JPH07123604A - Rechargeable battery charger - Google Patents

Abstract

(57) [Abstract] [Purpose] Rechargeable batteries with various charging characteristics such as nickel-cadmium batteries, nickel-hydrogen batteries, small sealed lead batteries, etc. Regardless of the same charging device, it is possible to provide a charging device that can charge a secondary battery in almost 100% in a short time. [Constitution] A measuring means for measuring a battery voltage and a battery temperature of a secondary battery is provided, and charge control is performed by a change in the battery voltage during charging suspension in charging by a pulse current, or a change in battery temperature and battery temperature during charging. It is a charging device.

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 sealed secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries and small sealed lead batteries.

[0002]

2. Description of the Related Art Secondary batteries mainly used as a power source for portable devices include nickel-cadmium batteries and small sealed lead batteries. To charge these secondary batteries, they must be charged by a charging method suitable for each secondary battery. FIG. 9 shows the charging characteristics of the nickel-cadmium battery. The battery voltage drop characteristics that occur at the end of charging, that is, the peak voltage at which the rate of change of the battery voltage changes from positive to negative, are detected, and the battery voltage drops from the peak voltage. This is detected and the charging current is controlled. FIG. 10 shows the charging characteristics of a small sealed lead battery, in which the charging current is controlled when the battery voltage reaches a constant voltage. Also, recently nickel-hydrogen batteries have been widely used. The nickel-hydrogen battery is characterized by less change in battery voltage and a larger temperature rise during charging, as compared with the nickel-cadmium battery. As described above, there are various batteries, and each battery has different charging characteristics. Due to this difference in charging characteristics, conventional nickel-cadmium batteries, small sealed lead batteries, and nickel-hydrogen batteries have been charged with dedicated chargers.

Further, even in the case of the same battery, the electrode of the secondary battery is inactivated depending on its storage condition. When the secondary battery that has been deactivated is charged, the charging characteristics differ from normal ones. For example, when charging, the peak does not appear in the range where it should appear, and the voltage gradually rises. Or, the first peak appears immediately after the start of charging (within a few minutes),
After that, the second peak may appear again at the charging completion point.

[0004]

As described above, according to the prior art, a dedicated charger for each of nickel-cadmium battery, nickel-hydrogen battery, and small sealed lead-acid battery is required, and depending on the history of the battery, For example, it is widely used as a charging method for nickel-cadmium batteries -ΔV
When a battery for long-term storage is charged by the charging device of the detection charging method, -ΔV cannot be detected and it becomes overcharged, or -ΔV is detected at the start of charging and charging is stopped assuming that charging is completed. However, there is a drawback that the required charging cannot be performed.

An object of the present invention is to provide a charging device capable of almost 100% surely charging in a short time without causing overcharging or insufficient charging regardless of the type and history of the battery.

[0006]

In order to solve the above problems, in the present invention, the battery temperature and the battery voltage are sampled by the sampling means as the information obtained from the battery, and the charging control is performed by the microcomputer. The battery temperature and the battery voltage are constantly monitored and the control is performed by either of them, and the charging control can be performed without changing the set value depending on the type of the battery.

Further, the battery voltage at the time of charging is different due to the difference in charging current, contact resistance, increase in internal resistance due to battery history, and the like. Therefore, the battery voltage is sampled when the pulse is stopped. Thereby, the battery voltage can be monitored regardless of the state of the battery.

Further, the charging characteristics of the secondary battery change depending on the ambient temperature. For example, if the temperature is high, the peak at the end of charging is less likely to appear. Therefore, charging is performed by changing the limit temperature and the set value according to the ambient temperature.

However, when the ambient temperature is high, the set value cannot be set too high in order to prevent the battery performance from deteriorating. Therefore, in this case, the set value is changed and the charging current is further reduced to suppress the rise in battery temperature and charging is performed.

