KR101776517B1 - Method and system for charging battery - Google Patents

Abstract

Disclosed are a method and system for charging a battery, capable of increasing a charging capacity in a battery cell by additionally charging the battery again if a preset time elapses after the supply of a charging current is blocked when a battery voltage reaches a maximum voltage in the charging of the battery by considering that a polarization voltage is increased due to an increase in internal impedance due to the deterioration of the battery. The method for charging a battery includes the steps of: supplying the charging current to the battery; blocking the supply of the charging current if the voltage detection value of the battery reaches a preset charging finish voltage; and performing an additional charging process by supplying the charging current until the voltage detection value of the battery reaches the charging finish voltage if the supply of the charging current is blocked and the voltage detection value of the battery is reduced below a preset critical voltage before a preset reference time elapses.

Description

[0001] METHOD AND SYSTEM FOR CHARGING BATTERY [0002]

The present invention relates to a battery charging method and system, and more particularly, to a battery charging method and system, and more particularly, to a battery charging method and system, And more particularly, to a battery charging method and system capable of increasing a charging capacity in a battery cell by additionally charging a battery again after a predetermined time elapses after shutting off.

Generally, a battery (or battery module) may include a plurality of battery cells connected in series. In such a battery, each battery cell may exhibit different degrees of deterioration during use due to various reasons such as a variation in the manufacturing process and a difference in application environment.

A battery cell having a high degree of deterioration has an increased internal impedance and accordingly a higher polarization voltage. The polarization voltage is a voltage generated when a current flows in the internal impedance. The larger the internal impedance or the larger the current flowing, the larger the polarization voltage.

In the case of charging a battery including a plurality of battery cells, since the charging current is supplied to the entire battery, voltages detected at the respective terminals are different in battery cells having different degrees of deterioration due to the difference in polarization voltage. A battery cell having a high degree of deterioration has a high internal impedance, so that a polarization voltage is higher than that of a battery cell having a low degree of deterioration, and the terminal voltage is also relatively high due to such a high polarization voltage.

The controller for controlling the charging of the battery determines the termination of the charging of the battery according to the result of detecting the terminal voltage of each battery cell. The battery cell having a high degree of deterioration first reaches the predetermined maximum charging voltage Accordingly, the battery cell having a low degree of deterioration has a problem that charging is stopped even though the battery cell still has a remaining charging capacity for charging. Even though the whole battery can store more energy, the charging is stopped and the capacity of the entire battery is reduced.

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.

KR 10-2013-0142807 A KR 10-2012-0091707 A

In view of the fact that the polarization voltage is increased due to an increase in internal impedance due to deterioration of the battery, the present invention prevents the supply of the charging current based on the battery cell having the largest voltage detection value at the time of charging the battery, And a battery charging method and system capable of increasing the charging capacity of the battery cell by charging the battery.

According to an aspect of the present invention,

Supplying a charging current to the battery;

Blocking the supply of the charging current when the voltage detection value of the battery reaches a predetermined charging end voltage;

When the voltage detection value of the battery decreases below a predetermined threshold voltage before the supply of the charging current is stopped and the predetermined reference time elapses, Supplying a current to further charge the battery;

And a battery charging method.

According to an embodiment of the present invention, when the voltage detection value of the battery is greater than the threshold voltage after the elapse of the reference time after the additional charging step, final charging of the battery may be terminated.

In an embodiment of the present invention, the additional charging may include: a controller for managing the battery wakes up at a predetermined time interval to detect the voltage of the battery and to compare the voltage detection value of the battery with the threshold voltage have.

In an embodiment of the present invention, the voltage detection value may be a voltage detection value detected in a battery cell having a maximum voltage among a plurality of mutually serially connected battery cells constituting the battery.

In an embodiment of the present invention, the charging current supplied to the battery in the additional charging step may have a value smaller than a charging current supplied to the battery in the supplying step.

According to an aspect of the present invention,

A voltage sensor for detecting a voltage of the battery;

A charger for supplying a charging current to the battery; And

And a controller for controlling the charging unit to adjust the charging current,

The controller stops supply of the charging current when the voltage detection value detected by the voltage sensor reaches a predetermined charging end voltage, and then, before the predetermined reference time elapses, The charging current is supplied to the battery charging system until the voltage detection value reaches the charging end voltage.

In one embodiment of the present invention, after the battery is further charged, the controller may finally end the charging of the battery if the voltage detection value after the elapse of the reference time is greater than the threshold voltage.

