KR20180031206A - Battery management system and method for protecting a battery from over-discharge - Google Patents

Abstract

The present invention relates to a battery management system, a battery pack, and a battery charging method. A battery management system according to an embodiment of the present invention includes a sensing unit including a voltage sensor for measuring a voltage of a battery module; And a control unit configured to determine whether or not the battery module is overdischarged based on the measured voltage, and output a discharge cutoff signal when it is determined that the battery module is in an overdischarge state. The control unit determines a reference voltage and a reference time based on the SOH of the battery module, and determines that the battery module is in an overdischarge state when the measured voltage is maintained for the reference time less than the reference voltage .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery management system and a battery management system for protecting a battery from over-

The present invention relates to a battery management system and a battery pack, and more particularly, to a battery management system and method for protecting a battery from over discharge.

2. Description of the Related Art In recent years, demand for portable electronic products such as notebook computers, video cameras, and portable telephones has rapidly increased, and electric vehicles, storage batteries for energy storage, robots, and satellites have been developed in earnest. Researches are being actively conducted.

Among the commercially available batteries, there are nickel cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium secondary batteries. Among them, lithium batteries have almost no memory effect compared with nickel-based batteries, It is very popular because it has very low energy density.

SOH (State Of Health) is a parameter that quantitatively represents the change in capacity as a battery is used. Such an SOH can generally be expressed as a percentage of full capacity to design capacity. The full charge capacity represents the maximum amount of charge the battery can actually accommodate and is distinct from the fixed value design capacity in that the number of charge and discharge cycles of the battery increases and gradually decreases as the battery ages.

There are many ways to estimate SOH. For example, there is a method of estimating the SOH using the internal resistance and temperature of the battery, a method of estimating the SOH through the full discharge test, and the like.

SOH can be used as an indicator of how much the capacity of the battery has decreased compared to the initial design capacity, that is, how much battery life is left. For example, the user can confirm the replacement timing of the battery by referring to the SOH of the battery notified to the external device.

On the other hand, as the time for which the battery is maintained in the over-discharge state becomes longer, a dendrite grows between the positive electrode plate, the negative electrode plate, or both of the battery. The separator is damaged by the dendrite, and the positive electrode plate and the negative electrode plate are short- An explosion phenomenon may occur.

A number of prior art techniques for protecting the battery from over discharge have been disclosed and most conventional techniques employ a method of determining whether the battery is in an overdischarged state simply by comparing the voltage of the battery with a predetermined threshold . If it is determined that the battery is in an overdischarge hazard state, by blocking the electrical connection between the battery and the load, it is possible to some extent prevent the above-mentioned problem in the event of overdriving of the battery.

However, as the SOH of the battery decreases, the discharge termination voltage, which is the voltage of the battery when the SOC (State Of Charge) is 0%, has an increasing characteristic. However, according to the prior art, It is judged whether or not the battery is overdischarged, so that the accuracy of the judgment is inevitably lowered. The inventor of the present invention has found that it is necessary to appropriately adjust the value of voltage as a reference for comparison in order to determine whether the battery is in an overdischarge state in accordance with the SOH of the battery.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a battery management apparatus and a battery management method for controlling a value of a voltage and / or a time as a reference for determining whether a battery is in an over- System, and method.

Other objects and advantages of the present invention will become apparent from the following description, and it will be understood by those skilled in the art that the present invention is not limited thereto. It is also to be understood that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations thereof.

A battery management system according to an aspect of the present invention includes: a sensing unit including a voltage sensor for measuring a voltage of a battery module; And a control unit configured to determine whether or not the battery module is overdischarged based on the measured voltage, and output a discharge cutoff signal when it is determined that the battery module is in an overdischarge state. The control unit determines a reference voltage and a reference time based on the SOH of the battery module, and determines that the battery module is in an overdischarge state when the measured voltage is maintained for the reference time less than the reference voltage .

Also, the control unit may gradually increase the reference voltage as the SOH of the battery module decreases.

Also, the control unit may gradually decrease the reference time as the SOH of the battery module decreases.

