JPH11341696A - Charging control method of battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cycle life-time characteristic of a charged battery, by changing over its charging current into a second current as responding to its kind, when the differential value of its voltage in the case of charging it by a first charging current exceeds a predetermined value. SOLUTION: When determining that a comparison value ΔVi-06 of a data Vi-06 preceding the present data by six sampling times which are stored in a battery-voltage storing means 531 exceeds a stored data ΔVmin of the minimum voltage increase value associated with the comparison value ΔVi-06 by a value not smaller than a predetermined value K, determining that a charged battery 2 has been charged to the vicinity of its fully charged state, a signal fed from a battery-kind determining means 6 is inputted to an input port 58 of a microcomputer 50 to determine whether the charged battery 2 is a nickel-hydrogen battery or not. When the charged battery 2 is a nickel-hydrogen battery, a signal LOW is inputted to the input port 58 of the microcomputer 50, and reversely, since a signal HIGH is inputted to the input port 58 when being a nickel-cadmium battery, whether the signal LOW is inputted to the input port 58 or not is determined. When determining that the signal LOW is inputted to the input port 58 and the charged battery 2 is a nickel-hydrogen battery, its charging current is reduced to improve the cycle life-time of the charged battery 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control method for a battery capable of charging a plurality of batteries having different battery types, such as a nickel cadmium battery (hereinafter referred to as a nickel cadmium battery) and a nickel hydride battery.

[0002]

2. Description of the Related Art In recent years, nickel-metal hydride batteries have begun to be widely used in recent years in response to demands for improving work efficiency by increasing the capacity of batteries and for batteries having excellent environmental resistance.

[0003]

However, since the hydrogen storage reaction of the hydrogen storage alloy of the negative electrode in charging a nickel-metal hydride battery is slower than the dissolution and precipitation reaction of cadmium in a nickel cadmium battery, it is assumed that rapid charging is performed with a current of about 4C. When a nickel-metal hydride battery is charged by a dedicated charging device for a nickel-cadmium battery, the cycle life characteristic is significantly reduced as compared with the nickel-cadmium battery as shown in FIG. SUMMARY OF THE INVENTION An object of the present invention is to provide a battery charge control method that solves the above-mentioned drawbacks, suppresses a decrease in cycle life characteristics even in a quick charge of a nickel-metal hydride battery, and can complete the charge in a short time even if it is a little. That is.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to charge a battery to be charged with a first charging current and detect a battery voltage, and when a differential value of the battery voltage with respect to time increases by a predetermined value or more, the battery to be charged is charged. This is achieved by switching the charging current to the second charging current that is smaller than the first charging current according to the battery type.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of a charging device provided with a battery charging control method according to the present invention. In the figure, 1 is an AC power supply, 2 is a battery set in which a plurality of rechargeable unit cells are connected in series, and a battery temperature detecting means 2A which is provided in contact with or close to the unit cells and detects a battery temperature, for example, a thermistor or the like. The battery to be charged is provided with a determination terminal 2B for determining whether the battery is a nickel-cadmium battery or a nickel-metal hydride battery. In this embodiment, only the battery 2 to be charged, which is a nickel-metal hydride battery, is provided with the determination terminal 2B.
Thus, it is determined whether the battery 2 to be charged is a nickel-cadmium battery or a nickel-metal hydride battery.

