Patent Description:
The present disclosure relates to a battery diagnosis apparatus, method and system, and more particularly, to a battery diagnosis apparatus, method and system capable of diagnosing a state of a battery cell.

As the battery is degraded, side reactions accompanied by generation of internal gas occur. If the side reaction continues and the amount of internal gas exceeds an allowable value, the junction portion of the battery is opened, and the battery reaches an EOL (End Of Life) state.

Therefore, in order to diagnose the state of the battery, it is required to measure the internal gas amount, but in the prior art, which can be exemplified by <CIT> and <CIT>, it is difficult to measure the internal gas amount of the battery in a non-destructive manner.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a battery diagnosis apparatus, method and system, which may determine an internal gas generation level of a battery based on an ohmic resistance of the battery in a non-destructive manner and diagnose a state of the battery according to the determined internal gas generation level.

In one aspect of the present disclosure, there is provided a battery diagnosis apparatus, comprising: an ohmic resistance determining unit configured to determine an ohmic resistance of a battery cell in each of a plurality of impedance profiles generated at different time points for the battery cell; a resistance change rate calculating unit configured to calculate a resistance change rate between the plurality of determined ohmic resistances; a gas generation level determining unit configured to determine an internal gas generation level of the battery cell based on the calculated resistance change rate; and a state diagnosing unit configured to diagnose a state of the battery cell according to the determined internal gas generation level.

The gas generation level determining unit may be configured to determine an internal gas generation level of the battery cell based on a region to which the calculated resistance change rate belongs among preset reference change rate regions.

The reference change rate regions may be preset as a first region less than a first reference resistance change rate, a second region equal to or greater than the first reference resistance change rate and less than a second reference resistance change rate, and a third region equal to or greater than the second reference resistance change rate according to the internal gas generation level.

The gas generation level determining unit may be configured to determine that the internal gas generation level is normal when the calculated resistance change rate belongs to the first region, determine that the internal gas generation level is warning when the calculated resistance change rate belongs to the second region, and determine that the internal gas generation level is danger when the calculated resistance change rate belongs to the third region.

The state diagnosing unit may be configured to diagnose that the state of the battery cell is a normal state when the internal gas generation level is determined as normal.

The state diagnosing unit may be configured to diagnose that the state of the battery cell is a warning state when the internal gas generation level is determined as warning and reduce at least one of a maximum allowable temperature and a maximum allowable SOC.

The state diagnosing unit may be configured to diagnose that the state of the battery cell is an unusable state when the internal gas generation level is determined as danger.

The battery diagnosis apparatus according to another aspect of the present disclosure may further comprise: a measuring unit configured to measure at least one of temperature, voltage and current of the battery cell; and a SOC estimating unit configured to estimate an SOC of the battery cell based on at least one of the measured voltage and current.

The ohmic resistance determining unit may be configured to select at least one impedance profile satisfying a predetermined condition among the plurality of impedance profiles based on the temperature of the battery cell measured by the measuring unit and the SOC of the battery cell estimated by the SOC estimating unit.

The resistance change rate calculating unit may be configured to calculate the resistance change rate based on the impedance profile selected by the ohmic resistance determining unit.

The ohmic resistance determining unit may be configured to select an impedance profile in which the temperature of the corresponding battery cell is equal to or higher than a reference temperature and the SOC of the corresponding battery cell is equal to or greater than a reference SOC, among the plurality of impedance profiles.

The battery diagnosis apparatus according to still another aspect of the present disclosure may further comprise a charge transfer resistance determining unit configured to determine a charge transfer resistance in each of the plurality of impedance profiles.

The resistance change rate calculating unit may be configured to further calculate a charge transfer resistance change rate between the plurality of determined charge transfer resistances.

The state diagnosing unit may be configured to further diagnose the state of the battery cell based on a result of comparing the calculated charge transfer resistance change rate and a reference resistance value.

The state diagnosing unit may be configured to diagnose that the state of the battery cell is a normal state when the calculated charge transfer resistance change rate is less than the reference resistance value.

The state diagnosing unit may be configured to diagnose that the state of the battery cell is a warning state when the calculated charge transfer resistance change rate is equal to or greater than the reference resistance value and reduce a maximum allowable C-rate for charging and discharging of the battery cell.

A battery diagnosis system according to still another aspect of the present disclosure may comprise: the battery diagnosis apparatus according to an aspect of the present disclosure; and an EIS unit configured to output an AC current to the battery cell, generate an impedance profile representing an impedance of the battery cell according to an output result of the AC current as a corresponding relationship between a real part and an imaginary part, and output the generated impedance profile to the battery diagnosis apparatus.

