JP2696491B2 - 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 method for charging a secondary battery such as a nickel cadmium battery or a nickel metal hydride battery by supplying a charging current thereto, and more particularly, to a voltage change .DELTA.
The present invention relates to a charging method for detecting full charge by detecting V.

[0002]

2. Description of the Related Art Conventionally, as a charging method for charging a secondary battery of this type by supplying a charging current, for example, there is a method called a -.DELTA.V method. That is, a secondary battery such as a nickel cadmium battery has a property that the voltage gradually increases as it is charged, reaches a peak when fully charged, and then drops when overcharged. Therefore, a charging method that utilizes this property to stop charging by detecting that the battery voltage has dropped by a predetermined amount from the peak value -ΔV has been conventionally performed.

[0003] However, in the conventional -ΔV method, the battery is charged even after being fully charged, so that the battery is overcharged, and the life of the battery is affected by generation of gas, deterioration of the electrodes, and the like. In particular, nickel-metal hydride batteries, which have recently been widely used, are more vulnerable to overcharging than nickel-cadmium batteries,
Since the voltage drop -V of the battery after full charge is small, -V
In the method, the timing of detecting the full charge is delayed, and there is a high possibility that the battery is deteriorated due to overcharging. Therefore, a charging method replacing the -ΔV method has been desired.

In order to solve such a problem, for example, as shown in FIG. 9, a nickel cadmium battery, a nickel metal hydride battery or the like has a property of increasing in temperature in proportion to the charged amount, and this is used. Various methods have been proposed. In the figure, the temperature rise for each charging rate of 5c, 3c, 1c is shown. FIG. 8 shows the basic configuration of a typical charging circuit. In the figure, 11 is a power supply unit, and Q is a switch element, for example, a transistor or FET is used. Reference numeral 13 denotes a battery pack in which a secondary battery and a thermistor Th are built. Reference numeral 12 denotes a charge control circuit. When the temperature of the secondary battery is detected by the thermistor Th in the battery pack 13 and the charge control circuit 12 determines that the battery is fully charged based on the detected temperature, the switching element Q
Is turned off to end charging.

[0005]

However, the method of detecting the full charge of the secondary battery by the indirect means of raising the temperature of the battery has a lack of reliability, and the correction for the influence of the outside temperature or the like is not performed. In addition, a commercially available battery that is required and sold as a single cell has a problem that temperature control cannot be performed because a temperature detection element (such as a thermistor) cannot be attached in shape.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a secondary battery such as a nickel cadmium battery or a nickel metal hydride battery, without detecting the temperature of the battery. An object of the present invention is to provide a charging method capable of performing safe and reliable charging without causing charging and overcharging.

[0007]

According to the present invention, there is provided a charging method for charging a secondary battery such as a nickel cadmium battery or a nickel metal hydride battery by supplying a charging current to the battery. Is divided into _{first to sixth} detection periods (T _{1 to} T ₆ ) based on charging characteristics due to a change in the charging voltage of the secondary battery, and the first detection period (T ₁ ) is defined as an undetected period. 2 detection period (T ₂ )
, The first + ΔV detection is the detection of the detection period of the voltage change (ΔV) of the first battery, and the detection of the third detection period (T ₃ ), that is, the first peak detection is the detection of the first battery voltage. The detection period of the peak value is detected, the detection of the fourth detection period (T ₄ ), that is, the second + ΔV detection is the detection period of the voltage change (ΔV) of the second battery, and the fifth detection period ( T ₅ ), that is, the second peak detection is 2
The detection period of the peak value of the battery voltage is detected and the sixth
The detection period (T ₆ ) is the detection of the voltage drop when the peak is not detected, that is, the period of −ΔV detection, and the voltage change (ΔV) of the secondary battery is detected for each detection period (T _{1 to} T ₆ ). Then, the voltage change (ΔV) of the secondary battery changes in each charging period (T ₁
To T ₆ ), the respective charging periods are recognized by detecting that the conditions are satisfied, and the charging periods (T ₂ , T ₃ ) are recognized.
Voltage change (ΔV) of the secondary battery at
If not, the process proceeds to the fifth detection period (T ₅ ), and the detection of the fifth detection period, that is, the second peak detection is normally detected, or the detection of the voltage drop when the peak detection is not performed, that is, At the point in time when −ΔV is detected, full charge is detected and the charging operation is terminated.