[0010]

When the charging of the secondary battery progresses and approaches the full charge, the battery voltage starts to rise rapidly. This is because the active material is increasingly converted to the state of charge. 90% to 95% of the active material of the secondary battery is approaching full charge.
When about% is chemically converted, oxygen starts to be generated.
This causes the internal pressure of the battery to rise and the temperature of the secondary battery to rise. Then, the battery voltage drops. By monitoring both the battery voltage and the battery temperature, regardless of the history of the battery, regardless of the history of the battery, it is possible to charge reliably and sufficiently without causing insufficient charging or overcharging. You can Further, generally, in a ΔV charger, a large value of ΔV is set in order to prevent detection of completion of charging due to malfunction such as noise. Therefore, it may be overcharged. However, according to the present invention, even in a battery having a small voltage change such as a nickel-hydrogen battery, since the battery temperature is sampled in accordance with the battery voltage, the charge control can be performed in accordance with the battery, and there is no fear of overcharging. .

Further, as in the present invention, since the battery voltage is sampled during charging suspension and the charging control is performed, the charging device provided in the charging device of the -ΔV detection charging system detects -ΔV at the initial stage of charging and charges the battery. It is not necessary to perform the ΔV prohibition control for preventing the completion.

Further, depending on the ambient temperature, the control temperature, the set value,
Also, by changing the charging current, the secondary battery can be sufficiently charged without being affected by the temperature change and without damaging the battery.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a charging device embodying the present invention. Reference numeral 1 is a battery pack of a secondary battery such as a nickel-hydrogen battery, and a secondary battery 11 and a temperature sensor 12 are built in the pack. Reference numeral 2 is a microcomputer, and the battery temperature and the battery voltage are read from the battery pack by the analog-digital converter. The microcomputer 2 processes the read battery temperature and battery voltage, and controls the pulse by turning the switch circuit on and off via the control circuit 3 to control the charging.

FIG. 2 shows an embodiment of the electronic circuit of the charging device according to the present invention. In the figure, the same symbols as in FIG. 1 indicate the same circuits or parts. The second microcomputer is CP
Built-in U (central processing unit) 21, memory 22, output port 23, input port A / D converter (analog / digital converter) 24, etc.
The voltage and temperature signals of the battery 11 are input to the A / D converter 24. This input is subjected to signal processing by the CPU 21 and the memory 22, and an output signal is generated at A and B of the output port 23. Here, as the temperature sensor 12, a thermistor whose resistance value changes according to temperature is used, but the temperature sensor 12 is not limited to this, and for example, a thermocouple may be used. Reference numeral 13 denotes a fixed resistor, which supplies a current to the temperature sensor 12.

The control circuit of 3 includes transistors 31, 32,
It is composed of resistors 33 and 34, and O of switch circuits 5 and 5 ′ is generated by the output signal from the microcomputer 2.
N and OFF are controlled. Switch circuit 5, 5 '
A transistor is suitable for this. When the switch circuit 5 is ON, a constant-current charging current flows through the battery 11, and when the switch 5 ′ is ON, a trickle current that compensates for the self-discharge of the battery 11 flows through the battery 11. .

