JPH10164766A - Charging control method and charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the capacity drop of deterioration of a battery by performing the charging while indicating the charging condition when it judges that the charging is required, and making the charging current very feeble or zero when it judges that the charging is not necessary and indicating the charging condition for a specified time. SOLUTION: A CPU 26 first judges whether the charging is by a charger 16 to not by means of a charge judger. This judging is performed in the following way. The voltage of the power line 42 between a diode 22 and the charge 16 is digitized and it is inputted into the CPU 26, and the CPU 26 judges if this voltage is at or over the specified voltage, and it allows a display to display it through a communication interface, and turns on an LED 54. Then, the data to show the degree of discharge is inputted into a charging necessity judger, and here it is judged whether the charging is necessary or unnecessary. Then, when judged that the charging is necessary, it sends to the charger 16 a signal to the effect that it stops the charging, and also turns on an LED 54 serving as a display for specified time. Hereby, the capacity drop or deterioration of the battery can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control method for preventing overcharge of a secondary battery represented by a nickel-cadmium battery, a nickel-metal hydride battery, and the like, and a charging device.

[0002]

2. Description of the Related Art In a rechargeable secondary battery, if the battery is charged without being sufficiently discharged after charging, the battery performance may be reduced. For example, in a nickel-cadmium battery, it is known that a phenomenon (memory effect) in which an apparent capacity is reduced when repeatedly charged in a state where the depth of discharge is shallow is remarkable.

In order to reduce the capacity due to such a memory effect, the operation of completely discharging the battery to a discharge end voltage within a range that does not cause overdischarge and then fully charging the battery again is repeated two or three times to reduce the capacity. Can be recovered. However, such an operation is time-consuming and troublesome.

[0004] Further, if charging is repeated in a state where the depth of discharge is shallow, there is also a problem that the internal pressure of the battery rises to cause liquid depletion, or the battery temperature rises to damage and deteriorate the internal separator.

Therefore, in order to prevent such a memory effect from occurring, and to prevent liquid depletion and deterioration of the separator, charging may not be performed when the depth of discharge is shallow even if a charge start command is issued. I have.

[0006]

2. Description of the Related Art A conventional charger is provided with a charging display device such as a lamp or an LED for indicating that charging is in progress during charging. When such a charger is provided with a function of preventing charging when the depth of discharge is shallow as described above, charging is performed even when a charging start command is issued by operating a charging start switch or the like. Display indication does not work,
The lamp or LED will not light. Therefore, the user (charging operator) may erroneously recognize that the charger is broken.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a battery having a shallow depth of discharge is not charged even if a charge start command is issued, so that the battery capacity is reduced or deteriorated. It is a first object of the present invention to provide a charging control method that prevents a user from mistakenly assuming that a charger is out of order, and that prevents a user from mistakenly assuming that a charger has failed. It is a second object of the present invention to provide a charging device directly used for performing the method.

[0008]

According to the present invention, a first object of the present invention is to provide a charge control method used for a battery with a battery management device for managing a charge / discharge state, in which it is determined whether or not charging is necessary from the degree of discharge of the battery. When charging is determined to be necessary, charging is performed while displaying the charging state, while when charging is determined to be unnecessary, the charging current is set to a very small value or 0 and a display indicating the charging state is performed for a predetermined time. And a charging control method.

The degree of discharge can be determined by, for example, whether or not a discharge command has been issued after the previous charge. For example, if a discharge command has been input even once, it is assumed that sufficient discharge has been performed and charging is performed. If there is no discharge command, control is performed so that discharging is not performed and charging is not performed. Can be.

When the discharge command has never been issued, the self-discharge amount of the battery is further obtained, and if the self-discharge amount is equal to or less than a predetermined value, charging may not be performed. Further, the degree of discharge may be determined based on the remaining capacity of the battery.

A second object of the present invention is to provide a charging device for use in a battery with a battery management device for managing a charging / discharging state, wherein a discharging degree detecting unit for detecting a discharging degree of the battery based on a charge start command. And a charging necessity determining unit that determines whether charging is necessary based on the detected degree of discharging, a charger that charges a battery when the charging necessity determining unit determines that charging is necessary, and during charging by the charger. A charging device comprising: a charging display unit that operates for a predetermined period of time when the charging necessity determining unit determines that charging is unnecessary and that indicates a charging state.

