WO2014068948A1

WO2014068948A1 - Charging device and method for controlling same

Info

Publication number: WO2014068948A1
Application number: PCT/JP2013/006377
Authority: WO
Inventors: 竜三杉原; 建史八木; 正吾住友
Original assignee: 三洋電機株式会社
Priority date: 2012-11-02
Filing date: 2013-10-29
Publication date: 2014-05-08
Also published as: JP2016012948A

Abstract

Provided are a charging device for an alkali secondary battery capable of increasing charging efficiency, and a method for controlling the charging device. A method for controlling a charging device is characterized by monitoring the voltage value of an alkali secondary battery (1) while supplying the alkali secondary battery (1) with constant current, and suspending charging when the variation in the voltage value per unit time shifts from an increase to a decrease over time in the case where the voltage value exceeds a reference voltage value indicating the upper limit of the flat part of the curve that represents voltage value characteristics during charging for the alkali secondary battery (1).

Description

Charging device and control method thereof

The present invention relates to a charging device for an alkaline secondary battery and a control method thereof, and more particularly, to a charging device used for a nickel hydride secondary battery or a nickel cadmium secondary battery method and a control method thereof.

In recent years, charging devices and charging methods for charging alkaline secondary batteries such as nickel metal hydride secondary batteries and nickel-cadmium secondary batteries used for portable electronic devices have been widely used. In such a charging apparatus, a control method in which a secondary battery is charged at a constant current, a full charge is detected by detecting a peak voltage of the voltage of the secondary battery, and the charging is stopped is generally used. For example, the charging device described in Patent Document 1 detects a voltage drop −ΔV (for example, 10 mV) from the peak voltage of the battery voltage, determines that it corresponds to peak voltage detection and full charge, and stops charging. . Then, it is detected that the change slope of the battery voltage has become extremely gentle in order to detect the voltage drop −ΔV. FIG. 9 is a schematic diagram showing the relationship between the charging time and the battery voltage in the conventional charging device described in Patent Document 1. In FIG. As shown in FIG. 9, in the conventional charging device described in Patent Document 1, specifically, the time T (n) required to increase the unit voltage of 10 mV / cell is 10 mV / cell last time. It is determined whether or not the time T (n-1) required for the rise has become twice or more, and such a case is detected as a peak voltage, and charging is stopped as full charge.

JP 2007-252086 A

However, in the conventional system, in the stage immediately before the completion of charging, the charging efficiency expressed as the ratio of the discharge capacity that can be taken out from the battery to the amount of charge used for charging the battery is greatly reduced. As a result, there is a problem that the discharge capacity stored in the battery does not increase with respect to the time spent for charging and the amount of charged electricity.
An object of this invention is to provide the charging device which improves charging efficiency, and its control method in view of the said problem.

In order to achieve the above object, a method for controlling a charging device according to one aspect of the present invention monitors a voltage value of the alkaline secondary battery while supplying a constant current to the alkaline secondary battery, and the voltage value is When the reference voltage value indicating the upper limit of the flat portion in the curve representing the voltage value characteristics during charging of the alkaline secondary battery is exceeded, the amount of change in the voltage value per unit time decreases from increase over time. Charging is stopped when turning to.

In another aspect, when the amount of change in the voltage value per unit time is equal to or greater than a predetermined value, the display may be displayed until charging is stopped.
In another aspect, the charging may be stopped before the voltage value of the alkaline secondary battery changes from increasing to decreasing with time.
In another aspect, the charging efficiency, which is the ratio of the discharge capacity that can be taken out from the alkaline secondary battery by discharging to the amount of charge used for charging the alkaline secondary battery, is in the range of 95% to 99%. In the configuration, the charging of the alkaline secondary battery may be stopped.

In another aspect, a set of time (TN, TN-1), (TN-2, TN-3) composed of two times separated by a unit time ΔT and in ascending order with respect to the natural number N, At each time included in (TN-4, TN-5) and (TN-6, TN-7), voltage values VN, VN-1, VN-2, VN-3 of the alkaline secondary battery, VN-4, VN-5, VN-6, and VN-7 are measured, and the voltage value change V′N indicated by the difference VN−VN-1 between the voltage value VN and the voltage value VN−1, and the voltage value The difference VN-2 between the voltage value VN-2 and the voltage value VN-3, and the difference VN-4- between the voltage value VN-4 and the voltage value VN-5. A voltage value change V′N-2 indicated by VN-5 and a voltage value change V′N-3 indicated by a difference VN-6−VN-7 between the voltage value VN-6 and the voltage value VN-7 Further, the difference V ″ N of the voltage value change indicated by the difference V′N−V′N−1 between the voltage value change V′N and the voltage value change V′N−1, and the voltage value change are calculated. The difference V′N−1 of the voltage value change indicated by the difference V′N−1−V′N−2 between the V′N−1 and the voltage value change V′N-2 and the voltage value change V′N -2 and the voltage value change V′N-3, a difference V′N-2 of the voltage value change indicated by the difference V′N−2−V′N-3 is calculated, and the voltage value change difference is calculated. When V ″ N−2 is positive and the voltage value change difference V ″ N−1 and the voltage value change difference V ″ N are both negative, The configuration may be such that charging is stopped.

