JPH08213055A - Charging method of battery pack and its device - Google Patents

Abstract

PURPOSE: To uniformly increase the capacity of respective unit secondary batteries while eliminating its dispersion even if dispersion of the capacity of the respective unit secondary batteries is caused at the beginning of charging in the case of charging a battery pack. CONSTITUTION: A charging method of battery pack and its device are provided with a constant current charging process to perform charging by supplying a charging current of a constant current to a battery pack 1 until voltage of the whole battery pack 1 formed by connecting unit secondary batteries 2a and 2b in series to each other becomes its almost full charging voltage and a constant voltage charging process to perform charging by giving constant voltage to the battery pack 1 in the second place. In the constant current charging process voltages of the respective unit secondary batteries 2a and 2b are momentarily detected by voltage detecting means 4a, and the constant current is carried as it is to the unit secondary battery 2a or 2b corresponding to the lowest voltage among these detecting voltages, and charging is performed, and a part of the constant current is distributed to the unit secondary battery 2b or 2a high in the detecting voltage by a distributing circuit part 5b or 5a, and charging is performed by a charging current less than the unit secondary battery 2a or 2b of the lowest voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of charging a battery pack and a device for charging the battery pack, in which a plurality of unit secondary batteries are connected in series.

[0002]

2. Description of the Related Art For a battery mounted in, for example, an electric vehicle, a large capacity output is required, so that an assembled battery in which a plurality of unit secondary batteries are connected in series is generally used.

When charging this type of assembled battery,
A constant current charging method is generally used, which has a relatively high charging efficiency and a relatively short charging time. In addition, for example, when charging an assembled battery including a lithium ion secondary battery or a lithium polymer secondary battery as a unit secondary battery, the internal resistance thereof is relatively high, and constant current charging alone is sufficient for charging. Since it is difficult, the charging voltage of the assembled battery (sum of charging voltage of each unit secondary battery)
A charging method is used in which constant current charging of the assembled battery is performed until a predetermined voltage is reached, and then charging is performed with a constant voltage corresponding to the full charge voltage of the assembled battery.

On the other hand, in the assembled battery, the capacity of each unit secondary battery may vary during manufacture, or the unit secondary battery may be used in various discharge modes or deteriorated with time. In many cases, there is a variation in the capacitance. In particular, such variations are likely to occur in the lithium ion secondary battery and the lithium polymer secondary battery.

Then, in the assembled battery in which the capacity of each unit battery varies as described above, if the assembled battery is charged by the above-mentioned charging method, each unit secondary battery is the same in constant current charging. Since the charging current flows for each unit secondary battery, the amount of charge per unit time is almost the same, so the momentary capacity of each unit secondary battery or the corresponding voltage of each unit secondary battery is , It will rise with the initial variation.

However, when charging is performed while the capacity and voltage of each unit secondary battery are varied in this way, for example, if the assembled battery is used to start discharging during charging, the assembly The discharge capacity of the battery is greatly affected by the unit battery with the lowest capacity, and the original performance cannot be exerted.If such discharging and charging are repeated, deterioration of the assembled battery over time is promoted. Will end up.

Even when the assembled battery does not start discharging during charging as described above, the timings at which the unit secondary batteries reach the fully charged state are different from each other. If the unit rechargeable battery that has the largest capacity at the beginning of charging is continuously charged to the overcharged state, The unit secondary battery having the smallest capacity at the beginning is in an undercharged state, and as a result, deterioration of the assembled battery over time is promoted.

Further, as described above, even when the constant voltage charging is performed after the constant current charging is performed up to the predetermined voltage of the assembled battery, the predetermined voltage is set to prevent the above-mentioned overcharging. It is necessary to set it to a value that is sufficiently lower than the full charge voltage of the assembled battery, and as a result, the period for constant voltage charging that tends to cause a decrease in charging efficiency is longer than that for constant current charging, and the assembled battery is It takes a long time to fully charge the battery.

[0009]

SUMMARY OF THE INVENTION The present invention solves such inconveniences, and even when there is a variation in the capacity of each unit secondary battery at the beginning of charging when the assembled battery is charged, the variation can be eliminated and evenly distributed. An object of the present invention is to provide a charging method and a charging device capable of increasing the capacity of each unit secondary battery.

Then, when the battery pack is fully charged by sequentially performing the constant current charging and the constant voltage charging, a uniform capacity increase is performed while eliminating the variation in the capacity of each unit secondary battery during the constant current charging. At the same time, it is an object of the present invention to provide a charging method and a charging device capable of efficiently fully charging an assembled battery without causing overcharge or undercharge of each unit secondary battery.

