JP2001314046A - Charging apparatus and method of battery pack and electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To charge a battery pack rapidly while avoiding degradation in the battery pack. SOLUTION: Battery temperatures of respective secondary batteries forming the battery pack are measured to detect the highest battery temperature. A current for charging the battery pack is set corresponding to the detected highest battery temperature, and the battery pack is charged with the set current. Since the battery temperature of the secondary battery changes depending upon a charging condition, when a charging current is set according to the highest battery temperature of the battery pack, large current can be flowed to the extent that the battery is not degraded. As a result, the battery pack can be prevented from being degraded and can be charged quickly. In particular, the current can be set according to the battery temperature, is suitable for equal charging in which the current temperature is apt to rise because the secondary battery may be kept in an overcharged condition intentionally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for quickly and uniformly charging a plurality of secondary batteries constituting a battery pack.

[0002]

2. Description of the Related Art Secondary batteries use up stored electricity,
Since it can be charged and used again, it is widely used as a power source for various electric devices. Also, in order to obtain a desired voltage value or current value according to the specifications of electric equipment, a so-called assembled battery in which a plurality of secondary batteries are combined is widely used.

In such an assembled battery, when charging and discharging are repeated, the amount of remaining electricity varies among the secondary batteries (unit cells) constituting the assembled battery. When such variations occur, the capacity of the assembled battery decreases for the following reasons. In other words, the rated charge amount or the rated discharge amount is determined in advance for the secondary battery, and the secondary battery is charged (overcharged) exceeding the rated charge amount or discharged (overdischarged) until the battery becomes less than the rated remaining amount of electricity. ) Then, the secondary battery is easily deteriorated. For this reason, when charging a battery pack in which the amount of remaining electricity of the secondary battery varies, a cell having a large amount of remaining electricity reaches the rated charge amount earlier than the other cells, and thus continues to be charged further. After all, all the secondary batteries cannot be charged up to the rated charge amount. In addition, when discharging the assembled battery, a cell having a small amount of remaining electricity reaches the rated remaining amount of electricity earlier than the other cells, so that the battery cannot be discharged any further, and the other secondary battery is discharged. It cannot be discharged to the rated remaining amount of electricity. For these reasons, if there is variation in the assembled battery, charging must be stopped before the entire assembled battery reaches the rated charge amount, and discharging must be stopped before the entire assembled battery reaches the rated remaining amount of electricity. Instead, the capacity of the battery pack is reduced as a result.

In order to avoid a decrease in the capacity of the assembled battery due to such a variation between the secondary batteries, special charging (equal charging) for equalizing the remaining amount of electricity between the secondary batteries is performed. If the regular charging is carried out regularly, the variation between the cells can be kept small, and the capacity of the assembled battery can be maintained.

[0005] The most basic principle of uniform charging is to intentionally overcharge a battery pack. That is, even if one secondary battery in the assembled battery is fully charged, charging is continued until another secondary battery is fully charged. Since the fully charged secondary battery is not charged any more,
If the charging is continued until the other secondary batteries are fully charged, all the secondary batteries can be made fully charged. Of course, charging the battery normally accelerates the deterioration of the overcharged secondary battery, as described above, so charging the battery with a small current over a long period of time avoids the deterioration of the overcharged battery. I do.

As a technique for quickly performing uniform charging, for example, a technique has been proposed in which, after normal charging, charging is temporarily stopped, and then equalizing charging is started after the battery temperature is lowered (Japanese Patent Laid-Open No. 4-351432). ). Normal charging allows quick charging since a larger current flows than equivalent charging, and can reduce the charging time as compared to performing uniform charging from the beginning. In addition, the normal charging has a larger current value than the uniform charging, and thus generates a large amount of heat of the battery. However, since the battery is once cooled and then uniformly charged, there is no possibility that the battery deteriorates due to an increase in the battery temperature. Alternatively, JP-A-9-294337
As described above, a technology has been proposed in which the state of charge of each secondary battery constituting a battery pack is detected, and a fully charged secondary battery is bypassed and charged, thereby quickly and uniformly charging the battery. In this case, since the secondary batteries do not become overcharged, all the secondary batteries can be quickly brought to a fully charged state by flowing a large current.

[0007]

However, in the method of charging evenly after the battery is cooled down after normal charging, it is not possible to start uniform charging until the battery temperature drops. There is a problem that it still takes time to perform. In addition, the method of detecting the state of charge of each secondary battery and bypassing the fully charged secondary battery can quickly perform equal charging, but a complicated mechanism for bypassing each secondary battery. There was a problem that it was necessary.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and provides a technique capable of quickly and uniformly charging an assembled battery using a simple mechanism. The purpose is to:

[0009]

Means for Solving the Problems and Their Functions and Effects In order to solve at least a part of the above-mentioned problems, the charging device of the present invention employs the following configuration. That is, a battery pack charging device configured by connecting a plurality of secondary batteries, a battery temperature detecting means for detecting the temperature of the secondary battery having the highest temperature among the secondary batteries, and the battery pack Charging current value setting means for setting a charging current value as a current value for charging the battery according to the detected battery temperature, and charging for supplying the current of the set charging current value to charge the battery pack. And a means.

A charging method according to the present invention corresponding to the above-described charging apparatus is a charging method for an assembled battery constituted by connecting a plurality of secondary batteries, wherein the temperature is the highest among the secondary batteries. The temperature of the secondary battery is detected, a current value for charging the battery pack is set according to the detected battery temperature, and the current of the set current value is supplied to charge the battery pack. That is the gist.

In the charging device and the charging method, the temperature of the battery having the highest temperature among the plurality of secondary batteries constituting the assembled battery is detected, and a current having a current value corresponding to the detected temperature is detected. Supply to charge the battery pack.

Since the battery temperature of the secondary battery changes in accordance with the state of charge, detecting the battery temperature makes it possible to supply a current having a value large enough not to deteriorate the battery. Therefore, the battery pack can be charged quickly without deteriorating the assembled battery.

[0013] In the charging device, it is detected whether or not the secondary battery is set to perform the uniform charging for charging while equalizing the amount of electricity stored in each of the secondary batteries, and it is set to perform the uniform charging. In such a case, a current value according to the battery temperature may be set to charge the battery pack.

