JP3393656B2 - Battery charging device and battery charging method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charging device and a battery charging method for charging a secondary battery such as a nickel-cadmium battery (hereinafter referred to as a nicad battery).

[0002]

2. Description of the Related Art Generally, when a charging current is increased in order to charge a secondary battery such as a nickel-cadmium battery in a short time, the gas consumption reaction rate at the cathode decreases as the temperature becomes lower.
It is necessary to reduce the charging current at low temperatures. Therefore, Japanese Patent Application No. 2-186764 filed by the applicant earlier
As disclosed in JP-A-4-340330, a charging method has been proposed in which the battery temperature is detected and the charging current is reduced if the battery temperature is below a set value.

[0003]

However, the gas consumption reaction rate of the battery decreases not only when the battery temperature is low, but also when the charging current is high or the amount of electricity remaining in the battery before charging, that is, the remaining amount. It also occurs when the capacity is low. Therefore, when trying to determine the charging current by simply detecting the battery temperature, it is necessary to allow the set battery temperature to have a margin, which is a problem in performing efficient short-time charging for a wide range of battery temperatures. Become. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to determine whether or not the gas consumption reaction rate is lowered so that charging can be performed with an appropriate charging current.

[0004]

Therefore, as shown in the charging curve 1b of FIG. 3, when the gas consumption reaction rate of the battery decreases as the temperature decreases, the internal resistance of the battery increases and the charging curve 1a is compared with the normal charging curve 1a. Paying attention to the fact that the battery voltage rises, the battery voltage detected at the initial stage of charging when charging with a medium level charging current is compared with the set voltage value, and when the detected battery voltage is higher than the set voltage value, the charging current is reduced. After that, the battery is charged with this small level charging current, and the detected battery voltage is the set voltage.
Larger level than mid-level charging current smaller than value
Charging with charging current, charging with this large level charging current
Large when the detected battery voltage is smaller than the second set voltage value
Continues charging at the level charging current, and the detected battery voltage becomes the second
Charging is performed at a medium level charging current that is larger than the set voltage value .

[0005]

[Operation] As a result , the charging current corresponding to the state of the battery for surely determining the state of the gas consumption reaction rate of the battery and charging
It is possible to charge, extending battery life because it charged without stress the battery at low temperatures it is possible over a wide range of battery temperature the charging time to a minimum.

[0006]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. Reference numeral 1 is an AC power source, 2 is a battery group to which a plurality of rechargeable batteries are connected, 3 is current detecting means for detecting a charging current flowing in the battery group 2, 4 and 5 are signal transmitting means including photocouplers, 10 Is a full-wave rectifier circuit 11 and a smoothing capacitor 1
A rectifying / smoothing circuit consisting of 2, a high-frequency transformer 21,
It is a charge control unit including a MOSFET 22 and a PWM control IC 23. The charge control means 20 is a single chip microcomputer (hereinafter referred to as a microcomputer) 5 which will be described later.
A signal from the output port 56 of 0 controls the start / stop of charging of the battery set 2. The PWM control IC 23 is a MOS
It is a switching power supply IC that adjusts the output voltage of the rectifying and smoothing circuit 10 by changing the drive pulse width of the FET 22. Three
Reference numeral 0 is a rectifying / smoothing circuit composed of diodes 31, 32, choke coil 33 and smoothing capacitor 34, and 40 is a battery voltage detecting means composed of resistors 41, 42 for detecting the battery voltage of the battery set 2. As is well known, the microcomputer 50 includes a CPU 51, a ROM 52, a RAM 53, a timer 54,
It is composed of an A / D converter 55, an output port 56, a reset input 57 and the like. The microcomputer 50 compares the battery voltage input from the battery voltage detection means 40 with a predetermined comparison reference voltage value in order to determine the state of gas consumption reaction speed of the battery, and based on the comparison result, charging current control means described later. 6
Send a signal to 0 to control the charging current. Also, start charging
A stop signal is generated via output port 56. 60 is an operational amplifier 61, 62, resistors 63a, 63b, 63c,
A charging current control unit composed of 64-66 and analog switches 67a and 67b.
67b is composed of, for example, a CMOSIC 4066 or the like. To reduce the charging current, the amplification degree by the operational amplifier 61 may be increased. That is, in order to maximize the charging current, the analog switches 67a and 67b are turned off to minimize the amplification degree of the operational amplifier 61. To reduce the charging current, only the analog switch 67b is turned on by the signal from the output port 56 of the microcomputer 50 and the amplification degree by the operational amplifier 61 is increased. To further reduce the charging current, only the analog switch 67a is turned on by the signal from the output port 56 of the microcomputer 50, and the amplification degree by the operational amplifier 61 is further increased. 70 is a power transformer 71, a full-wave rectifier circuit 72, a smoothing capacitor 73, a three-terminal voltage regulator 7
4. A constant voltage power supply including a reset IC 75, which serves as a power supply for the microcomputer 50, operational amplifiers 61 and 62, and the like. The reset IC 75 outputs a reset signal to the reset input 57 to initialize the microcomputer 50.