[0011]

In order to achieve the above object, a method for charging an assembled battery according to the present invention is a method for charging an assembled battery, which comprises a plurality of unit secondary batteries connected in series, wherein A step of feeding a charging current, a step of momentarily detecting the voltage of each unit secondary battery of the assembled battery at the time of feeding the charging current, and a step of detecting the voltage of each of the plurality of unit secondary batteries at each detection point of the voltage. Of these, the unit secondary battery with the lowest detected voltage is used as the reference unit battery, and the unit secondary batteries are charged so that the rate of voltage increase per unit time of the reference unit battery is higher than that of other unit secondary batteries. While controlling the current, the control of the charging current, when the detection voltage of the reference unit battery exceeds the detection voltage of at least one unit secondary battery of other unit secondary batteries, Next lowest unit secondary battery Characterized by comprising a current control process performed while sequentially updated reference unit cell as reference unit cell.

In the power feeding step, a constant-current charging current is fed to the assembled battery, and in the current control step, the constant-current charging current is passed to the reference unit battery as it is, and the other unit cells are charged. According to the detected voltage, the constant current charging current is distributed to the secondary flow paths connected in parallel to each unit secondary battery so that a charging current smaller than the constant current charging current is applied to the secondary battery. It is characterized by controlling to.

In the current control step, the control of the charging current is performed until the detected voltage of each unit rechargeable battery substantially reaches a predetermined voltage corresponding to a substantially full charge voltage of each unit rechargeable battery. After the detection voltage of the secondary battery substantially reaches a predetermined voltage, a constant voltage charging step of charging each unit battery by applying a constant voltage corresponding to the full charge voltage to the assembled battery is provided. To do.

Further, the unit secondary battery is a lithium ion secondary battery or a lithium polymer secondary battery.

In order to achieve the above object, the battery pack charging apparatus of the present invention is a battery pack charging apparatus in which a plurality of unit secondary batteries are connected in series, and is connected to the battery pack. A power supply means for supplying a charging current to the assembled battery,
Voltage detection means connected to each of the unit secondary batteries and momentarily detecting the voltage of each of the unit secondary batteries when the charging current is supplied by the power supply means, and each detection time of the voltage of each unit battery by the voltage detection means In the minimum voltage grasping means for grasping the lowest voltage among the detection voltages of the respective unit secondary batteries obtained from the voltage detecting means, and the charging current flowing through the respective unit secondary batteries can be adjusted in parallel with the respective unit secondary batteries. And a branching flow path connected to the unit secondary battery to increase the rate of voltage rise per unit time of the unit secondary battery corresponding to the minimum voltage grasped momentarily by the minimum voltage grasping unit, compared to other unit secondary batteries. And a charging current control means for controlling a charging current flowing through each unit battery by adjusting a shunt current flowing through each branching channel.

The power supply means is a constant current power supply means for supplying a constant current charging current to the assembled battery, and the charging current control means is the unit secondary battery for the minimum voltage unit secondary battery. The shunt current of the shunt flow path connected to the battery was cut off, and the constant-current charging current was allowed to flow to the unit secondary battery as it was, and the other unit secondary batteries were connected to the unit secondary battery. The charging current flowing through the unit secondary battery is controlled to be smaller than the constant current charging current by causing a shunt current corresponding to the detection voltage of the unit secondary battery to flow in each branch flow path.

Further, the constant voltage feeding means for applying a constant voltage to the assembled battery to charge each unit secondary battery, and the detection voltage of each unit battery obtained from the voltage detecting means is the abbreviation of each unit secondary battery. A charging method switching means for supplying a charging current to the assembled battery by the constant current power supply means until the predetermined voltage corresponding to a full charge voltage is substantially reached, and then charging the assembled battery by the constant voltage power supply means. The charging current control means controls the charging current of each unit secondary battery by the shunt current of each of the flow paths only when charging by the constant current feeding means.

Furthermore, each unit secondary battery is a lithium ion secondary battery or a lithium polymer secondary battery.

[0019]

According to the method of charging the assembled battery of the present invention, when the assembled battery is charged by supplying the charging current to the assembled battery, the voltage of each unit secondary battery is detected momentarily and the detection is performed. At each time point, the unit secondary battery with the lowest detection voltage is used as the reference unit battery, and each unit secondary battery is set so that the voltage rise rate of the reference unit secondary battery per unit time is larger than that of other unit secondary batteries. Since the charging current of the secondary battery is controlled, the unit secondary battery with the lowest detection voltage at each time of charging,
That is, the unit secondary battery having the lowest capacity is charged with a larger amount of charge than other unit secondary batteries, and the voltage rises fastest. In this case, the reference unit battery whose voltage rises fastest in this way eventually exceeds the voltage of the other unit secondary batteries, so that the reference unit secondary battery will now have the new lowest detected voltage. The updated reference unit secondary battery is charged with a larger amount of charge than other secondary batteries, and the voltage rises fastest. As a result, the voltage of each unit secondary battery constantly rises to the same voltage during the charging process of the assembled battery, and the capacity of each unit secondary battery rises substantially evenly.

