JPH1118314A - Method and equipment for charging lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and equipment for charging a lithiumion secondary battery, by which the battery can be charged to the most appropriate capacity under a charging circumstance. SOLUTION: When charging a battery pack 12 set in a charger 10 is started, a constant-current charging is conducted first with the fixed maximum charging voltage. When it is detected that the cell temperature of a secondary battery stored in the battery pack 12 has dropped from the maximum value, a constant- voltage charging is started. At the same time, a charging timer starts counting according to the ambient temperature. During the constant-voltage charging, a difference ΔTc in the cell temperature between the present one and the one prior to charging and a difference ΔTa in the ambient temperature between the present one and the one prior to charging are periodically calculated. In the case that these differences ΔT are smaller than preliminarily set values and the ratio of the charging current at the time of the constant current charging to the present one is smaller than a preliminarily set value, the charging timer is reset to extend or shorten the charging time.

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 lithium ion secondary battery for charging a lithium ion secondary battery and a charging apparatus for the same.

[0002]

2. Description of the Related Art In recent years, electronic devices such as mobile phones, notebook computers, and digital cameras have become smaller and lighter, and with the spread of them, it is possible to repeatedly charge and discharge as a power source for driving the electronic devices. Opportunities for using secondary batteries have increased. Such secondary batteries include nickel cadmium (Ni-Cd) batteries, nickel hydrogen (N
i-MH) batteries and lithium-ion batteries are generally known.

[0003] In particular, a lithium ion secondary battery is different from other secondary batteries in which water is involved in an electrochemical reaction involving water using an aqueous electrolyte solution. For example, an organic solvent such as a lithium salt is used for an electrolyte. Then, it is configured to generate electricity by an oxidation-reduction reaction caused by the transfer of electrons (lithium ions). In such a non-aqueous secondary battery,
Compared to other secondary batteries, the voltage between battery terminals in a single cell is high, and has the advantages of high capacity and high output,
Improvement of the performance of the non-aqueous secondary battery itself and a charging method for more effectively using the non-aqueous secondary battery are being studied.

[0004] For example, Japanese Patent Application Laid-Open No. 2-129670 discloses that a non-aqueous secondary battery is charged at a constant voltage, and when the charging current at that time becomes smaller than a set value, the charging current is cut off or the charging current is reduced. A charging device that keeps flowing only is disclosed. Japanese Patent Application Laid-Open No. H7-170669 discloses a charging circuit device that shifts generation of a time signal for stopping supply of a charging current in accordance with an increase in the ambient temperature of the charging circuit device.

[0005]

However, in the conventional charging method for charging a lithium ion secondary battery, the charging time is made substantially constant, or the charging is terminated when the charging current value reaches a set value. When charging is performed under temperature conditions, there is a problem that the capacity obtained as a result of charging varies even if conditions such as the battery cell temperature during discharging are equal.

As described above, the lithium ion secondary battery can be used even when electric charging conditions other than the battery cell are equal.
Compared to the discharge capacity after charging at normal room temperature (normal temperature), the battery is charged at a lower capacity at a lower temperature, and the capacity is increased at a higher temperature. However, there is a problem that optimal charge capacity cannot be ensured by simple charge control, because the battery life is short due to poor cycle deterioration.

An object of the present invention is to provide a method of charging a lithium ion secondary battery and an apparatus for charging the same, which can solve the above-mentioned drawbacks of the prior art and can secure an optimum charging capacity according to a charging environment. Aim.

[0008]

According to the present invention, there is provided a method of charging a lithium ion secondary battery for charging a lithium ion secondary battery, the method comprising the steps of:
Detects the ambient temperature of the secondary battery at the start of charging and the ambient temperature of the secondary battery during charging, detects the charging current during charging, and changes in the ambient temperature of the secondary battery at the start of charging and during charging And a change in the charging current for the secondary battery,
It is characterized by controlling a charging process for the secondary battery.

In this case, it is preferable to perform charging control for charging the secondary battery for a charging time according to the ambient temperature of the secondary battery at the start of charging.

In this method, the charging time for the secondary battery is counted, and the charging is terminated when a predetermined charging time is reached.
When controlling the charging process for the secondary battery, the charging time may be controlled by resetting the counting time.

In this case, the counting time may be reset according to the change in the ambient temperature of the secondary battery.

In this method, the secondary battery may be charged by constant-current charging at the initial stage of charging, and the charging may be switched to constant-voltage charging upon detecting that the cell temperature of the secondary battery has reached a maximum value.

This method also calculates the difference between the temperature of the secondary battery at the start of charging and the temperature during charging, recognizes the change in temperature of the secondary battery during charging, and compares the ambient temperature at the start of charging with the charging temperature. Calculates the difference between the ambient temperature during charging, recognizes the change in ambient temperature during charging, calculates the difference between the temperature change of the secondary battery during charging and the change in ambient temperature, and calculates the result of this calculation in advance. The charging process may be controlled when it is smaller than a predetermined value as compared with the set value.

In this case, the difference between the change in the temperature of the secondary battery being charged and the change in the ambient temperature is smaller than a preset value, and the charging current value currently being charged is smaller than that in the constant current charging. It is preferable to control the charging process when the charging current is smaller than the set value.

In this case, the difference between the change in the temperature of the secondary battery during charging and the change in the ambient temperature is smaller than a preset value, and the charging current value during the current charging is the setting of the charging current in the constant current charging. If it is smaller than the value, the count time may be reset so as to be longer than the current count time.

Also, in this method, the difference between the change in the temperature of the secondary battery being charged and the change in the ambient temperature is smaller than a preset value, and the charging current value currently being charged is smaller than the charging current in the constant current charging. When the current is smaller than the set value, the count time may be reset so as to be shorter than the current count time.

This method calculates a difference between the ambient temperature at the start of charging and the ambient temperature during charging, recognizes a change in the ambient temperature during charging, and determines whether or not the change is within an allowable range. It is preferable that the charging process is controlled by shortening or extending the charging time for the secondary battery according to the determination result.