[0014] Equal charging causes the secondary battery to be in an overcharged state, so that the battery is likely to be degraded unless an appropriate current value is set. Can be set to a large value. Therefore, the battery can be quickly and uniformly charged without deteriorating the assembled battery, which is preferable.

In such a charging device, when the battery temperature is equal to or higher than the predetermined first temperature, the battery may be charged with a smaller current value as the battery temperature increases.

If the battery temperature is too high, the battery will deteriorate. Therefore, when the battery temperature becomes equal to or higher than the predetermined temperature, it is preferable to reduce the current value as the battery temperature rises and suppress the heat generation of the battery, since there is no possibility that the battery is deteriorated.

In such a charging device, when the battery temperature is equal to or lower than the predetermined second temperature, the battery may be charged with a smaller current value as the battery temperature decreases.

When the battery temperature becomes too low, the internal resistance of the secondary battery increases. If an attempt is made to charge the battery by flowing a current in a state where the internal resistance of the battery is increased, the terminal voltage of the battery pack may increase to deteriorate the battery. Therefore, when the battery temperature becomes equal to or lower than the predetermined temperature, it is preferable to reduce the current value as the battery temperature decreases, since there is no possibility that the battery is deteriorated. When the battery temperature is equal to or higher than the predetermined first temperature, the current value is decreased as the battery temperature increases. When the battery temperature is equal to or lower than the predetermined second temperature, on the contrary, as the battery temperature decreases, the current value decreases. Needless to say, the current value may be reduced.

In such a charging device, the amount of electricity stored in the battery pack may be detected, and the battery may be charged at a current value set in accordance with the detected amount of electricity and the battery temperature.

Under the influence of the environment in which the battery pack is used,
The battery temperature may have a slightly higher value or a lower value. In such a case, if the battery is charged with a large current based only on the battery temperature, the battery may be overcharged and the battery may be deteriorated. In contrast,
It is preferable that the battery be charged with a current value set in accordance with the amount of electricity stored in the battery pack in addition to the battery temperature, since there is no risk of deterioration of the battery.

In the above charging device, the upper limit of the set current value may be set lower as the amount of electricity remaining in the battery pack is larger.

If the amount of electricity remaining in the assembled battery is large, the battery is likely to be deteriorated when a large current is applied. However, if the upper limit of the current value is reduced as the amount of remaining electricity is increased, the battery can be used. This is preferable because there is no risk of deterioration.

In an electric vehicle equipped with a power generator, an assembled battery, and a motor, and driven by using the electric power of the generator or the assembled battery to drive the motor, when the power of the assembled battery is reduced, the electric power is generated. Power must be supplied from the machine to charge the battery pack. While the battery pack is being charged, the power supplied to the electric motor may be reduced and the power performance of the vehicle may be reduced. Therefore, it is desirable that the battery be charged as quickly as possible. Based on such circumstances, the present invention can be understood as an electric vehicle including the above-described charging device. In the electric vehicle according to the present invention, the battery pack can be quickly charged, so that the period during which the power performance of the vehicle is reduced during charging is preferably reduced.
In addition, a generator driven by an engine, a fuel cell, or the like can be applied as the power generation device mounted on the electric vehicle.

Further, such an electric vehicle may have the following configuration. That is, an assembled battery configured by connecting a plurality of secondary batteries, an electric motor that drives a vehicle using the power of the assembled battery, and a power generation device that can generate power while the vehicle is running and charge the assembled battery And a battery temperature detecting means for detecting the temperature of the secondary battery having the highest temperature among the secondary batteries, and detecting the electric power used by the electric motor, and A charging current value, which is a charging current value, is set according to the detected power and the battery temperature, and the power of the set charging current value is controlled by controlling the power generation device. And a charging unit that supplies the battery pack to charge the battery pack.

In such an electric vehicle, the temperature of the battery having the highest battery temperature among the assembled batteries is detected, and the electric power used by the electric motor driving the electric vehicle is detected. The charging current value is set based on the charging current value. The battery pack is charged while the power generating device generates electric power corresponding to the set current value.

By setting the current value to be supplied to the battery pack in this way, for example, when a large electric power is required by the electric motor, the current value for charging the battery pack can be reduced. Therefore, it is preferable because it is possible to avoid a phenomenon that the power to be supplied to the electric motor during charging of the battery pack is reduced and the power performance of the vehicle is reduced.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to more clearly describe the operation and effect of the present invention, embodiments of the present invention will be described in the following order. A. First embodiment: A-1. Device configuration: A-2. E. Charging method of the first embodiment: B. Second embodiment: B-1. Equal charging method of the second embodiment: B-2. Modification: C.I. Example of application to electric vehicles:

A. First embodiment: A-1. Device configuration: FIG. 1 shows a charging device 10 of the first embodiment.
FIG. 5 is an explanatory diagram conceptually showing a state in which the battery pack 200 is charged using 0. The assembled battery 200 includes a plurality of secondary batteries 21.
0 are connected in series. The connection method of the secondary batteries is not limited to the series connection, and the secondary batteries may be connected in parallel, or may be connected so that the series and the parallel are mixed. Further, although the nickel-metal hydride battery is used as the secondary battery of this embodiment, the present invention can be applied to a well-known secondary battery such as a lithium ion battery and a nickel-cadmium battery.

The charging device 100 includes a power supply circuit 110 for supplying power to be charged to the battery pack 200, and a power supply circuit 110.
, A current detector 130 for detecting a current value charged in the battery pack, a battery temperature detector 132 for detecting the temperature of each secondary battery constituting the battery pack, A maximum temperature detection circuit 134 for detecting the highest temperature among the temperatures, a voltage detector 136 for detecting the terminal voltage of the assembled battery, a charge start switch SWa140 for instructing the control circuit 120 to start charging, and a uniform charge And a uniform charge start switch SWb142 for instructing the start of the operation. In this embodiment, a thermistor is used as the temperature detector 122. However, the present invention is not limited to this, and another known temperature detector such as a thermocouple can be applied.

The control circuit 120 includes a so-called central processing unit CPU, a RAM for temporarily storing data necessary for the operation, a ROM for storing programs and data for the operation, Is a well-known microcomputer provided with a timer and the like for detecting an error.

