6 is a flowchart of another embodiment. When the sealed secondary battery is charged, as shown in FIG. 7, the amount of change in the battery temperature is larger than that in the battery voltage near full charge, and control is easy to perform. Therefore, the charging at the intermittent charging portion is controlled by the battery temperature. When charging is started, battery temperature measurement is started, and full charging is continued until the battery temperature rises from the start of charging to the set value T. When the set value T is reached, it switches to intermittent charging. Two patterns are prepared for intermittent charging depending on the battery temperature at the end of full charging. In pattern 1, when the battery temperature is low, charging is still possible, the thinning interval is shortened, and charging is pushed in. On the contrary, in the pattern 2, when the battery temperature is high, the thinning interval is increased in order to reduce the adverse effect on the battery due to overcharging, and the charging time is lengthened in order to compensate for insufficient charging at high temperature. For example, in pattern 1, the pulse current output is turned OFF once in 10 times, and when this is repeated 3 times, the output is turned OFF twice, the number of outputs is reduced, and the charging current is reduced. In pattern 2, the pulse output is turned off 5 times out of 10 times, and if this is repeated 10 times, the number of outputs is reduced. As a result, optimum charging can be performed only by the battery temperature. Since the characteristics of the set temperatures T and Ta differ depending on the type of battery,
Set according to the battery.

[0014]

As described above, the present invention intends to charge the secondary battery by monitoring the battery voltage, the battery temperature and the charging time and controlling the charge amount by the intermittent charging section. By performing intermittent charging according to the above, optimum charging can be performed, and the industrial value is extremely great.

[Brief description of drawings]

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

FIG. 2 is a charging characteristic diagram when a sealed secondary battery is charged.

FIG. 3 is a diagram showing a flowchart of one embodiment according to the present invention.

FIG. 4 is a diagram showing a flowchart of another embodiment according to the present invention.

FIG. 5 is a diagram showing an example of a charging pattern of an intermittent charging unit.

FIG. 6 is a view showing a flowchart of still another embodiment according to the present invention.

FIG. 7 is a diagram showing charging characteristics of a sealed secondary battery.

[Explanation of symbols]

1 ... Pulse power supply, 2 ... Switch, 3 ... Microcomputer, 4 ... Analog-digital converter, 5 ... Sealed secondary battery.

Claims (3)

[Claims] 1. A charging control device for charging with a current having a pulse waveform, comparing an instantaneous cutoff voltage during charging with a set voltage, and controlling intermittent charging, trickle charging and charging current.
A charging control device characterized in that charging is completed according to the amount of change in charging current during intermittent charging. 2. The charging control device according to claim 1, wherein the charging pattern during the intermittent charging is determined by a battery voltage, a battery temperature, and a charging time. 3. The charge control device according to claim 1, wherein the interval of the charging current of the intermittent charging portion is changed only by the battery temperature.