The alkaline secondary battery may be a nickel hydride secondary battery or a nickel cadmium secondary battery.
The charging device according to one embodiment of the present invention is a charging device that charges an alkaline secondary battery, and is provided in a constant current power supply unit and a current path connecting the constant current power supply unit and the alkaline secondary battery. The voltage value of the switch unit and the alkaline secondary battery was monitored, and the voltage value exceeded the reference voltage value indicating the upper limit of the flat part in the curve representing the voltage value characteristics during charging of the alkaline secondary battery. In this case, the switch unit includes a control unit that cuts off the current to the battery when the amount of change in the voltage value per unit time changes from increasing to decreasing with time. .

In another aspect, the display device further includes a display, and the control unit displays the display until the charging is stopped when the amount of change in the voltage value per unit time becomes equal to or greater than a predetermined value. The structure characterized by making it may be sufficient.
In another aspect, the control unit causes the switch unit to cut off the current to the battery before the voltage value of the alkaline secondary battery changes from increasing to decreasing with time.
The structure characterized by this may be used.

In another aspect, the control unit has a charging efficiency of 95% to 99%, which is a ratio of a discharge capacity that can be taken out from the alkaline secondary battery by discharging to an amount of charge used for charging the alkaline secondary battery. In this state, the switch unit may be configured to cut off the current to the battery.
In another aspect, the control unit is composed of two times separated by a unit time ΔT, and a set of time (TN, TN-1), (TN-2, TN-3), (TN-4, TN-5), and (TN-6, TN-7) at the respective times included in the voltage values VN, VN-1, VN-2 of the alkaline secondary battery. , VN-3, VN-4, VN-5, VN-6, and VN-7, respectively, and a voltage value change V ′ indicated by a difference VN−VN−1 between the voltage value VN and the voltage value VN−1. N, a voltage value change V′N−1 indicated by a difference VN−2−VN−3 between a voltage value VN−2 and a voltage value VN−3, and a voltage value VN−4 and a voltage value VN−5 Voltage value change V'N-2 indicated by the difference VN-4-VN-5 and voltage value change V 'indicated by the difference VN-6-VN-7 between the voltage value VN-6 and the voltage value VN-7 N-3 is calculated, and further, a voltage value change difference V ″ N indicated by a difference V′N−V′N−1 between the voltage value change V′N and the voltage value change V′N−1. The voltage value change difference V ″ N−1 represented by the difference V′N−1−V′N-2 between the voltage value change V′N−1 and the voltage value change V′N-2, and the voltage value A voltage value change difference V ″ N-2 indicated by a difference V′N-2-V′N-3 between the change V′N-2 and the voltage value change V′N-3 is calculated, and the voltage When the value change difference V ″ N-2 is positive and the voltage value change difference V ″ N−1 and the voltage value change difference V ″ N are both negative, the alkali 2 The structure characterized by stopping the charge to a secondary battery may be sufficient.

With the above-described configuration, the charging device according to one embodiment of the present invention or the control method thereof can detect the inflection point of the voltage gradient in the battery voltage during charging, stop charging, and increase charging efficiency. .

It is a characteristic view which shows the relationship between the ratio with respect to the rated battery capacity of the amount of charge in the alkaline secondary battery which the inventors obtained by experiment, and the ratio with respect to the rated battery capacity of discharge capacity. It is a block diagram which shows the function structure of the charging device 100 which concerns on the one aspect | mode of embodiment. (A) It is the schematic of the curve showing the voltage value characteristic of the battery 1 which shows the relationship between the charging time and the battery voltage in the charging device 100 which concerns on the one aspect | mode of embodiment. (B) It is the schematic which shows the relationship between the charging time in the charging device 100 which concerns on the one aspect | mode of embodiment, and charging efficiency. It is a flowchart which shows the operation | movement regarding the charging operation of the charging device 100 which concerns on the one aspect | mode of embodiment. It is an experimental result which shows the relationship between the charging time and the battery voltage in the charging device 100 which concerns on the one aspect | mode of embodiment. It is an experimental result which shows the relationship between the charge time in the charging device 100 which concerns on the one aspect | mode of embodiment, the amount of charge electricity, and the discharge capacity. It is an experimental result which shows the relationship between the charging time in the charging device 100 which concerns on 1 aspect of embodiment, charging efficiency, and a discharge capacity ratio. It is an experimental result which shows the relationship between the charging time in the charging device 100 which concerns on the one aspect | mode of embodiment, and battery temperature. It is the schematic which shows the relationship between the charging time in the conventional charging device described in patent document 1, and a battery voltage.