According to another aspect of the present invention, there is provided a lithium ion secondary battery charging apparatus for charging a lithium ion secondary battery, wherein the secondary battery is charged with a constant voltage and a constant current. Means for generating a voltage and current for charging, a charge switch for turning on or off the output of the constant voltage / constant current charging means to supply the battery terminal of the secondary battery, and detecting an open battery terminal voltage of the secondary battery Terminal voltage detecting means, a current detecting means for detecting a charging current supplied from the charging means, a cell temperature detecting means for detecting a cell temperature of the secondary battery, and an ambient temperature detecting means for measuring an ambient temperature of the charging device. Means, and control means for generating a charge control signal for controlling on / off of the charge switch and controlling the charging process for the secondary battery, wherein the control means detects the voltage by the terminal voltage detecting means. Detecting means for monitoring the open terminal voltage of the secondary battery and the output of the charging means to detect the cell temperature and the ambient temperature; and charging timer means for subtracting the charging time for the secondary battery from a predetermined set time. The charging process is controlled by setting the counting time of the charging timer means based on changes in the charging current for the secondary battery, the open battery terminal voltage of the secondary battery, and the cell temperature.

In this case, the control means calculates the difference between the temperature of the secondary battery at the start of charging and the temperature during charging, recognizes the temperature change of the secondary battery during charging, and determines the ambient temperature at the start of charging. Calculate the difference between the ambient temperature during charging and the ambient temperature during charging, recognize the change in ambient temperature during charging, calculate the difference between the temperature change of the secondary battery during charging and the ambient temperature change, and calculate the calculation result. The charging process may be controlled by comparing with a predetermined value that is set in advance and, when the value is smaller than the predetermined value.

In this case, the control means determines that the difference between the change in the temperature of the secondary battery during charging and the change in the ambient temperature is smaller than a predetermined value, and that the charging current value during charging is lower than the predetermined value. When the charging current is smaller than the set value, the charging process may be controlled.

Further, it is preferable that the control means initializes the charging time corresponding to the ambient temperature at the start of charging in the charging timer means.

The control means may reset the counting time based on the difference between the ambient temperature at the start of charging and the ambient temperature during charging.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for charging a lithium ion secondary battery and a charging apparatus for the same according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, there is shown a block diagram of a charger to which the present invention is applied. This charger
10 is the charge output terminal (BV, BGND) and temperature detection terminal (T)
This is a charging device that can appropriately charge the battery pack 12 detachably connected to the battery pack according to the temperature. When charging the secondary battery housed in the battery pack 12, the charger 10 in the present embodiment first charges with a constant current having a predetermined maximum charging voltage, and then responds to a change in the cell temperature of the secondary battery. In particular, the charger 10 monitors the cell temperature of the secondary battery and the ambient temperature under the charging environment, and also controls the secondary battery. , The battery terminal voltage of the secondary battery, and the current at the time of charging are monitored, and appropriate charging processing is performed according to the monitoring results. In the following description, illustration and description of parts not directly related to the present invention are omitted, and symbols in which signals appear are represented by reference numerals of the signal lines.

The power supply input terminals (+ V) 100a and (G
The ND) 100b is connected to a DC power supply (not shown) that steps down and rectifies the AC power to a predetermined voltage, and receives a DC power supply voltage supplied from the DC power supply. The power input terminal 100b is connected to ground (GND). The output of the DC power supply is supplied to each section of the charger 10 and used as an operation power supply.

The constant voltage control circuit 14 has a power input terminal 100a, 1
This is a circuit that outputs the DC power applied to the power supply 00b at a constant voltage. The constant voltage control circuit 14 outputs a charge output for charging the secondary battery of the battery pack 12 to outputs 102a and 100b. The output 102a of the constant voltage control circuit 14 is connected to the emitter of the transistor 16 functioning as a charging switch, and the output 102a is further connected to the charging voltage input (Vre
g) Connected to 104.

Transistor 16 connects the charge output applied to the emitter to the collector according to its base potential,
A charging switch for switching a charging output supplied from the constant voltage control circuit 14. Transistor 16 collector
106 is an output terminal (B
V) 108. The base of transistor 16 is
The collector 112 of the transistor 22 is connected via a connection line 110, and the base 112 of the transistor 22 is connected via a resistor R2 to the charge switch output 114 of the charge control circuit 18, and has its emitter and ground connected via a resistor R3. (GN
D) is connected to

On the other hand, the output 102b of the constant voltage control circuit 14 is connected to a current limiting circuit 24. The current limiting circuit 24 limits the current from the battery ground terminal (BGND) 110 and returns the current to the constant voltage control circuit 14. , A circuit for detecting the current value. The current limiting circuit 24 supplies a current value signal indicating a voltage value corresponding to the detected current to the charging control circuit 18 connected via the connection line 118.

As shown in FIG. 6, the charging control circuit 18 performs constant-current charging at the beginning of charging, and when detecting that the cell temperature of the secondary battery has peaked, performs charging processing with constant-voltage charging. Control circuit. The charging control circuit 18 performs control for charging the secondary battery by a constant current / constant voltage charging method in which a charging process for charging the secondary battery at a constant voltage is continued during a period set by a charging timer described later. The charge control circuit 18 in the present embodiment has a function of controlling the charging process in accordance with the substantial change in the cell temperature of the secondary battery during the constant voltage charging process and the charging current to the secondary battery.

More specifically, the charge control circuit 18 turns on / off the transistor 16 and controls the supply of the charging voltage and the charging current to the secondary battery, so that the charger output voltage (Vreg) and the battery terminal voltage (Vbat ), And repeating this process at regular intervals until the count value of the charge timer decreases to zero.
In particular, the charge control circuit 18 has a function of resetting the set time of the charge timer according to the conditions such as the charge current value and the cell temperature value, and thereby performs a charge process by securing an appropriate charge time. Control. At this time, the charge control circuit 18 corrects the detected cell temperature according to a change in the ambient temperature, resets the timer time based on the corrected substantial cell temperature, and controls the charging time to an optimal time. I do. Further, the charging control circuit 18 determines a charging voltage during charging.
(Vreg) and a function of recognizing a decrease in the battery terminal voltage (Vbat) and stopping or terminating the charging process according to the abnormal situation. The charge control circuit 18 turns off the transistor 16 when the remaining time in the charge timer becomes zero,
Thereafter, when the detachment of the battery pack 12 from the charger 10 is detected, for example, by the presence or absence of the connection of a thermistor housed in the battery pack 12, the charging process is terminated.