The battery diagnosis system according to still another aspect of the present disclosure may further comprise: a heating unit configured to increase temperature of the battery cell such that the temperature of the battery cell becomes equal to or higher than a reference temperature; and a charging unit configured to charge the battery cell such that a SOC of the battery cell becomes equal to or greater than a reference SOC.

A battery pack according to still another aspect of the present disclosure may comprise the battery diagnosis apparatus according to an aspect of the present disclosure.

A battery diagnosing method according to still another aspect of the present disclosure may comprise: an ohmic resistance determining step of determining an ohmic resistance of a battery cell in each of a plurality of impedance profiles generated at different time points for the battery cell; a resistance change rate calculating step of calculating a resistance change rate between the plurality of determined ohmic resistances; a gas generation level determining step of determining an internal gas generation level of the battery cell based on the calculated resistance change rate; and a state diagnosing step of diagnosing a state of the battery cell according to the determined internal gas generation level.

According to one aspect of the present disclosure, based on the correlation between the ohmic resistance of the battery cell and the internal gas generation level of the battery cell, there is an advantage that the internal gas generation level and state of the battery cell may be diagnosed in a non-destructive manner from the resistance change rate of the ohmic resistance of the battery cell.

<FIG> is a diagram schematically showing a battery diagnosing apparatus <NUM> according to an embodiment of the present disclosure.

Referring to <FIG>, the battery diagnosis apparatus <NUM> may include an ohmic resistance determining unit <NUM>, a resistance change rate calculating unit <NUM>, a gas generation level determining unit <NUM>, and a state diagnosing unit <NUM>.

The ohmic resistance determining unit <NUM> may be configured to determine an ohmic resistance (Ro) of a battery cell in each of a plurality of impedance profiles generated at different time points for the battery cell.

Here, the battery cell refers to one independent cell that has a negative electrode terminal and a positive electrode terminal and is physically separable. For example, one pouch-type lithium polymer cell may be regarded as the battery cell.

In addition, the impedance profile may be a profile in which the impedance of the battery cell is expressed as a corresponding relationship between a real part (Zre) and an imaginary part (-Zim). The impedance profile will be described in detail with reference to <FIG> and <FIG>.

<FIG> is a diagram schematically showing an impedance profile according to an embodiment of the present disclosure. Specifically, <FIG> is a diagram schematically showing an example of the impedance profile.

Referring to <FIG>, the impedance profile may be expressed as an X-Y plane graph when X is set as a real part (Zre) and Y is set as an imaginary part (-Zim). In the embodiment of <FIG>, the ohmic resistance of the battery cell may be a starting resistance value of the impedance profile. Specifically, in the impedance profile, the resistance value of the real part (Zre) when the value of the imaginary part (-Zim) is <NUM> may be the ohmic resistance of the battery cell. Since the ohmic resistance is a widely known factor, it should be noted that a description of the ohmic resistance will be omitted.

<FIG> is a diagram schematically showing a plurality of impedance profiles according to an embodiment of the present disclosure. Specifically, <FIG> is a diagram showing a plurality of impedance profiles obtained by the ohmic resistance determining unit <NUM>.

In the embodiment of <FIG>, the ohmic resistance determining unit <NUM> may obtain first to ninth impedance profiles P1 to P9. Preferably, the first to ninth impedance profiles P1 to P9 may be impedance profiles generated at different time points for one battery cell. For example, the first to ninth impedance profiles P1 to P9 are impedance profiles for impedances measured at intervals of <NUM> hours for one battery cell under the condition that temperature and SOC (State Of Charge) are included within a predetermined range. Here, preferably, the first impedance profile P1 may be generated first, and the ninth impedance profile P9 may be generated most recently.

In addition, in the embodiment of <FIG>, the ohmic resistance determining unit <NUM> may determine the ohmic resistance in each of the first to ninth impedance profiles P1 to P9. Specifically, the ohmic resistance determining unit <NUM> may determine a resistance value of the real part (Zre) when the value of the imaginary part (-Zim) is <NUM> in each of the first to ninth impedance profiles P1 to P9 as the ohmic resistance for the corresponding impedance profile. Preferably, in the embodiment of <FIG>, the ohmic resistance of the first impedance profile P1 may be smallest, and the ohmic resistance of the ninth impedance profile P9 may be largest.

The resistance change rate calculating unit <NUM> may be configured to calculate a resistance change rate between the plurality of determined ohmic resistances.

Specifically, the resistance change rate calculating unit <NUM> may calculate a resistance change rate between the plurality of ohmic resistances determined by the ohmic resistance determining unit <NUM>. Preferably, the resistance change rate calculating unit <NUM> may calculate a resistance change rate between the plurality of ohmic resistances in consideration of time points at which the plurality of impedance profiles are generated.