The inverter circuit 4 is a pulse width control circuit 4
1, a transistor 42, a transformer 43, a shunt regulator 44, a photo coupler 45, and resistors 46 and 47, and outputs a constant DC voltage. The pulse width control circuit 41 is composed of a triangular wave generation circuit, a voltage comparison circuit, a reference voltage generation circuit, and the like. Recently, since an integrated circuit in which these circuits are integrated into one chip has been commercialized, it is easy to use this chip. Build a circuit. The input signal from the photocoupler 45 is compared with the triangular wave, and an output having a pulse width corresponding to the difference is generated from the pulse width control circuit 41. Therefore, the transistor 42 is turned on for the time corresponding to the width of the output pulse and the transformer 43 is turned on. A pulse current flows through. If the DC voltage obtained by rectifying the output voltage of the transistor 43 has a set value, control of that state is maintained. If the DC voltage does not reach the set value, that is, if the voltage at the intermediate point between the resistors 46 and 47 does not match the reference voltage of the shunt regulator 44, the current flowing into the photocoupler 45 changes, and the pulse width control circuit 41 changes. Correspondingly changes the output pulse width, and as a result, the DC voltage becomes the set value.
The shunt regulator 44 is also used in the pulse width control circuit 4
Similar to item 1, it is commercialized as an integrated circuit, and is equivalently represented by a configuration of a reference voltage generating circuit and an operational amplifier. Also, the control method is not limited to the described method,
It goes without saying that a configuration in which another winding is provided in the transformer 43 instead of the photocoupler and feedback is performed from that is also included in the present application. It is possible to obtain a constant DC voltage without necessarily using an inverter circuit, but in order to make a compact charging device, it is necessary to make the transformer, which is the largest component, small. The effect is that the size of the transformer can be made very small. The rectifier circuit 6 is a known circuit including diodes 61 and 62 and capacitors 63 and 64. Of these, the diode 62 needs to use a high frequency element.

Reference numeral 7 denotes a constant current circuit, which compares the voltage generated by the current flowing through the resistor 71 with the voltage across the Zener diode 73 having a constant voltage characteristic, and the transistor 72 makes the both voltages equal. Control. Current flowing through the resistor 71 I, the resistance R71, a Zener voltage V _Z, the emitter-base voltage of the transistor 72 V
If eb, the following equation holds.

I = (V _Z −V eb) / R 71 (1) The resistor 74 supplies current to the Zener diode 73 and the transistor 72. Equation (1) does not include the term of the load (battery 11 in this circuit), and the load can be charged with a constant current. At the time of actual charging, turn on the switch circuit 5 described above.
Therefore, the charging current I _o is expressed by the following equation.

I _o = (T _ON / (T _ON + T _OFF )) * I (2) where T _ON : ON time of the switch circuit 5 T _OFF : OFF time of the switch circuit 5 Therefore, charging the battery 11 The current I _o is turned on by the output signal from the microcomputer 2, the switch circuit 5 is turned on,
The OFF time can be controlled and changed. In the case of a simpler circuit configuration, the transistor 72 and the switch circuit 5 can be combined into one transistor. Further, there is another embodiment as the configuration of the constant current circuit 7 and a rectifying diode or the shunt regulator described above may be used instead of the Zener diode, and the transistor 72 may have a field effect other than the bipolar type. Shaped transistors can also be used.

In short, the present application has a construction in which a direct current constant voltage power source is formed by the inverter circuit 4, a constant current is made from it, and then the constant current is turned on and off by the switch circuit 5 to pulse-charge the battery 11. The voltage of 11 is detected by the microcomputer 2 during the charging suspension period and controls the switch circuit 5, so that the following effects are obtained.

(1) Since a high frequency inverter circuit is used, the shape of the transformer can be made significantly smaller than in the case of a commercial frequency, and the charger can be downsized.

(2) Since the constant voltage and the constant current are used,
Not affected by fluctuations in AC power supply.

(3) The charging current value to the battery can be easily changed by controlling the switch circuit by the microcomputer.

(4) Since the constant current pulse charging is used, an accurate charge amount can be easily obtained by integrating the ON time of the switch circuit 5.

(5) Since the battery voltage is detected during the period when the charging current is not flowing, an accurate value can be obtained without being affected by the charging current, the internal resistance of the battery, the contact resistance of the connection terminal connected to the battery, etc. Therefore, accurate charge control can be performed.