In addition, the charge control circuit 18 controls the secondary battery in the constant voltage charging process according to a charging current ratio corresponding to a ratio between a charging current value during charging and a charging current set and flowing during constant current charging. Has the function of controlling the charging process for. Specifically, the charge control circuit 18 calculates the charge current ratio by dividing the current charge current value by the set value of the constant current charge current, and compares whether the charge current ratio is smaller than the set value. It has a judgment function. The charge control circuit 18
When the charging current ratio is smaller than the set value, it is determined that the charging has progressed to some extent, and the set time of the charging timer is reset.

A temperature sensor 26 is connected to an input 120 of the charge control circuit 18, and the temperature sensor 26 is a temperature detecting element for detecting an ambient temperature of the charger 10. Charge control circuit 18
Has a function of recognizing the temperature value detected by the temperature sensor 26, storing the ambient temperature at the start of charging, and setting a charging timer time according to the ambient temperature.
Further, the temperature sensor 26 continuously detects the ambient temperature during charging, and the charging control circuit 18 has a function of performing charging control on the secondary battery based on a change in the temperature detected by the temperature sensor 26. Have. Temperature sensor 26 is a charger
It is arranged in a place that is not affected as much as possible by the heat generated in the internal circuit 10 and the battery pack 12.

The internal structure of the charge control circuit 18 will be described with reference to FIG. 2. The charge control circuit 18 in the present embodiment is preferably constituted by a microcomputer system, and various analog signals are inputted to inputs 104, 108, 116, 118 and 120. A detection circuit 202 for inputting and detecting, selectively selecting these and connecting to the output 200, and an A / D converter 204 for converting the value of the signal 200 output from the detection circuit 202 into a digital value
And a digital value converted data are received at an input 206, and a storage unit 208 for storing these data and a set value for charge control in a predetermined storage area, and a data stored in the storage unit 208. And a setting value input to an input 210 to perform various calculations, a calculation result 214 in the calculation processing unit 212, and a setting value 21 read from the storage unit 208.
6 and a reset processing unit that resets the charging timer time according to the comparison result and outputs a control signal for controlling on / off of the transistor 16 to an output 114.
218, and a charging timer 220 for counting by subtracting the charging time initially set according to the ambient temperature at the start of charging, wherein the charging time is reset and counted according to the determination result in the determination processing unit 218. And a timer 220. In the present embodiment, a basic charging time of 2.5 hours is set in advance in the charging timer 220, and if the ambient temperature is higher than 25 degrees according to the ambient temperature at the start of charging, the charging time is reduced, and If the ambient temperature is lower than 25 degrees, the charging time is set to extend the charging time. Also,
This time is subtracted from the start of constant voltage charging,
For example, the charging time is reset according to a situation such as a change in the ambient temperature or a change in the charging current ratio.

More specifically, the A / D conversion section 204 includes the detection circuit 20
Charge voltage (Vreg) 104 detected at 2 and battery terminal voltage
(Vbat) 108, the cell temperature value (Tc) 116 supplied from the battery pack 12 via the temperature detection terminal (T), the ambient temperature value (Ta) 120 measured by the temperature sensor 26, and the current limit This is an analog / digital conversion circuit which inputs current values 118 measured by the circuit 24 and sequentially converts them into digital values according to the accuracy of the charge control. A / D conversion circuit 204
Supplies these detected and converted digital signals to the arithmetic processing unit 212 and further supplies a digital signal representing the ambient temperature at the start of charging to the storage unit 208.
Also, the A / D conversion unit 204 supplies the charging voltage (Vreg) and the battery terminal voltage (Vbat) to a determination unit 218 described below,
At 218, these voltage drops are detected. Also, the A / D conversion unit 204 supplies the change in the resistance value detected via the temperature detection terminal (T) 116 to the determination processing unit 218, and determines the mounting state of the battery pack 12.

The storage unit 208 stores a charger at the start of charging.
This is a memory circuit that stores the ambient temperature of the charger 10 and various setting values for charge control as the environmental temperature of the charger 10. The storage unit 208 in the present embodiment has a storage area for storing a measured value of the ambient temperature at the start of charging, which is detected by the temperature sensor 26 and converted into a digital value. Further, the storage unit 208 has a function of storing a set value that defines a substantial change in cell temperature based on the ambient temperature at the start of charging and a set value of the charging current ratio. The storage unit 208 in this embodiment stores, for example, data indicating 0.5 degrees as the set value of the change in cell temperature, and stores data indicating 0.1 as the set value of the charging current ratio. The storage unit 208
The stored information is output to the arithmetic processing unit 212 as needed.

The arithmetic processing unit 212 is an arithmetic circuit that corrects a change in cell temperature during charging according to a change in environmental temperature. Specifically, the arithmetic processing unit 212 calculates a value Δ representing the difference between the current cell temperature value and the cell temperature value at the start of charging.
It has a function to calculate Tc.

[0037]

ΔTc = (current cell temperature−cell temperature before charging) Further, the arithmetic processing unit 212 calculates a value ΔTa representing the difference between the current ambient temperature value and the ambient temperature value at the start of charging. have.

[0038]

[Mathematical formula-see original document] ΔTa = (current ambient temperature−ambient temperature before charging) Further, the arithmetic processing unit 212 calculates a difference between the value ΔTc and the value ΔTa to obtain a value ΔT representing a substantial change in cell temperature. It has a function to calculate.

