JPH09285032A - Battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the full-charge of a battery securely regardless of the activeness or inactiveness of the battery by a method wherein an active battery full-charge detecting means which uses the battery voltage detection and an inactive battery full-charge detecting means which uses the battery temperature detection are provided. SOLUTION: A plurality of rechargeable unit cells are connected in series to each other. A battery temperature detecting means 2A which is so provided as to be brought into contacts with the unit cells and a battery voltage detecting means 40 consisting of resistors 41 and 42 are provided. The initial values of a voltage comparison value for the active battery full-charge detection in a memory means, a comparing battery voltage, the minimum battery temperature of a battery temperature memory and a temperature rise comparison value ΔTia for the inactive battery full-charge detection are set. A voltage before sampling is deducted from the battery voltage by an arithmetic means 51 to obtain ΔV. The newest battery temperature is received from the detecting means 2A and the minimum battery temperature is deducted from it to obtain ΔT. The values of ΔT and ΔTia are compared with each other. If ΔT is larger than ΔTia, it is judged that a battery assembly 2 is fully charged. Consequently, the full-charge can be detected securely.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a charging device for an alkaline electrolyte secondary battery such as a nickel-cadmium battery (hereinafter referred to as a nicad battery).

[0002]

2. Description of the Related Art As a full charge detection method for a charger for charging a NiCd battery, constant current charging is used to detect a voltage drop from a peak value at the end of charging, a ΔV detection method, and to improve the cycle life of the battery, A second-order differential detection method that detects a negative second-order differential value of a battery voltage during charging, which is less likely to be overcharged than the ΔV detection method, and detects that the battery temperature of a battery to be charged rises by a predetermined temperature. There is a ΔT detection method and the like.

[0003]

However, in the case of an inactive battery such as a new battery or a battery that has been left for a long time, the above-mentioned -Δ
The V detection method and the second-order differential detection method result in overcharge, which causes electrolyte leakage and the like, and reduces the cycle life characteristics of the battery. In addition, in the ΔT detection method, the temperature rise of the inactive battery becomes larger than that of the active battery, and conversely, the charging is stopped before the full charge and the capacity becomes insufficient. This is because, as can be seen from the charging characteristics shown in FIG. 3, the time-dependent change in the battery voltage (solid line) of the inactive battery becomes a gradual voltage increase compared to the battery voltage of the active battery (broken line), and the peak of the battery voltage at the end of charging. The occurrence of-becomes overcharged in the -ΔV detection method, and 2
Since the amount of change in the battery voltage is small in the differential detection method, A /
If the microcomputer is periodically loaded via the D converter, the amount of change in battery voltage cannot be reliably detected. Also ΔT
In the detection method, in the case of an inactive battery, the positive electrode active material inside the battery is in a highly crystalline state and is in a chemically stable state, which increases the internal impedance of the battery during charging and raises the temperature due to the active battery. However, there is a problem that charging is stopped before the battery is fully charged. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to make it possible to reliably detect a full charge regardless of whether the battery is active or inactive.

[0004]

The above object can be achieved by providing active battery full charge detection means for detecting battery voltage and inactive full charge detection means for detecting battery temperature.

[0005]

1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is an AC power source, 2 is a battery set including a battery temperature detecting means 2A for connecting a plurality of rechargeable unit cells in series and arranged in contact with or close to the unit cells to detect the battery temperature, 3 Is a current detecting means for detecting a charging current flowing through the battery set 2, 4 is a charging control signal transmitting means for transmitting a signal for controlling the start and stop of charging, and 5 is a charging current for feeding back a signal of the charging current to the PWM control IC 23. It is a 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 rectifying / smoothing circuit including a full-wave rectifying circuit 11 and a smoothing capacitor 12, 20 is a high frequency transformer 21, a MOSF.
A switching circuit including an ET 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. 30 is a diode 3
1, 32, choke coil 33, smoothing capacitor 34
The rectifying and smoothing circuit 40 is composed of resistors 41 and 42, and the battery voltage detecting means 40 divides the battery voltage of the battery group 2.
Reference numeral 50 denotes an arithmetic means (CPU) 51, a ROM 52, a RAM 5
3, timer 54, A / D converter 55, output port 5
6, a reset input port 57.
The RAM 53 incorporates a battery voltage storage unit 531 and a battery temperature storage unit 532 that store the sampled battery voltage and battery temperature. Reference numeral 60 is a charge current control means including operational amplifiers 61 and 62 and resistors 63 to 66, 70 is a power transformer 71, a full-wave rectifier circuit 72, smoothing capacitors 73 and 3.
A constant voltage power supply including a terminal regulator 74 and a reset IC 75, which 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 a reset input port 75 to bring the microcomputer 50 into an initial state. Reference numeral 80 denotes an inactive battery display means which includes an LED 81 and a resistor 82 and indicates that the charged battery group 2 is an inactive battery. 90 is a charging current setting means for setting the charging current.