The memory further stores a first lookup table indicating a plurality of reference voltages and reference times associated with each of a plurality of predetermined SOH intervals. In this case, the control unit may determine the reference voltage and the reference time associated with the SOH of the battery module by referring to the first lookup table.

The sensing unit may further include a temperature sensor for measuring a temperature of the battery module. The control unit may correct at least one of the reference voltage and the reference time based on the measured temperature.

In addition, the memory may store a second lookup table indicating a plurality of weights associated with each of a plurality of predetermined temperature intervals. In this case, the controller may refer to the second look-up table to select a weight associated with the measured temperature, and to use the selected weight to correct at least one of the reference voltage and the reference time.

In addition, when it is determined that the battery module is in an overdischarge state, the controller may output an alarm signal together with the discharge cutoff signal.

According to another aspect of the present invention, there is provided a battery pack comprising: the battery management system; And a battery module electrically connected to the battery management system.

According to another aspect of the present invention, there is provided an over-discharge protection method comprising: estimating an SOH of a battery module; Determining a reference voltage and a reference time for determining whether the battery module is overdischarged based on the estimated SOH; Determining whether the voltage of the battery module is lower than the reference voltage; Determining whether the voltage of the battery module is maintained below the reference voltage for the reference time; And performing a predetermined overdischarge protection operation when the voltage of the battery module is maintained below the reference voltage for the reference time or more.

The reference voltage and the reference time may be determined by referring to a lookup table representing a plurality of reference voltages and reference times associated with each of a plurality of predetermined SOH intervals, Time can be determined.

According to at least one of the embodiments of the present invention, it is possible to adjust the value of voltage and / or time as a reference for determining whether or not the battery is in an overdischarge state according to the SOH of the battery. As a result, the risk of explosion due to overdischarge can be reduced as compared with the above-described prior arts.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention. And should not be construed as limiting.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a functional configuration of a battery management system and a battery pack including the same according to an embodiment of the present invention; FIG.
FIG. 2 and FIG. 3 are graphs that are referred to in explaining an operation of the battery management system according to an embodiment of the present invention to separately adjust the reference voltage and the reference time based on the SOH of the battery module.
FIG. 4 and FIG. 5 are graphs that are referred to in explaining the operation of the battery management system according to another embodiment of the present invention to individually adjust the reference voltage and the reference time based on the SOH of the battery module.
6 and 7 are graphs that are referred to in explaining the operation of the battery management system 100 according to another embodiment of the present invention to individually adjust the reference voltage and the reference time based on the SOH of the battery module.
FIG. 8 shows a look-up table referred to by the battery management system according to another embodiment of the present invention for adjusting the reference voltage and the reference time according to the SOH of the battery module.
FIG. 9 shows a look-up table referenced by a battery management system according to another embodiment of the present invention for correcting a reference voltage and / or a reference time according to the SOH of the battery module.
10 is a flow chart illustrating a method of protecting a battery from over discharge, in accordance with an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise. In addition, the term " control unit " as described in the specification means a unit for processing at least one function or operation, and may be implemented by hardware or software, or a combination of hardware and software.

In addition, throughout the specification, when a portion is referred to as being "connected" to another portion, it is not necessarily the case that it is "directly connected", but also "indirectly connected" .

Hereinafter, a battery management system and a battery pack according to an embodiment of the present invention will be described.

FIG. 1 is a schematic view of a functional configuration of a battery management system 100 and a battery pack 1 including the same according to an embodiment of the present invention. Referring to FIG. In FIG. 1, the communication lines for data transmission and reception are indicated by dotted lines, and the power lines for charging and discharging are indicated by solid lines.

Referring to FIG. 1, a battery pack 1 includes a battery module 10, a charge / discharge circuit 20, and a battery management system 100.

The battery module 10 may include a plurality of battery cells connected in series or in parallel with each other. Of course, the battery module 10 may be composed of only one battery cell. At this time, the type of the battery cell is not particularly limited, and it can be constituted by a secondary cell such as a rechargeable lithium ion cell, a lithium polymer cell, a nickel cadmium cell, a nickel hydrogen cell, and a nickel zinc cell. It is obvious that the number of batteries included in the battery module 10 can be variously changed according to the voltage, current, capacity, or the like required for the battery module 10.