[0012]

FIG. 1 is an overall conceptual diagram showing one embodiment of the present invention, FIG. 2 is a diagram mainly explaining functions of a CPU, FIG. 3 is a flowchart showing an operation, and FIG. 4 is a first half of a charging mode operation in FIG. And FIG. 5 is a flowchart showing the latter half of the same.

1 and 2, reference numeral 10 denotes a motor, 12
Is a controller, 14 is a battery management device, and 16 is a charger. Battery management device 14 includes a battery 18 such as a nickel-cadmium battery. The AC supplied from the AC power supply 20 is rectified by the charger 16 and charges the battery 18 via the diode 22 in a predetermined charging mode.

The controller 12 supplies a predetermined current and voltage to the motor 10 using the battery 18 as a power source, and
Drive 0. For example, when the motor 10 is a DC motor, the controller 12 may be of a chopper type that controls on / off of the output voltage of the battery 18 at a predetermined duty.

The controller 12 controls the drive voltage and current of the motor 10 by continuously changing the duty based on the external signal B during normal operation. In a situation where discharge is prohibited, such as during charging, the controller 12 sets the duty to 0. That is, the voltage to the motor 10
The supply of the current is stopped, and the fact is displayed on the display device 24.

Reference numeral 26 denotes a battery CPU (microprocessor). Its function will be described later. Reference numeral 28 denotes a power supply circuit (FIG. 2), and the voltage of the battery 18 (for example, 24 V)
Is reduced to a predetermined voltage (for example, 5 V) to drive the CPU 26 and the like.

Reference numeral 30 denotes a current detector, and 32 denotes a voltage detector. The current detection unit 30 detects the charge / discharge current I of the battery 18 and converts it into a signal of a predetermined voltage and inputs the signal to the CPU 26. The voltage detector 32 converts the positive voltage V of the battery 18 into a signal of a predetermined voltage and inputs the signal to the CPU 26.

Numeral 34 denotes a battery temperature detecting section comprising a thermistor provided on the battery 18. More specifically, the battery temperature detecting section 34 amplifies a current change of the thermistor 34 which changes according to the battery temperature T, converts the current into a predetermined voltage, and inputs the voltage to the CPU 26.

In FIG. 2, reference numeral 36 denotes an EEPROM (Electrically
Erasable / Programmable Read Only Memory). E
The EPROM 36 stores various data used in the calculation by the CPU 26, for example, the type of the battery 18 and its characteristic data, a capacity reduction characteristic due to the battery temperature T, etc. And so on.

Next, the function of the CPU 26 will be described. CPU
26 performs an initialization process when an activation command is received from the controller 12 or the charger 16. Although the CPU 26 operates by software, its function is shown in a block diagram in FIG.

The CPU 26 first determines whether or not charging by the charger 16 is being performed by the charging determination section 40. This determination is the voltage V _c of the power line 42 between the diode 22 and the charger 16 is input to CPU26 digitizes, determines the voltage V _c is the charging if a predetermined positive voltage or a communication interface 38 Is displayed on the display device 24 via the LED, and the LED 54 described later is turned on. At this time, the charging method is determined from the magnitude of the charging current and is instructed to the charger 16, which will be described later.

During this charging, the CPU 26 calculates the amount of charge by the remaining capacity calculator 44 (FIG. 2). That is, the charge amount is determined by the product (ampere hour) of the current I detected by the battery current detection unit 30 and the charging time.

On the other hand, the CPU 26 may obtain the electric power from the product of the voltage and the current during charging, and may correct the charged amount according to the magnitude of the electric power (power correction). This correction is performed in consideration of the fact that the charging efficiency changes depending on the magnitude of the charging current and the charging method. This result is stored in the EEPROM 36, sent to the controller 12 via the communication interface 38 as necessary, and displayed on the display device 24.

The CPU 26 determines whether or not the battery is discharging from the flow direction of the battery current I. If it is determined that the battery is discharging, the remaining capacity calculator 44 calculates the amount of discharge. That is, the amount of discharge (ampere hours) is obtained by integrating time with the discharge current detected by the battery current detection unit 30. The remaining capacity calculation unit 44 obtains the current value of the remaining capacity by subtracting this from the remaining capacity stored in the EEPROM 36.

It is needless to say that the above-described correction by the power change (power correction) may be added to the present value. The corrected remaining capacity is stored in the EEPROM 36.
The result is sent to the controller 12 via the communication interface 38 and displayed on the display device 24.

Next, the charger 16 will be described. This charger 1
6 is an AC for converting AC supplied from the power supply 20 to DC.
It has a / DC converter 46, a charging current detector 48, a duty calculator 50, and an output controller 52. The duty calculation unit 50 determines a duty for outputting a charging current based on a charging method specified by the battery management device 14. The output control unit 52 outputs a signal (PWM signal) for on / off control of the switching element of the converter 46 in accordance with the duty.

The charger 16 has an LED (light emitting diode) 54 as a charge display section and an LE for driving the LED.
And a D driver 56. A signal indicating that the battery is being charged, which is sent from the battery management device 14, is input to the LED driver 56, and the LED 54 is turned on based on this signal.

In FIG. 2, reference numeral 57 denotes a discharge degree detecting section. The discharge degree detection unit 57 detects the battery 1 based on the charge start command.
8 is to detect the degree of discharge. Here, it is assumed that the charge start command is input, for example, by operating a charge start switch (not shown) provided in the charger 16. Alternatively, when the charge determination unit 40 determines that the voltage V _C of the power line 42 has become equal to or higher than a predetermined voltage, the charge start command may be input to the discharge degree detection unit 57.

Various data can be used as the judgment data of the discharge degree used by the discharge degree detecting section 57.
Here, it is determined from the data in the EEPROM 36 whether or not there has been a discharge command after the previous charge, and this is used as a material for determining the degree of discharge. In addition, the amount of self-discharge and the remaining capacity after the previous charge are used.

The data indicating the degree of discharge is input to the charging necessity judging section 58, where the necessity of charging is judged. For example, when no discharge has been performed since the last charge,
At this time, when the self-discharge amount is equal to or less than the predetermined value or when the remaining capacity is equal to or more than the predetermined value, it is determined that the charging is unnecessary. When it is determined that charging is not necessary, a signal to stop charging is sent to the charger 16 and the display device LE
D54 is turned on for a predetermined time. Such a state is referred to herein as “fake charging”.

Next, the operation will be described with reference to FIGS.
First and the voltage V _C of the power line 42 of the charger 16 is equal to or greater than the set value, by operating the charging start switch manually, the charging start command is input to the discharge degree detecting unit 57 (of FIG. 3 Step 100). Discharge degree detector 5
7, when the charge start command is input, the number of times of discharging after the previous charging is obtained based on the history data stored in the EEPROM 36.

The charge necessity judging section 58 judges necessity of charging based on the number of discharges. Here, if the number of discharges is 0, it is determined that charging is unnecessary (step 102). If the number of discharges is even one, it is determined whether the remaining capacity of the battery 18 is equal to or less than a predetermined value (step 104). Here, the remaining capacity is calculated by the remaining capacity calculation unit 44. Therefore, in this case, the remaining capacity calculation unit 44 also functions as a discharge degree detection unit that detects the degree of discharge.

If the remaining capacity is equal to or smaller than the predetermined value (step 104), the charging mode is entered (step 106). In this charging mode, as shown in FIGS. 4 and 5, a charging method is determined from an initial charging current, and charging according to the method is automatically performed. This operation will be described later.

In step 102, if no discharging has been performed since the previous charging, the charging necessity determining unit 5
In step 8, it is determined whether the previous charging was completely charged or ended with insufficient charging based on the data in the EEPROM 36 (step 108). When charging is incomplete, step 104 is entered. That is, if the remaining capacity is small, the charging mode 106 is entered.
to go into.

In step 110, the self-discharge amount is calculated, and the self-discharge amount is set to a predetermined value (for example, 400 mAh).
If so, the charging mode 100 is entered, and if so, the charging mode is entered (step 112). That is, without actually charging, the clocking by the false charging timer is started and only the LED 54 is turned on (step 11).
2). When a predetermined time set in the fake charging timer has elapsed (step 114), the LED 54 is turned off (step 116), and the fake charging mode ends. In the false charging mode, the charging current may be set to 0, but a minute current may be kept flowing.

The calculation of the self-discharge amount uses the characteristic of the rate of decrease in the remaining capacity with respect to the battery temperature T. In other words, the amount of self-discharge increases with an increase in the standing time and the battery temperature. Since this relationship is determined for the battery 18, this relationship is stored in the EEPROM 36 in advance. Therefore, if the battery temperature T and the time during which the battery 18 is left are obtained, the self-discharge amount can be obtained using this relational expression (or a map showing this relation).

The calculation of the amount of self-discharge can be performed by the remaining capacity calculator 44. Thus, in this embodiment,
The remaining capacity calculation unit 44 also serves as a discharge degree detection unit for calculating the self-discharge amount. When calculating the remaining capacity, the remaining capacity calculating unit 44 may perform correction based on the self-discharge amount.

Next, the charging mode (step 106) is shown in FIG.
5 will be described. When the power of the charger 16 is turned on and it is determined that the degree of discharging of the battery 18 is small, and the charging mode (step 106) is entered, the CPU 26 determines the battery temperature T based on the signal output from the thermistor 34 in the CPU 26. Ask for. The CPU 26 determines whether or not the battery temperature T is within a chargeable temperature range (0 <T <40 ° C.) (step 200 in FIG. 4). If it is not within this temperature range, it waits as it is and waits for it to enter this temperature range.

When the temperature falls within this temperature range, test charging is started (step 202). In this test charging, a constant voltage is applied to the battery 18 to determine the charging method, and the current I at this time is obtained. If the charging current I is, for example, about 1.5 amps, normal charging is suitable, and if it is about 5.0 amps, rapid charging is suitable. Accordingly the charging current I of these intermediate vicinity example 3.0 amps as the threshold value I ₀ is judged large or small or a more (step 204).

When the power of the charger 16 is turned on, the charging current I is unstable and fluctuates. Therefore, a slight delay time (about several milliseconds) is set, and the determination is made using the stable charging current I. The stability of the current I may be determined by calculating the rate of change (the amount of change per unit time) of the charging current I and determining that the rate of change has become equal to or less than a predetermined value. The current stability determination unit 62 in FIG. 2 determines the magnitude of the change rate. Also 6
4 is a charging system discrimination section for discriminating a charging method by comparing the charging current I and the threshold I _0.

The result of the determination of the charging method is transmitted to the charging control unit 6.
6 to perform charging control according to a predetermined charging method. The charging current I is If the threshold value of I ₀ below, to select the normal charge. In this embodiment, the -ΔV method is selected. This -Δ
The V method focuses on a point where the charging voltage reaches a maximum value at the end of charging and then drops in the Ni-Cd current.
It is determined that charging has ended when charging has ended. The calculation of −ΔV is performed by the −ΔV calculation unit 68 in FIG.

The CPU 26 sets the charging current I and the value of -ΔV, and also sets the range of the battery temperature T when using the -ΔV method (for example, 0 <T <40 ° C.) (step 206). In this charging method, the CPU 26 sets a 4.5-hour timer, and then starts the main charging (step 208).

[0043] If the charging current I is larger than the threshold I _0, selects the fast charging (step 204), as the rapid charge method is used here dT / dt method. This method focuses on a point at which the battery temperature T rises sharply at the end of charging, and ends charging when the rate of change dT / dt of the battery temperature T with respect to time becomes equal to or higher than a set value. This dT
The calculation of / dt is performed by the dT / dt calculation unit 70 in FIG.

When the quick charge is selected (step 204), the battery temperature T is set within a set range (for example, 5 <T <4).
0 ° C.) (step 21).
0) If not, wait until it enters. If the temperature falls within this temperature range, the charging current and termination condition of the rapid charging are set (step 212). That is, the value of dT / dt is set. And after setting the timer to 1.5 hours,
The main charging is started (step 214). At this time, the charging current I is controlled so as to have the value set in steps 206 and 212 described above.

During the main charging (FIG. 5, step 2)
16) The CPU 26 always determines whether or not the battery temperature T is within the temperature range according to the charging method (step 218). That is, if it is a normal charging method, 0 <T <40 ° C
It is determined whether or not the temperature is within 5 <T <40 ° C. for quick charging. If the temperature is not within these temperature ranges, the timer is temporarily stopped from measuring the time (step 220).

When the temperature falls within these temperature ranges, the timer starts counting time again.
It is determined whether or not the time set in 214 has overflowed (step 222). If overflow has occurred, charging is terminated. If the overflow has not occurred, the charging is continued as it is, and the charging is terminated when the charging end condition set in steps 206 and 212 is satisfied (step 214). The end of the charging is performed by the charging end determining unit 72 in FIG.

[0047]

[Other Embodiments] In the embodiment described above, the remaining capacity calculating section 44 also serves as a discharge degree detecting section for obtaining the remaining capacity and a discharge degree detecting section for obtaining the self-discharge amount. However, the present invention may configure them separately.

The number of discharges, the remaining capacity, and the amount of self-discharge after the previous charge are judged whether charging is necessary by using three kinds of judgment data. May be determined from the state of change. The most suitable judgment material and judgment method are used based on the type of battery and the degree of deterioration. The present invention can be applied to secondary batteries other than nickel-cadmium batteries, and the type of data indicating the degree of discharge and the determination method may be changed according to the characteristics of the battery.

[0049]

As described above, according to the first aspect of the present invention, it is determined whether or not charging is necessary based on the degree of discharge of the battery. When it is determined that charging is unnecessary, charging is performed for a predetermined time without charging. Is displayed only (fake charging mode), the user sees this display and thinks that charging is in progress, and there is no risk of erroneously recognizing that the charger is out of order. In addition, since unnecessary charging is not performed, a decrease in capacity and deterioration of the battery can be prevented.

As the judgment data indicating the degree of discharge, for example, the number of discharges since the previous charge can be used (claim 2). In addition, when there is no discharge, the self-discharge amount is further added as judgment data, and when the self-discharge amount is small, charging can be made unnecessary. The degree of discharging may be determined based on the remaining capacity of the battery. In this case, charging is not required when the remaining capacity is equal to or more than a predetermined value.

According to the fifth aspect of the present invention, there is provided a charging device used directly for carrying out this method.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an embodiment of the present invention.

FIG. 2 is a block diagram mainly showing functions of a CPU;

FIG. 3 is a flowchart showing an operation.

FIG. 4 is a flowchart showing the first half of the operation in the charging mode in FIG. 3;

FIG. 5 is a flowchart showing the latter half of the operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Motor 12 Controller 14 Battery management device 16 Charger 18 Battery 26 CPU 44 Remaining capacity calculation part as a discharge degree detection part 54 LED as a display device 57 Discharge degree detection part 58 Charging necessity determination part

Claims (5)

[Claims] In a charge control method used for a battery with a battery management device for managing a charge / discharge state, it is determined whether or not charge is necessary based on a degree of discharge of the battery, and when it is determined that charge is necessary, the charge state is determined. A charging control method comprising: performing charging while displaying a display indicating that charging is not necessary; and, when determining that charging is unnecessary, setting the charging current to a very small value or 0 and displaying a charge state for a predetermined time. 2. The charge control method according to claim 1, wherein the degree of discharge is determined from the presence or absence of a discharge command after the last charge stored in the battery management device, and if there is no discharge command, it is determined that charging is unnecessary. 3. The degree of discharge is determined by the amount of self-discharge after the previous charge when there is no discharge command in claim 2, and when the amount of self-discharge is less than a predetermined value, it is determined that charging is unnecessary. Item 2. The charge control method according to Item 2. 4. The charge control method according to claim 1, wherein the degree of discharging is determined based on the remaining capacity of the battery, and when the remaining capacity is equal to or greater than a predetermined value, it is determined that charging is not necessary. 5. A charging device for use in a battery with a battery management device that manages a charge / discharge state, comprising: a discharge level detection unit that detects a discharge level of the battery based on a charge start command; A charging necessity determining unit that determines the necessity of charging, a charger that charges the battery when the charging necessity determining unit determines that charging is necessary, and that the charging is not required during charging by the charger and the charging necessity determining unit is unnecessary. A charging display unit that is activated for a predetermined period of time when the determination is made to indicate a charging state.