The operation will be described with reference to the circuit diagram of FIG. 1 and the flowchart of FIG. When the power is turned on, the microcomputer 50 enters a standby state for connecting the battery group 2 (step 10
1). When the battery set 2 is connected, the microcomputer 50 determines the battery connection by the output signal of the battery voltage detection means 40, turns on only the analog switch 67b of the charging current control means 60 to set the medium amplification degree, and the charging current is set to the middle level. At the same time as setting the level to I2, a charging start signal is transmitted from the output port 56 to the PWM control IC 23 via the signal transmission means 4 to start charging (step 102). Simultaneously with the start of charging, the charging current flowing through the battery set 2 is detected by the current detecting means 3,
The difference between the charging current value and the reference value Vref is fed back from the differential amplifying means 60 to the PWM control IC 23 via the signal transmitting means 5. That is, when the charging current is large, the pulse width is narrowed, and in the opposite case, the pulse width is widened, a pulse proportional to the pulse width is applied to the high frequency transformer 21, and the rectifying / smoothing circuit 30 smoothes the direct current to make the charging current constant. keep. That is, the charging current is controlled to be a constant current via the current detection unit 3, the charging current control unit 60, the signal transmission unit 5, the charging control unit 20, and the rectifying / smoothing circuit 30. The output signal of the battery voltage detecting means 40 which detects the voltage of the battery group 2 is A / D
A / D conversion is performed by the converter 55, and the battery voltage value Vin1 is taken in (step 103). The input battery voltage value Vin1 is compared with the comparison set voltage value Vref1 in order to determine whether or not the gas consumption reaction speed of the battery has decreased (step 104). When Vin1> Vref1, only the analog switch 67a is turned on so that the charging current is smaller than the intermediate level I2.
Lower to a small level I3, then charge current at this small level
It continues charging at I3 (see step 105, Figure 4). When Vin1 <Vref1, the analog switch 67a,
67b is turned off and the charging current is larger than the medium level I2.
Raise to level I1 (step 106, see FIG. 6). Next, the output signal of the battery voltage detecting means 40 is A / D converted by the A / D converter 55 and taken in as the battery voltage value Vin2 (step 107). The input battery voltage value Vin2 is compared with the second comparison set voltage value Vref2 in order to determine whether or not the gas consumption reaction rate of the battery has decreased due to the increase in the charging current (step 108). Vin2> Vref2
At the time of, only the analog switch 67b is turned on to reduce the charging current to the intermediate level I2, and thereafter, the charging current of this intermediate level.
I2 continue charging (see step 109, Figure 5).
When Vin2 <Vref2, leave the charging current at the large level I1
To continue charging Te, the absence Step 11 0 to the determination of the full charge
Proceed . After determine by the full charge in step 110, the microcomputer 50 is a charge stop signal is transmitted to the PWM control IC23 via a signal transmission means 4 from the output port 56, to stop charging (step 111). Next, it is determined that the battery group 2 is taken out (step 112). When it is determined that the battery group 2 is taken out, the process returns to step 101 and stands by for charging the next battery group 2.

According to the above embodiment, step 104 is performed.
Change at the beginning of charging based on the battery temperature and remaining capacity.
The gas consumption reaction rate depending on the
Accordingly, the charging current is set to the large level I1 or the small level I3.
Battery, and charge with a charging current according to the battery temperature and remaining capacity.
U In addition, in step 108, based on the magnitude of the charging current,
The gas consumption reaction rate that changes based on
Gas consumption corresponding to the detection result
Set the charging current to medium level I2 or large level I1
Since it was turned on, when charging for a wide range of battery temperatures
The distance can be minimized.