The charging and discharging circuit 20 may include a charging unit 21 for charging the battery module 10 and a discharging unit 22 for discharging the battery module 10. The charge / discharge circuit 20 may be configured to selectively perform a charging operation and a discharging operation for the battery module 10. The charging unit 21 converts the power supplied from the external device 2 into a form required for the battery module 10, and supplies the converted power to the battery module 10. Conversely, the discharger 22 may convert the power supplied from the battery module 10 into a form required by the external device 2, and then supply the converted power to the external device 2. [ The external device 2 may be a charger or a load that consumes power.

For example, the charging unit 21 and the discharging unit 22 are configured to be capable of adjusting the voltage and current supplied to the battery module 10 or supplied from the battery module 10 in response to the PWM signal output from the controller 120, respectively (E.g., a MOSFET) that can be turned on or off.

The battery management system 100 is electrically connected to the battery module 10 and the charge / discharge circuit 20. For example, the battery management system 100 may be interconnected through a CAN (Controller Area Network) with the battery module 10 and the charge / discharge circuit 20.

The battery management system 100 measures and manages the overall state of the battery module 10 in order to ensure the safety and reliability of the battery module 10. The battery management system 100 measures and manages the overall state of the battery module 10, And is configured to control operations individually. The control operation performed by the battery management system 100 can be largely divided into a thermal control operation for cooling the battery module 10 and a charge state control operation.

Specifically, the battery management system 100 monitors the state (e.g., voltage, current, and temperature) of the battery module 10 in real time or periodically to keep the battery module 10 in an optimal state, When an abnormality of the electronic device 10 or other electronic parts electrically connected thereto is detected, a signal for informing the external device 2 of the abnormality can be outputted. Of course, it is obvious that it is possible to output a signal for individually starting or stopping the charging operation and the discharging operation for the battery module 10.

Particularly, the battery management system 100 can perform a battery protection function that prevents overcharge when the battery is charged and prevents over discharge when the battery is discharged.

The battery management system 100 basically includes a sensing unit 110 and a control unit 120. Optionally, the battery management system 100 may additionally include a cell balancing module.

The sensing unit 110 is basically configured to measure the voltage and current of each battery cell included in the battery module 10 and / or the battery module 10. [ The sensing unit 110 may be configured to further measure the temperature of the battery module 10 according to its implementation.

The sensing unit 110 includes a current sensor for measuring a current flowing through the battery module 10, a voltage sensor for measuring a terminal voltage between the positive and negative electrodes of the battery module 10, A temperature sensor may be included.

The current sensor can measure the charging current of the battery module 10 while the charging process of the battery module 10 is in progress. Also, the current sensor can measure the current rate based on the charging / discharging current of the battery module 10. [ The charging / discharging rate, also referred to as the C-rate, is expressed as a value obtained by dividing the discharging current or the charging current by the value of the design capacity (capacity) minus the unit. At this time, the design capacity may be a predetermined value at the time of manufacturing the battery module 10.

For example, if the full charge capacity of the battery module 10 is 1000 mAh (Apere-hour), the charge / discharge rate is 0.1 C if the charge current is 100 mA, the charge / discharge rate is 1 C if the charge current is 1000 mA, The charge / discharge rate can be measured at 5C.

The sensing unit 110 may repeatedly measure the current, the voltage, and the temperature of the battery module 10 every predetermined period. The measurement period for any one of the current, the voltage, and the temperature may be the same or different from the measurement period for the remainder can do.

The control unit 120 controls the overall operation of the battery management system 100. For example, the control unit 120 may execute software for at least one of measurement of voltage, current and temperature of the battery module 10, SOC calculation, SOH estimation, cell balancing, temperature management and overcharge and overdischarge determination. On the other hand, the technique for estimating the SOH based on the voltage, current, temperature, cumulative use time, etc. of the battery is well known in the art, and a detailed description thereof will be omitted.

The controller 120 may be implemented in hardware as application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays Processors, microprocessors, and other electronic units for performing other functions.