≪Background to the form for carrying out the present invention≫
FIG. 1 shows the ratio of the amount of charged electricity to the rated battery capacity (hereinafter abbreviated as charge ratio) and the ratio of the discharge capacity to the rated battery capacity (hereinafter referred to as discharge) in the alkaline secondary battery obtained by the inventors through experiments. FIG. 6 is a characteristic diagram showing a relationship with a capacity ratio).
Here, the “charged electricity amount” refers to the amount of electricity (mAh) used for charging, and in the case of constant current charging, it is the product of the current value and the charging time. “Discharge capacity” refers to a capacity (mAh) that is charged to a battery and can be taken out by discharge.

As shown in FIG. 1, until the charge electricity amount ratio is in the range of 80%, the charge electricity amount ratio and the discharge capacity ratio are almost proportional and the charging efficiency is close to 100%. However, when charging is continued exceeding the charge amount ratio of about 80%, the rate of increase of the discharge capacity ratio with respect to the increase of the charge amount ratio is gradually decreased, and the charge efficiency is decreased. Therefore, in order to charge to a capacity close to 100% as the discharge capacity ratio, it is necessary to charge until the charge electricity amount ratio reaches about 120%. In this case, a loss of about 20% as the charge electricity amount is required. Arise. In the conventional charging device that detects the full charge by detecting the peak voltage of the output voltage of the battery and stops the charging, the charging is performed until the charge amount ratio is about 120%. In this charging method, the loss of charge electricity becomes heat generation, which increases the temperature of the battery and causes deterioration of the life. However, the curve representing the ratio indicated by the broken line in FIG. 1 varies due to the influence of the surrounding environment and the like.

If it is possible to detect that the charge amount ratio is in the range of 80% to 100% during charging, and if charging can be stopped in this range, use a battery charged with high charging efficiency. Can do. Moreover, the heat_generation | fever which generate | occur | produces when the amount ratio of charge electricity exceeds 100% can be prevented, and the lifetime of a battery can be improved.
Therefore, the inventors diligently studied a method for detecting that the charging electricity amount ratio is in the range of 80% to 100% during charging, in order to realize a method of stopping charging in a state where charging efficiency is high, The inventors have arrived at a charging device and a control method thereof according to an aspect of an embodiment of the present invention.

Hereinafter, a charging device and a control method thereof according to an aspect of an embodiment of the present invention will be described with reference to the drawings.
<< Embodiment >>
<Configuration of charging device 100>
FIG. 2 is a block diagram illustrating an electrically functional configuration of charging apparatus 100 according to one aspect of the embodiment. As shown in FIG. 2, a charging device 100 according to one embodiment of the present invention is a charging device that charges an alkaline secondary battery 1 (hereinafter abbreviated as a battery 1) that is detachable from the device. The power supply part 2 which supplies an electric current, and the switch part 3 which supplies or interrupts | interrupts an electric current to a battery are provided. The charging device 100 further includes a control unit 4 that monitors the voltage value output from the battery 1 to detect an inflection point in the voltage gradient, and operates the switch unit 3 and the power supply unit 2. To instruct the switch unit 3 to supply current to the battery 1 or to interrupt the supply of current.
(Battery 1)
The charging device 100 charges an AA or AAA battery. As the alkaline secondary battery, for example, a nickel hydride secondary battery or a nickel cadmium secondary battery can be used. Also, 1 to 4 batteries 1 are detachably attached to the charging device 100, and the charging device 100 can charge them simultaneously.
(Power supply unit 2)
The power supply unit 2 is a constant current power supply that supplies a charging current to the battery 1. For example, power is supplied from a commercial power supply of AC 100V to 240V, and a constant current of 2.2A is output. When 3 to 4 batteries 1 are installed, the current supplied to each battery 1 is 550 mA, and when 1 to 2 batteries are installed, the current supplied to each battery 1 is 1.1 A. Become.
(Switch part 3)
The switch unit 3 is connected between the power source unit 2 and the battery 1, and supplies or blocks a charging current to the battery 1 based on a signal from the control unit 4 described later.
(Control unit 4)
The control unit 4 incorporates a microcomputer (not shown), outputs a charge on / off signal of the switch unit 3, and switches the switch unit 3 on and off to adjust the charging current. The switch unit 3 is turned on / off to adjust the duty ratio, and the battery 1 is charged with a constant current having a desired average current value.

In addition, the control unit 4 turns on and off the switch unit 3 during charging, periodically stops charging, and measures the output voltage of the battery 1 at the measurement point a. At this time, for example, charging is stopped for about 0.1 to 2.0 seconds during a period of about 1 to 5 seconds. This is because the battery voltage can be measured more accurately when charging is stopped. However, the configuration is not limited to this, and the battery voltage may be measured during charging.