For example, in the embodiment of <FIG>, the resistance change rate calculating unit <NUM> may set the ohmic resistance of the first impedance profile P1 as a criterion and calculate a resistance change rate between the ohmic resistances of the first to ninth impedance profiles P1 to P9.

For example, it is assumed that the ohmic resistance of each of the first to nth impedance profiles is determined as Ro_1 to Ro_n by the ohmic resistance determining unit <NUM>. The resistance change rate calculating unit <NUM> may calculate a ratio of Ro_n to Ro_1 as a resistance change rate. In this case, the resistance change rate calculating unit <NUM> may calculate the resistance change rate by calculating the formula of "Ro_n ÷ Ro_1".

As another example, the resistance change rate calculating unit may calculate a ratio of a difference between Ro_n and Ro_1 with respect to Ro_1 as a resistance change rate. In this case, the resistance change rate calculating unit <NUM> may calculate the resistance change rate by calculating the formula of "(Ro_n - Ro_1) ÷ Ro_1".

The gas generation level determining unit <NUM> may be configured to determine an internal gas generation level of the battery cell based on the calculated resistance change rate. That is, the gas generation level determining unit <NUM> may determine the internal gas generation level of the battery cell based on the resistance change rate calculated by the resistance change rate calculating unit <NUM>.

Specifically, the gas generation level determining unit <NUM> may be configured to determine the internal gas generation level of the battery cell based on a region to which the calculated resistance change rate belongs among preset reference change rate regions.

For example, the reference change rate regions may be preset as a first region, a second region, and a third region. Hereinafter, it will be described that the reference change rate regions are set as the first to third regions, but it should be noted that the reference change rate regions may be set to be more subdivided.

Preferably, the reference change rate regions may be configured to be preset according to the internal gas generation level as a first region less than a first reference resistance change rate, a second region equal to or greater than the first reference resistance change rate and less than a second reference resistance change rate, and a third region equal to or greater than the second reference resistance change rate.

The gas generation level determining unit <NUM> may determine a region to which the calculated resistance change rate belongs by substituting the calculated resistance change rate into the reference change rate regions. That is, the gas generation level determining unit <NUM> may determine a region to which the calculated resistance change rate belongs among the reference change rate regions.

For example, the gas generation level determining unit <NUM> may be configured to determine that the internal gas generation level is normal when the calculated resistance change rate belongs to the first region, and determine that the internal gas generation level is warning when the calculated resistance change rate belongs to the second region, and determine that the internal gas generation level is danger when the calculated resistance change rate belongs to the third region.

The state diagnosing unit <NUM> may be configured to diagnose the state of the battery cell according to the determined internal gas generation level. That is, the state diagnosing unit <NUM> may diagnose the state of the battery cell according to the internal gas generation level determined by the gas generation level determining unit <NUM>.

For example, in the previous embodiment, the gas generation level determining unit <NUM> may determine the internal gas generation level as normal, warning, or danger based on the calculated resistance change rate. To correspond to this, the state diagnosing unit <NUM> may diagnose the state of the battery cell as a normal state, a warning state or an unusable state.

Specifically, the state diagnosing unit <NUM> may be configured to diagnose the state of the battery cell as a normal state when the internal gas generation level is determined as normal.

In addition, the state diagnosing unit <NUM> may be configured to diagnose the state of the battery cell as a warning state when the internal gas generation level is determined as warning. Preferably, the state diagnosing unit <NUM> may be configured to reduce at least one of a maximum allowable temperature and a maximum allowable SOC of the battery cell in order to suppress generation of an internal gas of the battery cell. That is, for the corresponding battery cell, at least one of the maximum allowable temperature and the maximum allowable SOC may be set to be reduced.

In addition, the state diagnosing unit <NUM> may be configured to diagnose the state of the battery cell as an unusable state when the internal gas generation level is determined as danger.

That is, the battery diagnosis apparatus <NUM> according to an embodiment of the present disclosure has an advantage of diagnosing the internal gas generation level and state of the battery cell from the resistance change rate of the ohmic resistance of the battery cell in a non-destructive manner based on the correlation between the ohmic resistance of the battery cell and the internal gas generation level of the battery cell. For example, if the amount of internal gas generated by the battery cell is increased, the electron transporting power inside the electrode is reduced due to the internal gas, and the ohmic resistance of the battery cell may be sensitively increased due to the decrease in the ionic conductivity of the electrolyte. Therefore, the battery diagnosis apparatus <NUM> may diagnose the gas generation level and state of the battery cell based on the resistance change rate of the ohmic resistance by considering the relationship between the ohmic resistance and the amount of generated internal gas.