The control unit 120 may include a memory 121. The memory 121 may store various data commands and software required for the overall operation of the battery management system 100. The control unit 120 may refer to data and instructions stored in the memory 121 or may drive software to output a signal for controlling the operation of the charging and discharging circuit 20. [

The memory 121 may be a flash memory type 121, a hard disk type, an SSD type, a SDD type, a multimedia card type, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read- a memory, and a storage medium of at least one type.

1, one of the components of the battery pack 1 or the battery management system 100 is shown connected to the other through at least one connection line (i.e., a communication line or a power line) . It should be understood, however, that this is merely exemplary and that the actual implementation among the components of the battery management system 100 is not limited to the connection lines shown in FIG.

In addition, the battery management system 100 may have fewer components than those listed above, or may be further configured to include additional components not listed above.

Hereinafter, the reference voltage and the time for determining whether the battery module 10 is over-discharged for each SOH will be referred to as "reference voltage" and "reference time", respectively. For example, the controller 120 of the battery management system 100 determines that the battery module 10 is in the overdischarged state when the time when the voltage of the battery module 10 is continuously maintained below the reference voltage reaches the reference time . At this time, the control unit 120 may count the time from when the voltage of the battery module 10 reaches the reference voltage until the holding time reaches the reference time. A state in which the voltage of the battery module 10 is lower than the reference voltage and the time when it is maintained does not reach the reference time may be referred to as an " overdischarge suspected state ".

If the voltage of the battery module 10 is higher than the reference voltage, the battery module 10 is not determined to be in an overdischarge state regardless of the reference time.

The reference voltage and the reference time are adjusted by the battery management system 100 according to the SOH. The values of the reference voltage and the reference time adjusted for each SOH of the battery module 10 may be determined in advance through a preliminary experiment and stored in the memory 121. [ For example, while the SOH of the test module, which is another battery module having the same specification as that of the battery module 10, is changed, the discharge end voltage is periodically recorded and based on the recorded values of the discharge end voltage, ) Can be predetermined in advance.

The SOH-specific reference time may be set such that a characteristic change amount (e.g., a temperature change amount, a gas generation amount) due to the electrochemical reaction of the test module from a first time when the voltage of the test module reaches the discharge end voltage corresponding to the SOH reaches a predetermined threshold value Can be determined in advance on the basis of the result of measuring the time until reaching the predetermined time. For example, at any SOH, the temperature is periodically measured while maintaining the voltage of the test module at the discharge termination voltage associated with the SOH, and based on the time it takes for the measured temperature to increase by a predetermined amount , The reference time corresponding to the corresponding SOH can be determined.

Data representing the reference voltage and the reference time associated with each of the various SOHs may be designed in the form of a lookup table and stored in advance in the memory 121. [ For example, when the total range of SOH is from 0% to 100%, the reference voltage and the reference time can be predetermined for each 100 SOHs in units of 1%.

The control unit 120 may calculate the SOH of the battery module 10 in a predetermined period and acquire data indicating the reference voltage and reference time associated with the calculated SOH from the memory 121. [

In this case, when the SOH of the battery module 10 estimated at a specific point in time is located between two adjacent predetermined values, the controller 120 uses the interpolation method to calculate the reference value corresponding to the SOH of the battery module 10 At least one of the voltage and the reference time may be obtained.

Hereinafter, it is assumed that the initial values of the reference voltage and the reference time for determining whether the battery module 10 is overdischarged are V _i and T _i , respectively.

2 and 3 are graphs that are referred to in explaining the operation in which the battery management system 100 according to the embodiment of the present invention individually adjusts the reference voltage and the reference time based on the SOH of the battery module 10. [ to be.

2 and 3, BOL (Life Of Life), MOL (Middle Of Life) and EOL (End Of Life) are obtained by dividing the life of the battery module 10 according to predetermined rules, The reference voltage of the battery module 10 gradually increases and the reference time gradually decreases according to the order of Beginning Of Life, MOL (Middle Of Life), and EOL (End Of Life). At this time, the BOL and the MOL may be separated by the boundary of the first classification value S1, the MOL and EOL may be separated by the boundary of the second classification value S2. The first classification value S1 and the second classification value S2 may be pre- And may be a value that can be appropriately changed by a user or the like. Of course, in some cases, the SOH of the battery module 10 can be divided into fewer or more sections.