[0039]

ΔT = (ΔTc−ΔTa) Further, the arithmetic processing unit 212 performs a charging operation that indicates the ratio between the current charging current value during charging and the constant current charging set value stored in the storage unit 208. An arithmetic circuit having a function of calculating the current ratio r and supplying the calculated charging current ratio r to the determination processing unit 218.

[0040]

## EQU4 ## The charging current ratio r = (current charging current / set value of constant current charging) The arithmetic processing unit 212 sends the calculated value ΔT and the charging current ratio to the determination processing unit 218 connected to the output 214. .

The determination processing unit 218 includes various measurement results converted by the A / D conversion unit 204, the calculation results obtained by the arithmetic processing unit 212, the set values stored in the storage unit 208, and the ambient temperature at the start of charging. This is a functional unit that determines the appropriate charging process for the secondary battery based on the measured value of, and generates a charge control signal for turning on / off the transistors 16 and 22 according to the determination result, thereby performing the charge control.

The determination processing unit 218 according to the present embodiment will be described in detail.
Battery pack 12 is detected as
Has a function of determining whether or not the terminal voltage (Vbat) is within a chargeable voltage range. The determination processing unit 218 recognizes, for example, that the thermistor provided in the battery pack 12 is connected to the temperature detection terminal (T) 116 and the output terminal (BGND) 110 by a change in the resistance value between the terminals. Thereby, it is detected that the battery pack 12 is attached to and detached from the charger main body 10. However, the present invention is not limited thereto, and a detection element for detecting attachment / detachment of the battery pack 12 may be provided in the mounting portion, and the battery pack 12 may be detected according to the detection result.

The determination processing unit 218 calculates the difference between the cell temperature and the ambient temperature, and when detecting that this difference falls below the maximum value, switches from constant-current charging to constant-voltage charging and changes the ambient temperature at the start of charging. A timer time is set according to the temperature, and the charging timer 220 is started. Then, the judgment processing unit 218
Determines that the difference between the cell temperature and the ambient temperature is smaller than the set value, cuts off the charging current or resets the charging timer time according to the elapsed timer time at that time.

For example, the judgment processing unit 218 is
A comparison is made between the value ΔT supplied from 212 and the set value stored in the storage unit 208. Also, the judgment processing unit 218
If the value ΔT is smaller than the set value as a result of the comparison between the value ΔT and the set value, the charge current ratio r calculated by the arithmetic processing unit 212 and the set value stored in the storage unit 208 are further compared. Comparing large and small. The determination processing unit 218 resets the set time in the charging timer 220 when the charging current ratio r is smaller than the set value as a result of the comparison between the charging current ratio r and the set value. The reset time of the charging timer 220 includes 0,
In this case, the process proceeds to the charging completion process according to the charging process procedure.

Further, the judgment processing unit 218 controls the charge control signal 114 to a high level or a low level to turn on / off the transistors 22 and 16 in accordance with the charge processing procedure, and to charge the charge voltage (Vreg) and the battery terminal voltage (Vbat). Are turned off, the transistors 22 and 16 are turned off. Further, when determining the voltage drop during charging, the determination processing unit 218 performs the A / D control while controlling the transistors 22 and 16 to be in the ON state.
In response to the voltage value from the conversion unit 204, a decrease in the charging voltage (Vreg) and the battery terminal voltage (Vbat) is determined. In this case, the determination processing unit 218 determines the charging voltage (Vreg) and the battery terminal voltage (Vba
When it is determined that t) has decreased, the charge switch output 114 is output.
The transistors 22 and 16 are turned off by controlling to the low level. Accordingly, the determination processing unit 218 can determine that the battery terminal voltage (Vbat) has suddenly dropped due to, for example, a short circuit, and cut off the charging output (Vreg) from the battery pack 12. Further, the determination processing unit 218 outputs the charging output voltage (Vre
It has a function of determining whether or not g) is a voltage value sufficient to charge the battery pack 12, stopping charging according to the number of times charging is impossible, and outputting a display indicating a charging abnormality.

The charging timer section 220 is a time counting circuit that counts the timer set time set by the determination processing section 218. The charging timer unit 220 has a function of sequentially subtracting a time set according to the charging environment and continuing counting until the remaining time becomes “0”. In addition, charge timer section
In 220, the remaining time of the timer is reset by the determination processing unit 218. The time reset by the determination processing unit 218 includes zero, and in that case, the charging process can be immediately terminated. When the determination processing unit 218 sets a time exceeding zero, the charging time can be extended. In the charging timer 220 of the present embodiment, a reference time representing 2.5 hours based on a case where the ambient temperature is, for example, 25 degrees is set, and when the ambient temperature is lower than 25 degrees, a time longer than the reference time is set. When the ambient temperature is higher than 25 degrees, a time shorter than the reference time is set. These set times are further reset by the determination processing unit 218 according to changes in the ambient temperature and the cell temperature and changes in the charging current ratio.

The battery pack 12 in this embodiment will be described with reference to the exploded view of FIG.
Is a lithium ion (Lithium
-Ion) a secondary battery 500, a circuit board 502 for protecting the secondary battery, a detecting element 504 for detecting a surface temperature of the lithium ion secondary battery as a cell temperature, and an upper case for housing these components. 506 and a lower case 508.

The lithium ion secondary battery 500 is a non-aqueous secondary battery that uses an organic solvent of a lithium salt as an electrolyte and generates electricity by an oxidation-reduction reaction caused by the movement of lithium ions. In the lithium ion secondary battery 500 in this embodiment, two cylindrical battery cells 500 are connected in series by a connection plate 501, and the positive and negative electrodes at both ends thereof are connected to an output terminal (+) 510 of the circuit board and an output terminal (+) 510. Terminal
Connected to (-) 512. As a result, the battery pack 12
The nominal voltage of a single cell, e.g., twice 4.2 volts 8.
Generates a 4 volt DC voltage between the output terminals. These output terminals 510 and 512 are connected to the connection terminals
(+) 514 and (-) 516, respectively, and these connection terminals are connection points with the charger 10.

