JPH08308123A - Method for charging a plurality of lithium ion batteries - Google Patents

Abstract

PURPOSE: To charge a plurality of lithium ion batteries in a short time without increasing the output current of a battery charger. CONSTITUTION: When the charging mode of either one of lithium ion batteries which are charged with constant currents first is switched to a constant-voltage charging mode, the charging current gradually decreases. The other lithium ion battery is simultaneously precharged with a charging current corresponding to the decreased amount of the decreasing charging current. The output current of a battery charger is prevented from increasing by controlling the sum of the charging current which charges the main lithium ion battery to the constant voltage and the charging current which precharges the other battery to nearly the same value. In addition, the residual capacity of the lithium ion battery to be charged first is detected before starting the charging so as to minimize the charging time of the battery. In addition, the other lithium ion battery is precharged while the main battery is charged to a constant voltage for a fixed period of time after the charging mode of the main battery is switched to the constant-voltage charging mode from the constant-current charging mode and, thereafter, the other lithium ion battery is charged with a constant current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently charging a plurality of lithium ion batteries in a short time.

[0002]

2. Description of the Related Art A lithium ion battery is charged to a constant current and then charged to a constant voltage to be fully charged. The constant current charging is performed first because the charging is performed in a short time. The reason why the battery is switched to the constant voltage charging after the constant current charging is to prevent the battery voltage from abnormally rising and the battery performance from decreasing. Although constant voltage charging has the advantage of not degrading battery performance, it has the drawback that it takes time to fully charge because the charging current gradually decreases. For example, as shown in FIG. 1, if it takes 3 hours to charge one lithium ion battery 1A,
It takes as long as 9 hours to charge the three lithium ion batteries 1A, 1B, and 1C.

A method for shortening the charging time of a plurality of lithium ion batteries is described in JP-A-6-303729. In the charging method described in this publication, as shown in FIG. 2, three lithium ion batteries 1A, 1B, and 1C are charged with a constant voltage until a predetermined charging current is reached, and then three lithium ion batteries 1A, By charging 1B and 1C at the same time, the overall charging time is shortened.

[0004]

As shown in FIG. 2, when a charging current decreases, a method of charging a plurality of lithium ion batteries together is a method of charging without increasing the total charging current of the charging device. This is an excellent way to save time. However, even with this charging method, the charging time of the lithium ion battery is not actually shortened to a sufficiently satisfactory charging time. In the charging method shown in FIG. 2, the three lithium ion batteries 1A, 1B, 1C are charged at a constant voltage until a predetermined charging current is reached, and then the three lithium ion batteries 1A, 1B, 1C are simultaneously charged. Reduce charging time. Therefore, the time for charging the three lithium-ion batteries together can be lengthened, in other words, the charging time for charging each lithium-ion battery at a constant voltage can be shortened, and the overall charging time can be shortened. However, in reality, the charging time for simultaneously charging three lithium ion batteries cannot be made longer than that shown in the figure. The maximum total charging current when charging three lithium-ion batteries together is 1
This is because the charging current is limited to the constant current charging of each lithium ion battery.

If the output current of the charger can be increased, then 3
The total charging current of each lithium-ion battery can be increased. However, in this method, the output current of the charger needs to be designed to be large, which increases the cost of the charger. Further, according to this method, the charger does not reach the maximum output when charging one lithium-ion battery, so that it has a drawback that it cannot be effectively used.

The present invention was developed for the purpose of further shortening the charging time, and an important object of the present invention is to shorten a plurality of lithium ion batteries without increasing the output current of the charger. An object of the present invention is to provide a method of charging a plurality of lithium ion batteries that can be charged in time. Further, a second object of the present invention is to provide a charging method for a plurality of lithium ion batteries, which is capable of maximally charging the initially charged lithium ion battery in the shortest charging time.