In the above charging method of the present invention, when the assembled battery is charged with a constant current charging current,
By supplying a constant-current charging current to the reference unit battery as it is, the reference battery having the lowest detection voltage, which is appropriately updated in the charging process, is always efficiently charged with the constant-current charging current. Then, for each other unit secondary battery, by dividing the charging current of the constant current according to the detection voltage to the branch flow path connected in parallel to each unit secondary battery, each of the unit secondary The battery is charged with a current smaller than the constant-current charging current corresponding to the voltage, and each unit secondary battery is quickly charged to have an equal voltage and capacity.

When the constant voltage charging step is performed after the current control step to fully charge the assembled battery, each unit secondary battery is charged evenly as described above. The unit secondary batteries reach the predetermined voltage almost at the same time, and the constant voltage charging process starts from that time. Therefore, even if the predetermined voltage is set as the substantially full charge voltage of each unit secondary battery, overcharge or undercharge does not occur at the start of the constant voltage charging step, and furthermore, each unit secondary battery is almost fully charged. By starting the constant voltage charging step from the charged state, it becomes possible to shorten the time until the assembled battery is fully charged by the constant voltage charging step.

In this case, it is possible to shorten the constant voltage charging step as described above when charging the lithium ion secondary battery or the lithium polymer secondary battery, which is preferably charged with constant voltage finally. Thus, it becomes possible to efficiently perform full charge of the assembled battery including the lithium ion secondary battery or the lithium polymer secondary battery as a unit secondary battery.

Next, according to the battery pack charging apparatus of the present invention, when the charging current is supplied to the battery pack by the power supply means to charge the battery pack, the voltage is detected by the minimum voltage grasping means. Each unit secondary battery is controlled by the charging current control device so that the voltage increase rate per unit time of the unit secondary battery corresponding to the lowest voltage that is grasped momentarily via the detection unit is made larger than that of each other unit secondary battery. By adjusting the shunt current flowing through the shunt flow path connected in parallel to the battery, according to the charging method described above, the charging current of each unit secondary battery is controlled,
The unit secondary batteries are uniformly charged so that the voltages of the unit secondary batteries are always substantially equal to each other.

In this case, when the constant current power supply means is used as the power supply means, for the unit secondary battery having the lowest voltage, the shunt current flowing through the shunt flow path is cut off to supply power from the constant current power supply means. By supplying the charging current of the current as it is to the unit secondary battery having the lowest voltage, and for other unit secondary batteries, a shunt current corresponding to the detected voltage is caused to flow in the shunt channel corresponding to the unit battery. While the unit secondary battery having the lowest voltage is constantly and efficiently charged with the constant-current charging current, the unit secondary batteries are quickly charged to have mutually equal voltages and capacities corresponding to the voltages.

Further, when the constant voltage power supply means is provided, each unit secondary battery is charged while controlling each charging current by the charging current control means so that the detected voltage of each unit secondary battery becomes When the predetermined voltage corresponding to the substantially full charge voltage of the unit secondary battery is substantially reached, the constant voltage charging means performs constant voltage charging by the control of the charging method switching means to fully charge the assembled battery. Then, in this case, by starting the constant voltage charging by the constant voltage power supply means when the detected voltage of each unit secondary battery substantially reaches a predetermined voltage corresponding to the substantially full charge voltage of each unit secondary battery, At the start, overcharge or undercharge of each unit secondary battery does not occur, and moreover, the final constant voltage charging by the constant voltage power supply means is short.

Therefore, it is possible to efficiently fully charge the assembled battery including the lithium ion secondary battery or the lithium polymer secondary battery as a unit secondary battery, which is preferably charged with a constant voltage finally.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit diagram of the charging device according to the present embodiment.
FIG. 2 is a diagram showing the relationship between the open circuit voltage of the rechargeable battery and the remaining capacity of the assembled battery in this embodiment, and FIG. 3 is each unit when the assembled battery is charged by the charging device of this embodiment. FIG. 4 is a diagram showing how the voltage of the secondary battery changes, and FIG. 4 is a diagram showing how the voltage changes when each unit secondary battery of the assembled battery charged by the charging device of this embodiment is discharged. is there.

Referring to FIG. 1, reference numeral 1 denotes an assembled battery composed of, for example, two unit secondary batteries 2a and 2b connected in series,
3 is a power feeding unit (power feeding means) for feeding power to the assembled battery 1 when charging the assembled battery 1, and 4a and 4b are unit secondary batteries 2 respectively.
Voltage detection units (voltage detection means) 5a and 5b for detecting the voltages of a and 2b are shunt circuit units for appropriately shunting the charging currents flowing from the power feeding unit 3 to the assembled battery 1 with respect to the unit secondary batteries 2a and 2b, respectively. , 6 are charge controllers composed of a microcomputer or the like.