FIG. 7 shows a charge / discharge characteristic table of the lithium ion secondary battery 500. This characteristic table shows that the temperature around the charger 10 is 25 degrees for each of charging and discharging, the charging current value based on the nominal capacity is 1 C, the constant voltage constant current charging is performed, and the secondary charging is performed for 2 hours 30 minutes. 4 is an experimental relative comparison table of discharge temperature and discharge capacity for each charge temperature based on a case where the discharge capacity when the battery is discharged at 1 C is 100%. Based on the results of this experiment, the reference temperature (25
If the temperature is lower than (degree), the charging time needs to be extended for a certain time to obtain the nominal capacity, and if the temperature is high, the charging time may be shortened for a certain time. However, when extending the charging time, the charging time is limited within the maximum charging time range according to the battery characteristics of the secondary battery. In the present embodiment, data corresponding to such a result is stored in the storage unit 208,
Based on this, the charger 10 is configured to set a charging time according to the ambient temperature at the start of charging in the charging timer, and further reset the charging timer time according to a temperature change during subsequent charging. .

Returning to FIG. 5, the upper case 50 of the battery pack 12
A temperature detecting element 504 is provided between the battery cell 500 and the battery cell 500 so as to be in close contact with the battery cell 500. As the temperature detecting element 504 in this embodiment, a thin thermistor, a semiconductor sensor, or the like whose resistance value changes according to the temperature is advantageously applied. Although the temperature detection element 504 is arranged for one of the battery cells 500 in the figure, the temperature detection element 504 is placed between the two battery cells 500 so as to be in common contact with the two battery cells 500, for example. Can be arranged.
As described above, the temperature detecting element 504 may be disposed in a place where a temperature change due to heat generation of the battery cell 500 appears immediately, but is not limited thereto, and the temperature in the battery pack 12 becomes substantially equal to the cell temperature. In such a case, it may be arranged at a place where the temperature inside the battery pack is detected. One lead of the temperature detection terminal 500 is connected to a detection terminal (T) 518 for temperature detection provided on the circuit board 502, and the other lead is connected to a connection terminal (-) 512. This temperature detection terminal (T) 518
Is disposed so as to be connected to the detection terminal (T) of the charger 10 through the detection window 520 of the lower case 508.

The circuit board 502 includes an output terminal of the battery cell 500 and connection terminals 514, 516 of the lower case 508.
Between the terminals of the battery cell 500 and the battery pack 12
In the event of an abnormality such as a short circuit between the output terminals 514 and 516, the connection terminal 514 and 516 of the battery pack 12 and the battery cell 500 are disconnected.

On the other hand, a charger for charging the battery pack 12
The main body includes a battery pack 12 as shown in FIG.
And a battery ground terminal 110 connected to the connection terminals 514 and 516 of the battery pack 12, and a temperature detection terminal 116 connected to the detection terminal 518 of the battery pack 12. ing. Also the charger
In 10, a temperature sensor 26 for measuring the ambient temperature is provided, for example, inside the rear side surface of the charger 10 main body.

The battery pack 12 is mounted on the charger 10 as shown by an arrow in FIG.
, The battery ground terminal 110 and the temperature detection terminal 116 are connected to the connection terminals 514, 516 and the detection terminal 518 of the battery pack 12, respectively. FIG. 4 shows the mounted state.
In FIGS. 3 and 4, the engaging portion for attachment, the lock mechanism, and the removal mechanism are omitted to avoid complication of the drawings. Further, on the front surface of the charger 10, there is provided a display unit including a charging lamp indicating that charging is in progress, and an abnormality indicating lamp 400 which is lit when a charging abnormality occurs to notify the abnormality.

The charger 10 is provided with the attached battery pack.
Video equipment such as an electronic camera driven by the digital camera 12, information equipment including a computer system, and electronic equipment such as wireless and wired communication equipment may be included.In this case, the charged battery pack 12 is The electronic device can be operated by supplying power from the battery pack 12 to the electronic device while being attached to the device and the charger 10. In this case, even when the charger main body 10 and the battery pack 12 themselves are heated to some extent due to the operation of the electronic device, the temperature is recognized as the ambient temperature when charging the secondary battery, and the ambient temperature is recognized. Optimum charging processing can be performed according to and the cell temperature of the secondary battery.

The operation of the charger 10 according to the present embodiment having the above configuration will be described with reference to FIGS. First, DC power is supplied from a DC power supply device (not shown) to the terminal 100 of the constant voltage control circuit 14 and each part of the charger 10 to be in an operating state. In this initial state, the charge control signal 104 of the charge control circuit 18 is controlled to low level, the transistors 22 and 16 are turned off, and the output of the constant voltage control circuit 14 is disconnected from the terminals 108 and 110. I have.

In step 800 shown in FIG. 8, it is determined whether or not the battery pack 12 is mounted on the charger 10 based on, for example, a change in resistance between the temperature detection terminal (T) and the terminal (BGND). When the battery pack 12 is mounted on the main body of the charger 10, this is detected by a change in the resistance value between the terminals 116 and 110, and the process proceeds to step 802.

In step 802, the terminal voltage Vb of the secondary battery
Whether at is within the chargeable range is determined by the voltage between the terminals 108 and 110. If the voltage value is not within the chargeable voltage range, it is determined that charging is not possible, and the process proceeds to step 804. If the voltage value is within the chargeable range, the process proceeds to step 808. Step 804
It is determined whether or not the voltage Vreg104 is within a chargeable voltage range. If the voltage is within the chargeable voltage range, the process proceeds to step 806;
Proceed to. Proceeding to step 808, steps 802 and 804
The number of times the charging is determined to be impossible is counted, and then the process proceeds to step 810, where it is determined whether the number of times the charging is impossible has reached a preset N times. If the number of unchargeable times is N, the process proceeds to step 812. If the number of unchargeable times is not N, the process returns to step 802.

In step 806 following step 804, the value of the voltage Vreg is compared with the value of the voltage Vbat. If the value of the voltage Vreg is equal to or higher than the voltage Vbat, the process proceeds to step 900 shown in FIG. If so, go to step 812.