The data indicating the correlation between the SOH and the reference voltage as shown in FIG. 2 and the data indicating the correlation between the SOH and the reference time as shown in FIG. 3 may be stored in the memory 121 in advance.

In FIGS. 2 and 3, the slope of the reference voltage and the reference time follow the SOH in a straight line, but this is schematically shown for the sake of understanding only, and the scope of the present invention is not limited thereto. That is, as the SOH decreases, the reference voltage may increase linearly or nonlinearly, and the reference time may decrease linearly or nonlinearly.

When the reference voltage and / or the reference time for determining whether the battery module 10 is overdischarged is a constant value regardless of the SOH, that is, when the reference voltage and / or the reference time are held as initial values V _i and T _i , respectively, ) May cause various problems in terms of charge / discharge efficiency and safety.

For example, assume that the reference voltage for determining whether or not the over-discharge of the battery module 10 in Figure 2 is fixed to V _i. If, when the SOH of the battery module 10, S1, discharge end voltage of the battery module 10 will be greater than V _i. However, the since the voltage V _m1 of the battery module 10 has not been reached, the V _i, even if they already reach the discharge end voltage, voltage V _m1 of the battery module 10 in SOH is S1 is maintained below the discharge end voltage time The control unit 120 does not determine that the battery module 10 is in the overdischarge state.

As another example, assume that the reference time for determining whether the battery module 10 is overdischarged is fixed to T _i in FIG. If the voltage V _m2 of the battery module 10 measured at any point of time when the SOH of the battery module 10 is S1 is equal to or lower than V _i and the continuously held time is shorter than T _i , The controller 120 does not determine that the battery module 10 is in the overdischarged state.

According to the above two examples, even when the battery module 10 is already in the overdischarge state, the battery module 10 is continuously discharged to shorten the service life of the battery module 10, Irreversible damage may occur and the risk of explosion may increase.

The control unit 120 of the battery management system 100 may appropriately adjust the reference voltage and / or the reference time for determining over-discharge based on the SOH of the battery module 10. [ Thus, it is possible to alleviate the above-mentioned problems of the manner in which the reference voltage and / or the reference time for determining overdischarge are maintained as V _i and T _i , respectively, regardless of the SOH.

For example, when the SOH of the battery module 10 is S1, the reference voltage for overdischarge determination is adjusted to be V ₁ higher than V _i . If, because the voltage V _m1 of the battery module 10 is higher than Vi V not more than _1, the control part 120 according to the time maintained by V _m1 ≤ V _1, which is determined that the battery module 10 in the over-discharge state It is possible.

As another example, when the SOH of the battery module 10 is S2, the reference voltage is adjusted to V ₂ higher than V ₁ , and the reference time is adjusted to T ₂ shorter than T _i . Accordingly, when the voltage of the battery module 10 is kept lower than V ₂ for the reference time T ₂ , the controller 120 can determine that the battery module 10 is in the over-discharge state.

4 and 5 are graphs that are referred to in explaining the operation in which the battery management system 100 according to another embodiment of the present invention individually adjusts the reference voltage and the reference time based on the SOH of the battery module 10. [ to be.

Referring to FIG. 4, the controller 120 may adjust the reference voltage in a stepwise manner according to the SOH of the battery module 10. This is different from the method of continuously adjusting the reference voltage in the embodiment described above with reference to Fig.

Specifically, the controller 120 may divide the entire range of the SOH into at least two intervals, maintain the reference voltage constant during each interval, and increase the reference voltage from the point at which it is switched to another interval.

For example, as shown, the full range of SOH BOL, MOL and if divided into three sections of EOL, the BOL the while kept the same reference voltage from the initial value V _i MOL higher reference voltage than V _i V ₁₁ . Thereafter, the reference voltage is further raised to V ₁₂ in the EOL.