For example, when diagnosing the state of a plurality of battery cells collected for reuse, the battery diagnosis apparatus <NUM> according to an embodiment of the present disclosure may be used. The battery diagnosis apparatus <NUM> may obtain a plurality of impedance profiles for each of the plurality of battery cells, and non-destructively diagnose the internal gas generation level and state of each of the plurality of battery cells based on the plurality of obtained impedance profiles. A battery cell diagnosed as a normal state may be reused without additional setting change, but a battery cell diagnosed as a warning state may be reused after setting to reduce at least one of the maximum allowable temperature and the maximum allowable SOC. In addition, a battery cell diagnosed as an unusable state may not be reused. According to an embodiment of the present disclosure, since the internal gas generation level and state of the battery cell may be quickly and easily diagnosed using the ohmic resistance of the battery cell as described above, there is an advantage that the efficiency of diagnosing the state of the battery cell may be improved.

Meanwhile, the battery diagnosis apparatus <NUM> may further include a storage unit (not shown). The storage unit may store programs, data and the like required for operating the battery diagnosis apparatus <NUM>. That is, the storage unit may store data necessary for operation and function of each component of the battery diagnosing apparatus <NUM>, data generated in the process of performing the operation or function, or the like. The storage unit is not particularly limited in its kind as long as it is a known information storage means that can record, erase, update and read data. As an example, the information storage means may include RAM, flash memory, ROM, EEPROM, registers, and the like. In addition, the storage unit may store program codes in which processes executable by each component of the battery diagnosis apparatus <NUM> are defined.

Referring to <FIG>, the battery diagnosis apparatus <NUM> may further include a measuring unit <NUM> and an SOC estimating unit <NUM>.

The measuring unit <NUM> may be configured to measure at least one of temperature, voltage and current of the battery cell.

Preferably, the measuring unit <NUM> may measure the temperature of the battery cell. In addition, the measuring unit <NUM> may measure at least one of voltage and current of the battery cell.

More preferably, the measuring unit <NUM> may measure all of temperature, voltage and current of the battery cell.

The SOC estimating unit <NUM> may be configured to estimate the SOC of the battery cell based on at least one of the measured voltage and current.

For example, the SOC estimating unit <NUM> may estimate the SOC of the battery cell using an extended Kalman filter (EKF). As another example, the SOC estimating unit <NUM> may estimate the SOC of the battery cell using a current counting method (Coulomb counting, Ampere counting) for counting the current of the battery cell measured by the measuring unit <NUM>. Since the SOC estimating unit <NUM> estimates the SOC of the battery cell using a well-known method, a detailed description thereof will be omitted.

The ohmic resistance determining unit <NUM> may be configured to select at least one impedance profile satisfying a predetermined condition among the plurality of impedance profiles based on the temperature of the battery cell measured by the measuring unit <NUM> and the SOC of the battery cell estimated by the SOC estimating unit <NUM>.

Specifically, the ohmic resistance determining unit <NUM> may select only an impedance profile in which the temperature and SOC of the battery cell satisfy predetermined conditions among the plurality of impedance profiles. For example, even if the ohmic resistance determining unit <NUM> obtains <NUM> impedance profiles, if <NUM> impedance profiles satisfy the predetermined conditions for the temperature and SOC of the battery cell, the ohmic resistance determining unit <NUM> may select only the corresponding <NUM> impedance profiles.

In addition, the resistance change rate calculating unit <NUM> may be configured to calculate the resistance change rate based on the impedance profile selected by the ohmic resistance determining unit <NUM>.

For example, in the former embodiment, when the ohmic resistance determining unit <NUM> selects only <NUM> impedance profiles among <NUM> impedance profiles, the ohmic resistance determining unit <NUM> may determine the ohmic resistance of the battery cell in each of the <NUM> impedance profiles. In addition, the resistance change rate calculating unit <NUM> may calculate a resistance change rate between the determined <NUM> ohmic resistances.

Hereinafter, a condition in which the ohmic resistance determining unit <NUM> selects an impedance profile will be described in more detail with reference to <FIG> and <FIG>.

<FIG> is a diagram schematically showing a plurality of other impedance profiles according to an embodiment of the present disclosure.

The ohmic resistance determining unit <NUM> may be configured to select an impedance profile in which the temperature of the corresponding battery cell is equal to or higher than a reference temperature and an SOC of the corresponding battery cell is equal to or greater than a reference SOC, among the plurality of impedance profiles.