When the battery pack 200 is set in the charging device 100 and the charge start switch SWa140 is pressed, the control circuit 1
Under the control of 20, current flows from the power supply circuit 110 to the battery pack 200, and charging of the battery pack is started. Equivalent charge start switch SW instead of charge start switch SWa140
By pressing b142, the battery pack 200 can be charged evenly. As described above, the equal charge means the battery pack 200
This is a special charging method for charging while equalizing the amount of electricity remaining in each of the secondary batteries constituting the battery. Control circuit 120
Controls the power supply circuit 110 based on the output of the maximum temperature detection circuit 134 so that the battery pack 200 is charged with an appropriate current value in any case of charging. For this reason,
By using the charging device 100 of the present embodiment, it is possible to quickly charge the battery pack 200 without deteriorating the battery pack 200. The voltage detector 136 is connected to the battery pack 20 being charged.
Since the terminal-to-terminal voltage of 0 is detected, the charging can be stopped immediately when the terminal-to-terminal voltage becomes abnormally high.

A-2. Charging method of the first embodiment: The charging device 100 of the present embodiment as shown in FIG. 1 is charged at an appropriate current value according to the maximum temperature of the secondary battery, and thus deteriorates the battery pack 200. It can be charged quickly without the need. To explain this, first, the battery pack 20
The following describes an example in which 0 is charged uniformly.

FIG. 2 is an explanatory view conceptually showing that the current value to be charged to the secondary battery is set with respect to the maximum battery temperature of the secondary battery in the equalizing charging method of the first embodiment. It is. The maximum battery temperature shown in FIG.
00 means the temperature of the battery with the highest temperature among the plurality of secondary batteries. As shown in the figure, in the equalizing charging method of the first embodiment, when the maximum battery temperature is lower than the boundary temperature Tc at a predetermined boundary temperature Tc, the battery is charged at a constant current value A1. Boundary temperature Tc
If it is higher, it is set to charge with a current value A2 smaller than the current value A1. The current value A2 varies depending on the specifications of the battery pack 200 and the environment in which the battery pack is charged, but a suitable value can be selected from a range of 0.1 A (ampere) to 5 A by an experimental method, and Preferably, it takes a value of 0.5A to 2A. Current value A
1 is set to a current value substantially equal to the current value when a large current is supplied to the battery pack and the battery is rapidly charged.

Here, the meaning of the boundary temperature Tc in FIG. 2 will be described. FIG. 3 is an explanatory diagram showing a change in battery temperature when the secondary battery is charged with a constant current. The horizontal axis in FIG. 3 shows an index called SOC (State of Charge). The SOC is an index indicating how much power remains in the secondary battery, and the amount of electricity remaining in the secondary battery is the amount of electricity stored when the secondary battery is fully charged. Is defined as the divided value. SOC can be detected using various methods. Most directly, SOC can be calculated by measuring the specific gravity of the electrolytic solution of the secondary battery. In addition, a method of utilizing the correlation between the terminal voltage and the SOC, a method of calculating the SOC by integrating the charged amount of electricity and the discharged amount of electricity, and the like can also be applied.

As shown in FIG. 3, when the secondary battery is charged under the condition that the current value is constant, the battery temperature rises as the SOC increases. This is because Joule heat corresponding to the internal resistance of the secondary battery is generated when a current for charging flows. At the end of charging when the SOC reaches 100% (that is, when the secondary battery is fully charged), the battery temperature shows a characteristic of rapidly increasing. That is, as shown in FIG. 3, when the battery temperature is arranged with respect to the SOC, an inflection point at which the battery temperature sharply increases appears. The boundary temperature Tc shown in FIG. 2 means the battery temperature at this inflection point. In practice, the temperature at which the inflection point appears strictly does not need to be the boundary temperature Tc, and a temperature slightly higher than the temperature at the inflection point is used as the boundary temperature Tc, as described later.

The charging device 100 according to the first embodiment includes a battery pack 2
By setting the current value for charging 00 as shown in FIG. 2 according to the maximum battery temperature of the battery pack, it is possible to quickly and uniformly charge the battery pack without deteriorating the battery pack. .

FIG. 4 is a flowchart showing a flow of a process for performing equal charging by using the charging device 100 of the first embodiment. FIG. 5 shows a process for performing uniform charging by performing the process shown in FIG. It is an explanatory view showing a situation that is performed. Less than,
Referring to FIG. 5, according to the flowchart of FIG.
A description will be given of the equal charging method of the first embodiment.

As shown in FIG. 1, the battery pack 200 is set in the charging device 100, and the uniform charging start switch SWb is set.
When the user presses 142, the uniform charging shown in FIG. 4 starts. As shown in FIG. 4, when the uniform charging is started, first,
The maximum battery temperature Tmax of the battery pack 200 is detected (step S100). The maximum battery temperature Tmax of the battery pack 200 is the battery temperature of the battery with the highest temperature among the plurality of secondary batteries.

Next, the magnitude relation between the detected maximum battery temperature Tmax and the predetermined boundary temperature Tc is compared (step S).
102). If the maximum battery temperature Tmax is lower than the boundary temperature Tc (step S102: no), charging of the battery pack 200 with the current value A1 is started (step S104).

The change after the charging of the battery pack 200 is started at the current value A1 will be described with reference to FIG. FIG. 5 is an explanatory diagram showing changes in the SOC and the battery temperature of each secondary battery and the value of the current flowing through the battery pack after the start of charging. The upper row shows the SO of each secondary battery.
The change in C, the change in the battery temperature of each secondary battery in the middle part of the vertical axis, and the current value supplied by the battery pack are shown in the lower part of the vertical axis. Although the assembled battery 200 includes a plurality of secondary batteries (see FIG. 1), in order to avoid complicating the drawing, FIG. Only show.

As shown in the upper part of FIG. 5, at time t0 immediately after the start of charging, a large variation occurs in the SOC between the secondary batteries. When charging is started by flowing the current value A1 to the battery pack 200, the SOC of each secondary battery gradually increases. Here, since each secondary battery is connected in series, and the same value of current flows in each secondary battery, as shown in FIG. 5, the SOC of each secondary battery increases in substantially the same manner. To go.