[0008]

A secondary battery such as a nickel cadmium battery or a nickel metal hydride battery has charging characteristics as shown in FIG. That is, in the figure, the vertical axis indicates the voltage of the battery, and the horizontal axis indicates the charging time. The battery voltage shows a steep rise immediately after the start of charging, and its value is unstable. Then, after continuing a certain rise thereafter, it hardly rises for a certain period. Thereafter, the voltage rises again, and after reaching a peak and being fully charged, the voltage decreases.

The charging period of the secondary battery exhibiting such characteristics is divided into first to sixth periods based on the contents of the characteristics. That is, the period shown a steep rise immediately after the start of charging the first detection period T _1, then the period is referred to as second detection period T ₂ for a constant increase. Thereafter a period of voltage is hardly increased with the third detection period T _3, the detection period T ₄ the period of the fourth to rise again. The period during which the battery voltage reaches the peak as a detection period T ₅ of the fifth, the period in which the voltage after full charge drops with detection period T ₆ of the sixth.

[0010] By detecting the first to fifth charging periods, the full charge of the battery can be detected. That is, the voltage is unstable during the first detection period T ₁ , and the detection of the battery voltage is not performed, and the detection is replaced after a predetermined period elapses. The second charging period T ₂ are a detection period of change of the first battery voltage, this period is a period in which the battery voltage rises at a predetermined rate, the time period by detecting the rate of change Can be detected. This detection is referred to as first + ΔV detection. Third detection period T ₃ is a detection period of the peak value of the first battery voltage, since this period there is little change in the battery voltage, detecting the period by detecting the state of the voltage change little be able to. This detection is called first peak detection. Fourth detection period T ₄ of a detection period of the second battery change, since the battery voltage again rises at a predetermined rate, it is possible to detect the time period by detecting the rate of change This detection is referred to as second + ΔV detection. Fifth detection period T ₅ of a detection of a peak value of the second battery voltage, the secondary battery is fully charged, by its voltage to detect this because the change is eliminated peaks, the period detection it can. The sixth detection period T ₆ is a −ΔV detection period when peak detection is not performed, and is a period in which the battery voltage falls after reaching a peak due to full charge, and this period is detected by detecting this voltage drop. can do.

The state of the change is detected by detecting the voltage V that has changed during a predetermined time t _n , and each detection period T ₁
Depending on through T _5, the voltage change ΔV is detected as shown in FIG. 6 respectively as _{V 1 / t 1, V 2} / t 2 ···. Although not shown, detection is performed N _n times to optimize this detection. In this way, the first to fifth detection periods T _{1 to} T ₅ are sequentially detected, and the fifth detection period T 1
₅ That is, the full charge of the battery can be detected by the second peak detection. Further, even if not the second peak detection, sixth detection period T ₆ by -ΔV detection of made, charging is detected fully.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 to 4 are flowcharts illustrating the method of the present invention. Figure 1 is a diagram showing the flow of overall operation, a certain period from the start of charging showed a steep rise is the battery voltage, also was because its voltage unstable, the non-detection period T ₁ of this period, the voltage of the No detection is performed (S1). Next, when charging proceeds normally, the battery voltage starts increasing at a constant rate. Therefore, this period can be detected by detecting the constant voltage increase rate + ΔV, and this period is defined as the first + ΔV, and the first voltage change detection period T ₂
Is the first ΔV detection (S2). Next, when normal charging proceeds, a state in which the battery voltage hardly rises continues for a certain period of time. This first battery voltage peak value detection period T
_For the detection of _3, the state in which the battery voltage hardly changes for a certain period (peak state) may be detected, and the detection in this period is defined as the first peak detection (S3). When charging proceeds normally, the battery voltage starts increasing again at a constant rate. The detection of the second battery voltage change period T ₄ is as follows:
What is necessary is just to detect the rise rate + ΔV during a certain period, and the detection during this period is defined as the second + ΔV detection (S4). Then, when charging is normally performed and the battery is fully charged, the battery voltage hardly rises and reaches a peak. The detection period of the second battery voltage peak value is performed by detecting that the battery voltage is hardly changed for a certain period of time,
This detection is defined as a second peak detection (S5). This second
The peak of the battery voltage indicating full charge is determined by the peak detection of, or even if the second peak is not detected, the voltage drop after charging -ΔV is detected to detect T _6.
Full charge is detected (S6).

[0013] While such a charging operation by detecting the fully charged progresses normally charged in the ends, also terminated by total timer T ₁₀ for other safety ensuring. Further, a process different from the normal process is performed by a safety timer described later or an abnormal voltage change.