[0007]

The method of charging a plurality of lithium ion batteries of the present invention is an improvement of the method of charging a plurality of lithium ion batteries in sequence by performing constant voltage charging and then constant voltage charging. The charging method described in claim 1 of the present invention fully charges a plurality of lithium ion batteries with the charging current shown in FIG. This figure shows an example in which three lithium ion batteries are fully charged. As shown in this figure, first, one of the lithium ion batteries is charged with a constant current. When the main lithium-ion battery, which is being charged with a constant current, changes from constant current charging to constant voltage charging, the charging current gradually decreases. This is because the battery voltage gradually rises. When the charging current of the main lithium-ion battery that is being charged at a constant voltage decreases, another lithium-ion battery is precharged at the same time with the charging current corresponding to the decreased value. The sum of the charging current for charging the main lithium-ion battery at a constant voltage and the charging current for pre-charging another lithium-ion battery is controlled to be approximately equal,
Make sure that the output current of the charger does not increase.

In the method for charging a lithium ion battery according to claim 2 of the present invention, the remaining capacity of the lithium ion battery is first detected in order to shorten the charging time of the lithium ion battery to be charged first. . A lithium ion battery with a large remaining capacity can be fully charged in the shortest charging time.
Therefore, a lithium ion battery with a large remaining capacity is first charged with a constant voltage and a constant current.

Further, in the method for charging a plurality of lithium ion batteries according to claim 3 of the present invention, after the main lithium ion battery is changed from constant current charging to constant voltage charging, the main lithium ion battery is charged for a certain period of time. While charging the battery with a constant voltage, another lithium ion battery is precharged, and then the other lithium ion battery is switched to a constant current charging. A lithium ion battery, for example, is charged from about 70 to 90% when switched from constant current charging to constant voltage charging and charged for 30 minutes. In the charging method shown in FIG. 3, first, the lithium ion battery of ch1 is charged with constant voltage and constant current, the lithium ion battery of ch1 is charged with constant voltage for 30 minutes, and then the lithium ion battery of ch2 is charged with constant voltage and constant current. There is.

In this charging method, a lithium ion battery for constant voltage / constant current charging is switched by a timer, but the charging current for constant voltage charging is detected to switch the lithium ion battery for constant voltage / constant current charging. You can also

[0011]

According to the method of charging a plurality of lithium ion batteries of the present invention, the plurality of lithium ion batteries are fully charged in the shortest charging time without increasing the total charging current. FIG. 3 shows a charging current for charging three lithium ion batteries. In this charging method, the lithium ion battery is fully charged as follows. Step of Detecting Remaining Capacity of Three Lithium Ion Batteries Lithium ion batteries are sequentially charged with a constant current for a certain period of time to detect battery voltage. A lithium-ion battery having a high battery voltage has a large remaining capacity. The figure shows ch1, ch
In the order of 2 and ch3, the state of charging is shown assuming that the lithium ion battery has a large remaining capacity. Step of charging lithium ion battery of ch1 with constant voltage and constant current The lithium ion battery of ch1 with the largest remaining capacity is charged with constant voltage and constant current. The lithium ion battery of ch1 is first charged with a constant current, and is switched to a constant voltage charge when the battery voltage rises to a set voltage. When switched to constant voltage charging, the charging current gradually decreases. ch
When the charging current of the lithium-ion battery of No. 1 decreases, ch
Precharge the lithium-ion battery of No. 2. The charging current for precharging the lithium-ion battery of ch2 is ch1 and c
The total value of the charging current of the lithium ion battery of h2 is set to be the charging current for constant current charging. Since the charging current of the ch1 lithium-ion battery that is charged at a constant voltage gradually decreases, the ch2 lithium-ion battery is precharged with the decreased charging current. The charging current for precharging the lithium ion battery of ch2 gradually increases. ch
This is because the charging current for constant-voltage charging the lithium ion battery of No. 1 gradually decreases.