When the number of charging times is N and when the voltage Vreg
In step 812 when the value of the charge control signal is less than the voltage Vbat, the charge control signal is controlled to the low state and the charge switch is
The OFF state is maintained and controlled, and a charging abnormality indicator lamp 400 (not shown) is turned on.

In step 900, the resistance value of the thermistor disposed in the battery pack 12 is measured via the terminal 116, and the cell temperature of the secondary battery is detected. Next step 90
In 2, the ambient temperature of the charger 10 is detected based on the resistance value of the temperature sensor 26. The data representing the detected cell temperature and the ambient temperature, particularly data at the start of charging, is stored in the charge control circuit 18.
Is stored in the storage unit 208.

Next, the routine proceeds to step 904, where it is determined whether or not the cell temperature has decreased from the maximum value. If the cell temperature has decreased from the maximum value, the routine proceeds to step 906. In step 906, the charging time according to the ambient temperature detected at the start of charging is obtained and set based on the data corresponding to the charging / discharging characteristics at each temperature stored in the storage unit 208. For example, if the ambient temperature at the start of charging is 25 degrees, the charge timer time is set to 2 hours and 30 minutes. If the temperature is lower than that, for example, 0 degrees, 2
The time is extended by 30 minutes. Conversely, if the ambient temperature at the start of charging is higher than 25 degrees, a charging time shorter than 2 hours and 30 minutes is set. When the charging time is set and the counting by the charging timer 220 is started, the routine proceeds to step 908. In this case, if the charging timer 220 is already counting, the counting is continued and it is not restarted. If the cell temperature is not at the maximum, step 90
From 4 proceed to step 910.

At step 908, a process for determining whether or not to reset the charging timer 220 is performed. Specifically, in the time calculation process of the charge timer, in step 1100 shown in FIG. 11, the difference between the current cell temperature value and the cell temperature value at the start of charging is calculated by the calculation processing unit 212, and the value ΔTc of the calculation result is calculated. Is required. In the following step 1102, the difference between the current ambient temperature value and the ambient temperature value at the start of charging is calculated by the arithmetic processing unit 212, and the value ΔTa of the arithmetic result is obtained. Next, at step 1104, the difference between the value ΔTc and the value ΔTa is calculated by the calculation processing unit 212, and a value ΔT representing a substantial change in cell temperature is obtained.

In step 1106, the determination processing section 212 determines whether or not ΔT obtained in step 1104 is smaller than the set value. If smaller, the process proceeds to step 1108. If not, the process proceeds to step 906. Proceed to.

In step 1108, the current charging current value
A charging current ratio r representing a ratio between the constant current charging set value 118 and the constant current charging set value stored in the storage unit 208 is calculated by the arithmetic processing unit 212, and whether or not the calculated charging current ratio r is smaller than the set value. Is determined by the determination processing unit 218. If the charging current ratio r is smaller than the set value, the process proceeds to step 1110; otherwise, the process proceeds to step 906. Steps
At 1110, the counting time of the charging timer 220 is reset to, for example, 30 minutes.

Steps following steps 904 and 908
At 910, the transistors 22 and 16 are turned on by the charge control signal, and the output of the constant voltage control circuit 14 is supplied to the battery pack 12 via the terminals 108 and 110. Next, the routine proceeds to step 912, where it is determined whether or not the voltage Vreg has dropped below the range of a chargeable voltage. Steps 812 and 81 when the voltage drop is detected
Proceeding to step 4, the charge switch 16 is turned off and the charging abnormality indicator lamp 400 is further turned on.If not, the procedure proceeds to step 912 to determine whether the voltage Vbat is lower than the lowest chargeable voltage. If it is determined that the voltage is equal to or lower than the minimum voltage, the transistor 16 is controlled to be turned off, and the charging output of the charger 10 is stopped (step 916). Also,
If the voltage Vbat is a chargeable voltage in step 914, the process proceeds to step 1000 shown in FIG.

In step 1000, it is determined whether a predetermined time has elapsed. If not, step 10 is executed.
At 04, the values of the voltage Vreg and the voltage Vbat are further compared and calculated. If the value of the voltage Vreg is equal to or higher than the voltage Vbat, the process returns to step 802; otherwise, the process proceeds to step 1006. In step 1006, it is determined whether or not the values of the voltage Vreg and the voltage Vbat are substantially equal. If they are equal, the process proceeds to step 1008, and if not, the process returns to step 912.

In step 1008, it is determined whether or not the counting time of the charging timer 220 has become zero.
If so, the process proceeds to step 1010, and if the count time is not 0, the process proceeds to step 802. Step 1012
When the process proceeds to, the completion of charging is detected by removing the battery pack 12 from the charger, and a series of charging control processes ends.

In this embodiment, in particular, after the cell temperature reaches a peak, the process shifts from the constant current charging to the constant voltage charging process. At this time, the counting of the charging timer 220 is started. in this case,
An appropriate charging time according to the ambient temperature at the start of charging is set in the charging timer 220. Further, the difference between the current cell temperature and the cell temperature at the start of charging, and the difference between the current ambient temperature and the ambient temperature at the start of charging are determined, and the difference is further determined. Charge timer 22 when the difference between
By resetting the counting time of 0, the charging process can be controlled. That is, in the present embodiment, charging is performed by setting an appropriate charging time, and furthermore, charging is controlled in accordance with a change in cell temperature and a change in ambient temperature, so that an optimal charging capacity is secured according to the charging environment. Thus, the secondary battery can be charged.

For example, the charging time can be shortened when the ambient temperature rises during the constant voltage charging process. Even when the ambient temperature is constant, the charging time can be shortened according to the rise in the cell temperature. , And the charging time is extended according to the decrease in the cell temperature, so that an optimal charging capacity can be secured. When the charging time is extended, if the maximum charging time of the secondary battery is specified, the charging time is extended within that range.