Further, the control unit 4 outputs a charging voltage / current control signal to the power supply unit 2 and controls the power supply unit 2 to be on or off.
Details of the charge control method in the control unit 4 will be described later.
(Temperature sensor 5)
The temperature sensor 5 detects the temperature of the battery 1 and outputs a temperature signal to the control unit 4. The temperature sensor 5 is composed of a thermistor or the like. The battery 1 is attached to the charging device 100 and the battery 1 and the temperature sensor 5 are in close contact with each other, or the battery 1 is disposed at a position where the temperature of the battery 1 can be monitored appropriately without contact. The temperature sensor 5 is thermally connected. When the temperature of the battery 1 exceeds a predetermined temperature, the control unit 4 stops charging. For example, when the battery temperature exceeds 60 to 65 ° C., the control unit 4 turns off the switch unit 3 and stops charging. Thereafter, when the battery temperature falls to a chargeable temperature, the control unit 4 turns on the switch unit 3 again and resumes charging after continuing.

Further, the control unit 4 determines a predetermined voltage value V0 described later corresponding to the battery temperature.
(LED6 (charge status display))
The LED 6 receives a signal from the control unit 4 and displays a charging state such as a charging state or a full charging state. For example, during charging, the control unit 4 explicitly turns on the LED 6 by turning on the LED 6 as “charging state display”.

(LED7 (energy saving induction lamp))
Normally, charging is started when the environmental temperature at the start of charging is in the range of −5 to 40 ° C. Furthermore, if charging is started when the environmental temperature at the start of charging is in the range of 5 to 30 ° C., charging can be performed with high charging efficiency. Therefore, when charging starts when the environmental temperature is in the range of 5 to 30 ° C., the control unit 4 lights the LED 7 as an “energy saving induction lamp” for a predetermined time, for example, 10 minutes. Thereby, it is possible to display to the user that the battery can be charged with relatively high charging efficiency as compared with the case of charging in a low temperature environment of less than 5 ° C or a high temperature environment of more than 30 ° C. . Here, the environmental temperature when charging is started can be measured using the temperature sensor 5. This is because the temperature sensor 5 indicates the same temperature as the environmental temperature since the charging is before the battery is heated to a high temperature. In addition, it is also possible to provide a separate temperature sensor in a place where it is difficult to be affected by the temperature of the battery and components in the case of the charging device.

Further, when the charging is continued and the voltage change amount ΔV per unit time ΔT becomes a predetermined value or more,
The control unit 4 turns on the LED 7 as a display. The predetermined value refers to, for example, a case where the increase in battery voltage per unit time is 3 mV or more during about 1.5 to 2.5 minutes. Then, the lighting of the LED 7 is continued until the charging is stopped, and when the charging is stopped, the LED 7 is turned off. As will be described later, in the charging device of the present embodiment, charging is stopped in a state where high charging efficiency is maintained. It is possible to display to the user that the energy saving charging is performed by turning on the LED 7.

<About charge control in the control unit 4>
FIG. 3A is a schematic diagram of a curve representing the voltage value characteristic of the battery 1 showing the relationship between the charging time and the battery voltage in the charging device 100 according to one aspect of the embodiment. As shown in FIG. 3 (a), in the curve representing the voltage value characteristics during charging of the battery 1, after starting charging, the battery voltage first increases rapidly, and then the flat portion where the voltage gradually increases is shown. Show. Thereafter, the rising slope increases again to reach a peak at the charging time B, and then shows a curve that goes down the peak and reaches the charging time C. For such battery voltage characteristics, the control unit 4 performs control based on the following three types of criteria.
(1) After starting charging, the control unit 4 determines whether or not the predetermined time T0 has elapsed, and continues charging until the predetermined time T0 has elapsed. This is because, in an inactive battery such as a nickel metal hydride secondary battery that has been used for a long period of time or has been repeatedly charged at a shallow depth of discharge and thus has a memory effect, when this is charged, it is within this predetermined time T0. This is because a peak voltage may occur, and these are detected to prevent erroneous detection of full charge.
(2) In order to prevent detection of an inflection point, which will be described later, from a flat portion in the battery voltage characteristic curve shown in FIG. 3, the control unit 4 will be described later until it reaches a predetermined voltage value V0 or more (3 ) Detection based on the criteria is not performed. The predetermined voltage value V0 is the upper limit voltage value of the flat portion in the curve representing the voltage value characteristics when the battery 1 is charged, and is about 1.38V to 1.45V at a battery temperature of about 20-30 ° C. Desirably, the value is about 1.40V or more and 1.43V or less, for example, about 1.42V.
(3) The control unit 4 monitors the voltage value output from the battery 1, and when the voltage value is equal to or higher than the predetermined voltage value V0, the change amount ΔV of the voltage value per unit time ΔT increases with time. Detects that it started to decrease. In that case, the switch unit 3 is made to cut off the current supply to the battery 1.