[0009]

As described above, according to the present invention, the state of the gas consumption reaction rate of the battery is surely discriminated and the battery is charged with the charging current corresponding to the gas consumption reaction rate. The charging time can be minimized. In addition, since the battery can be charged at low temperatures without applying stress, the battery life can be extended.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a charging device of the present invention.

FIG. 2 is a flowchart showing an embodiment of a control method of the charging device of the present invention.

FIG. 3 is a graph showing charge curves at normal temperature and low temperature.

FIG. 4 is a graph showing the relationship between battery temperature, battery voltage and charging current.

FIG. 5 is a graph showing the relationship between battery temperature, battery voltage and charging current.

FIG. 6 is a graph showing the relationship between battery temperature, battery voltage and charging current.

[Explanation of symbols]

Reference numeral 20 is a charge control means, 40 is a battery voltage detection means, 50 is a microcomputer, and 60 is a charge current control means.

Continued front page       (56) Reference JP-A-2-97234 (JP, A)                 JP-A-51-60941 (JP, A)                 Actual Kaihei 2-68642 (JP, U)                 Actual development Sho 63-100928 (JP, U)

Claims (4)

(57) [Claims] 1. A charging control means for controlling charging of a secondary battery so as to charge with a medium level charging current at an initial stage of charging,
Battery voltage detecting means for detecting the battery voltage during charging, comparing means for comparing the battery voltage from the battery voltage detecting means with a set value, and the comparing means for reducing the gas consumption reaction rate of the battery.
When the battery voltage at the initial stage of charging is determined to be higher than the set value based on the increase of the internal resistance of the battery, the charging current is lowered, and thereafter, the charging current control means for charging with this small level charging current is provided. Battery charger. 2. When the detection battery voltage is smaller than a set value, the charging current is set to a large level charging current larger than a medium level.
Constant and charging by an atmospheric level charge current, a large level charge electrostatic
When detecting the battery voltage when the current is higher than the second set value, return to the medium level charging current to charge and detect
Large level when it is determined that the battery voltage is lower than the second set value
The battery charging device according to claim 1 , wherein the charging with the charging current is continued . 3. A charging current provided between the power source and the battery.
Control means for controlling the supply and stop of electricity, and the battery during charging
Battery voltage detecting means for detecting voltage, and battery voltage detecting means
Charger that compares the set voltage with the battery voltage from the stage
Charge current control means for controlling the magnitude of the current and comparison means
Receiving the comparison result, charging current
And a control means for controlling the texture, the control means
Set the battery voltage at the initial stage of charging to charge at the level charging current
When it is judged to be larger than the value, the charging current is smaller than the medium level.
Control to perform charging with a small level of charging current,
Charge current when it is judged that the battery voltage in the period is smaller than the set value
Is charged with a large charging current that is higher than the medium level.
To control the battery power during charging with a large level of charging current.
Large level charging when it is judged that the pressure is lower than the second set value
It controls to continue charging with electric current, and
It is determined that the battery voltage during current charging is higher than the second set value.
Controls to perform charging with a medium level charging current when disconnected.
A battery charging device characterized by the above. 4. A battery charging method comprising the following steps. a Charging with a medium level charging current at the beginning of charging. The battery voltage at the time of charging of ba is detected and set with the detected battery voltage.
Compare fixed values. c When the detection battery voltage is higher than the set value, the charging current is
Set to a small level charging current smaller than the bell charging current,
When the charging current is small, the charging current is
Set to the charging current of the battery. d Small level charging when the detection battery voltage is higher than the set value
Charge with current. ￲Large level charging when the detected battery voltage is lower than the set value
Charge with current. The battery voltage during charging at fe is detected and
The second set value is compared. g When the detected battery voltage is larger than the second set value, the charging current
Set to a medium level charging current and set the charging current to a high level when it is small.
Set to charging current. h When the detected battery voltage is higher than the second set value,
Charge with charging current. j Large level when the detected battery voltage is lower than the second set value
Charge with charging current.