In general, when the SOC of the battery cell is equal to or greater than a certain level, the amount of internal gas generated by the battery cell may increase as the temperature of the battery cell increases. That is, when the SOC of the battery cell is less than the certain level, the amount of internal gas generated by the battery cell itself is small, and thus the amount of internal gas generated by the battery cell may not increase even if the battery cell has high temperature. Therefore, the ohmic resistance of the battery cell related to the amount of internal gas generated by the battery cell may be increased when both the temperature and the SOC of the battery cell satisfy predetermined conditions.

Specifically, the plurality of impedance profiles shown in <FIG> are impedance profiles generated when the temperature of the battery cell is equal to or higher than the reference temperature and the SOC of the battery cell is equal to or greater than the reference SOC.

For example, in the embodiment of <FIG>, the reference temperature may be <NUM>, the temperature of the battery cell may be <NUM>, the reference SOC may be <NUM>%, and the SOC of the battery cell may be <NUM>%. That is, the plurality of impedance profiles shown in <FIG> are impedance profiles generated at a constant cycle for a battery cell at high temperature and in a fully charged state.

Conversely, the plurality of impedance profiles shown in <FIG> are impedance profiles generated when the temperature of the battery cell is equal to or higher than the reference temperature but the SOC of the battery cell is less than the reference SOC.

For example, in the embodiment of <FIG>, the reference temperature may be <NUM>, the temperature of the battery cell may be <NUM>, the reference SOC may be <NUM>%, and the SOC of the battery cell may be <NUM>%. That is, the plurality of impedance profiles shown in <FIG> are impedance profiles generated at a constant period for a battery cell at a high temperature and in a fully discharged state.

In addition, the plurality of impedance profiles of <FIG> and <FIG> are profiles for the impedance measured by outputting the same current to the battery cell. That is, the difference between the impedance profiles of <FIG> and <FIG> is the SOC of the battery cell at the time of measurement.

Referring to <FIG>, it may be clearly seen that the ohmic resistance of the battery cell increases as time elapses (e.g., as the process progresses from the first impedance profile P1 to the ninth impedance profile P9).

On the other hand, referring to <FIG>, it may be confirmed that the ohmic resistance of the battery cell is maintained within an approximate range even if time elapses. This is, in the case of <FIG>, since the SOC of the battery cell is <NUM>%, the internal gas of the battery cell itself is not generated or the amount of gas generation itself is small. Thus, even if the temperature of the battery cell is high, the ohmic resistance of the battery cell may be maintained within an approximate range.

That is, in order to diagnose the state of the battery cell in consideration of the correlation between the internal gas generation level of the battery cell and the resistance change rate of the ohmic resistance of the battery cell, the temperature of the battery cell at the time of measurement of the impedance must be equal to or higher than the reference temperature, and the SOC of the battery cell must also be equal to or greater than the reference SOC.

For example, according to the embodiment of <FIG>, even when the battery cell is seriously degraded and is in an unusable state, since the resistance change rate of the ohmic resistance is very small, there is a problem that the internal gas generation level may be erroneously diagnosed as normal and the state of the battery cell may be erroneously diagnosed as a normal state. Specifically, according to the embodiment of <FIG>, since the internal gas itself of the battery cell is not generated or the amount itself is small, the resistance change rate of the ohmic resistance is calculated low, and the battery cell may be erroneously diagnosed as in a normal state according to the low calculated resistance change rate.

Therefore, the battery diagnosis apparatus <NUM> according to an embodiment of the present disclosure has an advantage of more accurately diagnosing the internal gas generation level and state of the battery cell by considering both the temperature and the SOC of the battery cell at the time of measurement of the impedance.

Referring to <FIG>, the battery diagnosis apparatus <NUM> may further include a charge transfer resistance determining unit <NUM>.

The charge transfer resistance determining unit <NUM> may be configured to determine a charge transfer resistance (Rct) in each of the plurality of impedance profiles.

Here, the charge transfer resistance refers to a resistance generated in an oxidation reaction or a reduction reaction of lithium ions at the electrode material interface. It should be noted that since the charge transfer resistance is a well-known factor, a description of the charge transfer resistance itself will be omitted.

As described above, when the value of the imaginary part (-Zim) in the impedance profile is <NUM>, the resistance value of the real part (Zre) is the ohmic resistance (Ro) of the battery cell, which may be determined by the ohmic resistance determining unit <NUM>.

Alternatively, the charge transfer resistance (Rct) may be determined based on the difference between the ohmic resistance (Ro) of the battery cell and the resistance value (RTP) of a target peak TP in the impedance profile. Due to the characteristics of the impedance profile, the resistance value (RTP) of the target peak TP is always greater than the ohmic resistance (Ro), so the charge transfer resistance may be determined according to the formula of "the resistance value of the target peak TP (RTP) - the ohmic resistance (Ro)".