Referring to FIG. 5, the controller 120 may adjust the reference time according to the SOH of the battery module 10 in a stepwise manner. This is different from the method of continuously adjusting the reference time in the embodiment described above with reference to Fig.

Specifically, the control unit 120 may classify the entire range of the SOH into at least two intervals, maintain the reference time constant during each interval, and reduce the reference time from the point of time of switching to another interval.

For example, in the As illustrated, a full range of SOH when the classification into the three sections of the BOL, MOL and EOL, BOL the while kept the same reference voltage from the initial value T _i MOL shorter the reference time than T _i T ₁₁ . Then, the reference time is further shortened to T ₁₂ in the EOL.

According to the embodiment described above with reference to Figs. 4 and 5, since the reference voltage and / or the reference time are kept constant while the SOH of the battery module 10 is in the common section, It is possible to realize a function of preventing over discharge while reducing the amount of calculation required for changing the reference voltage and / or reference time from time to time.

4 and 5, the entire range of the SOH is divided into three sections of BOL, MOL, and EOL. However, the number of sections and their widths can be freely changed as needed .

6 and 7 are diagrams for explaining the operation in which the battery management system 100 according to another embodiment of the present invention individually adjusts the reference voltage and the reference time based on the SOH of the battery module 10 Graph.

Referring to FIG. 6, the controller 120 may classify the entire range of the SOH into at least two intervals, and change the control method of the reference voltage when switching from one interval to the next interval. The control unit 120 may adjust the reference voltage by combining the above-described method with reference to FIG. 2 and the method described above with reference to FIG.

For example, as shown in the figure, when the entire range of the SOH is classified into three sections of BOL, MOL and EOL, the control section 120 continuously increases the reference voltage from the V _i in the BOL, and V _Lt ; RTI ID = 0.0 > _{21. &} Lt; / RTI & Then, the control unit 120 may increase the reference voltage in the EOL back continuously from V _21.

Referring to FIG. 7, the controller 120 classifies the entire range of the SOH into at least two intervals, and when the interval is switched from one interval to the next interval, the control unit 120 can change the adjusting method of the reference time. The control unit 120 may adjust the reference voltage by combining the above-described method with reference to FIG. 3 and the method described above with reference to FIG.

For example, as shown in the figure, when the entire range of the SOH is classified into three sections of BOL, MOL and EOL, the controller 120 keeps the reference time at the BOL equal to the initial value T _i , The time can be continuously reduced from T ₂₁ shorter than T _i . Then, the control unit 120 may maintain a reference time T ₂₂ to the short end than the reference time of the MOL EOL.

Of course, the graphs of the reference voltage and the reference time according to the SOH shown in FIGS. 6 and 7 are illustrative, and the waveforms shown in the respective graphs can be variously set.

FIG. 8 shows a look-up table referred to by the battery management system 100 according to another embodiment of the present invention to adjust the reference voltage and the reference time according to the SOH of the battery module 10. FIG. As described above, the look-up table can be stored in the memory 121 in advance.

Referring to FIG. 8, the look-up table L1 may be written with data representing a plurality of reference voltages and reference times associated with each of a plurality of predetermined SOH intervals.

Assuming that the total range of SOH is 0 to 100%, it is assumed that the SOH is divided into 20 sections with 5%. In this case, in the look-up table L1, a plurality of reference voltages associated with each of a total of 20 intervals classified can be recorded. In other words, the number of reference voltages recorded in the look-up table L1 is also 20, and it can correspond one-to-one with 20 intervals.

In addition, the look-up table L1 may further record a plurality of reference times associated with each of the 20 intervals. The number of reference times recorded in the lookup table L1 is also 20, which can correspond one-to-one with 20 intervals.

When the SOH of the battery module 10 is estimated, the control unit 120 refers to the data recorded in the lookup table L1 to obtain one reference voltage and one reference time associated with the most recently estimated SOH have.