When a current flows through each secondary battery, Joule heat is generated by the internal resistance, so that the battery temperature gradually increases. As is well known, the amount of Joule heat generated is proportional to the square of the current value and the resistance value, respectively. Here, since the current values flowing through the respective secondary batteries are the same, and the internal resistance is not so much different between the batteries, the amount of generated Joule heat is almost equal in each of the secondary batteries. , The battery temperature of each secondary battery increases in substantially the same manner. Although each secondary battery is incorporated in the same battery pack and used in the same manner, the battery temperature varies slightly between batteries immediately after the start of charging due to slight differences in battery cooling conditions, internal resistance, etc. ing. FIG.
In step S100, the temperature of the battery 1 indicated by a dashed line in FIG. 5 is detected.

When the battery is charged at the current value A1, the battery having the highest SOC at the start of charging (battery 2 indicated by a solid line in FIG. 5) is charged fastest, and the SOC becomes 10%.
When the battery is charged to nearly 0%, the battery temperature starts to rise sharply as described above with reference to FIG. As a result, the temperature of the battery 2 indicated by the solid line is detected as the maximum battery temperature.

This will be described with reference to the flowchart of FIG. 4. When the detected maximum battery temperature Tmax is equal to the boundary temperature Tc.
The charging is continued at the current value A1 until it exceeds (steps S100 to S104). During charging, in step S106, it is confirmed that the terminal voltage of the battery pack 200 has not abnormally increased. If the terminal voltage has abnormally increased (step S106: no), an alarm lamp (not shown) indicating a voltage abnormality Is turned on (step S108),
Stop charging.

When the battery 2 is charged at the current value A1, as described above with reference to FIG. 5, the battery temperature rises rapidly as the battery 2 is charged to nearly 100% SOC, and eventually the battery temperature reaches the boundary temperature Tc. Is detected (step S102: yes). In the present embodiment, as described above, considering that there is a slight variation in the battery temperature before the start of charging, in order to facilitate detection of the battery charged to the SOC of nearly 100%, The temperature Tc is set to be higher than the temperature at the inflection point shown in FIG.

When the maximum battery temperature Tmax exceeds the boundary temperature Tc, a timer is set (step S11).
0), the value of the current flowing through the battery pack 200 is changed to A2, and charging is continued at the current value A2 (step S112). As shown in the lower part of FIG. 5, the current value A2 is set to a value smaller than the current value A1. While charging with the current value A2,
It is confirmed that the terminal voltage of the battery pack 200 has not risen abnormally (step S114), and charging is continued until the time set in step S110 has elapsed (step S1).
16).

Here, the manner in which each secondary battery is charged by charging with the current value A2 will be described with reference to FIG. 5 again. The time when the maximum battery temperature Tmax exceeds the boundary temperature Tc and the current value is changed from A1 to A2 is defined as t1. During the period from time t0 to time t1 immediately after the start of charging, all the secondary batteries are charged in substantially the same manner, and at time t1, the variation in the SOC of each secondary battery does not decrease. Also, the SOC of the secondary battery indicated as Battery 2
Has reached almost 100%, but the SOC of the secondary batteries indicated as Battery 1 and Battery 3 has not yet reached 100%.

In this state, when charging is continued with the charging current value reduced from A1 to A2, the SOC of battery 1 and the SOC of battery 3 whose SOC has not reached 100% gradually increase. . The increase rate of the SOC after time t1 is slower than the increase rate of the SOC from time t0 to time t1 because the charge current value decreases from A1 to A2. Further, after the SOC of the battery 2 reaches 100%, the battery 2 cannot be charged any more, so that it is maintained at 100%. Thus, after charging at time t1, the secondary battery whose SOC has reached 100% is not charged any more, and the SOC becomes 1
Since only the secondary batteries that have not reached 00% are charged, the SOCs of all the secondary batteries converge toward 100% as the batteries are charged.

Here, in the equal charging method of the first embodiment, after the maximum battery temperature Tmax reaches the boundary temperature Tc,
The reason why the current value is reduced from A1 to A2 will be described.

In general, even if the secondary battery is fully charged, if the current continues to flow for further charging, the secondary battery cannot store any more electric power, so the input electric energy is converted into heat. As a result, it is known that the battery temperature rises to accelerate the deterioration of the battery. In the charging method of the first embodiment, in order to avoid such deterioration due to a rise in battery temperature, when any of the secondary batteries in the assembled battery approaches a fully charged state, the battery temperature further rises. The current value is reduced to the extent that it does not. If the current value is reduced to some extent, the amount of heat generated and the amount of heat radiated from the secondary battery can be balanced, so that an increase in battery temperature can be avoided. The current value for avoiding a rise in the battery temperature varies depending on the internal resistance of the secondary battery, heat radiation conditions, and the like, and is thus experimentally obtained in advance. FIG.
Is a current value obtained by such an experiment.

In the equalizing charging method of the first embodiment, after the maximum battery temperature Tmax reaches the boundary temperature Tc, the battery 2 is charged at the current value A2 thus obtained, so that the battery 2 is charged in a fully charged state. Nevertheless, as shown in the interruption of FIG. 5, the battery temperature of the battery 2 is maintained at a substantially constant value.
That is, there is no possibility that the deterioration of the battery 2 is accelerated by charging after the time t1. Battery 1 that has not reached full charge
For battery 3 and after changing the charging current value to A2, the battery temperature tends to decrease slightly. This is because the battery 1 and the battery 3 do not generate heat as much as the battery 2 for charging the supplied power, so that the balance between the amount of heat generation and the amount of heat radiation is inclined to the heat radiation side.

Thus, when the time set in step S110 of FIG. 4 has elapsed, the equal charging method of the first embodiment ends.

In the equalizing charging method of the first embodiment described above, until one of the secondary batteries constituting the assembled battery 200 is charged to near the SOC of 100%, the charging is substantially equal to the normal charging. Charges rapidly with a large current. When any one of the secondary batteries is charged to around the SOC of 100%, all the secondary batteries are charged to the SOC of 100% by continuously charging at a preset current value so as not to raise the battery temperature. As described above, in the first embodiment, after the battery is rapidly charged with a large current, the charging is continuously started with a small current value without providing a cooling time for the battery as in the conventional equal charging method. Therefore, the time required for uniform charging can be shortened accordingly. Of course, if the charging current is small, it takes much time to fully charge all the secondary batteries, but in this embodiment, all the secondary batteries are charged in advance with a large current, Since switching to charging by current is performed, charging with a small current is sufficient only for variations in the amount of charge of each secondary battery. Therefore, charging can be completed quickly with a small current value.

Further, in the equalizing charging method of the first embodiment, the equalizing charging can be easily performed by detecting the maximum battery temperature of the secondary battery and switching the current value according to the detected maximum battery temperature. That is, unlike the equal charging method proposed as the prior art, a complicated mechanism such as detecting the SOC of each secondary battery and bypassing the current flowing through the secondary battery that has reached the SOC of 100% is not required. It is possible to perform uniform charging with a simple mechanism.

The use of the above-described equal charging method has an advantage that the equal charging can be reliably performed without strict setting of conditions. That is, as described above,
After the maximum battery temperature Tmax reaches the boundary temperature Tc, the battery is charged for a predetermined time at the current value A2. Even if the charging time is set to be somewhat longer, the amount of heat generated by the battery and the amount of heat radiation are balanced. Never rises. Therefore, by setting the charging time to be somewhat longer, it is possible to reliably perform the uniform charging. Conversely, even if the charging time is set short, as described above, after the SOC of one of the secondary batteries reaches 100%, the SOC of the other secondary battery increases by the amount charged. Therefore, the variation in the SOC can be reliably improved.

In the uniform charging method described above, charging is stopped when the terminal voltage of the battery pack rises abnormally. However, the battery temperature rises abnormally, not limited to the terminal voltage. In such a case, it is also preferable to stop charging. Depending on the type of rechargeable battery, the terminal voltage does not increase very much, or the terminal voltage starts to decrease when the battery temperature rises.Therefore, charging is performed by detecting that the battery temperature has risen abnormally. Is preferably stopped because the deterioration of the assembled battery can be avoided.

In the above description, the case of equal charging has been described as an example. However, the charging method of the first embodiment is effective not only for equal charging but also for normal charging. That is, when performing normal charging, a large current is supplied to the battery pack to rapidly charge the battery until the SOC becomes almost 100%. At this time, if a secondary battery that is overcharged beyond its full charge occurs in the battery pack, the battery pack will deteriorate, so if it is detected that a fully charged secondary battery has occurred in the battery pack, charging will be stopped. finish. The full charge of the secondary battery can be detected by using various methods such as detecting a change in terminal voltage.However, when the battery pack is composed of a large number of secondary batteries, the detection is performed. Accuracy may decrease.

Here, when the charging method of the first embodiment is used, the maximum battery temperature Tmax of the battery pack being charged is detected, and when the maximum battery temperature Tmax exceeds the boundary temperature Tc, the current value is reduced to a lower value. Switch and continue charging. As described above with reference to FIG. 3, the battery temperature rises sharply shortly before the SOC reaches 100%. Therefore, by detecting the maximum battery temperature Tmax, any one of the secondary batteries in the battery pack can be charged to SOC1.
It can be detected that the battery has been charged to the vicinity of 00%.

In this way, the secondary battery in the battery pack is
Immediately before reaching 0%, the current value is reduced, and when any of the secondary batteries reaches a fully charged state, charging is terminated. When the secondary battery is fully charged, a known method such as detecting a change in terminal voltage can be applied. With this configuration, the current value is reduced immediately before the battery is fully charged, and the fully charged secondary battery can be detected while the battery is slowly charged, so that the detection accuracy can be improved. Further, even if the detection timing of the full charge is slightly delayed, only a small current flows through the secondary battery, so that deterioration of the battery can be avoided.

On the other hand, when the battery is charged with a constant current value to the end without detecting the battery temperature, the detection timing of the fully charged secondary battery is slightly delayed.
A large current flows through the secondary battery, causing the battery to deteriorate. For this reason, if the battery pack is composed of a large number of secondary batteries, charging should be terminated early to avoid battery deterioration due to delay in detection of a fully charged secondary battery. In some cases, it must be done. Even in such a case, if the charging method of the first embodiment is applied,
The assembled battery can be charged sufficiently and quickly without deteriorating the battery.

B. Second embodiment: In the charging method of the first embodiment described above, the current value can take only two kinds of values, and the current value is determined by the detection result of the maximum battery temperature Tmax of the assembled battery. It was decided based on. On the other hand, the current value may be changed according to the detected maximum battery temperature Tmax. Hereinafter, the charging method of the second embodiment in which various current values are set according to the maximum battery temperature Tmax will be described.

B-1. Equal charging method of second embodiment: second
The charging method of the embodiment can implement the charging device 100 of the first embodiment shown in FIG. However, in the charging method of the first embodiment, the control circuit 120 uses the maximum temperature detection circuit 134 to determine the maximum battery temperature T of the battery pack 200.
The current value is switched between two levels based on the detected maximum battery temperature Tmax. On the contrary,
In the charging method of the second embodiment, the control circuit 120 calculates a current value to be passed to the battery pack 200 based on the maximum battery temperature Tmax. Hereinafter, similar to the description in the first embodiment,
First, taking the case where the battery pack 200 is charged equally as an example,
A charging method according to the second embodiment will be described.

FIG. 6 is an explanatory view conceptually showing that the current value to be charged to the secondary battery is set with respect to the maximum battery temperature of the assembled battery in the equal charging method of the second embodiment. is there. As shown, in the equalizing charging method of the second embodiment, the current value is set to decrease from A1 to A2 as the battery temperature increases from the temperature Td to the temperature Te. When the battery temperature becomes higher than the temperature Te, the current value is set to a constant value A2 regardless of the battery temperature. As the current values A1 and A2, the current values used in the charging method of the first embodiment described above can be used.

When the battery temperature is in the range from the temperature Tb to the temperature Td, the current value is set to a constant value A1 regardless of the battery temperature. When the battery temperature is in the range from the temperature Ta to the temperature Tb, the current value increases from A1 to A as the battery temperature decreases.
The current value is set to a constant value A2 regardless of the battery temperature when the battery temperature falls below the temperature Ta.