FIG. 3 is a flow chart showing the charge control algorithm of the present invention. When the secondary battery is connected to charge the battery by the charging device and the charging is started, the microcomputer 2 determines whether the battery temperature measured by the temperature sensor 12 of the battery pack is within the setting T _a ≧ T _o ≧ T
_b (T _a : maximum chargeable temperature, T _o : battery temperature, T _b :
Perform the minimum chargeable temperature). If the battery temperature is out of the setting, charging will not be performed due to temperature abnormality. Here, the set temperature is set according to the performance of the battery and the usage status of the charger. In this example, T _a = 40 ° C. and T _b = 0 ° C. Next, the battery voltage is measured and it is determined whether it is less than or equal to the set voltage value. If the voltage is equal to or lower than the set voltage, preliminary charging (for example, 10 ms charging) is performed.
If the set voltage is not exceeded even if this is repeated several times (for example, three times), charging is not performed due to battery abnormality. It is necessary to set the set voltage according to the number of batteries to be charged.

When the battery temperature and the battery voltage clear the set values of the charging device, the charging current is determined for the secondary battery and charging is started by the pulse current. If the battery temperature is high at the start of charging, change the current value. For example, when the normal setting is 100%, the current value is 50% and the battery limit temperature value is high. As a result, temperature rise due to charging can be suppressed and charging can be performed even at high temperatures. The change of the current value can be easily performed by changing the pulse interval, that is, turning on / off the switch by the microcomputer.

When charging is started, the microcomputer 2 reads the battery temperature measured by the temperature sensor 12 built in the battery pack and compares it with the limit temperature T _o ≧ T _c
(T _o : battery temperature, T _c : limit temperature upper limit value). If the temperature exceeds this limit temperature, charging is stopped. Temperature T _c
In the case of this example, since the chargeable temperature was set to 0 to 40 ° C, the temperature was set to 55 ° C, which is 15 ° C higher than this. Next, according to the battery temperature data read by the microcomputer,
When the temperature rise is detected, ΔT _o ≧ ΔT _a (ΔT _o : rate of change of battery temperature, ΔT _a : upper limit of temperature rise) is determined, and if this is satisfied, it is determined that charging is completed and trickle charging is switched to. In the case of this embodiment, the value of the temperature increase upper limit ΔT _a is set to 1
The temperature was 2 ° C. per minute.

Next, when the pulse charging is stopped, the battery voltage of the secondary battery is read by the microcomputer, and the determination of voltage drop ΔV ≧ V _a (V _a : voltage setting value) is performed. When the voltage drop exceeds the set value, the quick charge shifts to trickle charge. When the ambient temperature is 20 ° C., 10 to 20 mV / cell is suitable as the voltage setting value V _a , and in this embodiment, it is 2
It was set to 0 mV / cell. Even if the voltage drop does not exceed the set value of the battery voltage, if the parallel state continues for a certain time, the trickle charging is started at the same time. In this embodiment, t = 10 minutes.

The determination of the battery temperature and the battery voltage is repeated, and T _o ≧ T _c , ΔT _o ≧ ΔT _a , or ΔV ≧ V _a ,
Alternatively, when the condition that the parallel state of the battery voltage continues for a certain time or longer is obtained, the microcomputer issues a charge stop command signal and shifts to trickle charging. Further, in the case of the present embodiment, the trickle charging is started after the completion of charging is detected, but the charging may be stopped.

The charging current depends on the pulse shown in FIG. T ₁
Is a pulse charge ON period, and T ₂ is a charge rest period. The battery voltage is sampled during this charging suspension period T ₂ .
Since the ON / OFF of the pulse is controlled by the switch circuit by the microcomputer, the charging current can be easily changed. In this embodiment, T ₁ is 9 ms and T ₂ is 1.
Although it is set to ms, it can be changed by a micro computer.

Next, a description will be given of a test example in which the charging device of the above-described embodiment was actually used to charge a nickel-cadmium battery, a nickel-hydrogen battery, and a sealed lead battery.