As described above, the curve representing the voltage value characteristic during charging of the battery 1 shows a flat portion where the voltage gradually rises, and then the slope of the rise once increases. However, the charging time B reaches its peak. Here, an inflection point in the gradient of the battery voltage value generated during the charging time A is detected. Specifically, the control unit 4 monitors the voltage value V output from the battery 1, and calculates the amount of change ΔV in the voltage value per unit time ΔT when the voltage value is equal to or greater than the predetermined voltage value V0. When ΔV changes from increasing to decreasing with time, the voltage is detected as an inflection point. In the present embodiment, in order to prevent erroneous detection due to noise or the like, the inflection point is detected when a decrease in ΔV is detected twice in succession. Such an inflection point has been found by the inventors 'examination by the inventors' experiments that the above-described charging electricity amount ratio is in the range of 80% to 100%. By detecting this inflection point in the control unit 4, it is possible to stop charging in a state where the charge electricity amount ratio is in the range of 80% to 100%.

FIG. 3B is a schematic diagram illustrating a relationship between charging time and charging efficiency in the charging device 100 according to one aspect of the embodiment. As shown in FIG. 3 (b), by detecting the inflection point at the charging time A and stopping the charging, the charging efficiency is lowered when the charging is continued beyond the charging time B and the energy loss caused thereby. Can be prevented.
<About operation of charging device 100>
The operation of the charging apparatus 1 having the above configuration will be described using a flowchart. FIG. 4 is a flowchart showing an operation related to the charging operation of charging apparatus 100 according to one aspect of the first embodiment.
(Step 0 (S0))
In step 0 (S0), the controller 4 determines whether or not the predetermined time T0 has elapsed after the start of charging, and repeats step 0 (S0) until the predetermined time T0 elapses to continue charging. This is because an inactive battery such as a nickel metal hydride secondary battery in which a memory effect has occurred may generate a peak voltage within this predetermined time T0, and prevent these from being erroneously detected as full charge. Because. The predetermined time T0 is counted by a timer built in the control unit 4 to determine whether the predetermined time T0 has elapsed. The predetermined time T0 uses, for example, 3 minutes and a current of 0.3 It (about A for an AA battery). When the predetermined time T0 has elapsed, the process proceeds to the next.

When the temperature indicated by the temperature sensor 5 is in the range of 5 to 30 ° C. when charging is started, the control unit 4 turns on the LED 7 for a predetermined time, for example, 10 minutes.
(Step 1 (S1))
In step 1 (S1), the control unit 4 measures the output voltage V of the battery 1 at the measurement point a in FIG. 1 during charging. Then, after the unit time ΔT has elapsed, the output voltage V of the battery 1 is measured again. Then, a voltage change ΔV that is a change amount of the voltage V is calculated, and charging is stopped when a positive (> 0) ΔV is not detected. On the other hand, if positive (> 0) ΔV is detected, ΔV is stored in the memory built in the control unit 4 and then the process proceeds to the next.

The unit time ΔT is preferably in the range of about 1.5 minutes to 2.5 minutes. When the time is shorter than 1.5 minutes, since the time interval is short and the voltage change is small, it is necessary to accurately measure small voltage fluctuations separately from noise or the like, which increases the cost of the apparatus. On the other hand, if the time interval is increased beyond 3 minutes, the time resolution for detecting the inflection point will be low, and the inflection point may be detected after the peak voltage is exceeded. It may not be detected correctly.