Here, the battery temperature Tb and the battery temperature Td
The meaning of is described. FIG. 7 is an explanatory diagram showing a change in battery temperature when the secondary battery is charged under the condition of a constant current value, with the SOC of the secondary battery being plotted on the horizontal axis. As described above in the first embodiment, there is an inflection point at which the battery temperature sharply increases as the SOC increases. As shown in FIG. 7, the battery temperature Td is:
The temperature is almost set at the inflection point. Also, the battery temperature T
e is the temperature immediately before the SOC reaches 100% (for example, SO
C is set to 95%).

In FIG. 6, the reason why the smaller the current value is set as the temperature decreases even in the range where the battery temperature is equal to or lower than the temperature Tb is as follows. That is, when the battery temperature decreases, the internal resistance of the battery tends to increase. When a large current flows in a state where the internal resistance is increased, the terminal voltage may increase and the secondary battery may be broken. In order to avoid such a case, when the battery temperature becomes lower than the predetermined temperature Tb, the current value is reduced. The value of the temperature Tb is determined experimentally in advance because it varies depending on the specifications of the secondary battery and the setting of the current value A1. Further, if the current value is reduced to some extent, it is not necessary to further reduce the current value.

The process of uniformly charging the assembled battery using the charging method of the second embodiment can be performed in substantially the same manner as the charging method of the first embodiment. Hereinafter, the charging process of the second embodiment will be described with reference to the flowchart of FIG. 4 used in the description of the charging method of the first embodiment.

Also in the second embodiment, when the uniform charging process is started, first, the maximum battery temperature Tma
x is detected (corresponding to step S100 in FIG. 4). Next, the magnitude relation between the detected maximum battery temperature Tmax and the predetermined temperature Te is compared (corresponding to step S102). As described with reference to FIG. 7, the temperature Te is a temperature at which one of the secondary batteries in the battery pack is considered to have almost 100% SOC, and usually, the maximum battery temperature Tmax is the temperature Tmax.
It is lower than e.

Subsequently, a current value is calculated from the detected maximum battery temperature Tmax based on the relationship shown in FIG. 6, and charging of the battery pack 200 is started with the calculated current value (step S1).
04). As in the case of the first embodiment, the terminal voltage of the battery pack is detected during charging (corresponding to step S106), and if the terminal voltage rises abnormally, an alarm lamp indicating voltage abnormality is turned on (corresponding to step S108). ) Stop charging. Not only the terminal voltage but also an abnormal rise in battery temperature may be detected to stop charging. Thus,
The maximum battery temperature Tmax is detected again, and the above processing is repeated.

As the charging is continued, the SOC of each of the secondary batteries in the battery pack gradually increases, and the temperature of each of the secondary batteries also gradually increases (see FIG. 7). Eventually, the SOC of one of the secondary batteries will be 100%
When the temperature increases to the vicinity, the maximum battery temperature Tmax reaches the temperature Td. Therefore, the charging is further continued while the current value is gradually decreased according to the setting of FIG.

When the maximum battery temperature Tmax reaches the temperature Te (corresponding to step S102: yes), the timer is set (corresponding to step S110), and then the battery pack is slowly charged with the current value A2 (corresponding to step S112). That is, since the maximum battery temperature Tmax has reached the temperature Te,
Since it is considered that the SOC of one of the secondary batteries has reached almost 100%, the SOC of the uncharged secondary battery is reduced to 10% by charging the battery with a small current value for a predetermined time.
It is increased to 0%.

When the charging with the constant current value A2 is continued until the predetermined time elapses, the equalizing charging process of the second embodiment ends. During charging at the current value A2, it is confirmed that the terminal voltage of the battery pack 200 has not abnormally increased (corresponding to step S106), and if abnormally increased, the charging is stopped. Also, during charging at the current value A2,
When the maximum battery temperature Tmax falls below the temperature Te due to factors related to the cooling performance of the battery pack, such as the usage environment of the battery pack, the battery may be charged again with the current value A1 until the battery temperature reaches the temperature Te. . Alternatively, the set value of the current value A2 may be corrected to a slightly higher value according to the maximum battery temperature Tmax, and charging may be performed with the corrected current value A2 + α. This is preferable because even charging can be performed completely within the same charging time, or if the amount of charged current is detected, uniform charging can be performed more quickly.

In the equalizing charging process of the second embodiment described above, the current value can be gradually reduced from the point in time when the battery temperature reaches a temperature at which the battery temperature starts to rise rapidly with charging. As described above, if the current value is gradually decreased from the timing at which the temperature starts to rise rapidly, a large amount of current can be supplied to the battery pack while avoiding a rise in battery temperature. As a result, the battery pack can be quickly and uniformly charged without deteriorating the battery.

In the above description, the case of equal charging has been described as an example. However, the charging method of the second embodiment is not limited to the case of equal charging as in the charging method of the first embodiment, and normal charging is performed. It is also effective in cases. That is, when a large current is supplied to the battery pack and the battery is rapidly charged, the maximum battery temperature Tmax of the battery pack is detected, and when the battery temperature is equal to or higher than the predetermined temperature, the current value is gradually decreased, so that the charging end timing is delayed. However, it is preferable because there is no possibility that the battery is deteriorated.

B-2. Modification: In the second embodiment described above, the current value to be passed through the battery pack is the maximum battery temperature Tma
was set according to x, but in addition to the maximum battery temperature,
The current value may be set in consideration of the SOC of the battery pack. In a modification of the charging method of the second embodiment described below, the current value is set based on the maximum battery temperature and the SOC of the battery pack.

FIG. 8 is an explanatory diagram showing a state in which an appropriate current value is set according to the maximum battery temperature and the SOC of the battery pack in a modification of the second embodiment. As shown, in the modification of the second embodiment, the same relationship between the battery temperature and the current value shown in FIG. 6 is set for each SOC of the assembled battery. That is, even at the same battery temperature,
When the SOC of the battery pack is high, the current value is set to a small value, and when the SOC is low, the current value is set to a large value.