The assembled battery 1 is, for example, a lithium ion secondary battery as the unit secondary batteries 2a and 2b, and the full-charge rated voltage of each unit secondary battery 2a and 2b is 4.2V. The full-charge rated voltage of is 8.4V.

As shown in FIG. 2, the relationship between the open circuit voltage and the capacity (remaining capacity) of each unit secondary battery 2a, 2b is such that the remaining capacity increases as the open circuit voltage increases (roughly proportional to each other). Relationship), and the open circuit voltage and the remaining capacity have a one-to-one correspondence.

The power supply unit 4 issues a command to the charge controller 6 to the power supply unit 7, a constant current for performing constant current charging of the battery pack 1 and a constant voltage for performing constant voltage charging from the output of the power supply unit 7. And a constant current / constant voltage generation section 8 which is switchably generated by the. In this case, the constant current / constant voltage generation unit 8 generates a constant current of 1 A during constant current charging, and the constant voltage generated during constant voltage charging is 8.4 V, which is the same as the full-charge rated voltage of the assembled battery 1.

The power supply unit 7 and the constant current / constant voltage generation unit 8
According to the configuration of the present invention, the constant current feeding means and the constant voltage feeding means are configured together.

The shunt circuit portions 5a and 5b have the same structure, and each of the unit secondary batteries 2a and 2b has a switch 9 connected to the positive electrode side and a changeover switch 10 from the preceding stage of the switch 9. It is constituted by a pair of branch channels 11 and 12 connected in parallel to each unit secondary battery 2a and 2b through. In this case, the shunt channel 11 has a variable resistor 11a whose resistance value is variable according to a command from the charge controller 6.
When a changeover switch 10 is turned to the arrow x side in FIG. 1, a part of the charging current supplied to the assembled battery 1 is shunted to the branch flow passage 11 according to the resistance value of the variable resistor 11a. It flows as an electric current. In addition, the shunt channel 12 is for diverting the charging current supplied to the assembled battery 1 without flowing to the unit secondary battery 2a or 2b corresponding to the shunt channel 12,
When the changeover switch 10 is turned to the side of the arrow y in FIG. 1 and the switch 9 is opened in conjunction with this, the charging current supplied to the assembled battery 1 corresponds to the unitary secondary battery 2a or 2b. Flow into the branch flow channel 12 without flowing into the flow path.

The switch 9 and the changeover switch 10 are
For example, it is configured by using a semiconductor switch element such as a transistor or an FET, and its operation is performed by a command from the charge controller 6.

The charge controller 6 has, as its main functional configuration, a shunt circuit section 5 corresponding to each unit secondary battery 2a, 2b for charging current flowing in each unit secondary battery 2a, 2b.
The minimum voltage of the voltages of the unit secondary batteries 2a and 2b detected by the charging current control unit 13 (charging current control unit) and the voltage detection units 4a and 4b, which are controlled via a and 5b, is grasped. Minimum voltage grasping section 14 (minimum voltage grasping means)
And a charging method switching control section 15 (charging method switching means) for instructing the constant current / constant voltage generating section 8 to switch the charging method of the assembled battery 1. These functional configurations operate as described below based on the voltages of the unit secondary batteries 2a and 2b detected by the voltage detection units 4a and 4b when the assembled battery 1 is charged.

Next, the charging operation of the assembled battery 1 using the charging device of this embodiment will be described.

First, in a state in which the power feeding unit 4 is connected to the assembled battery 1 and each switch 9 is closed by the charging current control unit 13 of the charging controller 6, the charging controller 6 causes the charging system switching control unit 15 to supply power. Instruct the constant current / constant voltage generation unit 8 of the unit 4 to perform constant current charging. At this time, the constant current / constant voltage generating unit 8 generates a constant current of 1 A and supplies the constant current to the assembled battery 1 as its charging current. As a result, constant current charging of the assembled battery 1 is started.

In parallel with this, each voltage detection unit 4
a and 4b momentarily detect the voltage of each connected unit secondary battery 2a and 2b, and output the detected voltage to the charge controller 6. Then, the minimum voltage grasping unit 14 of the charge controller 6 grasps the lowest voltage among the detected voltages of the unit secondary batteries 2a and 2b moment by moment. Furthermore, the charging current control unit 13 of the charging controller 6 uses the unit secondary battery 2a or 2b having the lowest voltage as a reference unit battery, and sets the reference unit battery to a charging current larger than that of another unit secondary battery 2b or 2a. So that each of the flow dividing circuits 5a, 5b
Control.