In an embodiment of the present invention, the controller may wake up at predetermined time intervals to compare the voltage detection value with the threshold voltage.

In one embodiment of the present invention, the controller can determine the reference time based on the number of times the wakeup is performed.

In one embodiment of the present invention, the battery includes a plurality of battery cells connected in series, and the voltage sensor is implemented in a plurality of detecting voltages of each of the plurality of battery cells, And may be a voltage detection value detected in a battery cell having a maximum voltage among battery cells.

In an embodiment of the present invention, the controller may adjust the charging current supplied to the battery when the battery is further charged to have a value smaller than a charging current supplied to the battery immediately before the charging.

According to the method and system for charging a battery having the above-described means for solving the above-mentioned problems, when the deteriorated battery cell included in the battery can not be sufficiently charged by the polarization voltage, after the priority charging is completed, The electric energy to be charged in the deteriorated battery cell can be maximized.

Accordingly, the battery charging method and system can maximize the charging capacity even in the case of an old battery, thereby preventing the fuel consumption of the vehicle from deteriorating.

1 is a block diagram showing a battery charging system according to an embodiment of the present invention.
2 is an equivalent circuit diagram of a battery cell included in a battery.
3 is a flowchart showing a battery charging method according to an embodiment of the present invention.
FIG. 4 is a diagram showing a comparison between a terminal voltage change during charging of a battery cell having a low degree of deterioration and a battery cell having a high degree of deterioration, and a voltage variation of the battery cell according to a battery charging method according to an embodiment of the present invention.

Hereinafter, a battery charging method and system according to various embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram showing a battery charging system according to an embodiment of the present invention.

Referring to FIG. 1, a battery charging system according to an embodiment of the present invention includes a battery 10 including a plurality of battery cells 11, a plurality of voltage detecting units (not shown) The charging current i supplied from the charger 30 to the battery 10 is controlled by controlling the sensor 12 and the charger 30 and the charger 30 that provide the charging current i to the battery 10 And a controller 20 for controlling the operation of the apparatus.

The battery 10 is also commonly referred to as a battery module, and may include a plurality of battery cells 11 connected in series. The charging current i supplied from the charger 30 can be supplied to the battery 10 to charge each of the plurality of cells 11 and the charging state SoC Charge increases as the voltage increases.

2 is an equivalent circuit diagram of the battery cell 11 included in the battery 10. 2 is an equivalent circuit diagram considering the electrical characteristics of a lithium ion battery cell. The lithium ion battery cell has an open circuit voltage (OCV) (Ve) and a polarization voltage (Ve, Vp) due to internal impedance, As shown in FIG. That is, the terminal voltage (measured voltage: Vt) of the lithium ion battery cell according to the equivalent circuit diagram shown in FIG. 2 can be expressed by Equation (1).

[Formula 1]

Vt = Ve + Vi + Vp

Since the polarization voltage is generated only when current flows, the terminal voltage of the battery cell becomes equal to the open circuit voltage (Vt = Ve) under the condition that no current flows. That is, the open circuit voltage is a value indicating the energy capacity of the actual battery cell.

On the other hand, in the case where the current (i) flows, equation (1) can be expressed by the following equations (2) and (3).

[Formula 2]

Vt = Ve + i * Ri + i * (composite impedance of RC circuit)

[Formula 3]

)와 전류(i)에 의해 실제로 에너지를 제공할 수 있는 전압이 아닌 분극 전압이 발생하게 된다. 이 분극전압은 전류(i)가 크고 내부 임피던스(

)가 클수록 더 큰 값을 갖게 된다.That is, the internal impedance of the battery cell (

) And the current (i) cause a polarization voltage that is not a voltage that can actually provide energy. This polarization voltage has a large current (i) and an internal impedance (

The larger the value, the greater the value.

When the battery is charged, the current (i) flows through the battery cell, so that the polarization voltage due to the internal impedance is necessarily generated. The voltage detected at the terminal of the battery cell by the polarization voltage has a value larger than the open circuit voltage Ve corresponding to the actual usable energy and the detection voltage of the battery cell is provided to the controller 20. [

The controller 20 controls the charging in consideration of the detection voltage including the polarized voltage, so that the charging can be stopped in a state in which sufficient energy is not charged in the actual battery cell.