This takes the following into consideration. The battery temperature of the secondary battery slightly fluctuates depending on the environmental temperature in which the assembled battery is placed. In particular, even when the battery pack is not charged or discharged for a while, the battery temperature gradually changes under the influence of the environmental temperature. That is, just because the battery temperature is low, the SOC of the battery pack is not always small. In particular, when the battery pack has not reached thermal equilibrium, the SOC of the battery pack
Is high, but the battery temperature is low. In such a case, if the battery is charged with a large current value just because the maximum battery temperature Tmax is low, the battery temperature may rise rapidly and the battery may be deteriorated. On the other hand, as in the modification of the second embodiment shown in FIG. 8, as the SOC of the battery pack increases, if the current value is set lower, the battery pack reaches a thermal equilibrium state. Even before, it is preferable because there is no possibility that a large current flows to deteriorate the battery.

As shown in FIG. 8, instead of setting the relationship between the battery temperature and the current value for each SOC of the assembled battery, a simple setting as shown in FIG. 9 can be used. That is, an upper limit value is provided for the current value, and the higher the SOC of the battery pack is, the lower the upper limit value of the current value is. This is preferable because, even though the SOC of the battery pack is a high value, there is no possibility that a large current value flows to deteriorate the battery.

C. Example of application to electric vehicle: The electric vehicle frequently repeats discharging and charging of the battery pack during traveling.
That is, the vehicle normally travels by driving the electric motor with the electric power stored in the battery pack, and travels while performing an operation of charging the battery pack with electric power generated by the motor when the vehicle decelerates, that is, a so-called regenerative operation. When charging and discharging are repeated frequently as described above, the variation in the SOC between the secondary batteries constituting the battery pack gradually increases, and the capacity of the battery pack decreases. If the capacity of the battery pack is reduced, the cruising distance of the electric vehicle is shortened. Therefore, it is necessary to periodically charge the battery pack to restore the capacity of the battery pack. However, since the running state of the vehicle is constantly changing, it is desirable to complete the uniform charging as quickly as possible. As described above, the charging device of the present embodiment can be quickly and uniformly charged, and thus is suitable as a charging device for an assembled battery for an electric vehicle. In the following, using the charging device of the present embodiment,
An embodiment for charging a battery pack for an electric vehicle will be briefly described.

FIG. 10 is an explanatory diagram showing the configuration of a hybrid vehicle equipped with the charging device of this embodiment. A hybrid vehicle is a vehicle that uses an engine and an electric motor as power sources. As shown, the hybrid vehicle includes an engine 210, a control unit 220 for controlling the engine, a motor 230, an assembled battery 240, a drive circuit 250, and the like. The output of the engine 210 is transmitted to the axle 260 via the motor 230 to rotate the wheels. By supplying the electric power stored in the battery pack 240 to the motor 230 via the drive circuit 250, the output of the motor 230 can rotate the axle 260. The battery pack 240 includes a maximum battery temperature detector 242. The highest battery temperature detector 242 detects the battery temperature of the highest temperature secondary battery among the plurality of secondary batteries constituting the battery pack 240. The drive circuit 250 is an inverter configured using a semiconductor element. The drive circuit 250 converts the DC current of the battery pack 240 into an AC current having an appropriate current value and frequency under the control of the control unit 220, and supplies the AC current to the motor 230. The drive circuit 250 incorporates a current detector and a voltage detector, and can detect a current value charged and discharged by the battery pack 240 and a terminal voltage of the battery pack 240.

The hybrid vehicle having the above configuration has
Depending on the driving conditions of the vehicle, the two power sources of the engine 210 and the motor 230 are selectively used, and further, by storing extra power as electric energy,
Energy efficiency of the entire vehicle can be improved.

FIG. 11 is a flowchart showing the flow of the process for performing the uniform charging in the hybrid vehicle described above. The processing illustrated in FIG. 11 is performed by the CPU incorporated in the control unit 220. Further, in the present embodiment, based on temporal information such as the running time of the vehicle and the number of times of charging / discharging, the uniform charging is performed on a semi-periodical basis. Of course, S of the battery pack 240
It is also possible to detect variation in OC and start uniform charging.

When the uniform charging process is started, first, the maximum battery temperature Tmax is detected (step S200). The maximum battery temperature Tmax is determined by using a maximum battery temperature detector 242 built in the battery pack 240. Next, a magnitude relationship between the maximum battery temperature Tmax and the set temperature Te is determined (step S202). In this embodiment, the battery temperature and the current value are set as shown in FIG.
Indicates that one of the rechargeable batteries in the battery pack has almost the SOC 100
%.

If the maximum battery temperature Tmax is lower than the set temperature Te, a current value is calculated based on the relationship shown in FIG. 9 (step S204). The SOC of the battery pack is calculated by integrating the amount of electricity charged and discharged by the battery pack. When the SOC is calculated by such a method, a calculation error may occur. However, in the present embodiment, uniform charging is periodically performed, and the SOC is reset to 100% each time. Even when the SOC is calculated, the calculation error can be sufficiently reduced.

After the calculation of the current value, the current value is corrected according to the driving conditions of the vehicle (step S206). For example, when a large power is required, such as when the vehicle suddenly starts, a large current must be supplied to the motor 230. In such a case, the required current is supplied to the motor by reducing the charging current.

The current value corrected in accordance with the vehicle driving conditions is supplied to the battery pack 240 for charging (step S2).
08). The charging of the battery pack 240 is performed by the control unit 220.
The electric power generated by the motor 230 under the control of
This is performed by supplying the battery pack 50 to the battery pack 240.

The above series of processing is repeated until the maximum battery temperature Tmax of the battery pack 240 exceeds the set temperature Te. When the maximum battery temperature Tmax exceeds the set temperature Te, the current value flowing through the battery pack is once set to A2 (step S210), and the integrated value of the current charged into the battery pack is reset (step S212). That is, the maximum battery temperature T
After the max reaches the set temperature Te and the SOC of any of the secondary batteries in the battery pack reaches almost 100%, the battery is not fully charged by supplying a predetermined amount of current. The SOC of the secondary battery is increased to almost 100%. Therefore, in order to integrate the charged current value, the integrated value of the charging current is reset. Subsequently, after the set current value is corrected according to the driving condition of the vehicle (step S214), the battery pack is charged with the corrected current value (step S216). At this time, a value obtained by multiplying the value of the current flowing through the battery pack by the time is stored as a charge integrated value. Next, it is determined whether or not the integrated charge value has reached a predetermined amount (step S218).
Returning to step S214, the subsequent series of processing is repeated. If it is determined that the battery has been charged by the predetermined amount (step S
218: yes), end the equal charging.