Reference numeral 3 denotes a current detecting means for detecting a charging current flowing through the battery 2 to be charged, 4 denotes a charging control signal transmitting means for transmitting a signal for controlling start and stop of charging, and 5 denotes a PWM signal which will be described later. It is a charging current signal transmission unit that returns to the control IC 23. The charging control transmission signal means 4 and the charging current signal transmission means 5 comprise a photocoupler or the like. Reference numeral 6 denotes a battery type discriminating means for discriminating whether the battery 2 to be charged is a nickel cadmium battery or a nickel hydride battery. Reference numeral 7 denotes a pull-up resistor to 5V. LOW is input to the input port 58 of the microcomputer 50, and HIGH is input to the input port 58 for a nickel-cadmium battery. 10 is a rectifying / smoothing circuit including a full-wave rectifying circuit 11 and a smoothing capacitor 12, 20 is a high-frequency transformer 21, MOSFET 22
And a switching circuit comprising a PWM control IC 23. The PWM control IC 23 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 MOSFET 22. 30 is a diode 31, 3
2. A rectifying / smoothing circuit including a choke coil 33 and a smoothing capacitor 34, and a battery voltage detecting means 40 including resistors 41 and 42 and an input protection diode 43, for dividing the terminal voltage of the battery 2 to be charged. Numeral 50 denotes arithmetic means (CPU) 5
1, a microcomputer comprising a ROM 52, a RAM 53, a timer 54, an A / D converter 55, output ports 56a and 56b, a reset input 57, and an input port 58. CPU
Reference numeral 51 compares the latest battery voltage or battery temperature with the battery voltage or battery temperature before a plurality of samplings for each sampling. The RAM 53 includes a battery voltage storage unit 531 for storing a predetermined number of past sampling voltages and a battery temperature storage unit 532 for storing a predetermined number of past sampling temperatures. Reference numeral 60 denotes operational amplifiers 61 and 62, resistors 63 and 6
A charging current control means consisting of 4, 65, 66; 70 a power transformer 71, a full-wave rectifier circuit 72, a smoothing capacitor 7;
A constant voltage power supply comprising a three-terminal regulator 74 and a reset IC 75;
And so on. The reset IC 75 outputs a reset signal to a reset input 75 to bring the microcomputer 50 into an initial state. Reference numeral 80 denotes charging current setting means for setting a charging current, which changes a voltage value applied to the inverting input terminal of the operational amplifier 62 in accordance with a signal from the output port 56b.

Next, an embodiment of the battery charge control method of the present invention will be described with reference to the circuit diagram of FIG. 1 and the flowcharts of FIGS. When the power is turned on, the microcomputer 50
The connected battery 2 enters the connection standby state (step 10).
1). When the battery 2 to be charged is connected, the microcomputer 50 determines this from the signal from the battery voltage detecting means 40, and outputs the PW signal from the output port 56b through the charging control signal transmitting means 4.
A charging start signal is transmitted to the M control IC 23, a charging current setting reference voltage value Vi0 is applied to the operational amplifier 62 from the output port 56b via the charging current setting means 80, and charging is started with the charging current I0 (step 102). ). At the same time as the start of charging, the charging current flowing through the battery 2 to be charged is detected by the current detecting means 3, and the difference between the voltage corresponding to this charging current and the charging current setting reference value Vi0 is determined by the charging current control means 60.
The signal is fed back to the PWM control IC 23 via the signal transmission means 5. That is, when the charging current is large, a pulse with a narrowed pulse width is supplied to the high-frequency transformer 21 when the pulse width is widened. Current detection means 3, charging current control means 60, signal transmission means 5, switching circuit 2
0, the charging current is reduced to a predetermined current value I through the rectifying and smoothing circuit 30.
Control is performed so as to be 0.

Next, full charge detection control is performed. Voltages Vi-06 to Vi-01 up to six samplings earlier as data stored in the battery voltage storage means 531; latest battery voltage Vin
And the comparison value ΔV between the data Vi-06 before sampling 6 and
i-06, data ΔVmin storing the minimum voltage rise value in the comparison value, data ΔVmax storing the maximum voltage rise value, and the minimum battery temperature Tmin are each initially reset (step 103), and the sampling timer is started. (Step 104). When the sampling timer time Δt has elapsed (step 105), the sampling timer is started again (step 10).
6).