Further, the control unit 4 turns on the LED 7 when the voltage change amount ΔV per unit time ΔT becomes equal to or greater than a predetermined value. The predetermined value refers to, for example, a case where the increase in battery voltage per unit time is 3 mV or more during about 1.5 to 2.5 minutes.
(Step 2 (S2))
In step 2 (S2), the control unit 4 has a battery voltage equal to or higher than a predetermined voltage value (for example, 1.42 V) that is an upper limit voltage value of a flat portion in a curve representing a voltage value characteristic when the battery 1 is charged. It is determined whether or not. If it does not reach the predetermined voltage value, the process returns to step 1 (S1) to continue charging. On the other hand, when it exceeds the predetermined voltage value, it proceeds to the next.
(Step 3 (S3))
In step 3 (S3), the control unit 4 compares ΔV calculated in step 1 (S1) with ΔV calculated in step 1 (S1) in the previous loop. If the calculated ΔV is increased compared to the previously calculated ΔV, or if ΔV is calculated for the first time this time, the process returns to step 1 (S1) and charging is continued. On the other hand, when ΔV calculated this time is smaller than ΔV calculated last time, the identification information indicating that ΔV has decreased is stored in the memory built in the control unit 4 and then the process proceeds to the next.
(Step 4 (S4))
In step 4 (S4), the control unit 4 determines whether or not ΔV detected in step 3 (S3) has decreased in the previous loop based on the presence or absence of the identification information stored in the control unit 4. . If the control unit 4 has identification information indicating that ΔV has decreased in the previous loop, it is determined that ΔV has decreased continuously twice. In that case, charging is stopped. On the other hand, when there is no identification information and it cannot be said that ΔV has decreased in the previous loop, the process returns to step 1 (S1) to continue charging.
<Experimental result>
As described above, the charging experiment was performed using the charging device 100 according to one aspect of the described embodiment. The battery 1 was a nickel metal hydride secondary battery having a battery capacity of 1900 mAh, four batteries were connected in parallel, and a constant current of 2.2 A was supplied from the power supply unit 2 to perform charging. In the experiment, the battery 1 was charged while measuring the voltage value output from the battery 1 and the temperature of the battery surface, and the discharge capacity, which is the capacity that can be taken out by discharging after different charging times, was measured. The results will be described below with reference to the drawings.
(Relationship between charging time and battery voltage)
FIG. 5 is an experimental result showing the relationship between the charging time and the battery voltage in the charging apparatus 100. 3 shows a curve representing voltage value characteristics during charging of the battery 1 in the charging apparatus 100. As shown in FIG. 5, after the battery voltage starts charging, the battery voltage rapidly increases first, and after about 1 hour, a flat portion where the voltage gradually increases is shown. After that, after exceeding about 1.42 V which is the voltage value V0 indicating the upper limit of the flat portion in the curve representing the voltage value characteristic at the time of charging that the alkaline secondary battery has, the rising slope increases again and the charging time B In the charging time of 3.6 hours, the peak was reached, and after that, the characteristic passed the peak and decreased.

In this experiment, the inflection point of the voltage gradient at which the change amount Δ of the voltage value per unit time ΔT turns from increasing to decreasing with the lapse of time was 3.4 hours charging time indicated by A. In the charging device 100, as described above, when the amount of change in the voltage value per unit time has changed from increasing to decreasing with the passage of time, the control unit 4 causes the switch unit to cut off the current to the battery. By adopting, charging was able to be stopped by detecting the inflection point of the voltage gradient at the charging time of 3.4 hours.

In addition, in this experiment, in addition to the operation experiment of the charging device 100 that detects the inflection point and stops the charging, the charging experiment is performed under the condition that the charging is stopped at different charging times, and the charging time exceeds 3.4 hours. The battery voltage, battery temperature, and discharge capacity were also measured over time.
(Relationship between charging time, amount of charge and discharge capacity)
FIG. 6 is an experimental result showing the relationship between the charging time, the charge electricity amount, and the discharge capacity in the charging apparatus 100. As shown in FIG. 6, the amount of charged electricity is proportional to the charging time. On the other hand, the discharge capacity is proportional to the charging time up to about 3.2 hours, but thereafter, the slope gradually decreases and reaches the battery capacity of 1900 mAh in the charging time of about 3.8 hours. At that time, the amount of charged electricity was about 2090 mAh, and an extra amount of charged electricity of about 10% was required to charge to the rated battery capacity of 1900 mAh.
(Relationship between charging time, discharge capacity ratio and charging efficiency)
FIG. 7 shows experimental results showing the relationship between the charging time, the charging efficiency, and the discharge capacity ratio in the charging apparatus 100. The discharge capacity ratio is the ratio of the discharge capacity to the rated battery capacity of 1900 mAh at each charging time. As shown in FIG. 7, the discharge capacity ratio is proportional to the charging time up to about 3.2 hours, but thereafter, the slope gradually decreases and reaches about 100% at the charging time of about 3.8 hours. On the other hand, the charging efficiency shows a high value of about 99% or more until about 3.2 hours, but after that, gradually decreases and is about 95% at the charging time 3.6 h indicating the peak voltage, the discharge capacity ratio. However, it decreases to about 91% at a charging time of about 3.8 hours reaching about 100%.

As described above, the charging device 100 is configured to stop charging at a charging time of 3.4 hours indicated by point A by detecting an inflection point in the voltage gradient of the battery 1 and stopping charging. The charging efficiency in the charging time of 3.4 hours is about 99%, and higher charging efficiency can be realized as compared with the conventional method in which charging is stopped after detecting the peak voltage.
Further, in charging device 100, by detecting an inflection point in the voltage gradient of battery 1 and stopping charging, the voltage value of battery 1 changes from increasing to decreasing over time in charging time 3.6 hours. The charging is stopped before the point. That is, as described above, the unit time ΔT is set in the range of about 1.5 to 2.5 minutes, the inflection point in the voltage gradient of the battery 1 is detected, and the charging is stopped, so that the voltage value of the battery 1 is changed over time. Charging can be stopped before point B, which turns from increasing to decreasing as time passes. The charging efficiency in the charging time of 3.6 hours is about 95%, and higher charging efficiency can be realized as compared with the conventional method in which the charging is stopped after detecting the peak voltage.
(Relationship between charging time and battery temperature)
FIG. 8 shows experimental results showing the relationship between the charging time and the battery temperature in the charging apparatus 100. As shown in FIG. 8, the battery temperature first rises after charging is started, and shows a constant value of about 25.5 ° C. after about 1 hour. Thereafter, after a charging time of 3.4 hours indicated by point A has elapsed, the temperature rapidly increases and shows about 28.5 ° C. at a charging time of 3.6 hours indicated by charging time B. Then, the charging capacity ratio rises to about 34 ° C. in the charging time of about 3.8 hours when it reaches about 100%.