The voltage of the battery cell has a value corresponding to the charging target voltage at the time when charging is stopped, but the voltage due to the internal impedance (particularly, the capacitor Cdl) disappears with the lapse of time, and the terminal voltage of the battery cell gradually decreases And converges to the open circuit voltage Ve.

As the chargeable and dischargeable battery cells are repeatedly charged, the internal impedance is increased due to ion precipitation due to the generation of impurities, and the actual energy storage capacity is reduced. That is, as the deterioration of the battery cell is increased, the internal impedance is increased, and accordingly the polarization voltage (V _i + V _p ) due to the internal impedance during charging The value rises more rapidly as deterioration progresses.

In the process of charging the battery including the plurality of battery cells, the controller 20 determines the charge stop according to the maximum voltage among the terminal voltages of the plurality of battery cells. Therefore, when the deterioration degrees among the battery cells are different from each other, The charging states of the respective battery cells become different from each other.

That is, in a battery cell having a relatively low degree of deterioration, charging is terminated when the terminal voltage of the battery cell having the maximum voltage fails to reach the maximum value, that is, when charging is not sufficiently completed, When the voltage is extinguished, the low terminal voltage is reduced to the open circuit voltage, which may cause a disruption to the charge capacity to the user using the battery.

Therefore, it is necessary to reduce the influence of the decrease in the charging capacity due to the polarization voltage of the battery cell during charging and to terminate the charging while minimizing the terminal voltage difference according to the deterioration degree between the battery cells. The deviation can be solved.

The voltage sensor 12 may be installed at both ends of the battery cell 11 to detect the terminal voltage of the battery cell 11. [ The voltage detected by the voltage sensor 12 may be a voltage value including a polarization voltage due to the internal impedance of the battery cell 11. In this case,

The charger 30 may be understood as a concept of a charging system including various circuits as an element for providing the charging current i to the battery 10 and may be realized by controlling the size of the current i May be understood as the concept of a particular circuit within the charging system. That is, in various embodiments of the present invention, it should be understood that the charger 30 includes all elements capable of providing a charge current whose size is determined by the control of the controller 20. Circuit elements for outputting a current controlled in size by the controller 20 correspond to techniques known in the art, and a further detailed description thereof will be omitted.

The controller 20 receives the value of the terminal voltage of the battery cell 11 included in the battery 10 from the voltage sensor 12 and controls the magnitude of the charging current output from the charger 30 accordingly To the charger 30, the control signal for controlling the charging / In particular, in various embodiments of the present invention, the controller 20 determines whether or not the charging current is supplied and / or the charging current (or the charging current) according to the voltage detection value detected in each battery cell 11, i can be adjusted. The controller 20 can use the detected value of the charging current i detected using the current sensor 40 disposed at the output terminal of the charger 30 to adjust the magnitude of the charging current i.

The control techniques performed in the controller 20 will be more clearly understood from the description of the battery charging method according to one embodiment of the present invention.

FIG. 3 is a flowchart showing a method of charging a battery according to an embodiment of the present invention. FIG. 4 is a graph showing changes in terminal voltage during charging of a battery cell having a low degree of deterioration and a battery having a high degree of deterioration, FIG. 5 is a graph showing a comparison of voltage changes of a battery cell according to a battery charging method according to an embodiment of the present invention.

3, when the charging of the battery 10 is started, the controller 20 controls the charging device 30 to charge the charging current i to the battery 10, A step S11 of supplying the charging current i to the charger 30 by the controller 20 when the voltage detection value of the battery 10 reaches a preset charging end voltage When the voltage detection value of the battery 10 is decreased to a predetermined threshold voltage or less (S15) before the supply of the charging current is stopped and the preset reference time elapses (S13), the voltage of the battery 10 And a step (S11) of supplying the charging current by further charging until the detected value reaches the charging end voltage.

In this embodiment of the present invention, the voltage detection value of the battery 10 may use the largest value among the voltage detection values detected by the voltage sensor 12 provided in each of the plurality of battery cells 11. [ This is to prevent overcharging of the plurality of battery cells 11 connected in series, and it is determined whether or not the charging current i is supplied based on the battery cell having the largest voltage detection value.

On the other hand, as described above, since the internal impedance of the battery cell having a low degree of deterioration is small, the influence of the polarization voltage is small, and thus the magnitude of the terminal voltage gradually increases during charging in which the charging current is supplied. On the other hand, since a battery cell having a high degree of deterioration has a large internal impedance, when a current is supplied, the polarization voltage greatly increases, and the magnitude of the terminal voltage increases rapidly during charging.

The graph on the left side of FIG. 4 shows terminal voltage changes due to charging of battery cells having relatively low deterioration, and the middle graph shows terminal voltage changes due to charging of battery cells having a high deterioration degree.

4, in the case of a battery cell having a low degree of deterioration, when the terminal voltage rises to a predetermined threshold voltage and the supply of the charging current is interrupted, the threshold voltage and the open- . On the other hand, when the battery cell having a high degree of deterioration is simply charged as in the conventional case, the battery terminal voltage rapidly rises due to the internal impedance. Therefore, when the battery cell voltage detection value reaches the threshold voltage, The difference from the open-circuit voltage Ve of the battery cell is large. Accordingly, when the plurality of battery cells are charged together, the controller 20 determines the end of charging based on the battery cell having the maximum voltage detection value. Therefore, the battery cell having a relatively low deterioration degree is further raised to the open circuit voltage There is a problem that charging is stopped even though there is a possibility. Further, even in the case of a deteriorated battery cell, it is possible to store more power when the influence of the polarization voltage due to the internal impedance is excluded, but whether the battery is charged or not is determined based on the voltage detection value detected by the voltage sensor 12 So that the amount of charge is reduced. Furthermore, these problems reduce the charge capacity of the entire battery.

Therefore, in view of such a problem, the various embodiments of the present invention can prevent the charging current (i) from being supplied based on the battery cell having the largest voltage detection value at the time of battery charging, It is intended to be able to charge the battery cell with more power by charging the battery further.

To this end, as shown in the rightmost graph of Fig. 4, various embodiments of the present invention supply charge current (i) to battery 10 preferentially when battery charging is started, Charging of the charging current i is performed based on the maximum voltage detection value among the voltage detection values provided by the voltage sensor 12 that detects the voltage of each battery cell 11 (S11) (S12).

In step S12, the controller 20 first blocks the supply of the charging current (i) when the maximum voltage detection value reaches a predetermined charging end voltage (cell maximum voltage). If the maximum voltage detection value is decreased to a predetermined threshold voltage or less (S15) before the predetermined reference time A elapses (S14), the charger 30 is controlled for further charging so that the charging current (i) To be supplied to the battery (10). At this time, the threshold voltage is determined based on the state of charge (SOC) of the predetermined battery cell, and may be, for example, a value corresponding to the open circuit voltage Ve of the deteriorated battery cell.

To this end, the controller 20 periodically wakes up at a predetermined time interval after interrupting the supply of the charge current i (S14), and when the wakeup is performed, the voltage detected by the voltage sensor 12 It is possible to determine whether the maximum voltage detection value is reduced to a predetermined threshold voltage or less (S15).

On the other hand, the battery cell has a charge state-open circuit voltage relationship determined in advance by the battery cell manufacturer.

For example, this relationship may be as shown in the following table.

Open circuit voltage (V) Charging state (SOC) (%) 4.0 100 3.9 95 3.8 90 ... ... 2.1 5 2.0 0

The determination of whether the maximum voltage detection value is decreased to a predetermined threshold voltage or less in step S15 is based on the magnitude of the open circuit voltage depending on the charging state of the battery cell 11. [ For example, when the charging state (SOC) of the battery cell is reduced to a desired level during the stabilization of the battery cell by interrupting the supply of the charging current (i), the charging state The voltage detection value is further reduced than the corresponding value. Therefore, this threshold voltage can be appropriately determined in accordance with the charge state-open circuit voltage relationship determined beforehand in manufacturing the battery cell.

The controller 20 preferentially cuts off the supply of the charging current i and then stabilizes the internal impedance of the battery cell. As a result, the maximum voltage detection value decreases to a predetermined threshold voltage or less within a preset reference time In addition, even when the charging current i is supplied to the battery, the supply (i) of the additional charging current can be made until the maximum voltage detection value reaches a predetermined charging end voltage.

At this time, while the internal impedance of the battery cell 11 is regenerated, the voltage detection value of the battery cell 11 reaches the charge end voltage within a time earlier than the actual open circuit voltage rises, ), The open circuit voltage also rises more than when charging by the previous charge current. That is, as shown in the rightmost graph of FIG. 4, when the open-circuit voltage Ve2 of the battery cell charged by the charging current supply during the additional charging is larger than the open-circuit voltage Ve1 of the battery cell charged by the initial charging current supply Value.