Next, the divided voltage value obtained by dividing the battery voltage by the battery voltage detecting means 40 is A / D converted by the A / D converter 55, and is taken in as the battery voltage Vin (step 10).
7). Then, a difference ΔVi−06 between Vin and the data Vi−06 before six samplings is obtained by the calculating means 51 (step 108), and ΔVi−06 is a predetermined value K from ΔVmin.
(K is a predetermined number of bits when the battery voltage is converted into a digital value by using an A / D converter.) It is determined whether the battery voltage has increased by a large amount, that is, when the battery voltage peaks at the end of charging. Then, it is determined whether or not the amount of change in the battery voltage has become larger than a predetermined value (step 109).
If ΔVi−06−ΔVmin is smaller than the predetermined value K, it is determined whether or not ΔVin−06 is negative (step 110). If ΔVin−06 is negative, ΔV−06 is negative.
Min is updated to 0 (step 111), and ΔVi−
If 06 is positive, step 111 is skipped and $ Vi
−06 and ΔVmin are compared (step 112).
If ΔVi-06 is smaller than ΔVmin, ΔVi-0
6 is updated as ΔVmin (step 113),
Vi-05 is Vi-06, Vi-04 is Vi-05, ...
.., Vin is replaced with Vi-01, and the respective storage data are transferred to the storage area one sample before (step 114).
The processing from step 105 is performed again. If １１２Vi-06 is larger than △ Vmin in step 112, step 113 is skipped, and the process of step 114 is performed in the same manner as described above.

[0010] In step 109, {Vi-06}
If it is determined that it is larger than Vmin by a predetermined value K or more,
It is determined that the battery 2 has been charged to near full charge, and a signal from the battery type determination means 6 is input to the input port 58 of the microcomputer 50 to determine whether the battery 2 is a nickel-metal hydride battery. (Step 115). Battery 2 to be charged
Is a nickel-metal hydride battery, LOW is input to the input port 58 of the microcomputer 50. Conversely, if the battery is a nickel-cadmium battery, HIGH is input to the input port 58, and LOW is input to the input port 58. Is determined. When HIGH is input to the input port 58, charging is performed with the charging current kept at I0 (step 116). LOW is input to the input port 58,
If it is determined that the battery to be charged 2 is a nickel-metal hydride battery, the charging current is reduced to I1 (I1 <I0) in order to improve the cycle life characteristics of the battery to be charged 2 (step 117). At this time, since the battery voltage also drops, the voltages Vi-06 to Vi-0 up to six samples before and the latest battery voltage V
Reset the comparison value △ Vi-06 between in and the data Vi-06 six samples before (step 118).

Subsequently, the sampling timer is started (step 119). Sampling timer time Δt
Has elapsed (step 120), the sampling timer is started again (step 121), and the divided voltage value obtained by dividing the battery voltage by the battery voltage detecting means 40 is again A / D.
A / D conversion is carried out by the converter 55 and taken in as the battery voltage Vin (step 122). The output of the battery temperature detecting means 2A of the battery 2 to be charged is A / D converted by the A / D converter 55 and taken in as the battery temperature Tin (step 122). Step 12
3).

Further, a difference ΔVi−06 between Vin and the data Vin−06 before sampling 6 is obtained by the calculating means 51 (step 124), and ΔVi−06 and data ΔVmax for storing the maximum voltage rise value are obtained. (Step 125), and in response to whether △ Vi-06 is smaller than △ Vmax by a predetermined value P or more, that is, in response to approaching the peak of the battery voltage at the end of charging, the amount of change in the battery voltage becomes the predetermined value P It is determined whether or not it has become smaller. ΔVmax−ΔVi−
When 06 ≧ P, the microcomputer 50 sets the output port 56
b, a charge stop signal is transmitted to the PWM control IC 23 via the charge control signal transmitting means 4 to stop charging (step 132). Next, it is determined that the battery to be charged 2 is taken out (step 133). If it is determined that the battery to be charged 2 is taken out, the process returns to step 101 and waits for charging the next battery to be charged 2. .

In step 125, ΔVmax−ΔV
When i−06 ≧ P is not satisfied, the arithmetic means 51 compares the latest battery temperature Tin with the minimum battery temperature Tmin which is the storage data of the battery temperature storage means 532 (step 126), and when Tin−Tmin ≧ S, At a certain time, that is, when the battery temperature rises by a predetermined temperature rise value S or more, it is determined that the battery 2 to be charged is fully charged.
2. The processing of step 133 is performed.