As described above, the charging device 100 is configured to stop charging at the charging time of 3.4 hours indicated by point A. The battery temperature at the charging time of 3.4 hours is about 25.5 ° C., and charging can be stopped before the rapid temperature rise starts. Compared with the conventional configuration in which charging is stopped after detecting the peak voltage. Battery temperature can be reduced.
<Summary>
As described above, the charging device 100 and the control method thereof according to the embodiment of the present invention monitor the voltage value output from the battery 1 and, when the voltage value is equal to or higher than the predetermined voltage value, per unit time When the amount of change in the voltage value changes from increasing to decreasing with the passage of time, the switching unit 3 is provided with a control unit that cuts off the current to the battery. Thereby, since the inflection point of the voltage gradient of the battery voltage during charging can be detected and charging can be stopped, the charging efficiency expressed as the ratio of the discharge capacity to the amount of charge can be increased. In addition, the heat generation of the battery that occurs when the charge amount ratio exceeds 100% can be prevented, and the battery life can be increased.
<Modification>
As mentioned above, although embodiment of the charging device 100 which concerns on the one aspect | mode of embodiment, and its control method was described, it is also possible to modify the illustrated charging device 100 as follows, and this invention is the above-mentioned embodiment. Of course, the charging device 100 is not limited to that shown in FIG.
(1) In the charging device 100 according to one aspect of the embodiment, the control unit 4 calculates a voltage change ΔV that is a change amount of the output voltage V of the battery 1 before and after the unit time ΔT during charging, and increases or decreases By detecting this, the inflection point of the voltage gradient is detected. However, the control unit 4 only needs to detect an increase / decrease over time of the change amount of the voltage value per unit time, and may be configured as follows. For example, in the modification, the control unit 4 detects the battery voltage at each charging time, and calculates the charging time ΔT required for the unit voltage change ΔV during charging from the battery voltage. And it was set as the structure which detects the inflection point of a voltage gradient by detecting the increase / decrease. Also in this case, similarly to the charging device 100 according to the embodiment, the charging can be stopped by detecting the inflection point of the voltage gradient of the battery voltage during charging.
(2) In charging apparatus 100 according to one aspect of the embodiment, control unit 4 calculates voltage change ΔV that is the amount of change in output voltage V of battery 1 before and after unit time ΔT during charging, and performs twice. Δ continuously
The charging is stopped when V decreases. However, the control unit 4 only needs to accurately detect increase / decrease in the voltage gradient, and may have the following configuration. For example, in a modification, the control unit 4 may be configured to stop charging when ΔV decreases three or four times in succession. Such a configuration can be realized by shortening the interval of the unit time ΔT as compared with the charging device 100 and increasing the detection accuracy of the battery voltage, and can detect the inflection point of the voltage gradient more accurately.
<Supplement>
Each of the embodiments described above shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, steps, order of steps, and the like shown in the embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the embodiment, steps that are not described in the independent claims indicating the highest concept of the present invention are described as arbitrary constituent elements constituting a more preferable form.

Further, for easy understanding of the invention, the scales of the components shown in the above-described embodiments may be different from actual ones. The present invention is not limited by the description of each of the above embodiments, and can be appropriately changed without departing from the gist of the present invention.
Furthermore, although there are circuit components, lead wires, and other members on the board in the charging device, various aspects can be implemented based on ordinary knowledge in the technical field of lighting devices and the like regarding electrical wiring and electrical circuits. The description of the present invention is omitted because it is not directly relevant. Each figure shown above is a schematic diagram, and is not necessarily illustrated strictly.

The charging device and the control method of the charging device according to the present invention include, for example, alkaline secondary batteries such as nickel hydride secondary batteries and nickel-cadmium secondary batteries used in home or public facilities, or portable electronic devices for business use. Can be suitably used for a charging device for charging the battery, a control method thereof, and the like.