FIG. 5 shows an ambient temperature of 20 ° C. and a charging current of 1.0 A
Charging characteristics obtained by charging at (a) nickel-cadmium battery (nominal capacity 700 mAh), (b) nickel-hydrogen battery (nominal capacity 1100 mAh), (c)
Is a sealed lead battery (2Ah / 20HR). (A) is the charging characteristics of a nickel-cadmium battery, curve A is the battery voltage at the time of charging, curve A'is the battery voltage at the time of pulse rest, and curve B is the battery temperature. The transition from quick charge to trickle charge is that the battery voltage during the pulse rest of curve A'is 2
It has just dropped by 0 mV, and the control of the nickel-cadmium battery is -Δ in the flowchart of FIG.
V ≧ V _a . (B) is the charging characteristics of the nickel-hydrogen battery, curve C is the battery voltage at the time of charging, curve C'is the battery voltage at the time of pulse rest, and curve D is the battery temperature. As shown in the figure, the change in battery voltage is smaller than that of nickel-cadmium batteries, and a voltage drop of 20 mV cannot be obtained. But,
It is possible to control the state of charge by increasing the temperature,
The curve D controls ΔT _o ≧ ΔT _a . (C) is the case of a sealed lead battery. The curve E is the battery voltage during charging, and the curve E'is the battery voltage during the pulse rest. After the start of charging, the battery voltage reached a peak, and when the parallel state continued for 10 minutes, the trickle charging was started. As described above, depending on the type of the battery, the trickle charging is performed by the appropriate control.

When each battery was discharged, a nickel-cadmium battery of 697 mAh (1.0 C discharge), a nickel-hydrogen battery of 1074 mAh (1.0 C discharge), and a sealed lead battery of 1.93 Ah (0.1 A discharge) were used. The discharge capacity was obtained.

FIG. 6 shows a nickel-cadmium battery charged at an ambient temperature of 20 ° C. Curve F is 10 after manufacturing
The curve G shows the battery voltage after the cycle charging / discharging, and the curve G shows the battery voltage obtained by charging the battery after the charging / discharging for about 200 cycles. Curves F'and G'represent the change in battery voltage during pulse charge suspension of the respective batteries. A difference in the battery voltage during charging appears between 10 cycles and 200 cycles, but there is almost no difference between cycles in the battery voltage change during pulse charge suspension. Charging is controlled by a 20 mV drop in battery voltage for both batteries as well. Regarding the battery voltage during charging, the battery that has been charged and discharged for 200 cycles drops earlier as shown in the figure, and this causes a difference in the charged amount when the charge control is performed.

FIG. 7 shows the charging characteristics when the nickel-cadmium battery is charged by the present charging device when the ambient temperature is 5, 20, 35 ° C. Curve A'is ambient temperature 20
C, curve H'is ambient temperature 5 C, curve I'is ambient temperature 35
It is the battery voltage when the pulse is stopped at ℃. At an ambient temperature of 20 ° C, the charge amount is 103% of nominal capacity, and at an ambient temperature of 5 ° C, it is 101
%, The ambient temperature of 35 ° C. is 108%, and charging is performed without overcharging even when the ambient temperature changes. The setting values of the charging device were set as shown in Table 1 (the setting values changed depending on the ambient temperature).

[0037]

[Table 1]

FIG. 8 shows nickel at an ambient temperature of 40 ° C.
A hydrogen battery is charged, curves J and K are battery voltages, curves L and M are battery temperatures, and curves N and O are charging currents, the former of which is based on pulse charging (see the charging device of the present embodiment. Similarly, charging is performed with a pulse having a charging ON time of 9 ms and a charging OFF time of 1 ms, and charging is completed at a charging amount of 100%), the latter being due to the charging device of the present invention. From the curve L in the figure, the amount of charge is 1 for pulse charging.
At 00%, the temperature rises to 74 ° C., which may lead to deterioration of battery characteristics. Therefore, in the present invention, when the ambient temperature is high, the charging current is changed from the first charging current to the second charging current, and the limiting temperature is changed from the first limiting temperature to the second limiting temperature to perform charging. In the case of this embodiment, the second charging current 500
mA and the second limiting temperature of 60 ° C. As a result, the temperature rise is suppressed as shown by the curve M in the figure, and 100% charge (in the case of the present embodiment, charge control by ΔT was performed at 102%) is possible.