More specifically, at present, for example, if the detection voltage of the unit secondary battery 2a is lower than the detection voltage of the unit secondary battery 2b, and the detection voltage of the unit secondary battery 2a is the lowest voltage. The charging current control unit 13 includes the shunt circuit unit 5
The branch channels 11 and 12 are disconnected from the unit secondary battery 2a without connecting the changeover switch 10a of a to either side of the branch channels 11 and 12. At this time, the constant-current charging current (1 A) generated by the constant-current / constant-voltage generating unit 8 flows through the unit secondary battery 2a as it is, and the unit secondary battery 2a is charged.

On the other hand, the unit secondary battery 2 on the high detection voltage side
As for b, the charging current control unit 13 uses the shunt circuit unit 5b.
The changeover switch 10 is connected to, for example, the side of the shunt channel 11 provided with the variable resistor 11a so that a part of the constant current charging current is shunted to the shunt channel 11 and the remaining constant current is passed to the unit secondary battery 2b. . In this case, the diversion channel 1 of the diversion circuit unit 5b
The magnitude of the shunt current flowing in 1 is adjusted by adjusting the resistance value of the variable resistor 11a according to the detection voltage, and the detection voltage of the unit secondary battery 2b is larger than the detection voltage of the unit secondary battery 2a. The resistance value of the variable resistor 11a of the shunt flow path 11 is adjusted so that a large amount of shunt current flows through the shunt flow path 11 of the shunt flow path circuit section 5b. When the detected voltage of the unit secondary battery 2b is higher than the detected voltage of the unit secondary battery 2a by a predetermined amount or more, the charging current control unit 13 divides the shunt circuit unit 5.
The changeover switch 10b of b is connected to the shunt channel 12 and the switch 9 of the shunt circuit unit 5b is opened to shunt all the charging current of the constant current to the shunt channel 12 to recharge the unit secondary battery 2
No charging current is passed through b.

As a result, a larger charging current than the unit secondary battery 2b flows through the unit secondary battery 2a having a low detection voltage, and the rate of voltage increase per unit time due to the charging is the unit secondary battery 2b. It is larger than the battery 2b. Therefore, the detection voltage of the unit secondary battery 2a eventually exceeds the detection voltage of the unit secondary battery 2b. In this case, the charging current control unit 13 then uses the unit secondary battery 2b having the newly lowest detected voltage as a reference unit battery, and the unit secondary battery 2b receives the constant-current charging current as it is. The diversion circuit unit 5b is controlled so as to flow (disconnect the changeover switch 10 of the diversion circuit unit 5b from both diversion channels 11 and 12). Further, for the unit secondary battery 2a having a higher detection voltage, the shunt circuit unit 5a is controlled so as to divert part or all of the constant-current charging current to the shunt channel 11 or 12 of the shunt circuit unit 5a. To do. Hereinafter, such control of the charging current is performed every moment. When the detected voltages of the unit secondary batteries 2a and 2b are the same, the charging current control unit 13 causes the constant-current charging current to flow to the unit secondary batteries 2a and 2b without being shunted. .

By controlling the charging currents flowing through the unit secondary batteries 2a and 2b in this manner, when the detection voltages of the unit secondary batteries 2a and 2b are different at the start of charging the assembled battery 1, that is, When the remaining capacities of the unit secondary batteries 2a and 2b are varied, the unit secondary batteries 2a and 2b, for example, as shown in FIG. Rise so that they have almost the same voltage. Then, as shown in FIG. 2, since the voltages of the unit secondary batteries 2a and 2b and the remaining capacities are approximately proportional to each other, the remaining capacities of the unit secondary batteries 2a and 2b also rise substantially evenly. I will go.

As described above, in the constant current charging performed while controlling the charging current, the sum of the detection voltages of the unit secondary batteries 2a and 2b, that is, the voltage of the entire assembled battery 1 is the above-mentioned value of the assembled battery 1. It is performed until the full charge rated voltage (8.4V) is reached. In this case, as described above, each unit secondary battery 2a, 2
Since the voltage of b rises evenly, when the voltage of the whole assembled battery 1 reaches the full-charge rated voltage (8.4V) (time Tc in FIG. 3), each unit secondary battery 2a, 2b is discharged. All the voltages are substantially equal to the full-charge rated voltage (4.2V). Therefore, at the end of the constant current charging, neither the overcharge nor the undercharge of each unit secondary battery 2a, 2b has occurred.

When the voltage of the entire assembled battery 1 reaches the full-charge rated voltage (8.4 V) in this way, the charging method switching control unit 15 of the charging controller 6 then causes the constant current / constant of the power feeding unit 4 to change. Instruct the voltage generator 8 to perform constant voltage charging. At this time, the constant current / constant voltage generation unit 8 generates a constant voltage that is the full-charge rated voltage (8.4V) of the battery pack 1 and applies it to the battery pack 1. Also, in conjunction with this, the charging current control unit 13
Disconnects the flow dividing channels 11 and 12 of the flow dividing circuit units 5a and 5b from the unit secondary batteries 2a and 2b by the changeover switch 10 and maintains the state.

As a result, the constant voltage charging of the assembled battery 1 is started, and the unit secondary batteries 2a, 2b of the assembled battery 1 are finally charged to the fully charged state by the constant voltage charging. In this embodiment, the total charging time of the above-mentioned constant current charging and constant voltage charging was set to 2.5 hours. Since constant voltage charging is performed in a state where the voltages of the unit secondary batteries 2a and 2b are substantially the same voltage, even in the constant voltage charging, the unit secondary batteries 2a and 2b are finally charged. Evenly charged to full charge.

By charging the battery pack 1 as described above,
As described above, each unit secondary battery 2a, 2b of the assembled battery 1
Are charged evenly, even if the assembled battery 1 is used during the charging and the discharging is started, the respective unit secondary batteries 2a, 2b of the respective unit secondary batteries 2a, 2b at that time are mutually charged. There is almost no variation in capacity, so that the battery pack 1
The original performance can be exhibited with the capacity corresponding to the sum of the unit secondary batteries 2a and 2b.

When the assembled battery 1 charged to the fully charged state as described above is discharged with a constant current of, for example, 0.5 A, the voltage of each unit secondary battery 2a, 2b becomes as shown in FIG. The discharge performance of each unit secondary battery 2a, 2b decreases due to the charging of the assembled battery 1 as described above even if the discharge progresses without causing a large difference. It shows that they are uniform with each other.

Further, each unit secondary battery 2a of the assembled battery 1,
Since 2b is charged evenly, even if the switching from constant current charging to constant voltage charging is performed when the voltage of the battery pack 1 reaches its full charge rated voltage (8.4V), each unit 2 at that time is The voltage of the secondary batteries 2a and 2b is almost the full-charge rated voltage (4.2V), and overcharge or undercharge does not occur. By performing constant current charging with a relatively high charging efficiency until each unit secondary battery 2a, 2b substantially reaches the full-charge rated voltage in this way, the constant voltage charging thereafter can be performed for a relatively short time. Each unit secondary battery 2a of the battery 1,
2b can be surely charged to the fully charged state, whereby the total charging time until the assembled battery 1 is fully charged can be shortened.

[0049]

[Comparative Example 1] A lithium ion secondary battery, which is the same as the unit secondary batteries 2a and 2b of the assembled battery 1, is used as a unit secondary battery and three assembled batteries are connected in series. From the state in which the voltage of No. 1 was varied, the battery was charged by constant current charging and subsequent constant voltage charging. In this case, in the constant current charging, the voltage of the entire assembled battery becomes 12.6V (4.2V × 3) which is the full-charge rated voltage while the constant current of 1A is supplied to each unit secondary battery as it is. The subsequent constant voltage charging was performed by applying the full charge rated voltage (12.6 V) to the assembled battery. The total charging time was 2.5 hours, which was the same as in the above-mentioned example.

FIG. 5 shows how the voltage of each unit secondary battery changes when such charging is performed.

As is clear with reference to FIG. 5, the voltage of each unit secondary battery is charged while the variation at the start of charging is generated, and the unit secondary battery with the highest voltage has its full charge rating. There is a tendency that the battery is charged to a voltage exceeding the voltage (4.2 V) and is in an overcharged state. Similarly,
The unit secondary battery having the lowest voltage is charged only to a voltage lower than the full-charge rated voltage (4.2V), and there is a tendency to be in an undercharged state. Then, as is clear from comparison between the comparative example 1 and the example shown in FIG. 3, the assembled battery 1 according to the example was overcharged or undercharged. It turns out that it is effective in charging evenly without charging.

[0052]

[Comparative Example 2] A lithium ion secondary battery, which is the same as the unit secondary batteries 2a and 2b of the assembled battery 1, is used as a unit secondary battery, and two assembled batteries are connected in series. From the state in which the voltage was varied, the battery was charged by constant current charging and subsequent constant voltage charging, and then the assembled battery was discharged at a constant current of 0.5A. In this case, in the constant current charging, the voltage of the entire assembled battery becomes 8.4 V (4.2 V × 2) which is the full-charge rated voltage, while the constant current of 1 A is directly applied to each unit secondary battery. The subsequent constant voltage charging was performed by applying the full charge rated voltage (8.4 V) to the assembled battery.

FIG. 6 shows how the voltage of each unit secondary battery changes during discharging in this case. Although the change in the voltage of each unit secondary battery at the time of charging is not shown in the figure, the voltage of each unit secondary battery at the end of charging varied as in Comparative Example 1.

As is apparent from FIG. 6, when the assembled battery is discharged while the charging voltage of each unit secondary battery varies, the difference in voltage between the unit secondary batteries causes the progress of discharge. It can be seen that the unit secondary battery having a lower voltage rapidly decreases in voltage in a relatively short time and becomes an over-discharged state as compared with a unit secondary battery having a lower voltage. . This indicates that the discharge performance of the assembled battery is largely controlled by the unit secondary battery having a low voltage (low capacity), and the original discharge performance cannot be exhibited. On the other hand, in the battery pack 1 that has been charged according to the above-described embodiment, as shown in FIG. 4, the unit secondary batteries 2a and 2b are discharged substantially evenly. It is understood that the battery 1 can exhibit the original discharge performance up to a sufficient discharge amount for a relatively long period.

In the above embodiment, the charging of the assembled battery 1 having two lithium ion secondary batteries as the unit secondary batteries 2a and 2b has been described as an example, but more unit secondary batteries are connected in series. It is needless to say that the battery pack connected to can also be charged in the same manner as in the above-mentioned embodiment, and a lithium polymer secondary battery having the same characteristics as the lithium ion secondary battery is referred to as a unit secondary battery. The assembled battery can be charged in the same manner as in the above embodiment.

Further, in the above-mentioned embodiment, in order to charge the assembled battery having the lithium ion secondary battery as a unit secondary battery, which is difficult to be fully charged only by constant current charging, after the constant current charging, I tried to do constant voltage charging,
In charging an assembled battery that is another type of unit secondary battery that can be brought to a fully charged state only by constant current charging, control of the charging current for each unit secondary battery is performed as in the above embodiment. The assembled battery may be charged only by performing constant current charging. Further, the constant current at the time of charging may be changed appropriately.

Further, in the above embodiment, the unit secondary batteries 2a, 2 corresponding to the respective shunt circuit parts 5a, 5b are provided.
Although the shunt 12 and the switch 9 for shunting all the charging current to b are provided, it is also possible to omit them, and a plurality of shunts each provided with fixed resistors having different resistance values. May be connected to each unit secondary battery in parallel using a switch element so as to be switchable.

[0058]

As is apparent from the above description, according to the method of charging the assembled battery of the present invention, the voltage of each unit secondary battery of the assembled battery is momentarily detected at the time of supplying the charging current, and the voltage At each detection time, the unit secondary battery with the lowest detection voltage is used as the reference unit battery, and each unit secondary battery is set so that the rate of voltage increase per unit time of that reference unit battery is larger than that of each other unit secondary battery. While controlling the charging current of the battery,
When the detection voltage of the reference unit battery exceeds the detection voltage of at least one unit secondary battery of the other unit secondary batteries, the control of the charging current is performed by the unit secondary battery having the lowest other detection voltage. By performing the above as the next reference unit battery while sequentially updating the reference unit battery, the unit secondary batteries of the assembled battery can be charged evenly so that their capacities are substantially the same.

Then, while supplying a constant-current charging current to the assembled battery, the constant-voltage charging current is supplied as it is to the reference unit battery having the lowest voltage, and the other unit secondary batteries are detected. By charging a charging current that is smaller than the charging current of the constant current according to the voltage so as to charge, the lowest voltage, that is, while efficiently charging the unit secondary battery with the low capacity, always with the constant current, The unit rechargeable batteries can be charged with an equal mutual capacity, and thus the unit rechargeable batteries can be uniformly charged as efficiently as possible.

Furthermore, when charging is performed while controlling the charging current of each unit secondary battery, a constant voltage is applied to the assembled battery and constant voltage charging is performed until the assembled battery is fully charged. By charging while controlling the charging current of the secondary battery,
Since each unit rechargeable battery is charged evenly, it should be charged without causing overcharging or undercharging of each unit rechargeable battery until the voltage of each unit rechargeable battery reaches almost full charge voltage. As a result, the time required for the subsequent constant voltage charging can be shortened as much as possible, and the total charging time can be shortened.

Therefore, particularly, it is possible to improve the efficiency of the assembled battery constituted by using the lithium ion secondary battery or the lithium polymer secondary battery as the unit secondary battery, which is preferably subjected to the constant voltage charging finally, without causing overcharging or undercharging. Can be charged well.

Further, according to the battery pack charging apparatus of the present invention, not only the same effects as those of the above-described charging method can be obtained, but also a charging apparatus having such effects can be provided with a simple structure. .

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an example of a battery pack charging device of the present invention.

FIG. 2 is a diagram showing the relationship between the voltage and capacity of a unit secondary battery of an assembled battery charged by the device of FIG.

FIG. 3 is a diagram showing how the voltage of each unit secondary battery changes when the assembled battery is charged by the device of FIG.

FIG. 4 is a diagram showing how the voltage changes when each unit secondary battery of the assembled battery charged by the device of FIG. 1 is discharged.