Although the embodiment in which the charging control is performed using the cell temperature of the secondary battery has been described above, the time calculation processing of the charging timer can be performed regardless of the change in the cell temperature. Specifically, the charging timer time calculation processing shown in FIG.
The procedure is performed as shown in FIG. In order to perform such a charging timer time calculation process, the charging processing circuit 18 shown in FIG. 1 calculates a change in the ambient temperature during charging and calculates a difference between the ambient temperature at the start of charging and the current ambient temperature. If the difference is larger than the allowable amount, the charging timer time is shortened, and if the difference is smaller than the allowable amount, the charging timer 220 is reset so that the charging timer time is shortened. Perform control.

Therefore, in this embodiment, the charge control circuit 18
The storage unit 208 stores an allowable temperature value representing an allowable value of the change in the ambient temperature, and the determination processing unit 218 determines the magnitude of the change in the ambient temperature based on the allowable temperature value. Other parts of the charger configured as described above may have the same configuration as that of the above-described embodiment, and the operation of this charger may be the same processing as that shown in FIGS. Calculation of the charging timer time of this charger (step
908 (FIG. 9) will be described below with reference to FIG. 12. In step 1200, the difference between the current ambient temperature value and the ambient temperature value at the start of charging is calculated by the arithmetic processing unit 212, and the arithmetic operation is performed. The resulting value ΔTa is determined. Next, the process proceeds to step 1202, where the value ΔTa calculated in step 1200 is stored in the storage unit 208.
It is determined whether or not the value is larger than the allowable temperature range stored in the CPU. If the value ΔTa is larger than the allowable temperature range, the process proceeds to step 1204, and a flag for reducing the timer time is set. Conversely, if the value ΔTa is below the allowable temperature range, the process proceeds to step 1206, and if the value ΔTa is substantially equal to the allowable temperature range, the process proceeds to step 1210; otherwise, the process proceeds to step 1208 to extend the timer time. Flag is set.

In step 1210, the current charging current value 118
And a constant current charging set value stored in the storage unit 208, the charging current ratio r is calculated by the arithmetic processing unit 212, and whether the calculated charging current ratio r is smaller than the set value is determined. Is determined by the determination processing unit 218. Charge current ratio r
Is smaller than the setting, the process proceeds to step 1212; otherwise, the process proceeds to step 910 shown in FIG.

In Step 1212, Step 1204 or 12
The timer time for resetting the charging time is determined according to the latest flag set in 08, and the counting time in the charging timer 220 is reset accordingly. As a result, in this embodiment, the charging control is performed such that the charging timer time is shortened or extended based on the rise or fall of the value ΔTa obtained by correcting the current ambient temperature by the ambient temperature before charging, and , And a charger free from undercharging and overcharging can be provided. For this reason, cycle deterioration of the secondary battery can be appropriately prevented.

As described above, from the charging temperature characteristic of the lithium ion secondary battery, when a constant current and a constant voltage are applied, the cell temperature becomes maximum at the transition from the constant current region to the constant voltage region, and the cell temperature becomes constant in the constant voltage charging region. As the charging current decreases, the cell temperature also decreases. Then, the charging is started by setting the charging time according to the ambient temperature before charging, and when the difference between the cell temperature and the ambient temperature becomes smaller than the set value, it is determined whether the charging timer time is extended or shortened. Judge and control charging. Therefore, the charging is controlled while comparing the difference between the actual ambient temperature, the cell temperature, and the ambient temperature, so that the lithium ion secondary battery can obtain the optimal charging capacity in the charging environment. Further, even when the change in the cell temperature is not monitored, the charging time can be controlled by resetting the timer time from the state of the change in the ambient temperature. As a result, for example, since overcharging is prevented when the ambient temperature rises, deterioration of the battery cell can be prevented, and insufficient charging can be prevented from occurring when the ambient temperature falls. Therefore, there is provided a charger capable of appropriately charging the battery pack while minimizing cycle deterioration. Also,
If the change in the ambient temperature is small and almost constant, the charging time is set longer as the cell temperature decreases,
Conversely, when the cell temperature rises, it is set longer, and in these cases, an appropriate charge control function works. In addition, since the temperature of the battery pack can be detected during charging, for example, when an abnormality occurs inside the cell and the temperature of the cell becomes high, this temperature rise is detected and the charging process can be immediately stopped. it can.

[0075]

As described above, according to the present invention, the ambient temperature of the secondary battery at the start of charging, the ambient temperature of the secondary battery during charging, and the charging current during charging are detected, respectively, to start charging. Control the charging time in accordance with the ambient temperature at the time of charging, and further, in accordance with the change in the ambient temperature and the change in the charging current of the secondary battery at the start of charging and during charging, the charging process for the secondary battery is initially performed. Since the length is set longer or shorter than the setting, an optimal charging process can be performed. As a result, appropriate full charge can be obtained while preventing damage to the secondary battery such as overcharging, and the cycle life of the secondary battery can be appropriately maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a charging device to which the present invention is applied.

FIG. 2 is a block diagram showing an example of an internal configuration of a charge control circuit shown in FIG.

FIG. 3 is an external view showing a charging device and a battery pack in the embodiment.

FIG. 4 is a diagram showing a mounting state of the charging device and the battery pack in the embodiment.

FIG. 5 is an exploded view showing an internal configuration of the battery pack in the embodiment.

FIG. 6 is a diagram showing changes in charging current and cell surface temperature in a constant current voltage charging process.

FIG. 7 is a table relatively showing a discharge capacity according to a charge / discharge temperature of a lithium ion secondary battery in an example.

FIG. 8 is a flowchart showing a charging process control in the embodiment.

FIG. 9 is a flowchart illustrating charging process control in the embodiment.

FIG. 10 is a flowchart showing a charging process control in the embodiment.

FIG. 11 is a flowchart illustrating a charging timer time calculation process in the charging process control in the embodiment.

FIG. 12 is a flowchart showing another embodiment of the charging timer time calculation processing.