In step 126, Tin-Tmi
When it is determined that n ≧ S is not satisfied, ΔVi−06 and ΔVm
ax (step 127), and if △ Vi-06 is larger than △ Vmax, the value of △ Vi-06 is changed to △ Vm.
ax is updated (step 128). If △ Vi-06 is smaller than △ Vmax, step 128 is skipped and Tin and Tmin are compared (step 127).

In step 129, Tin becomes Tmi
When it is determined to be smaller than n, the value of Tin is set to Tmin
(Step 128), and when it is determined that Tin is larger than Tmin, Step 128 is skipped, and Vi-05 is Vi-06, and Vi-04 is Vi-0.
5,..., Vin is Vi-01 and each stored data is 1
Transfer to storage area before sampling (step 13
1) The processing from step 120 is performed again.

FIG. 4 shows the charging characteristics of a nickel-metal hydride battery charged by the charging device provided with the battery charging control method of the present invention. As shown in the figure, the switching of the charging current is performed when the differential value of the battery voltage with respect to time rises by a predetermined value or more, and after the charging current is switched, the charging is performed when the predetermined value of the differential value with respect to the battery voltage drops by a predetermined value. Has stopped. It should be noted that there is no problem if charging is stopped when the battery temperature rises by a predetermined value or more after switching the charging current.

FIG. 5 shows the cycle life characteristics of the battery 2 to be charged, which is a nickel-metal hydride battery charged by the battery charger of the present invention and the conventional battery charger. It can be seen that the cycle life characteristic is greatly improved as shown in the figure by reducing the charging current near the full charge as described above.

In the above-described embodiment, the battery type is determined after determining that the differential value of the battery voltage with respect to time has risen by a predetermined value or more (step 109). Step 10 for making a determination
The processing may be performed between 1 and the step 109.

[0019]

According to the present invention, there is provided a battery charge control method capable of suppressing a decrease in cycle life characteristics even in a quick charge of a nickel-metal hydride battery and completing the charge in a short time even a little. Can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a charging device provided with a battery charging control method of the present invention.

FIG. 2 is a flowchart showing an embodiment of a battery charge control method according to the present invention.

FIG. 3 is a flowchart illustrating an embodiment of a battery charge control method according to the present invention.

FIG. 4 is a graph showing charging characteristics of a nickel-metal hydride battery charged by a charging device provided with the battery charging control method of the present invention.

FIG. 5 is a graph showing cycle life characteristics of a battery to be charged, which is a nickel-metal hydride battery charged by a battery charger provided with the battery charge control method of the present invention and a conventional battery charger.

FIG. 6 is a graph showing cycle life characteristics of a charged battery charged by a conventional charging device.

[Explanation of symbols]

2 is a battery to be charged, 2A is a battery temperature detecting means, 6 is a battery type determining means, 40 is a battery voltage detecting means, 50 is a microcomputer, 60 is a charging current control means, and 80 is a charging current setting means.

Claims (4)

[Claims] 1. A charging control method for charging a plurality of charged batteries of different battery types, wherein the charged battery is charged with a first charging current, a battery voltage is detected, and a differential value of the battery voltage with respect to time is provided. A charge current is switched to a second charge current smaller than the first charge current in accordance with the type of the battery to be charged, when the battery charge rises by more than a predetermined value. 2. The battery to be charged is a nickel cadmium battery and a nickel hydride battery. When it is determined that the battery to be charged is a nickel cadmium battery, the battery to be charged is a nickel hydride battery without switching the charging current. 2. The method according to claim 1, wherein the charging current is switched when it is determined that the battery is present. 3. The method according to claim 1, wherein after switching the charging current, the battery temperature of the battery to be charged is detected, and if the battery temperature rises by a predetermined value or more, the charging is stopped. Item 3. The battery charge control method according to Item 2. 4. The method according to claim 1, wherein after switching the charging current, the battery voltage of the battery to be charged is detected, and the charging is stopped if a differential value of the battery voltage with respect to time falls from a maximum value by a predetermined value or more. The battery charging control method according to any one of claims 1 to 3, characterized in that: