JP3336790B2 - Battery life judgment device for 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 an apparatus for determining the life of a battery set of a charger for charging a secondary battery such as a nickel-cadmium battery (hereinafter referred to as a nickel-cadmium battery).

[0002]

2. Description of the Related Art Generally, a rechargeable battery is used as a power source for a portable device, and is removed from the device each time the battery capacity is exhausted, charged by a charging device, and then attached to the device again for use. Repeated use becomes possible many times. However, these batteries deteriorate from initial characteristics as shown in FIG. 3 as charging and discharging are repeated, and there is a limit to the number of times charge and discharge can be used repeatedly. Heretofore, such a determination of the life of a battery has been made individually by the user of the device based on experience and the like.

[0003] The life of a battery depends on the mode in which the internal impedance increases due to leakage of the electrolyte from the inside of the battery and the capacity decreases as shown in FIG. Although there is an internal short circuit caused by a decrease in strength, especially in a battery group in which a plurality of unit cells are connected in series, due to the variation in the capacity of each unit cell, the unit cell with the smallest capacity in the assembled battery is overcharged. Overdischarged,
In most cases, the former mode reaches the end of life.

[0004]

However, when the battery life is determined based on the user's experience, when the user notices a decrease in the capacity, the unit cells in the battery pack continue to be overcharged and overdischarged. However, during charging, the electrolyte in the battery is discharged into the charging device, corroding electronic components and the like, and causing a failure of the charging device. In addition, devices used under a high load, such as electric power tools, consume a great deal of battery power, and there is a demand for knowing the time to replace the battery, but this cannot be sufficiently satisfied. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned disadvantages of the prior art and to make it possible to reliably determine the life of a battery set in a charger. Another object of the present invention is to ensure that discriminated in response to battery set life battery temperature.

[0005]

In order to achieve the above object, in the battery life determining apparatus of the battery charger according to the present invention, the life of the battery whose battery capacity has started to decrease is reduced as shown in FIG. Noting that cause rapid voltage rise, to detect the battery voltage after initial charging at a predetermined current, you determine the voltage value said detectable is a predetermined lifetime determined voltage value or more when the battery life
I is intended was Unishi. Further, by changing the charging current and / or charging time at the time of the initial charging based on the battery temperature, it is possible to accurately determine the life .

[0006]

In the above battery life determining apparatus, the life of the battery is determined based on whether the battery voltage at the beginning of charging is equal to or higher than a predetermined life determining voltage value.

[0007]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes an AC power supply, and 2 denotes a battery set in which a plurality of rechargeable unit cells are connected in series, and a battery temperature detecting means comprising a thermistor or the like for detecting a battery temperature in contact with or close to the unit cells. 2A is built in.
Reference numeral 3 denotes current detecting means for detecting a charging current flowing through the battery set 2, 4 denotes a charging control signal transmitting means for transmitting a signal for controlling start and stop of charging, and 5 denotes charging for returning a signal of the charging current to the PWM control IC 23. It is a current signal transmission means. The charging control transmission signal means 4 and the charging current signal transmission means 5 are composed of, for example, a photocoupler. 10 is a full-wave rectifier circuit 1
A rectifying / smoothing circuit comprising 1 and a smoothing capacitor 12;
Is a switching circuit composed of a high-frequency transformer 21, a MOSFET 22, and 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. Reference numeral 30 denotes a rectifying / smoothing circuit including diodes 31, 32, a choke coil 33, and a smoothing capacitor 34. Reference numeral 40 denotes a battery voltage detecting unit including resistors 41 and 42, which divides the terminal voltage of the battery set 2. Numeral 50 denotes arithmetic means (CPU) 51, ROM 52, RAM 53, timer 5
4. A microcomputer comprising an A / D converter 55, an output port 56, and a reset input port 57. The RAM 53 has a built-in battery voltage storage unit 531 and a battery temperature storage unit 532 that store the sampled battery voltage and battery temperature, respectively. Reference numeral 60 denotes operational amplifiers 61 and 62, resistors 63 to 6
6, a charging current control means 70;
1. A constant-voltage power supply including a full-wave rectifier circuit 72, a smoothing capacitor 73, a three-terminal regulator 74, and a reset IC 75, and serves as a power supply for the microcomputer 50, the charging current control means 60, and the like. The reset IC 75 outputs a reset signal to the reset input port 57 to bring the microcomputer 50 into an initial state. Reference numeral 80 denotes a battery life display unit that includes an LED 81 and a resistor 82 and displays the life of the battery set 2. Reference numeral 90 denotes charging current setting means 90 for setting a charging current. A charging current setting reference voltage value applied to the inverting input terminal of the operational amplifier 62 in accordance with a signal from the output port 56, that is, a charging current value to be passed. Is to change.

Before describing the discriminating operation of the present invention, the battery voltage characteristics during charging of a normal battery set 2 (hereinafter referred to as a normal battery set) and a battery set 2 having expired (hereinafter referred to as a "lifetime battery set") will be described. .

FIG. 4 shows the battery voltage when the life battery set 2 is charged with the charging current Iα, and shows that the battery voltage has risen to the life determination reference voltage Vrα or more at the beginning of charging. FIG.
Indicates the battery voltage when the normal battery set 2 having a low temperature is charged with the charging current Iα, and indicates that the battery voltage is equal to or higher than the life determination reference voltage Vrα at the initial stage of charging. FIG. 6 shows the charging current Iβ (Iα>I>
β) indicates the battery voltage at the time of charging, and indicates that the battery voltage is not higher than the life determination reference voltage Vrβ at the beginning of charging. FIG. 7 shows the battery voltage when the normal battery set 2 that has been left for a long time but the temperature is not low is charged with the charging current Iα.
Although the voltage rises at the beginning of charging, it is smaller than the voltage rise of the battery pack 2 of life. FIG. 8 shows the battery voltage when the battery pack 2 whose temperature is not low is charged with the charging current Iα, and shows that the battery voltage has risen to the lifetime determination reference voltage Vrα or more at the beginning of charging. FIG. 9 shows the battery voltage when the low-temperature battery pack 2 is charged with the low-temperature charging current Iβ, and shows that the battery voltage has risen above the low-temperature lifetime determination reference voltage Vrβ at the beginning of charging. . FIG. 10 shows the battery voltage when the normal battery set 2 whose temperature is not low is charged with the charging current Iα, and shows that the battery voltage has not risen above the life determination reference voltage Vrα at the initial stage of charging. As described above, the temperature of the battery set 2 at the start of charging is detected,
Initial charging is performed by appropriately setting the charging currents Iα and Iβ and the charging times tα and tβ in accordance with the detected temperature, and detecting whether or not the battery voltage after the initial charging is equal to or higher than the life determination reference voltages Vrα and Vrβ. By doing so, it becomes possible to determine whether the battery pack 2 is a normal battery pack or a life battery pack. Hereinafter, such life determination will be described with reference to the flowcharts of FIGS.

When the power is turned on, the microcomputer 50 enters a standby state for connection of the battery set 2 (step 101). Battery pack 2
Is connected, the microcomputer 50 determines the connection of the battery set 2 by the signal of the battery voltage detecting means 40, and A / D converts the temperature of the battery set 2, ie, the output signal of the battery temperature detecting means 2A, by the A / D converter 55. The battery temperature Tin before the start of charging is captured (step 102), and the battery temperature Tin before the start of charging is acquired.
Is subtracted from the reference temperature Tref to determine whether the battery is low or high (step 103).

In the positive case, it is determined that the battery temperature is not low, and the charging current setting reference voltage V corresponding to the charging current Iα is determined.
α, the life determination reference voltage Vrα (Vrα corresponds to the charging current Iα, and Vrα becomes larger if the charging current is set larger, and Vrα becomes smaller if the charging current is set smaller) and the initial charging time tα is set (step 104). ), PWM control I from the output port 56 via the charge control signal transmitting means 4
A charging start signal is transmitted to C23, and charging is started with the charging current Iα (step 105). The charging current flowing through the battery set 2 is detected by the current detecting means 3 simultaneously with the start of charging, and the difference between the voltage corresponding to the detected charging current and the reference voltage Vα from the charging current setting means 90 corresponding to the output of the output port 56 is calculated. From the charging current control means 60 via the signal transmission means 5,
Feedback is applied to the PWM control IC 23. That is, when the charging current is large, the pulse width is narrowed, and when the charging current is large, the pulse having the widened pulse width is applied to the high-frequency transformer 21 and smoothed to a direct current by the rectifying and smoothing circuit 30 to keep the charging current constant. That is, the current detecting means 3, the charging current control means 60, the charging current signal transmitting means 5, the switching circuit 20, the rectifying and smoothing circuit 3,
Through 0, the charging current is controlled to have a predetermined current value Iα.

Next, battery life determination is performed. Initial setting of initial charging maximum battery voltage value Vm to 0 (step 10)
6) Then, the latest battery voltage value Vx is inputted from the start of the initial charging (step 107), and the battery voltage value Vx is stored in the battery voltage storage means 531. The latest battery voltage value Vx and the battery voltage storage means 531 are stored. Is compared with the initial charging maximum voltage value Vm up to the previous input stored in the memory (step 10)
8). If positive in step 108, the Vx value is set to Vm
The initial charging maximum voltage value of the battery voltage storage unit 531 is rewritten (step 109), and it is checked whether the initial charging time tα has elapsed (step 110).
If the time has not elapsed, the processing of steps 107 to 110 is performed again. If negative in step 108, the process jumps to step 110 without performing the process in step 109. If the time tα has elapsed in step 110, the difference between the initial charging maximum battery voltage value Vm and the life determination reference voltage Vrα is compared and calculated (step 111), and if positive, the charged battery group 2 is determined to have the battery life. Then, the microcomputer 50 generates an output of the battery life from the output port 56, makes the LED 81 of the battery life display means 80 emit light (step 113), and outputs a charge stop signal from the output port 56 via the charge control signal transmitting means 4 to the PWM. The charge is transmitted to the control IC 23 to stop the charging (step 114). Then battery pack 2
Is determined to be taken out (step 115). When it is determined that the battery set 2 is taken out, the process returns to step 101 and waits for charging the next battery set 2A.

If the result in step 111 is negative, the battery set 2 is determined to be a normally usable battery set 2, and the full charge detection process is continuously performed. As is well known, there are various detection methods for full charge detection. For example, the battery set 2 is detected as in the case of -ΔV detection in which a predetermined amount of ΔV drop from a known peak voltage value at the end of charging is detected and charging is stopped. Is detected (step 112), and if full charge is determined, the microcomputer 5
0 transmits a charge stop signal to the PWM control IC 23 to stop charging (step 114), determines that the battery set 2 is to be removed (step 115), and returns to step 101 when it is determined that the battery set 2 is removed. , Next battery pack 2
Wait for charging. If it is determined in step 112 that the battery is not fully charged, step 112 is repeated.
Return to

If the result in step 103 is negative, it is determined that the battery temperature is low, and the charging current Iβ (Iα> I
β) (Vα> V)
β), life determination reference voltage Vrβ (Vrβ also corresponds to charging current Iβ similarly to Vrα, and the difference from Vrα varies depending on the values of charging currents Iα and Iβ) and initial charging time t.
β (tβ ≧ tα) is set (step 116). Thereafter, the same initial charge, battery life determination and full charge determination as in steps 105 to 112 are performed in steps 116 to 124, and the life of the battery set 2 is determined. In step 113, the LED 81 is caused to emit light, and when the battery set 2 is normal and full charge is detected, charging is stopped in step 114.

In the above embodiment, it is determined whether or not the battery temperature Tin at the start of charging of the battery set 2 is lower than the reference temperature Tref to determine whether or not the battery is a low-temperature battery. Although the determination reference voltages Vrα and Vrβ and the magnitude of the battery voltage are detected to determine whether or not the battery pack has reached the end of life, the reference temperature is subdivided, and the discrimination reference voltage is subdivided in accordance with the subdivided reference temperature. You may.

The battery set 2 is a battery set 2 having the same number of cells.
However, the number of unit cells may be detected, and the determination reference voltages Vrα and Vrβ corresponding to the detected number of unit cells may be used. That is, as disclosed in Japanese Patent Application No. 5-93081, entitled "Charge Control Method for Battery Charging Apparatus", filed by the applicant of the present invention, the battery voltage is detected by charging the battery for a predetermined time with a small current at the beginning of charging. The number may be detected, and the reference voltages Vrα and Vrβ corresponding to the detected number of cells may be used.

As a matter of course, in the above embodiment, the discrimination reference voltages Vrα and Vrβ are determined by the set charging current Iα,
The determination reference voltages Vrα and Vrβ are set large when the charging currents Iα and Iβ are set large, and set small when the charging currents Iα and Iβ are set small. That is, the determination reference voltages Vrα and Vrβ change according to the charging currents Iα and Iβ and the battery temperature.

There are also various types of unit cells constituting the battery set 2, from a standard type which is charged with a current of 1 C or less to a standard type.
There are various types and types of quick charging capable of charging up to about C. In the above embodiment, the charging currents Iα and Iβ are set in accordance with the types of these unit cells.

Table 1 shows an example of the determination reference voltage corresponding to the battery temperature, the number of cells, and the charging current. The battery group 2 is assumed to be composed of a quick-charging type unit cell (1700 mAh), the nominal voltage of one unit cell is 1.2 V, and the battery group 2 is 7.2 V (six unit cells). ),
There are four types, 9.6 V (8 unit cells), 12 V (10 unit cells), and 24 V (20 unit cells), and the charging current Iα is 4C.

[0020]

[Table 1]

The battery low temperature determination reference value Tref is set to 0 ° C.
Table 2 shows an example of the determination reference voltage corresponding to the number of cells when the charging current Iα is 3C and Iβ is 1C. As in Table 1 above, battery set 2 is a fast charging type unit cell (1700 m
Ah).

[0022]

[Table 2]

[0023]

According to the present invention as described above, according to the present invention, battery set life battery temperature, charging current, it is possible to reliably and accurately detect regardless. In addition, it is possible to prevent the life battery group from being discriminated in the early stage of charging and the charging of the life battery group, that is, the unnecessary charging from being started. Further, it is not necessary to add a special element for determining the life, and it is possible to provide an operation effect such that a charger provided with the life determining device can be provided at low cost.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing one embodiment of the present invention.

FIG. 3 is a graph showing cycle life characteristics of a battery.

FIG. 4 is a graph showing charging characteristics when a battery having a lifetime is charged.

FIG. 5 is a graph showing charging characteristics when a normal battery with a low battery temperature is charged with a normal charging current.

FIG. 6 is a graph showing charging characteristics when a normal battery is charged at a low battery temperature.

FIG. 7 is a graph showing charging characteristics when a battery left for a long time is charged.

FIG. 8 is a graph showing charging characteristics when a battery with a low battery temperature and a long life is charged.

FIG. 9 is a graph showing charging characteristics when a battery having a low battery temperature and a long life is charged.

FIG. 10 is a graph showing charging characteristics when a normal battery is charged when the battery temperature is not low .

[Explanation of symbols]

2 is a battery set, 2A is a battery temperature detecting means, 40 is a battery voltage detecting means, 50 is a microcomputer for determining battery life, 60 is charging current control means , 80 is battery life display means, and 90 is charging current setting means. is there.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 31/36 H01M 10/42-10/48 H02J ⁷ /00-7/12

Claims (4)

(57) [Claims] 1. A battery charger for charging a battery set comprising a plurality of unit cells connected in series and temperature detecting means for detecting the temperature of the unit cells, wherein a battery voltage detecting means for detecting a battery voltage of the battery set. And battery set life determining means for determining the life of the battery set when the output of the battery voltage detecting means is equal to or greater than a predetermined life determining voltage, wherein the charging current and / or the charging based on the battery temperature detected at the start of charging are provided. A battery pack life discriminating device for a charger, wherein a battery voltage after charging for a time is determined to be a battery pack having a life time equal to or greater than the life discrimination voltage. 2. The apparatus according to claim 1, wherein when the battery temperature detected at the start of charging is lower than a predetermined value, the charging current is reduced and the charging time is lengthened. . 3. When the battery temperature is below a predetermined value detected at the start of charging, the life determination cell group life discriminating device charger battery voltage according to claim 1, wherein it has greatly. 4. The battery pack life determining device for a charger according to claim 1, wherein a life determining voltage of said battery life determining means is changed in accordance with said charging current.