Next, the operation of full charge detection 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 101). When the battery set 2 is connected, the microcomputer 50 determines from the signal of the battery voltage detection means 40 that the battery set 2 is connected, and the output start signal from the output port 56 to the PWM control IC 23 via the charge control signal transmission means 4. Is transmitted to start charging (step 102). The charging current flowing in the battery set 2 at the same time as the charging is started
The difference between the detected charging current value and the reference value Vref is fed back to the PWM control IC 23 from the operation amplification means 60 via the charging current signal transmission means 5. The current detection means 3, the operation amplification means 60, the signal transmission means 5, the switching circuit 20, and the rectifying / smoothing circuit 30 control so that the charging current becomes constant.

Next, full charge detection control is performed. Battery voltage comparison value for active battery full charge detection of battery voltage storage means 531
Vmax and comparative battery voltage Ei for each sampling
-5 to Ei are initially set (step 103), and the minimum battery temperature Tmin of the battery temperature storage means 532 is set.
Then, the temperature rise comparison value ΔTia for detecting the full charge of the inactive battery is initially set (step 104), and the battery voltage / battery temperature sampling timer is started (step 105). When the sampling timer time Δt has elapsed (step 106), the sampling timer is restarted again (step 107). Next, the output signal of the battery voltage detecting means 40 obtained by dividing the voltage of the battery group 2 is A / D converted by the A / D converter 55 and taken in as the battery voltage Vin (step 108), and the battery voltage V is calculated by the calculating means 51.
The battery voltage Ei-5 before 6 sampling is subtracted from in, and Δ
V is calculated (step 109). Further, the output signal from the battery temperature detecting means 2A is A / D converted by the A / D converter 55 and fetched as the latest battery temperature Tin (step 110), and the calculating means 51 minimizes the battery temperature Tin and the battery temperature storing means 532. The battery temperatures Tmin are compared (step 111), and when Tin is small, the battery temperature storage means 53
The data of Tin is stored in the minimum battery temperature Tmin of 2 (step 112), and the latest battery temperature Ti is calculated by the calculating means 51.
The minimum battery temperature Tmin is subtracted from n to obtain ΔT (step 113).

Next, the magnitude of ΔV and ΔVmax obtained in step 109 is discriminated (step 114). ΔV
Is smaller than ΔVmax, the microcomputer 50 transmits a charge stop signal from the output port 56 to the PWM control IC 23 via the charge control signal transmission means 4 to stop charging (step 115). Next, it is determined that the battery set 2 is taken out (step 116), and if it is determined that the battery set 2 is taken out, the process returns to step 101 and stands by for charging the next battery set 2.

At step 114, ΔV is ΔVmax
In the above case, the value of ΔVmax is set to ΔV, and the battery voltage at each sampling of the battery voltage storage means 531 is rewritten (step 117).

Next, the difference between ΔT obtained in step 113 and the temperature rise comparison value ΔTia for detecting the full charge of the inactive battery is determined (step 118). The temperature rise comparison value ΔTia for detecting the full charge of the inactive battery is set to a value larger than the temperature rise value ΔTa for detecting the full charge of the normal active battery as shown in FIG. 3, and the inactive battery is detected by the −ΔV detection method. It is set to a value smaller than the temperature rise value ΔTb at the time point. Δ
When T is larger than ΔTia, it is determined that the battery group 2 is fully charged, and charging is stopped in step 115. ΔT is ΔT
When it is ia or less, the process returns to step 106 and the same process is continuously performed.