1 Battery (Alkaline secondary battery)
2 Power supply unit 3 Switch unit 4 Control unit 5 Temperature sensor 6 LED (Charge status display)
7 LED (energy saving induction lamp)

Claims

Monitoring the voltage value of the alkaline secondary battery while supplying a constant current to the alkaline secondary battery;
When the voltage value exceeds a reference voltage value indicating an upper limit of a flat portion in a curve representing a voltage value characteristic during charging of the alkaline secondary battery, the amount of change in the voltage value per unit time is elapsed over time. A method for controlling a charging device, wherein charging is stopped when a change is made from increase to decrease.
The method for controlling a charging apparatus according to claim 1, wherein when the amount of change in the voltage value per unit time is equal to or greater than a predetermined value, the display is displayed until the charging is stopped.
The charging device control method according to claim 1, wherein the charging is stopped before the voltage value of the alkaline secondary battery changes from increasing to decreasing with time.
In a state where the charging efficiency, which is the ratio of the discharge capacity that can be taken out from the alkaline secondary battery to the amount of charge used for charging the alkaline secondary battery by discharging, is in the range of 95% to 99%, the alkaline secondary battery The charging device control method according to claim 3, wherein charging of the battery is stopped.
A set of time (TN, TN-1), (TN-2, TN-3), (TN-4, TN-) composed of two times separated by a unit time ΔT in ascending order with respect to the natural number N. 5) and voltage values VN, VN-1, VN-2, VN-3, V of the alkaline secondary battery at each time included in (TN-6, TN-7).
Measure N-4, VN-5, VN-6, VN-7,
Voltage value change V′N indicated by the difference VN−VN−1,
Voltage value change V′N−1 indicated by the difference VN−2−VN−3,
Voltage value change V′N−2 indicated by the difference VN−4−VN−5,
The voltage value change V′N-3 indicated by the difference VN-6−VN-7 is calculated,
Further, the difference V ″ N of the voltage value change indicated by the difference V′N−V′N−1,
A difference V ′ ″ N−1 in voltage value change indicated by a difference V′N−1−V′N−2;
The voltage value change difference V ″ N−2 indicated by the difference V′N−2−V′N−3 is calculated,
When the voltage value change difference V ″ N-2 is positive and the voltage value change difference V ″ N−1 and the voltage value change difference V ″ N are both negative, 5. The method for controlling a charging device according to claim 1, wherein charging of the alkaline secondary battery is stopped.
The method for controlling a charging device according to any one of claims 1 to 5, wherein the alkaline secondary battery is either a nickel-hydrogen secondary battery or a nickel-cadmium secondary battery.
A charging device for charging an alkaline secondary battery,
A constant current power supply,
A switch unit provided in a current path connecting the constant current power source unit and the alkaline secondary battery;
When the voltage value of the alkaline secondary battery is monitored and the voltage value exceeds the reference voltage value indicating the upper limit of the flat portion in the curve representing the voltage value characteristics during charging of the alkaline secondary battery, the unit time A control unit that causes the switch unit to cut off a current to the battery when the amount of change in the per-voltage value changes from increasing to decreasing with the passage of time;
A charging device comprising:
The display device further includes a display, and when the amount of change in the voltage value per unit time is equal to or greater than a predetermined value, the control unit displays the display until charging is stopped. Item 7. The charging device according to Item 7.
The control unit causes the switch unit to cut off the current to the battery before the voltage value of the alkaline secondary battery changes from increasing to decreasing with time.
The charging device according to claim 7.
In the state where the charging efficiency, which is the ratio of the discharge capacity that can be taken out from the alkaline secondary battery by discharging to the amount of charge used for charging the alkaline secondary battery, is in the range of 95% to 99%, Blocking the current to the battery in the switch unit;
The charging device according to claim 9.
The control unit is composed of two times separated by a unit time ΔT, and a set of time (TN, TN-1), (TN-2, TN-3), (TN -4, TN-5), and (TN-6
, TN-7) at each of the times included in the voltage values VN, VN-1,
Measure VN-2, VN-3, VN-4, VN-5, VN-6, VN-7,
Voltage value change V′N indicated by the difference VN−VN−1,
Voltage value change V′N−1 indicated by the difference VN−2−VN−3,
Voltage value change V′N−2 indicated by the difference VN−4−VN−5,
The voltage value change V′N-3 indicated by the difference VN-6−VN-7 is calculated,
Further, the difference V ″ N of the voltage value change indicated by the difference V′N−V′N−1,
A difference V ′ ″ N−1 in voltage value change indicated by a difference V′N−1−V′N−2;
The voltage value change difference V ″ N−2 indicated by the difference V′N−2−V′N−3 is calculated,
When the voltage value change difference V ″ N-2 is positive and the voltage value change difference V ″ N−1 and the voltage value change difference V ″ N are both negative, The charging device according to claim 7, wherein charging to the alkaline secondary battery is stopped.
The charging device according to any one of claims 7 to 11, wherein the alkaline secondary battery is either a nickel metal hydride secondary battery or a nickel cadmium secondary battery.