FIG. 5 is a diagram showing how the voltage of each unit secondary battery changes when the assembled battery is charged in Comparative Example 1.

FIG. 6 is a diagram showing how the voltage of each unit secondary battery changes when the assembled battery charged in Comparative Example 2 is discharged.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Assembly battery, 2a, 2b ... Unit secondary battery (lithium ion secondary battery), 3 ... Power feeding means, 4a, 4b ... Voltage detection means, 11, 12 ... Dividing channel, 13 ... Charging current control means, 1
4 ... Minimum voltage grasping means, 15 ... Charging method switching means.

Claims (8)

[Claims] 1. A method of charging an assembled battery comprising a plurality of unit secondary batteries connected in series, a power feeding step of feeding a charging current to the assembled battery, and each unit of the assembled battery at the time of feeding the charging current. A step of momentarily detecting the voltage of the secondary battery, and a unit secondary battery having the lowest detection voltage among the plurality of unit secondary batteries at each detection time of the voltage is set as a reference unit battery, and the reference unit battery While controlling the charging current of each unit secondary battery so that the rate of voltage increase per unit time of each unit secondary battery is greater than that of the other unit secondary batteries, the control of the charging current is performed by detecting the reference unit battery voltage. When the detection voltage of at least one unit secondary battery among other unit secondary batteries is exceeded, the unit secondary battery having the lowest other detection voltage is set as the next reference unit battery and the reference unit batteries are sequentially updated. Equipped with a current control process A method of charging a battery pack, characterized in that the. 2. The power supplying step supplies a constant current charging current to the assembled battery, and the current controlling step applies the constant current charging current to the reference unit battery as it is, and the other unit units. According to the detected voltage, the constant current charging current is distributed to the secondary flow paths connected in parallel to each unit secondary battery so that a charging current smaller than the constant current charging current is applied to the secondary battery. The method for charging an assembled battery according to claim 1, wherein 3. The current control step is carried out until the detected voltage of each unit secondary battery substantially reaches a predetermined voltage corresponding to a substantially full charge voltage of each unit secondary battery, and controls each charging unit. After the detection voltage of the secondary battery substantially reaches a predetermined voltage, a constant voltage charging step of charging each unit battery by applying a constant voltage corresponding to the full charge voltage to the assembled battery is provided. The method of charging the assembled battery according to claim 1 or 2. 4. The method of charging an assembled battery according to claim 3, wherein the unit secondary battery is a lithium ion secondary battery or a lithium polymer secondary battery. 5. A charging device for an assembled battery comprising a plurality of unit secondary batteries connected in series, a power supply means connected to the assembled battery for supplying a charging current to the assembled battery, and each unit secondary battery. A voltage detection unit connected to a battery for detecting the voltage of each unit secondary battery momentarily when the charging current is supplied by the power supply unit, and the voltage detection unit at each time when the voltage of each unit battery is detected by the voltage detection unit. The minimum voltage grasping means for grasping the minimum voltage of the detected voltage of each unit secondary battery obtained from the, and the shunt connected in parallel to each unit secondary battery so that the charging current flowing through each unit secondary battery can be adjusted. And the unitary secondary battery corresponding to the lowest voltage momentarily grasped by the lowest voltage grasping means per unit time to flow into each branch passage so as to make the rate of increase in voltage per unit time larger than that of each other unit secondary battery. Shunt current Charging of the assembled battery, characterized in that a charging current control means for controlling the charging current flowing through each unit cell and integer. 6. The power supply means is a constant current power supply means for supplying a constant current charging current to the assembled battery, and the charging current control means is a unit secondary battery for the minimum voltage unit secondary battery. The shunt current of the shunt flow path connected to the battery was cut off, and the constant-current charging current was allowed to flow to the unit secondary battery as it was, and the other unit secondary batteries were connected to the unit secondary battery. The charging current flowing through the unit battery is controlled to be smaller than the charging current of the constant current by causing a shunt current according to the detection voltage of the unit secondary battery to flow in each branch flow path. Battery pack charger. 7. A constant voltage feeding means for applying a constant voltage to the assembled battery to charge each unit secondary battery, and a detection voltage of each unit battery obtained from the voltage detecting means is an abbreviation for each unit secondary battery. The charging current is supplied to the assembled battery by the constant current supply means until the predetermined voltage corresponding to the full charge voltage is substantially reached,
After that, it comprises a charging system switching means for charging the assembled battery by the constant voltage power supply means, and the charging current control means divides the charging current of each unit secondary battery into each of the shunts only when charging by the constant current power supply means. 7. The battery pack charging apparatus according to claim 5, wherein the charging is controlled by a shunt current of the path. 8. The battery charger for an assembled battery according to claim 7, wherein each of the unit secondary batteries is a lithium ion secondary battery or a lithium polymer secondary battery.