Step of charging the lithium ion battery of ch2 with constant voltage and constant current After charging the lithium ion battery of ch1 with constant voltage for a certain period of time, the main lithium ion battery that is charged with constant voltage and constant current is
Switch from h1 to ch2. The lithium ion battery of ch2 is first charged with a constant current, and when the battery voltage reaches the set voltage, it is switched to the constant voltage charging. When the ch2 lithium-ion battery is charged at a constant voltage, the charging current gradually decreases. In order to keep the output current of the charger constant, the lithium ion battery of ch1 is precharged with a charging current corresponding to the decrease value of the charging current of the lithium ion battery of ch2. As the charging of the lithium ion batteries of ch2 and ch1 progresses, the total value of the charging current of the lithium ion batteries of ch2 and ch1 decreases, and the output current of the charger gradually decreases. To precharge. That is, the lithium ion batteries of ch1 and ch3 are precharged while the lithium ion batteries of ch2 are charged with a constant voltage.

Step of charging the lithium ion battery of ch3 with constant voltage and constant current After charging the lithium ion battery of ch2 with constant voltage for a certain period of time, the main lithium ion battery that is charged with constant voltage and constant current is
Switch from h2 to ch3 lithium-ion battery. c
The lithium ion battery of h3 is first charged with a constant current, and when the battery voltage reaches the set voltage, it is switched to the constant voltage charging. When the lithium-ion battery of ch3 comes to be charged with a constant voltage, the charging current gradually decreases. In order to make the output current of the charger constant, the lithium ion battery of ch2 is precharged with the charging current corresponding to the decrease value of the charging current of the lithium ion battery of ch3. However, when the lithium ion battery of ch1 is not fully charged, the lithium ion battery of ch1 is precharged instead of ch2.
When the lithium ion battery of ch2 is fully charged, ch2
The charging of the lithium ion battery of 3 is completed, and the lithium ion battery of ch3 is charged at a constant voltage until it is fully charged.

The charging method for a plurality of lithium ion batteries according to the present invention, as illustrated in FIG. 3 showing a preferred embodiment thereof, shows that if the charging current decreases when the lithium ion battery is charged at a constant voltage, The other lithium-ion battery is precharged with the charging current corresponding to the reduced value to shorten the total charging time. Therefore, there is a feature that a plurality of lithium ion batteries can be charged very efficiently in a short time without increasing the output current of the charger.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate a charging method for embodying the technical idea of the present invention,
The present invention does not specify the charging method of a plurality of lithium ion batteries as the following method.

FIG. 4 shows a charging circuit used in the method of charging a plurality of lithium ion batteries of the present invention. The charging circuit shown in this figure includes a power supply 2 that converts an input commercial power supply of AC100V (AC120V in the US) into a charging voltage of a lithium-ion battery 1 and outputs the output of the power supply 2, and each lithium-ion battery. A charge control element 3 that is connected between the positive electrode of No. 1 and controls the charging current of each lithium ion battery 1, the charge control element 3, and the lithium ion battery 1.
The diode 4 and the current detection resistor 5 which are connected in series between and, and the voltage across the current detection resistor 5 are detected,
A current / voltage detection unit 6 that detects the charging current of each lithium ion battery 1, a total current detection resistor 7 that detects the total value of the charging current of the plurality of lithium ion batteries 1, a charging current and a battery voltage of the lithium ion battery 1. And detect
And a microcomputer 8 for controlling the charge control element 3.

The power supply 2 is a constant voltage constant current power supply that controls the maximum values of the output voltage and the output current to be constant. The output voltage of the power supply 2 is set to a voltage value for charging the lithium ion battery 1 with a constant voltage, and the maximum output current is set to a current value for charging one lithium ion battery 1 with a constant current.

The charge control element 3 is a transistor for controlling the charge current of each lithium ion battery 1. The charge control element 3 can use an FET instead of a transistor.
The transistor or FET adjusts the internal resistance to control the charging current of the lithium ion battery 1.