In the above embodiment, the full charge detection method for an inactive battery is the ΔT detection method which detects the temperature rise above a predetermined temperature and stops charging.
No. 93518, Japanese Patent Laid-Open No. 2-246739, Japanese Utility Model Publication No. 3-
The ΔT / Δt detection method described in Japanese Patent Publication No. 34638 may be used to control charging by detecting that the battery temperature increase rate (temperature gradient) per predetermined time during charging becomes equal to or higher than a predetermined value. In this case, the temperature gradient value ΔTi for detecting the full charge of the inactive battery is set to a value larger than the temperature gradient value ΔTm for detecting the full charge of the normal active battery as shown in FIG.
The temperature rise gradient value ΔTn at the time when the inactive battery is detected by the −ΔV detection method is set to a value smaller than that, and the temperature rise gradient value for each sampling time is set to a predetermined temperature for full charge detection. The full charge detection process may be performed by performing a comparison calculation with the gradient value ΔTi.

Further, since the temperature rise of the battery group 2 until full charge differs depending on the battery temperature at the start of charging, a predetermined temperature rise comparison value ΔTia (= K) of the ΔT detection method of the above embodiment.
Is the battery temperature at the start of charging or the minimum battery temperature Tmin
It is preferable to set each of them because the detection accuracy becomes higher. For example, the battery temperature at the start of charging or the minimum battery temperature is 0 to 10 ° C, 10 to 25 ° C, 25 to 40 ° C and 40, respectively.
If the temperature rise comparison value ΔTia for detecting the full charge of the inactive battery is set to 30K, 25K, 20K and 15K at -60 ° C, the accuracy of detecting the full charge of the inactive battery is further improved.

Of course, in the above embodiment, the full charge of the active battery is detected by the second differential detection method, but the voltage drop at the end of charge is detected to stop the charge -Δ.
You may make it detect by a V detection method.

[0014]

As described above, according to the present invention, by providing the full charge detection means corresponding to the activation and inactivation of the battery set, the full charge can be surely performed regardless of the activation and inactivation of the battery set. You will be able to detect.

[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 for explaining the operation of the charging device of the present invention.

FIG. 3 is a graph showing charging characteristics of an active battery set and an inactive battery set.

[Explanation of symbols]

Reference numeral 2 is a battery group, 2A is temperature detecting means, 3 is charging current detecting means, 40 is battery voltage detecting means, and 50 is a microcomputer.

Claims (7)

[Claims] 1. A battery voltage detecting means for detecting a battery voltage of a battery to be charged, and an active battery full charge detecting means for detecting a full charge of an active battery based on an output of the battery voltage detecting means.
Battery temperature detecting means for detecting the battery temperature of the battery to be charged,
A battery charging device comprising an inactive battery full charge detecting means for detecting a full charge of an inactive battery based on an output of the battery temperature detecting means. 2. The inactive battery full charge detection means includes a battery temperature storage means for storing at least the latest battery temperature, a minimum battery temperature and an inactive battery full charge detection temperature rise comparison value, and at each sampling time. The latest battery temperature is compared with the minimum battery temperature to obtain the minimum battery temperature, and charging is stopped when the difference between the latest battery temperature and the minimum battery temperature becomes larger than the temperature rise comparison value for detecting the full charge of the inactive battery. 2. The battery charging device according to claim 1, wherein the battery charging device comprises an arithmetic means for generating a signal. 3. The temperature rise comparison value for detecting the full charge of the inactive battery is set larger than the temperature rise value at which the active battery is fully charged and smaller than the temperature rise value at which the inactive battery is overcharged. The battery charging device according to claim 2. 4. The battery charging according to claim 2, wherein the temperature rise comparison value for detecting the full charge of the inactive battery is changed in accordance with the battery temperature at the start of charging or the minimum battery temperature. apparatus. 5. The temperature rise value at which the inactive battery is overcharged is the temperature rise value when the battery voltage drops from the peak value by a predetermined amount during charging of the inactive battery. 3. The battery charging device described in 3. 6. A battery temperature storage means for storing at least the latest battery temperature, a battery temperature before a predetermined sampling, and a temperature gradient value for detecting an inactive battery full charge, and each sampling time. For each time, the latest battery temperature is compared with the battery temperature before the predetermined sampling to obtain the temperature gradient value, and a charge stop signal is generated when the obtained temperature gradient value is larger than the temperature gradient value for inactive battery full charge detection. 2. The battery charging device according to claim 1, wherein the battery charging device comprises: 7. The temperature gradient value for detecting the full charge of the inactive battery is larger than the temperature gradient value at which the active battery is fully charged and smaller than the temperature gradient value at which the inactive battery is overcharged. The battery charging device according to claim 5.