If the battery pack of the electric vehicle is uniformly charged using the method described above, the battery pack is rapidly charged with a large current while the maximum battery temperature is low, so that the battery pack can be quickly charged uniformly. . In addition, since the current value is gradually decreased as the maximum battery temperature increases, the battery is charged while the increase in the battery temperature is suppressed. Therefore, there is no possibility that the battery temperature will increase significantly and deteriorate the battery. In the above description, the case of equal charging is described as an example. However, it is needless to say that, similarly to the above-described various embodiments, not only equal charging but also normal charging is preferable. .

Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist of the invention.

For example, the above-described electric vehicle has been described as employing a so-called parallel hybrid system capable of transmitting the output of the engine directly to the axle. However, the output of the engine is exclusively used for power generation. And a serial hybrid type electric vehicle in which only the output of the electric motor is transmitted to the axle.

In the above-described electric vehicle, a power generator such as a fuel cell may be mounted in place of the engine, and the electric motor may be driven by electric power from the power generator and electric power from the battery pack.

[Brief description of the drawings]

FIG. 1 is an explanatory view conceptually showing the structure of a charging device according to the present embodiment.

FIG. 2 is an explanatory diagram showing a state in which a current value is set with respect to a battery temperature in the charging method of the first embodiment.

FIG. 3 is an explanatory diagram in which battery temperatures when charging a secondary battery with a constant current are arranged with SOC as a horizontal axis.

FIG. 4 is a flowchart illustrating a flow of a process of performing equal charging using the charging method according to the first embodiment.

FIG. 5 is an explanatory diagram showing that the battery temperature and the SOC of each secondary battery gradually change when uniform charging is performed using the charging method of the first embodiment.

FIG. 6 is an explanatory diagram showing a state in which a current value is set for a battery temperature in the charging method of the second embodiment.

FIG. 7 is an explanatory diagram showing a setting method of a set temperature used as a threshold in the charging method of the second embodiment.

FIG. 8 is an explanatory diagram showing a state in which a current value is set for a battery temperature and an SOC in a charging method according to a modification of the second embodiment.

FIG. 9 shows a charging method according to another modification of the second embodiment.
FIG. 4 is an explanatory diagram showing a state where a current value is set for a battery temperature and an SOC.

FIG. 10 is an explanatory diagram conceptually showing a configuration of an electric vehicle to which the charging method of the present embodiment is applied.

FIG. 11 is a flowchart showing a flow of a process for uniformly charging the battery pack mounted on the electric vehicle by using the method of the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 charging device 110 power supply circuit 120 control circuit 122 temperature detector 130 current detector 132 battery temperature detector 134 maximum temperature detection circuit 136 voltage detector 140 charging start switch SWa 142 uniform charging start Switch SWb 200: assembled battery 210: engine 210: secondary battery 220: control unit 230: motor 240: assembled battery 242: maximum battery temperature detector 250: drive circuit 260: axle

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/44 101 H02J 7/00 P H02J 7/00 B60K 9/00 CF term (Reference) 5G003 AA01 AA07 BA03 CA02 CB01 CC07 DA04 DA12 EA05 FA06 GC05 5H030 AA02 AS08 BB01 DD08 FF22 FF41 FF42 5H115 PG04 PI14 PI16 PI22 PI29 PU01 PU25 PU26 QN03 QN12 TI02 TI05 TI10 TR19 TU12 TU16

Claims (7)

[Claims] 1. A battery charger for an assembled battery comprising a plurality of secondary batteries connected to each other, comprising: battery temperature detecting means for detecting the temperature of the secondary battery having the highest temperature among the secondary batteries; A charging current value, which is a current value for charging the battery pack,
A charging apparatus comprising: a charging current value setting unit configured to set according to the detected battery temperature; and a charging unit configured to supply the current having the set charging current value to charge the assembled battery. 2. The charging device according to claim 1, wherein the charging current value setting unit is configured to determine that the battery temperature is equal to a predetermined first temperature.
A charging device that sets the charging current value to a smaller value as the battery temperature increases when the temperature is equal to or higher than the temperature. 3. The charging device according to claim 1, wherein the charging current value setting unit is configured to control the battery temperature to a predetermined second value.
A charging device that sets the charging current value to a smaller value as the battery temperature decreases when the battery temperature is equal to or lower than the temperature. 4. The charging device according to claim 1, further comprising: a remaining amount of electricity detecting unit that detects an amount of remaining electricity in the battery pack, wherein the charging current value setting unit includes the detected battery temperature and the detected battery temperature. A charging device, which is means for setting the charging current value according to the detected remaining amount of electricity. 5. The charging device according to claim 4, wherein the charging current value setting means includes an upper limit value setting means for setting an upper limit value of the charging current value, and wherein the upper limit value setting means performs the detection. A charging device that sets the upper limit to a smaller value as the amount of remaining electricity increases. 6. An assembled battery formed by connecting a plurality of secondary batteries, an electric motor for driving a vehicle using the electric power of the assembled battery, and power generation during the running of the vehicle to charge the assembled battery And a battery temperature detecting means for detecting a temperature of the secondary battery having the highest temperature among the secondary batteries, and detecting electric power used by the electric motor, A charging current value setting means for setting a charging current value, which is a current value for charging the assembled battery, in accordance with the detected power and the battery temperature; and controlling the power generation device to obtain the set charging current value. And an equalizing charging means for equalizing charging of the battery pack by supplying the same power. 7. A method of charging a battery pack configured by connecting a plurality of secondary batteries, comprising detecting a temperature of a secondary battery having the highest temperature among the secondary batteries, and charging the battery pack. A charging method for setting the current value to perform the charging according to the detected battery temperature, and charging the battery pack with the set current value.