For example, when the SOH of the battery module 10 is estimated to be 90% , the controller 120 can select 3.20 V and 180 seconds among the reference voltages and reference times recorded in the look-up table L1 . If the SOH of the battery module 10 is estimated to be 50% after the aging of the battery module 10 is advanced, the controller 120 reads a plurality of reference voltages recorded in the lookup table L1, , 3.30V and 150 seconds can be selected. It should be noted that as the SOH of the battery module 10 becomes lower, the reference voltage selected by the controller 120 becomes higher and the reference time becomes shorter.

The control unit 120 can directly use the reference voltage and / or the reference time obtained from the lookup table L1 to determine whether the battery module 10 is overdischarged. Alternatively, the control unit 120 may correct the selected reference voltage and / or the reference time according to the temperature of the battery module 10. This will be described later with reference to FIG.

9 shows a look-up table referred to when the battery management system 100 according to another embodiment of the present invention is referred to for correcting the reference voltage and / or reference time according to the SOH of the battery module 10. [

Referring to FIG. 9, the lookup table L2 may be a set of data representing a plurality of predetermined temperature intervals and a plurality of weights associated with each temperature interval. The lookup table L2 may be stored in advance in the memory 121 like the lookup table L1.

Specifically, the number of temperature intervals recorded in the lookup table L2 and the number of weights are the same and can be corresponded one to one.

The control unit 120 may refer to the lookup table L2 to select one weight among the plurality of weights related to the temperature interval to which the temperature of the battery module 10 measured by the temperature sensor belongs. At this time, the point of time when the SOH of the battery module 10 is estimated and the point of time when the weight is selected can be synchronized.

Assume that other conditions except the temperature of the battery module 10 are common and constant. The higher the temperature of the battery, the more active the electrochemical reaction in the battery. As a result, even if there is no change in the SOC and the SOH of the battery module 10, the voltage of the battery module 10 can be increased as the temperature of the battery module 10 increases. Therefore, the look-up table L2 can be designed such that the temperature interval having a relatively high value is associated with a relatively small weight. It is possible to correct the reference voltage and the reference time obtained from the lookup table L1 appropriately using the weight obtained from the lookup table L2 to improve the accuracy of the determination as to whether overdischarge is caused.

For example, suppose that the temperature measured by the temperature sensor at the time when the SOH of the battery module 10 is estimated at 90% is 47 ° C. In this case, the control unit 120 may acquire a reference voltage of 3.20 V and a reference time of 180 seconds from the look-up table L1 and obtain a weight of 0.90 from the look-up table L2. Then, the control unit 120 may apply the obtained weight 0.90 according to a predetermined rule to 3.20 V and / or 180 seconds to correct the reference voltage and / or the reference time obtained from the look-up table L1. For example, the control unit 120 may multiply the weight value 0.90 by the reference voltage 3.20 V and the reference time 180 seconds to calculate the corrected reference voltage 2.88 V and the corrected reference time 162 seconds. In this case, the control unit 120 can determine that the battery module 10 is in the over-discharge state only when the voltage of the battery module 10 whose SOH is 90% is maintained at 2.88 V or lower for 162 seconds or longer.

10 is a flow chart illustrating a method of protecting a battery from over discharge, in accordance with an embodiment of the present invention. The method shown in Fig. 10 may be performed by the control unit 120 of the battery management system 100 described above.

Referring to FIG. 10, in step S1010, the SOH of the battery module 10 is estimated. The SOH of the battery may be estimated on the basis of the voltage, current or temperature measured continuously or periodically for a predetermined time measured by the sensing unit 110 before the step S1010 is started.

In step S1020, a reference voltage and a reference time for determining whether the battery module 10 is overdischarged are determined based on the SOH estimated through the step S1010. As the SOH decreases, the controller 120 increases or decreases the first initial value (V _{i in} FIG. 2) and the second initial value (T _{i in} FIG. 3) according to a predetermined method, The reference voltage and the reference time can be adjusted accordingly.

Specifically, the control unit 120 can access the look-up table L1 to obtain the reference voltage and / or the reference time associated with the SOH of the battery module 10. [ When step S1020 is completed, step S1030 is performed.

In step S1030, it is determined whether the voltage of the battery module 10 has reached the reference voltage determined through step S1020. If the result of the determination in step S1030 is YES, step S1040 is started.