The current / voltage detector 6 A / D-converts the voltage across each current detection resistor 5 and inputs it to the microcomputer 8. A voltage proportional to the charging current of the lithium-ion battery 1 is generated at both ends of the current detection resistor 5. Further, the current / voltage detector 6 A / D-converts the battery voltage of each lithium-ion battery 1 and inputs it to the microcomputer 8. Furthermore, the current / voltage detector 6 also detects the voltage across the total current detection resistor 7 as A /
D-convert and input to the microcomputer 8.

The microcomputer 8 calculates the digital signal input from the current / voltage detector 6 to detect the charging current and battery voltage of each lithium ion battery 1 and the total value of the charging current, and to detect each lithium ion battery. The charging current of the battery 1 is controlled. The microcomputer 8 controls the charge control element 3 and adjusts the charge currents of the three lithium ion batteries 1 to be constant. However, as shown in FIG. 3, after one or two lithium ion batteries are fully charged, control is performed so that the total value of the charging current does not exceed the set value. The microcomputer 8 turns on the charging control element 3 connected to the lithium-ion battery 1 for constant-voltage / constant-current charging, and the other charging control elements 3 turn off or control internal resistance to control the charging current.

The charging circuit shown in FIG. 4 charges three lithium ion batteries according to the following flow chart. The present invention does not specify that the number of lithium ion batteries to be charged is three. It goes without saying that the number of lithium-ion batteries to be charged can be two or four or more. Further, in the following charging method, the remaining capacity of the lithium ion battery is first detected, and the lithium ion battery having the largest remaining capacity is charged in order. The following example shows the charging process when the remaining capacity of the lithium-ion battery is larger in the order of ch1, ch2, ch3.

[Step of Detecting Remaining Capacity of Three Lithium Ion Batteries] (1) In the steps s1 to s15 of FIG. 5, the three lithium ion batteries are charged with a constant current (T1) at a constant current for a battery voltage. To detect. The battery voltage of each lithium-ion battery is detected in the following steps. Start timer T1. Start constant current charging of any lithium ion battery. Detects the voltage of the rechargeable lithium-ion battery. The steps to are looped until the time for charging the lithium-ion battery with constant current exceeds the set time (T1) of the timer T1. The set time of the timer T1 is preferably set to 10 msec. When the time for constant current charging exceeds the set time of the timer T1, the constant current charging of the lithium ion battery is stopped and the next lithium ion battery is charged with constant current.

(2) The microcomputer calculates the remaining capacity of the lithium ion battery from the detected battery voltage in steps s16 to s27. Since a battery having a high battery voltage has a large remaining capacity, the battery voltages are compared to determine the remaining capacity of each lithium ion battery.

[Step of charging the ch1 lithium ion battery with a constant voltage and constant current] (1) In step S1 and S2 of FIG. 6, the constant voltage constant current charging of the ch1 lithium ion battery is started and c
The charging current of the lithium ion battery of h1 is detected. ch
In order to charge the lithium ion battery of No. 1 with constant voltage and constant current, the microcomputer turns on the charge control element connected to the lithium ion battery of ch1. (2) From the charging current detected in step S3, ch
It is determined whether the lithium ion battery of No. 1 has changed from constant current charging to constant voltage charging. When the constant current charging is changed to the constant voltage charging, the charging current decreases. Therefore, when the detected charging current is lower than the set value, it is determined as constant voltage charging. (3) When the ch1 lithium ion battery is charged with a constant voltage, the timer T2 is started in the step S4, and the precharge of the ch2 lithium ion battery is started in the step S5. The charging current for precharging the ch2 lithium-ion battery in parallel with ch1 is shown in FIG.
As shown in, the charging current of the ch1 lithium ion battery is set to a decrease value. The charging current of the ch2 lithium ion battery is adjusted by the microcomputer controlling the internal resistance of the charge control element connected to the ch2 lithium ion battery.