In particular, upon further charging, the controller 20 may control the charger 30 to provide a charging current to the battery 10 having a magnitude less than the magnitude of the charging current provided upon its previous charging. As described above, the magnitude of the divided voltage determined by the internal impedance of the battery cell is almost proportional to the magnitude of the supplied current. Therefore, when the magnitude of the current is small, the magnitude of the divided voltage appears small, so that the influence of the divided voltage on the voltage detection value detected by the battery cell can be reduced. Since the time required for the additional charging is considerably shorter than the time required for the initial charging, if the charging current is reduced at the time of the additional charging, the battery cell can be charged with more power while minimizing the charging time delay.

The controller 20 may first interrupt the supply of the charging current and then compare the voltage detection value of the battery cell 11 with the threshold voltage at predetermined time intervals through periodic wakeup. In particular, since the controller 20 is woken up at predetermined time intervals, the elapsed time after the charge current interruption can be confirmed according to the number of wake-up times. That is, if the reference time for judging the additional charge is n (natural number) times of the wakeup period, the controller 20 determines that the maximum voltage detection value is lower than the threshold voltage when the wake- The charger can be controlled to initiate an additional charge. On the other hand, if the maximum voltage detection value exceeds the threshold voltage when the controller wakes up more than n times after the interruption of the charge current, the controller finally terminates the charging of the battery and informs the driver I can notify you.

As described above, according to various embodiments of the present invention, when the deteriorated battery cell included in the battery can not be sufficiently charged due to the polarization voltage, the battery cell is stabilized after the first charge is completed, The electric energy to be charged into the battery cell can be maximized.

Accordingly, the various embodiments of the present invention can maximize the charging capacity even in the case of a battery having a long usage period, thereby preventing a fuel efficiency deterioration of the vehicle.

Although the present invention has been shown and described with respect to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as hereinafter claimed It will be apparent to those of ordinary skill in the art.

10: Battery 11: Battery cell
12: voltage sensor 20: controller
30: charger 40: current sensor

Claims (11)

Supplying a charging current to the battery;
Blocking the supply of the charging current when the voltage detection value of the battery reaches a predetermined charging end voltage;
When the voltage detection value of the battery decreases below a predetermined threshold voltage before the supply of the charging current is stopped and the predetermined reference time elapses, Supplying an electric current to further charge the battery,
Wherein the magnitude of the charging current supplied to the battery in the additional charging step is smaller than the magnitude of the charging current supplied to the battery in the supplying step. The method according to claim 1,
Further comprising ending charging of the battery if the voltage detection value of the battery is greater than the threshold voltage after the reference time elapses after the additional charging step. The method according to claim 1,
Wherein the additional charging step includes the step of waking up the controller managing the battery at a predetermined time interval to detect the voltage of the battery and comparing the voltage detection value of the battery with the threshold voltage How to charge the battery. The method according to any one of claims 1 to 3,
Wherein the voltage detection value is a voltage detection value detected in a battery cell having a maximum voltage among a plurality of mutually serially connected battery cells constituting the battery. delete A voltage sensor for detecting a voltage of the battery;
A charger for supplying a charging current to the battery; And
And a controller for controlling the charging unit to adjust the charging current,
The controller stops supply of the charging current when the voltage detection value detected by the voltage sensor reaches a predetermined charging end voltage, and then, before the predetermined reference time elapses, The charging current is supplied and charged further until the voltage detection value reaches the charging end voltage,
Wherein the controller adjusts the magnitude of the charging current supplied to the battery when the battery is further charged to have a value smaller than the magnitude of the charging current supplied to the battery immediately before the charging. The system of claim 6,
Wherein after the battery is further charged, if the voltage detection value after the elapse of the reference time is greater than the threshold voltage, charging of the battery is terminated. The method of claim 6,
Wherein the controller wakes up at a predetermined time interval to compare the voltage detection value with the threshold voltage. The method of claim 8,
Wherein the controller determines the reference time based on the number of wake-up times. The method according to any one of claims 6 to 9,
Wherein the battery includes a plurality of battery cells connected in series and the voltage sensor is implemented as a plurality of detectors for detecting a voltage of each of the plurality of battery cells,
Wherein the voltage detection value is a voltage detection value detected in a battery cell having a maximum voltage among the plurality of battery cells. delete

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