Next, the first + ΔV detection (S2) will be described in detail. FIG. 2 is a flowchart showing the flow.
Through the non-detection period T ₁ (S1) a first detection period T ₂
When you enter the (S2), first, total timer T _10, it is determined whether or not the timer up (S20). The total timer T ₁₀ is is configured to the maximum time allowed for the charging operation, and starts counting with the charging operation start, forcibly charging operation and the time is up is so terminated (S7) . Next, it is determined whether or not the time of the safety timer T has expired (S21). This safety timer determines the maximum time allowed as the first + ΔV detection, and when the time is up, the process is forcibly shifted to the second peak detection (S5).

Next, when the voltage rise rate ΔV is abnormally large, that is, when the voltage rise at a certain time t ₅ is V ₅ LS
If it is more than B, it is determined that no abnormal increase in the normal charged state (S22), and further the detected abnormal rise continuously detected N ₅ times that is set as the number of times that this detection is optimized It is determined whether or not it is (S23). If so, the abnormality detection is optimized, and the processing is shifted to the second peak detection (S5). Otherwise, the processing is performed again from the beginning (S20). . Here, V _n LSB represents a change in voltage during a certain time t _n .

Next, when the rate of increase ΔV of the battery voltage is abnormally small, that is, when the voltage rise during a certain time t ₆ is V
If it is equal to or less than ₆ LSB, it is determined that the abnormal rise is lower than the normal state of charge (S24), and as described above, in order to correct the abnormal rise, whether or not this abnormal rise has been detected N ₆ times Is determined (S25), and if so, the second
The processing shifts to peak detection (S5), otherwise returns to the first processing (S20).

If no abnormal rise in voltage is detected, it is determined whether or not the voltage rises during a normal charge state.
A first + ΔV detection is performed. That is, the fixed time t ₁
Is determined to be equal to or greater than V ₁ LSB, and if so, it is determined whether the number N _{1 of} times for further optimizing the detection is detected (S27). And if it is detected _once N proceeds to the second detection period T ₂ is that detected the next step S _3, the flow returns to again otherwise start processing (S20).

Next, the first peak detection (S3) will be described in detail. First, total timer T ₁₀ is examined, (S
30) If it is determined that the time is up, the process is forcibly terminated (S7). Further, the safety timer T is checked (S31).
A sufficient time allowed as 3 is set, and when the time is up, the process forcibly shifts to the second peak detection (S5).

Next, when the rate of increase in the battery voltage is large, that is, when the voltage rises at a certain time t ₅ is V ₅ L
If the value is equal to or larger than SB, it is determined to be abnormally high (S32).
It is determined whether or not the detected number N ₅ times to optimize this (S33), and if so, the second peak detection (S5)
Then, if not, the process returns to the beginning (S30).

If no abnormal rise is detected, it is determined whether or not it is the first peak. That is, it is determined whether or not the voltage rise at the fixed time t ₂ is equal to or less than V ₂ LSB, and (S
34), further if so, the detection is judged whether or not the detected number N ₂ times to be optimized (S35), as a first peak detection if so, the third detection period T ₃
Is detected, the process proceeds to the next step (S4), and otherwise returns to the first process (S30).

Next, the second + ΔV detection (S4) will be described in detail. FIG. 4 is a flowchart showing the flow. First, examine the total timer T ₁₀ (S4
0) Next, the point of checking the safety timer T (S41) is the same as described above, and the maximum time allowed for the second + ΔV detection is set in the safety timer T.

Then, whether or not the voltage rise is abnormal, that is, the voltage rise during the fixed time t ₇ is equal to or less than V ₇ LSB (S42), and the number of times N ₇ times to optimize this detection is detected (S43) Is determined that the rate of rise of the voltage is abnormally small, and forcibly proceeds to the next step (S5).
Otherwise, the process returns to the first process (S40).

If no abnormality is detected, the second + ΔV
Detection is performed. That is, if the voltage rises at a predetermined time t ₃ is V ₃ LSB or more (S44), it is determined whether or not the detected number of detections N ₃ times to optimize this (S4
5) If so, the fourth detection period is detected as the second + ΔV detection, and the process proceeds to the next step (S
5) Otherwise, return to the first process (S40).

Next, the second peak detection (S5) will be described. Since this is the final stage of the detection step,
Safety timer T is not used, examine the total timer T _10,
If the count amplifier is used, the operation is forcibly terminated (S
7) If not, perform second peak detection. That is, it is determined whether or not the voltage rise at the fixed time t ₄ is equal to or less than V ₄ LSB, and the number N ₄ times of optimizing the voltage rise is detected. If so, it is determined that the voltage is the peak voltage (S6), and the operation is performed. It is terminated (S7), otherwise, repeating the detection until the incremented examined total timer T ₁₀ again.