[Explanation of symbols]

 10 Charger 12 Battery pack 14 Constant voltage control circuit 16 Transistor (charge switch) 18 Charge control circuit 26 Temperature sensor 108,110 Charge output terminal 116 Temperature detection terminal

Claims (16)

[Claims] 1. A method for charging a lithium ion secondary battery that charges a lithium ion secondary battery, the method comprising: an ambient temperature of the secondary battery at the start of charging; and an ambient temperature of the secondary battery during charging. And detecting a charging current during charging, based on a change in ambient temperature of the secondary battery at the start of charging and during charging, and a change in charging current for the secondary battery. A method for charging a lithium ion secondary battery, comprising: controlling a charging process for a battery. 2. The method for charging a lithium ion secondary battery according to claim 1, wherein the method charges the secondary battery for a charging time according to an ambient temperature of the secondary battery at the start of the charging. A charging method for a lithium ion secondary battery, comprising: 3. The method for charging a lithium ion secondary battery according to claim 1, wherein the charging is terminated when the charging time for the secondary battery reaches a predetermined charging time. When controlling the charging process for the battery,
A method for charging a lithium ion secondary battery, wherein the charging time is controlled by resetting the counting time. 4. The method for charging a lithium ion secondary battery according to claim 3, wherein the counting time is reset according to a change in the ambient temperature of the secondary battery. How to charge the ion secondary battery. 5. The method for charging a lithium ion secondary battery according to claim 1, wherein the secondary battery is charged by constant current charging at an initial stage of charging, and the cell temperature of the secondary battery is maximized. A method for charging a lithium-ion secondary battery, characterized in that the charging is switched to constant voltage charging upon detecting that the value has reached a value. 6. The method for charging a lithium ion secondary battery according to claim 1, wherein the method calculates a difference between a temperature of the secondary battery at the start of charging and a temperature during charging. Recognizing the temperature change of the secondary battery, calculating the difference between the ambient temperature at the start of charging and the ambient temperature during charging, and recognizing the change in the ambient temperature during charging, Calculating the difference between the temperature change and the change in the ambient temperature, comparing the calculation result with a preset value, and controlling the charging process when the difference is smaller than a predetermined value. How to charge a lithium ion secondary battery. 7. The method for charging a lithium ion secondary battery according to claim 6, wherein a difference between a temperature change of the secondary battery during the charging and a change of the ambient temperature is set in advance. And controlling the charging process when the charging current value during the current charging is smaller than the set value of the charging current in the constant current charging. Method. 8. The method for charging a lithium ion secondary battery according to claim 7, wherein a difference between a temperature change of the secondary battery during the charging and a change of the ambient temperature is set in advance. When the charging current value during the current charging is smaller than the set value of the charging current in the constant current charging, the counting time is reset so as to be longer than the current counting time. To charge a lithium ion secondary battery. 9. The method for charging a lithium ion secondary battery according to claim 7, wherein a difference between a temperature change of the secondary battery during the charging and a change of the ambient temperature is set in advance. When the charging current value during the current charging is smaller than the set value of the charging current in the constant current charging, the counting time is reset so as to be shorter than the current counting time. To charge a lithium ion secondary battery. 10. The method for charging a lithium ion secondary battery according to claim 1, wherein the method calculates a difference between an ambient temperature at the time of starting charging and an ambient temperature during charging, and calculates the difference between the ambient temperature during charging and the ambient temperature during charging. Recognizing a change in the ambient temperature, determining whether the change is within an allowable range, and controlling the charging process by shortening or extending the charging time for the secondary battery according to the determination result. A method for charging a lithium ion secondary battery, comprising: 11. A lithium ion secondary battery charging apparatus for charging a lithium ion secondary battery, comprising: charging means for generating a voltage and a current for charging the secondary battery with a constant voltage and a constant current; A charge switch for turning on or off the output of the constant voltage / constant current charging means to supply the battery terminal of the secondary battery; a terminal voltage detecting means for detecting an open battery terminal voltage of the secondary battery; Current detection means for detecting a charging current supplied from a charging means; cell temperature detection means for detecting a cell temperature of the secondary battery; ambient temperature detection means for measuring an ambient temperature of the charging device; and the charging switch Control means for generating a charge control signal for controlling on / off of the battery and controlling a charging process for the secondary battery, wherein the control means detects the terminal voltage detection means. Monitoring means for monitoring the open terminal voltage of the secondary battery and the output of the charging means, and detecting the cell temperature and the ambient temperature; and subtracting a charging time for the secondary battery from a predetermined set time. A charging timer means for controlling a charging process by setting a counting time of the charging timer means based on a charging current to the secondary battery, an open battery terminal voltage of the secondary battery, and a change in the cell temperature. A charging device for a lithium ion secondary battery, characterized in that: 12. The charging device for a lithium ion secondary battery according to claim 11, wherein the control unit calculates a difference between a temperature of the secondary battery at the start of charging and a temperature during charging. Recognize the temperature change of the secondary battery, calculate the difference between the ambient temperature at the start of charging and the ambient temperature during charging, recognize the change in the ambient temperature during the charging,
The difference between the temperature change of the secondary battery during the charging and the change in the ambient temperature is calculated, and the calculation result is compared with a predetermined value set in advance. A charging device for a lithium ion secondary battery, comprising: 13. The lithium ion secondary battery charging apparatus according to claim 12, wherein the control unit determines that a difference between a temperature change of the secondary battery during charging and a change of the ambient temperature is the predetermined value. A charging current value during charging is smaller than a set value of charging current in constant current charging, wherein the charging process is controlled. 14. The charging device for a lithium ion secondary battery according to claim 11, wherein the control unit initializes a charging time according to an ambient temperature at the start of the charging in the charging timer unit. Charging device for a lithium ion secondary battery. 15. The charging device for a lithium ion secondary battery according to claim 11, wherein the control unit resets the counting time based on a difference between an ambient temperature at the start of charging and an ambient temperature during charging. A charging device for a lithium ion secondary battery, wherein the charging device is set. 16. An electronic apparatus comprising the charging device according to claim 11, and operated by a secondary battery attached to the charging device.