[0039]

EFFECTS OF THE INVENTION According to the present invention, in any type of battery, neither insufficient charging nor overcharging occurs, and
Since the battery voltage is measured when the charging is stopped, the influence of the history of the battery can be prevented and the battery can be charged surely and sufficiently.

Further, in the present invention, since the limit temperature and the set temperature are changed according to the ambient temperature of the secondary battery, the secondary battery can be charged almost 100% surely without being affected by the temperature change.

[Brief description of drawings]

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

FIG. 2 is a detailed circuit diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart of the present invention.

FIG. 4 is a diagram showing a charging current of the charging device of the present invention.

FIG. 5 is a diagram showing charging characteristics by the charging device of the present invention.

FIG. 6 is a diagram showing charging characteristics by the charging device of the present invention.

FIG. 7 is a diagram showing charging characteristics by the charging device of the present invention.

FIG. 8 is a diagram showing charging characteristics of the charging device of the present invention.

FIG. 9 is a diagram showing charge characteristics of a nickel-cadmium battery.

FIG. 10 is a diagram showing charging characteristics of a sealed lead battery.

[Explanation of symbols]

1 is a battery pack, 11 is a secondary battery, 12 is a temperature sensor,
13 is a fixed resistor, 2 is a microcomputer, 21 is C
PU, 22 is memory, 23 is output port, 24 is A / D
Converter, 3 is a control circuit, 31 and 32 are transistors, 3
3, 34 are resistors, 4 are inverter circuits, 41 is a pulse width control circuit, 42 is a transistor, 43 is a transformer, 44
Is a shunt regulator, 45 is a photo coupler, 46 and 4
7 is a resistor, 5 is a switch circuit, 5'is a switch circuit, 6
Is a rectifier circuit, 61 and 62 are diodes, 63 and 64 are capacitors, 71 is a resistor, 72 is a transistor, and 73 is a zener diode.

Claims (4)

[Claims] 1. A charging device for charging a secondary battery with a current having a pulse waveform, a sampling means for sampling the battery temperature of the secondary battery and a battery voltage when the pulse is stopped, and a means for updating and storing the sampling value. If the battery temperature sampled by the sampling means exceeds a control temperature, or if the amount of change in the sampled battery temperature exceeds a set value, or a sampling value is sampled. The charging device for a secondary battery, characterized in that charging is stopped or switched to a small current when the battery voltage does not change for a certain period of time or the voltage drop of the sampled battery voltage exceeds a set value. . 2. A pulse width control circuit, a feedback circuit that feeds back to the control circuit, a transformer, an inverter circuit that obtains a constant DC voltage with a transistor as a constituent element, a reference voltage generating element, a resistor, and a transistor as the constituent elements. A constant current circuit that creates a constant current from the circuit, a switch circuit that turns the constant current on and off, a value of the battery voltage that is taken into the microcomputer when the switch circuit is in a cut-off state, that is, during a current charging pause period, The microcomputer turns on the switch circuit.
2. The charging device for a secondary battery according to claim 1, wherein the charging device controls OFF and OFF. 3. The set value of the battery voltage and the limiting temperature for stopping the charging or switching the minute current changes according to the battery temperature at the start of charging sampled by the sampling means. Rechargeable battery charger. 4. When the battery temperature at the start of charging sampled by the sampling means is high, the limiting temperature is changed from the first limiting temperature to the second limiting temperature, and the charging current is changed to the first charging current. The rechargeable battery charging device according to claim 1, wherein the rechargeable battery is charged by switching from the charging current to the second charging current.