In step S1040, it is determined whether or not the time at which the voltage of the battery module 10 is kept below the reference voltage is equal to or longer than the reference time. That is, it is determined whether the battery module 10 is in an overdischarged state. If the result of the determination in step S1040 is YES, step S1050 is started.

In step S1050, execution of a predetermined over-discharge protection operation is instructed. Specifically, the over-discharge protection operation includes at least one of an output of the discharge cut-off signal and an output of the alarm signal.

When the control unit 120 outputs the discharge cutoff signal, the charge / discharge circuit 20 prevents the discharge of the battery module 10 from further proceeding in response to the charge cutoff signal. Thereafter, the charge / discharge circuit 20 can wait until the discharge resume signal is received from the control unit 120. [ When the control unit 120 outputs an alarm signal, the alarm signal can be transmitted to the external device 2 communicably connected to the battery pack 1. [ The external device 2 can output at least one of visual feedback, auditory feedback and tactile feedback in response to an alarm signal.

In the above-described embodiments, the reference voltage and the reference time are all adjusted in accordance with the change of the SOH. However, the scope of the present invention is not limited thereto. For example, either the reference voltage or the reference time may be fixed to an initial value regardless of the SOH, and the other may be adjusted according to the SOH.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative, The present invention is not limited to the drawings, but all or some of the embodiments may be selectively combined so that various modifications may be made.

1: Battery pack
10: Battery module
20: charge / discharge circuit
21:
22: discharge unit
100: Battery management system
110: sensing unit
120:
121: Memory

Claims (10)

A sensing unit including a voltage sensor for measuring a voltage of the battery module; And
And a control unit configured to determine whether the battery module is overdischarged based on the measured voltage and to output a discharge cutoff signal when it is determined that the battery module is in an overdischarge state,
Wherein,
Determining a reference voltage and a reference time based on SOH of the battery module,
And determines that the battery module is in an overdischarge state if the measured voltage is maintained for the reference time to be less than or equal to the reference voltage.
The method according to claim 1,
Wherein,
Wherein the reference voltage is gradually increased as the SOH of the battery module decreases.
3. The method of claim 2,
Wherein,
Wherein the reference time is gradually reduced as the SOH of the battery module decreases.
The method according to claim 1,
Further comprising a memory for storing a first lookup table indicating a plurality of reference voltages and reference times associated with each of a plurality of predetermined SOH intervals,
Wherein,
And determines a reference voltage and a reference time associated with the SOH of the battery module with reference to the first lookup table.
5. The method of claim 4,
The sensing unit includes:
Further comprising a temperature sensor for measuring a temperature of the battery module,
Wherein,
And corrects at least one of the reference voltage and the reference time based on the measured temperature.
6. The method of claim 5,
The memory comprising:
Storing a second lookup table representing a plurality of weights associated with each of a plurality of predetermined temperature intervals,
Wherein,
Referring to the second lookup table, selecting a weight associated with the measured temperature,
And corrects at least one of the reference voltage and the reference time using the selected weight.
The method according to claim 1,
Wherein,
And outputs an alarm signal together with the discharge cutoff signal when it is determined that the battery module is in an overdischarge state.
The battery management system according to any one of claims 1 to 7, And
A battery module electrically connected to the battery management system;
And a battery pack.
Estimating SOH of the battery module;
Determining a reference voltage and a reference time for determining whether the battery module is overdischarged based on the estimated SOH;
Determining whether the voltage of the battery module is lower than the reference voltage;
Determining whether the voltage of the battery module is maintained below the reference voltage for the reference time; And
Performing a predetermined over-discharge protection operation when the voltage of the battery module is maintained to be equal to or lower than the reference voltage for the reference time;
Wherein the battery module is detachably connected to the battery module.
10. The method of claim 9,
Wherein the step of determining the reference voltage and the reference time comprises:
Wherein the reference voltage and the reference time associated with the estimated SOH are determined by referring to a lookup table representing a plurality of reference voltages and reference times associated with each of a plurality of predetermined SOH intervals.

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