The above periods T _{1 to} T ₅ , safety timer T, total timer T ₁₀ , voltage V _n (V ₁ , V ₂ ...)
..) And time tn (t ₁ , t _2, ...) May be set to optimal values depending on conditions such as the charging current and charging time of the secondary battery. Thus, by sequentially detecting each of the detection periods T _{1 to} T ₅ corresponding to the charging characteristics of the secondary battery, secondary full charge can be reliably detected.

Next, an example of a charging apparatus for carrying out the present invention will be described with reference to FIG. In FIG., F ₁ is the fuse, removing 1 AC line filter constituted by a conventional inductor and capacitor, 2 rectifier diode bridge-connected, SW _1, SW ₂ switch for the power supply, C ₁ ripple power 3 is a main switching circuit for turning on / off a power supply circuit, and 4 is usually formed of a series circuit of a resistor and a capacitor, and is a snubber for removing a beard voltage at the time of reverse recovery. Circuit, T is a switching transformer, D ₁ and D ₂ are rectifying diodes, 5 is a smoothing circuit composed of a smoothing capacitor and a choke coil, etc., 6 is a three-terminal regulator of a power supply IC, and 7 is a voltage. A detection constant current circuit, T _L is a photocoupler, 8 is a control unit including a CPU, a RAM, a ROM, and the like, and 9 is an oscillation that supplies a clock signal and the like to the control unit. vessel,
10 is an analog switch for switching the input of the control unit, Q
A and QB are switching elements for turning ON / OFF the charging current and the like, and E ₁ and E ₂ are charging batteries.

One of the AC input terminals 11 and 12 is connected to an AC line filter 1 for preventing noise from entering a power supply line via a fuse F ₁ , and is further connected to a rectifier 2. Switch S
It is connected to W ₁ SW ₂ . The other end of the switch SW ₁ is connected to one of the primary winding of the transformer T for switching is connected to one end of the smoothing capacitor C ₁ and the snubber circuit 4, the other end of the switch SW ₂ is a smoothing capacitor C ₁ and connected to the other end of the snubber circuit 4 and the other of the primary winding of the transformer T via the main switching circuit 3. The secondary winding of the transformer T has two outputs, one of which is input to the smoothing circuit 5 using a rectifying diode D ₁ , from which it is output as DC + 5 V via a three-terminal regulator 6. , the smoothing circuit 5 other is through the diode D ₂
And output as DC + 3V therefrom. The other secondary winding of the transformer T is input to the smoothing circuit 5 is connected to GND through a current detection resistor R ₁ therefrom. DC + 3V one end and the other end of the output and the current detection resistor R ₁ is inputted to the voltage detection constant current circuit 7, the voltage detecting constant current circuit 7 is connected to the main switching circuit 3 by the light through the photo-coupler T _L . The connection up to this point constitutes the power supply unit of the charging device.

The DC +5 V is input to the control unit 8 as a power source and is connected to the control unit 8 via two LEDs D ₅ and D ₆ , and the oscillator 9 is still connected to the control unit 8. DC + 3V output is the switching element Q
A, QB, respectively, through a backflow prevention diode D ₃ ,
Through D _4, it is connected to the positive electrode of the battery E _1, E _2,
The negative electrodes are each grounded. The backflow prevention diodes D ₃ and D ₄ are respectively connected with detection resistors R ₂ and R ₃ on the anode side and detection resistors R ₅ and R ₄ on the cathode side, and these detection resistors R ₂ , R ₃ and R ₄ are connected. , R
The other of ₅ is connected to the analog switch 10. The signal sequence from the analog switch 10 is connected to the three-control unit 8. Further, the bases (gates) of the switch elements QA and QB and the control unit 8 are connected. This constitutes a charge control unit.

[0029] In the charging device of such a configuration, the power supply unit, the output current and the output voltage detected by the current detection resistor R _1, to control the main switching circuit, generally obtain two output DC + 3V and + 5V It is a simple switching power supply, and the description is omitted. The control unit 8 is mounted with, for example, a program in which the method of the present invention is input to a storage element such as a ROM, and the CPU executes the program. The LED D _5, D ₆ intended to be lit during charging as an indicator, the battery E ₁ respectively for charging,
To view it E ₂ is being charged. The oscillator 9 has a built-in crystal oscillator, and supplies, for example, a clock for executing a program and a clock signal for various timers to the control unit 8. The analog switch 10 switches the detection resistors R ₂ , R ₃ , R ₄ , and R ₅ according to an instruction from the control unit and sends the detected voltage to the control unit 8, so that the voltages and charging of the batteries E ₁ and E ₂ are performed. Detect the current. Then, the control unit controlled by the method of the present invention controls the switching elements QA and QB to perform an appropriate charging operation on the detected battery voltage and charging current.