That is, the charge transfer resistance determining unit <NUM> may determine the target peak TP in each of the plurality of impedance profiles, and determine the charge transfer resistance of each impedance profile based on the difference between the resistance value (RTP) of the determined target peak TP and the ohmic resistance (Ro) determined by the ohmic resistance determining unit <NUM>.

For example, in the embodiment of <FIG>, the impedance profile may include a target peak TP. Specifically, the target peak TP may be a peak in which an instantaneous change rate of the imaginary part (-Zim) with respect to the real part (Zre) in the impedance profile is <NUM> and which has a downward convex open shape. That is, based on the target peak TP, as the resistance value of the real part (Zre) increases, the instantaneous change rate of the imaginary part (-Zim) with respect to the real part (Zre) may change from negative to positive.

For example, in the embodiment of <FIG>, the charge transfer resistance determining unit <NUM> may determine the charge transfer resistance for each of the first to ninth impedance profiles P1 to P9. Here, the charge transfer resistance of the first impedance profile P1 may be smallest, and the charge transfer resistance of the ninth impedance profile P9 may be largest. That is, the magnitudes of the charge transfer resistances of the first to ninth impedance profiles P1 to P9 may be sequentially increased.

The resistance change rate calculating unit <NUM> may be configured to further calculate a charge transfer resistance change rate between the plurality of determined charge transfer resistances.

That is, the resistance change rate calculating unit <NUM> may calculate a resistance change rate for the plurality of ohmic resistances determined by the ohmic resistance determining unit <NUM>, and calculate a charge transfer resistance change rate for the plurality of charge transfer resistances determined by the charge transfer resistance determining unit <NUM>.

The state diagnosing unit <NUM> may be configured to further diagnose the state of the battery cell based on a result of comparing the calculated charge transfer resistance change rate and the reference resistance value.

Specifically, the state diagnosing unit <NUM> may be configured to diagnose the state of the battery cell as a normal state when the calculated charge transfer resistance change rate is less than the reference resistance value.

In addition, the state diagnosing unit <NUM> may be configured to diagnose the state of the battery cell as a warning state when the calculated charge transfer resistance change rate is equal to or greater than the reference resistance value. In addition, the state diagnosing unit <NUM> may be configured to reduce the maximum allowable C-rate for charging and discharging of the battery cell. Here, the C-rate (Current rate) means a charge/discharge rate of the battery cell.

That is, when the state of the battery cell is diagnosed as a warning state, the state diagnosing unit <NUM> may reduce the maximum allowable C-rate of the battery cell in order to reduce the charge transfer resistance. Accordingly, the maximum allowable values of the charging C-rate and the discharging C-rate of the battery cell may be reduced.

For example, when diagnosing the state of a plurality of battery cells collected for reuse, the battery diagnosis apparatus <NUM> according to an embodiment of the present disclosure may further consider the charge transfer resistance as well as the ohmic resistance. A battery cell diagnosed as a normal state based on the charge transfer resistance may be reused without additional setting change, but a battery cell diagnosed as a warning state may be reused after the maximum allowable C-rate is set to be reduced.

As such, the battery diagnosis apparatus <NUM> according to an embodiment of the present disclosure may diagnose the state of the battery cell based on the ohmic resistance of the battery cell determined from the impedance profile, and also diagnose the state of the battery cell based on the charge transfer resistance determined from the impedance profile. That is, since the battery diagnosis apparatus <NUM> may diagnose the state of the battery cell in two ways, there is an advantage that the state of the battery cell may be diagnosed more accurately.

<FIG> is a diagram schematically showing a battery diagnosis system <NUM> according to another embodiment of the present disclosure.

Referring to <FIG>, the battery diagnosis system <NUM> may include a battery diagnosis apparatus <NUM> and an EIS unit <NUM>.

The EIS unit <NUM> may be configured to output an AC current to the battery cell and generate an impedance profile representing the impedance of the battery cell as a corresponding relationship between the real part (Zre) and the imaginary part (-Zim) according to the output result of the AC current.

Specifically, the EIS unit <NUM> may be configured to perform EIS (Electrochemical Impedance Spectroscopy). Therefore, the EIS unit <NUM> may apply a minute AC current to the battery cell to measure the impedance of the battery cell, and generate an impedance profile representing the impedance as a corresponding relationship between the real part (Zre) and the imaginary part (-Zim).

The EIS unit <NUM> may be configured to output the generated impedance profile to the battery diagnosis apparatus <NUM>.