The microcomputer controls the total value of the charging currents of the lithium ion batteries of ch1 and ch2 to be equal to the charging current for charging one lithium ion battery with a constant current. At this time, the total value of the charging current is not controlled by adjusting the charging current of the ch1 lithium-ion battery that is charged with a constant voltage. The charge control element connected to the lithium-ion battery of ch1 is kept in the ON state, and
The lithium ion battery of h1 is charged with a constant voltage at a set voltage. The charging current of the lithium ion battery of ch2 is controlled by a current corresponding to the decrease value of the charging current of the lithium ion battery of ch1 to control the total value of the charging current to be constant. That is, the charge control element connected to the lithium ion battery of ch1 is turned on, the internal resistance of the charge control element connected to the lithium ion battery of ch2 is adjusted, the charge of the lithium ion battery of ch1 is given priority, and the remaining The lithium ion battery of ch2 is precharged with the current of.

(4) When the set time of the timer T2 has elapsed in step S6, the constant voltage charging of the lithium ion battery of ch1 is stopped in step S7. When the constant voltage charging of the lithium ion battery of ch1 is stopped, the lithium ion battery of ch2 shifts to constant voltage constant current charging. ch1
After stopping the charging of the lithium ion battery of, the full charge of the lithium ion battery of ch1 is displayed in step S8.

(5) Thereafter, as shown in FIG. 7, in steps S9 and S10, the charging current of the lithium ion battery of ch2 to be charged with constant voltage and constant current is detected, and the lithium ion battery of ch2 is kept constant. It is determined whether the current charging has been switched to the constant voltage charging. This is because the charging current of the ch2 lithium ion battery decreases from constant current charging to constant voltage charging.

(6) When the lithium ion battery of ch2 is charged with a constant voltage, the timer T2 is started in step S11, and the precharge of the lithium ion batteries of ch1 and ch3 is performed in steps S12 and S13. Start. In this charging state, the ch2 lithium ion battery is charged at a constant voltage, and the ch1 lithium ion battery is precharged prior to the ch3 lithium ion battery. Therefore, when the charging currents of the ch2 and ch1 lithium ion batteries decrease below the output current of the power supply, the ch3 lithium ion batteries are charged with a current corresponding to the decrease value. That is, ch2, ch1, ch3
In this order, the charging current of the lithium-ion battery is controlled with priority. Therefore, as shown in FIG. 3, ch2 and ch1
The charging current of the lithium ion battery of No. 3 gradually decreases, and the charging current of the ch3 is charged with the charging current corresponding to the decreased value.

The charging current of the lithium ion batteries of ch1 and ch3 is adjusted by controlling the internal resistance of the charge control element connected to the lithium ion batteries of ch1 and ch3 by the microcomputer. Even in this state, the microcomputer is
The total value of the charging currents of the lithium ion batteries of h1 and ch3 is controlled so as to be equal to the charging current for constant current charging of one lithium ion battery. At this time, the charge control element connected to the ch1 and ch2 lithium ion batteries is turned on, and the internal resistance of the charge control element connected to the ch3 lithium ion battery is controlled by the microcomputer to determine the total value of the charging current. Hold constant.

(7) When the set time of the timer T2 has elapsed in step S14, constant voltage charging of the ch2 lithium ion battery is stopped in step S15. When the constant voltage charging of the lithium ion battery of ch2 is stopped, ch3
The lithium ion battery will be charged with a constant voltage and a constant current. After the charging of the ch2 lithium ion battery is stopped, the full charge of the ch2 lithium ion battery is displayed in step S16.

(8) Since the lithium ion battery of ch1 is fully charged when the set time of the timer T2 has passed,
Stop charging the lithium ion battery of ch1. However,
Furthermore, continue to charge the lithium-ion battery of ch1, c
When the charging current of the lithium ion battery of h1 reaches the set value, the charging of the lithium ion battery of ch1 can be terminated.

(9) After that, as shown in FIG.
In steps 19 and 19, the charging current of the ch3 lithium ion battery to be charged with constant voltage and constant current is detected, and it is determined whether or not the lithium ion battery of ch3 has been switched from constant current charging to constant voltage charging.