It should be noted that such a charging device is merely an example for carrying out the method of the present invention, and may be any type of device as long as the present invention can be carried out. It may be of a type that reduces the pressure. Also, one or more batteries E ₁ and E ₂ may be used for charging.

[0031]

As described above, according to the present invention, the first to sixth periods are provided in accordance with the charging characteristics of a secondary battery such as a nickel cadmium battery or a nickel metal hydride battery according to a voltage change. since it was decided to detect the full charge of the battery by detecting a period T ₁ through T ₅ of the fifth,
It is possible to safely charge the secondary battery, detect full charge, and charge the battery without overcharging or over / undercharging without requiring battery temperature detection. In addition, even when the second peak is not detected, the full charge can be reliably detected since -ΔV is detected.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the overall processing flow of an embodiment of the present invention.

FIG. 2 is a flowchart showing details of first + ΔV detection (S2).

FIG. 3 is a flowchart showing details of first peak detection (S3).

FIG. 4 is a flowchart showing details of a second + ΔV detection (S4).

FIG. 5 is a diagram showing a relationship between a battery voltage and a charging time.

FIG. 6 is a diagram showing a change ΔV in battery voltage for each charging period.

FIG. 7 is a diagram showing an example of a charging device for implementing the present invention.

FIG. 8 is a diagram showing an example of a conventional charging device.

FIG. 9 is a diagram showing a relationship between a charge amount and a battery temperature.

[Explanation of symbols]

1 AC line filter 2 rectifier 3 main switching circuit 4 snubber circuit 5 and smoothing circuit 6 3 terminal regulator 7 voltage detector constant current circuit 8 control unit 9 oscillator 10 analog switches 1a, 1b AC input terminals F ₁ Fuse SW _1, SW ₂ switches C ₁ smoothing capacitor T transformer T _L photocoupler R ₁ current detecting resistor _{D 5, D 6 LED QA,} QB switching element D _3, D ₄ blocking diode _{R 2, R 3, R 4} , R 5 detection resistor E _1, E ₂ battery 11 power supply unit 12 a charging control circuit 13 battery pack T _b thermistor Q switch element

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-328627 (JP, A) JP-A-63-140629 (JP, A) JP-A-63-294227 (JP, A) JP-A-2- 193534 (JP, A) JP-B 62-23529 (JP, B2)

Claims (1)

(57) [Claims] In a charging method for charging a secondary battery such as a nickel cadmium battery or a nickel metal hydride battery by supplying a charging current, a period until the charging is completed is determined based on a charging characteristic due to a change in charging voltage of the secondary battery. The first to sixth detection periods (T _{1 to} T
₆ ), the first detection period (T ₁ ) is defined as a non-detection period, and the detection of the second detection period (T ₂ ), that is, the first + ΔV detection is performed based on the voltage change (ΔV) of the first battery. Detection of the detection period, detection of the third detection period (T ₃ ), that is, detection of the first peak is detection of the detection period of the peak value of the first battery voltage, and detection of the fourth detection period (T ₄ ). That is, the second + ΔV detection is the detection of the detection period of the voltage change (ΔV) of the second battery, and the detection of the fifth detection period (T ₅ ), that is, the second peak detection is the peak value of the second battery voltage. , And the sixth detection period (T ₆ ) is the detection of a voltage drop when no peak is detected, that is, the period of −ΔV detection, and the second detection period (T _{1 to} T ₆ ) is used for each detection period (T _{1 to} T ₆ ). Battery voltage change (Δ
V), and the change in the voltage of the secondary battery (ΔV) is determined for each charging period (T ₁ 〜
Each charging period is recognized by detecting that the condition indicating T ₆ ) is satisfied, and the voltage change of the secondary battery during the charging period (T ₂ , T ₃ ).
If (ΔV) does not satisfy the condition, the fifth detection period
The process proceeds to (T ₅ ), and the battery is fully charged at the time when the detection of the fifth detection period, that is, the second peak detection is normally detected, or the detection of the voltage drop when the peak detection is not performed, that is, the −ΔV detection is performed. A charging method comprising: detecting a charging operation;