For example, the EIS unit <NUM> may transmit the generated impedance profile to the ohmic resistance determining unit <NUM> and the charge transfer resistance determining unit <NUM> of the battery diagnosis apparatus <NUM>.

As another example, the EIS unit <NUM> may transmit the generated impedance profile to the storage unit of the battery diagnosis apparatus <NUM>. In this case, the ohmic resistance determining unit <NUM> and the charge transfer resistance determining unit <NUM> may access the storage unit to acquire the impedance profile generated by the EIS unit <NUM>.

Also, referring to <FIG>, the battery diagnosis system <NUM> may further include a heating unit <NUM> and a charging unit <NUM>.

The heating unit <NUM> may be configured to increase the temperature of the battery cell so that the temperature of the battery cell is equal to or higher than a reference temperature.

The charging unit <NUM> may be configured to charge the battery cell such that the SOC of the battery cell is equal to or greater than the reference SOC.

Preferably, the operation of the heating unit <NUM> and the charging unit <NUM> may be controlled by a battery management system. For example, the operation of the heating unit <NUM> and the charging unit <NUM> may be controlled by the state diagnosing unit <NUM>.

As described above, referring to <FIG>, when the temperature of the battery cell is equal to or higher than the reference temperature and the SOC of the battery cell is equal to or greater than the reference SOC, the ohmic resistance of the battery cell may be gradually increased in the plurality of impedance profiles.

Therefore, since the temperature of the battery cell becomes equal to or higher than the reference temperature by the heating unit <NUM> and the SOC of the battery cell becomes equal to or greater than the reference SOC by the charging unit <NUM>, the impedance profile generated by the EIS unit <NUM> under this condition may be selected as an impedance profile used to diagnose the state of the battery cell. That is, based on the impedance profile generated in this condition, the state of the battery cell may be diagnosed.

Therefore, the battery diagnosis system <NUM> may diagnose the state of the battery cell based on the corresponding impedance profile only when the temperature and SOC of the battery cell satisfy the predetermined condition, so the accuracy and reliability of the state diagnosis of the battery cell may be high.

The battery diagnosis apparatus <NUM> according to the present disclosure may be applied to a BMS (Battery Management System). That is, the BMS according to the present disclosure may include the battery diagnosis apparatus <NUM> described above. In this configuration, at least some components of the battery diagnosis apparatus <NUM> may be implemented by supplementing or adding functions of the configuration included in the conventional BMS.

In addition, the battery diagnosis apparatus <NUM> according to the present disclosure may be provided to a battery pack <NUM>. That is, the battery pack <NUM> according to the present disclosure may include the above-described battery diagnosis apparatus <NUM> and at least one battery cell. In addition, the battery pack <NUM> may further include electrical equipment (a relay, a fuse, etc.) and a case.

<FIG> is a diagram schematically showing an exemplary configuration of a battery pack <NUM> according to still another embodiment of the present disclosure. Referring to <FIG>, the battery pack <NUM> may include a battery diagnosis apparatus <NUM>, an EIS unit <NUM>, a heating unit <NUM>, and a charging unit <NUM>.

For example, in the embodiment of <FIG>, the battery diagnosis apparatus <NUM> may be connected to first to fourth sensing lines SL1 to SL4. Preferably, the first to fourth sensing lines SL1 to SL4 may be connected to the measuring unit <NUM> of the battery diagnosis apparatus <NUM>.

The measuring unit <NUM> may measure the temperature of the battery cell B through the first sensing line SL1.

In addition, the measuring unit <NUM> may measure a positive electrode voltage of the battery cell B through the second sensing line SL2 and measure a negative electrode voltage of the battery cell B through the third sensing line SL3. In addition, the measuring unit <NUM> may measure the voltage of the battery cell B by calculating a difference between the measured positive electrode voltage and negative electrode voltage of the battery cell B.

Also, the measuring unit <NUM> may be connected to a current measuring element A through the fourth sensing line SL4. Here, the current measuring element A may be a current system or a shunt resistor. Therefore, the measuring unit <NUM> may measure the current of the battery cell B through the fourth sensing line SL4. <FIG> shows an embodiment in which the current measuring element A is provided between a negative electrode of the battery cell B and a negative electrode terminal P- of the battery pack <NUM> as a preferred embodiment, but the current measuring element A may also be provided between a positive electrode of the battery cell B and a positive electrode terminal P+ of the battery pack <NUM>.