(10) When the ch3 lithium ion battery is charged with a constant voltage, the timer T2 is started in the step S20, and in the step S21,
Start the pre-charging of the ch2 lithium ion battery. At this time, although not shown in FIGS. 3 and 8, when the ch1 lithium ion battery is not fully charged, the ch1 lithium ion battery can be precharged prior to the ch2 lithium ion battery. When precharging the lithium ion batteries for both ch1 and ch2,
The lithium ion battery of ch1 is precharged prior to the lithium ion battery of 2. Therefore, ch3 and ch1
When the charging current of the lithium ion battery of No. 2 is smaller than the output current of the power supply, the lithium ion battery of ch2 is charged with the current corresponding to the decrease value. That is, ch3, c
The charging current of the lithium ion battery is controlled with priority in the order of h1 and ch2. However, when the ch1 lithium ion battery is not precharged, the ch2 lithium ion battery is charged with a charging current corresponding to the decrease value of the charging current of the ch3 lithium ion battery as shown in FIGS.

The charging current of the ch2 lithium ion battery is adjusted by controlling the internal resistance of the charge control element connected to the ch2 lithium ion battery by the microcomputer. Even in this state, the microcomputer controls the total value of the charging currents of the ch3 and ch2 lithium ion batteries to be equal to the charging current for constant current charging of one lithium ion battery. At this time, the charge control element connected to the ch3 lithium ion battery is turned on, and the microcomputer controls the internal resistance of the charge control element connected to the ch2 lithium ion battery to keep the total value of the charging current constant. Hold.

(11) When the set time of the timer T2 has elapsed in the step S22, the full charge of the ch3 lithium ion battery is displayed (step S23), and the charging of the ch2 lithium ion battery is stopped (step S2).
4). This is because the lithium ion battery of ch2 is fully charged when the set time of the timer T2 has elapsed. However,
Detects the charging current of the lithium ion battery of ch2, c
It is also possible to stop the charging of the lithium ion battery of h2.

(12) Further, in steps S25 to S27, the lithium ion battery of ch3 is charged with a constant voltage during the set time of the timer T2, and when the set time of the timer T2 has elapsed, the lithium ion battery of ch3 is charged. To stop.

In the above flow chart, when the set time of the timer T2 has elapsed, the lithium ion batteries for constant voltage and constant current charging are switched one after another. However, the method for charging a plurality of lithium ion batteries of the present invention does not use a timer. Then, it is possible to switch the lithium ion battery for constant voltage and constant current charging by detecting that the charging current of the main lithium ion battery for constant voltage and constant current charging has decreased to a set value.

[0038]

According to the method of charging a plurality of lithium ion batteries of the present invention, a plurality of lithium ion batteries can be charged in a shorter time than the conventional charging method. When the main lithium-ion battery that is charging changes from constant-current charging to constant-voltage charging and the charging current decreases, the reduced charging current is used to pre-charge other lithium-ion batteries at the same time. Because there is. To charge the lithium-ion battery, it is necessary to perform constant voltage charging and then constant voltage charging. In the state of constant voltage charging, the charging current decreases and it takes time to fully charge. Therefore, it takes a considerable time to charge all of the plurality of lithium ion batteries. According to the method for charging a plurality of lithium ion batteries of the present invention,
When the charging current decreases in the constant voltage charging state, the decrease amount of the current is used for the preliminary charging of other lithium ion batteries. Therefore, a plurality of lithium ion batteries can be charged at the same time, and the charging time can be shortened. Further, the charging current can be supplied to the plurality of lithium-ion batteries to efficiently utilize the output current of the charging device.

Furthermore, the output current of the charging device is set as a current value for charging one lithium-ion battery with constant current, and even if the charging current decreases due to constant voltage charging,
The reduced charging current can be output within the output current range. Therefore, the output of the charging device can be efficiently used to charge the lithium ion battery without increasing the output current of the charging device.