One end of the EIS unit <NUM> may be connected between the positive electrode terminal P+ of the battery pack <NUM> and the positive electrode of the battery cell B, and the other end may be connected between the negative electrode terminal P- of the battery pack <NUM> and the negative electrode of the battery cell B. In addition, the EIS unit <NUM> may measure the impedance of the battery cell B after outputting a minute AC current. Thereafter, the EIS unit <NUM> may generate an impedance profile of the battery cell B and transmit it to the battery diagnosis apparatus <NUM>.

One end of the heating unit <NUM> may be connected to the positive electrode of the battery cell B, and the other end may be connected to the negative electrode of the battery cell B. In addition, the operation of the heating unit <NUM> is controlled by the battery diagnosis apparatus <NUM> (particularly, the state diagnosing unit <NUM>), and when the heating unit <NUM> is operated, the temperature of the battery cell B may increase.

One end of the charging unit <NUM> may be connected to the positive electrode terminal P+ of the battery pack <NUM>, and the other end may be connected to the negative electrode terminal P- of the battery pack <NUM>. In another embodiment, one end of the charging unit <NUM> may be directly connected to the positive electrode of the battery cell B, and the other end may be directly connected to the negative electrode of the battery cell B, similarly to the heating unit <NUM>. The operation of the charging unit <NUM> may be controlled by the battery diagnosis apparatus <NUM> (particularly, the state diagnosing unit <NUM>), and when the charging unit <NUM> is operated, the battery cell B may be charged.

<FIG> is a diagram showing a battery diagnosing method according to still another embodiment of the present disclosure.

Here, each step of the battery diagnosis method may be performed by the battery diagnosis apparatus <NUM>. Hereinafter, for convenience of explanation, content overlapping with the previously described content will be briefly described or omitted.

The battery diagnosing method may include an ohmic resistance determining step (S100), a resistance change rate calculating step (S200), a gas generation level determining step (S300), and a state diagnosing step (S400).

The ohmic resistance determining step (S100) is a step of determining an ohmic resistance of the battery cell B in each of a plurality of impedance profiles generated at different time points for the battery cell B, and may be performed by the ohmic resistance determining unit <NUM>.

For example, in the embodiment of <FIG>, the ohmic resistance determining unit <NUM> may obtain first to ninth impedance profiles P1 to P9. In addition, the ohmic resistance determining unit <NUM> may determine the ohmic resistance of the battery cell B in each of the first to ninth impedance profiles P1 to P9.

The resistance change rate calculating step (S200) is a step of calculating a resistance change rate between the plurality of determined ohmic resistances, and may be performed by the resistance change rate calculating unit <NUM>.

For example, in the embodiment of <FIG>, when the ohmic resistance is determined in each of the first to ninth impedance profiles P1 to P9 by the ohmic resistance determining unit <NUM>, the resistance change rate calculating unit <NUM> may calculate a resistance change rate for the <NUM> ohmic resistances.

The gas generation level determining step (S300) is a step of determining an internal gas generation level of the battery cell B based on the calculated resistance change rate, and may be performed by the gas generation level determining unit <NUM>.

The gas generation level determining unit <NUM> may determine an internal gas generation level corresponding to a region to which the calculated resistance change rate belongs by substituting the resistance change rate calculated by the resistance change rate calculating unit <NUM> to a preset reference change rate region.

The state diagnosing step (S400) is a step of diagnosing the state of the battery cell B according to the determined internal gas generation level, and may be performed by the state diagnosing unit <NUM>.

The state diagnosing unit <NUM> may diagnose the state of the battery cell B to correspond to the internal gas generation level of the battery cell B determined by the gas generation level determining unit <NUM>.

For example, if the internal gas generation level is normal, the state diagnosing unit <NUM> may diagnose that the state of the battery cell B is a normal state. If the internal gas generation level is warning, the state diagnosing unit <NUM> may diagnose that the state of the battery cell B is a warning state. If the internal gas generation level is danger, the state diagnosing unit <NUM> may diagnose that the state of the battery cell B is an unusable state.

The embodiments of the present disclosure described above may not be implemented only through an apparatus, a method and a system, but may be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present disclosure or a recording medium on which the program is recorded.

Claim 1:
A battery diagnosis apparatus (<NUM>), comprising:
an ohmic resistance determining unit (no) configured to determine an ohmic resistance of a battery cell in each of a plurality of impedance profiles generated at different time points for the battery cell;
a resistance change rate calculating unit (<NUM>) configured to calculate a resistance change rate between the plurality of determined ohmic resistances; wherein the battery diagnosis apparatus is characterised by comprising:
a gas generation level determining unit (<NUM>) configured to determine an internal gas generation level of the battery cell based on the calculated resistance change rate; and
a state diagnosing unit (<NUM>) configured to diagnose a state of the battery cell according to the determined internal gas generation level.