Further, even if the main lithium ion battery and another lithium ion battery are charged at the same time, the total charging current of these is constant. That is, since the total value of the charging current is the current value for charging one lithium-ion battery with a constant current, the output current of the charger is not increased, and a plurality of lithium-ion batteries can be used without changing the set value of the output current. Can be charged at the same time. Therefore, the output current can be used efficiently without using the device as a high-output charger, and the cost for increasing the size and power of the device can be reduced. According to the charging method of the present invention, charging can be performed more efficiently and at a higher speed than when a charging device having a similar current capacity is used in the conventional method. Furthermore, since the total value of the output current is used as the rated current of the charger without reducing the output current, the power of the device can be utilized to the maximum and highly efficient charging can be performed.

Furthermore, according to the method for charging a plurality of lithium ion batteries of the present invention, the lithium ion battery to be charged first can be obtained in the minimum charging time. The charging method of the present invention compares the remaining capacities of the respective lithium-ion batteries before starting charging and sequentially charges the lithium-ion batteries having the largest remaining capacity among the plurality of lithium-ion batteries, so that the lithium having the largest remaining capacity is used. The ion battery is charged first, and charging is completed in the minimum time. Therefore, a lithium-ion battery that has been charged can be obtained in the shortest time.
Furthermore, since charging is sequentially completed from the lithium ion battery which can be charged in a short time, the lithium ion battery fully charged faster can be used in combination with the effect of charging in a short time.

[Brief description of drawings]

FIG. 1 is a graph showing a change over time of a charging current when charging is performed by a conventional method of charging a plurality of lithium ion batteries.

FIG. 2 is a graph showing a change with time of a charging current when the conventional lithium ion batteries are charged by another method.

FIG. 3 is a graph showing a change over time of the charging current when the method of charging a plurality of lithium ion batteries according to the embodiment of the present invention is used for charging.

FIG. 4 is a circuit diagram of a charging device according to a method of charging a plurality of lithium ion batteries according to an embodiment of the present invention.

5 is a flowchart of a charging device according to a method of charging a plurality of lithium ion batteries shown in FIG.

6 is a flowchart of a charging device according to a method of charging a plurality of lithium ion batteries shown in FIG.

7 is a flowchart of a charging device according to a method of charging a plurality of lithium ion batteries shown in FIG.

8 is a flowchart of a charging device according to a method of charging a plurality of lithium ion batteries shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lithium ion battery 1A ... Lithium ion battery 1B ... Lithium ion battery 1C ... Lithium ion battery 2 ... Power supply 3 ... Charge control element 4 ... Diode 5 ... Current detection resistance 6 ... Current voltage detection part 7 ... Total current detection resistance 8 ... Microcomputer

Claims (3)

[Claims] 1. A charging method for charging a plurality of lithium-ion batteries in order by constant-current charging and then constant-voltage charging, wherein the main lithium-ion battery being charged is changed from constant-current charging to constant-voltage charging for charging. When the current decreases, another lithium ion battery is charged at the same time by precharging another lithium ion battery with a charging current corresponding to the decrease value of the charging current of the main lithium ion battery, and another lithium ion battery. A method for charging a plurality of lithium ion batteries, characterized in that the sum of the charging current and the charging current for precharging is controlled to be substantially equal. 2. The method for charging a plurality of lithium ion batteries according to claim 1, wherein the remaining capacities of the plurality of lithium ion batteries are detected, and the lithium ion battery having a large remaining capacity is first charged with a constant voltage and constant current. 3. After the main lithium ion battery is switched from constant current charging to constant voltage charging, another lithium ion battery is preliminarily charged while the main lithium ion battery is being charged at constant voltage for a certain period of time, and then another lithium ion battery is charged. The method for charging a plurality of lithium ion batteries according to claim 1, wherein the lithium ion batteries are switched to constant current charging.