Patent Description:
Particularly, the present disclosure relates to an apparatus and a method for preventing a safety accident of a battery pack due to a battery cell deviation by detecting a characteristic of an undervoltage defective battery cell in an early stage.

A battery pack is an assembly manufactured such that a module is assembled by welding and accommodating a single battery cell in a housing, and then a plurality of modules are connected by a busbar or a wire. In the battery pack, a defect of a battery cell is frequently generated. An example of a state monitoring of a storage battery can be found for instance in <CIT>.

When a defect is generated in one of the battery cells of the battery pack, the corresponding battery cell may have an internal resistance (IR) that is extremely varied when charged or discharged.

That is, a voltage higher than a normal battery cell is formed in a charging state, and a voltage lower than the normal battery cell is formed in a discharging state.

Here, when the charging or the discharging is repeatedly performed although an undervoltage defective battery cell is generated, an overall output of the battery pack may be degraded.

Particularly, in case of an energy storage system (ESS) in which a plurality of battery packs are connected, the ESS may not be efficiently used due to a deviation between battery packs of the ESS because one defective battery cell causes reduction in output of the battery pack including the defective battery cell.

Also, when the undervoltage defective battery cell is continuously charged or discharged, short-circuit may be generated in the defective battery cell, and when the short-circuit is generated, ignition or safety limitation may occur.

Thus, in an exemplary embodiment, an apparatus and a method for detecting the undervoltage battery cell in an early stage are suggested.

(Related art document) Korean Registered Patent No. <CIT> or <CIT>.

The present disclosure provides an apparatus and a method for detecting an undervoltage defective battery cell of battery cells of a battery pack.

The present disclosure also provides a method for safely using a battery pack by detecting an undervoltage defective battery cell in an early stage.

The present invention provides a battery pack as defined by the independent claim <NUM> and two methods for detecting a defective battery cell of a battery pack as defined by the independent claims <NUM> and <NUM>. Preferred embodiments are defined in the appended dependent claims. In accordance with an exemplary embodiment, the battery pack including a plurality of battery cells includes a battery management system (BMS) configured to control the battery pack. Here, the BMS includes: an internal resistance value calculation module configured to calculate an internal resistance value for each battery cell directly after the battery pack is charged or discharged for a predetermined time; a maximum internal resistance valued battery cell detection module configured to detect a battery cell having a biggest internal resistance value of the calculated internal resistance values; and a defective battery cell determination module configured to determine a defective battery cell on the basis of a detected number as the battery cell having the biggest internal resistance value for each battery cell.

The internal resistance value calculation module may repeatedly calculate the internal resistance value directly after the battery pack is charged or discharged for a predetermined time.

The maximum internal resistance valued battery cell detection module may detect the battery cell having the biggest internal resistance value of the calculated internal resistance values for each battery cell directly after the battery pack is charged or discharged for a predetermined time and count the detected number of the battery cell detected as the battery cell having the maximum internal resistance value.

The defective battery cell determination module may determine a battery cell having a detected number, which is the number detected as the battery cell having the maximum internal resistance value, equal to or greater than a predetermined detected number as a defective battery cell when the battery cell having the detected number, which is the number as the battery cell having the maximum internal resistance value, equal to or greater than the predetermined detected number is present.

The battery pack may further include an alarm part configured to transmit an alarm signal to the outside when the battery cell determined as a defect in the defective battery cell determination module is present.

The internal resistance value may be a direct current internal resistance (DCIR) value calculated by a DCIR calculation method.

In accordance with another exemplary embodiment, a method for detecting a defective battery cell of a battery pack including a plurality of battery cells includes: a charging process of charging the battery pack for a predetermined time; an internal resistance value calculation process of calculating an internal resistance value for each of the plurality of battery cells by a battery management system (BMS) directly after the charging process; a detected number counting process of detecting a battery cell having a biggest internal resistance value of the plurality of battery cells and counting a detected number of the detected battery cell having the biggest internal resistance value by the BMS; and a defective battery cell determination process of determining a battery cell having the greatest number detected as the battery cell having the biggest internal resistance value by the BMS after repeatedly performing the charging process, the internal resistance value calculation process, and the detected number counting process at a frequency of a predetermined time with predetermined repetition times.

In the defective battery cell determination process, the BMS may determine all battery cells of the battery pack as a normal state when the battery cell having the detected number, which is the number detected as the battery cell having the biggest internal resistance value for each battery cell, equal to or greater than a predetermined detected number is not present.

In accordance with yet another exemplary embodiment, a method for detecting a defective battery cell of a battery pack including a plurality of battery cells includes: a discharging process of discharging the battery pack for a predetermined time; a direct current internal resistance (DCIR) value calculation process of calculating an internal resistance value for each of the plurality of battery cells by a battery management system (BMS) directly after the discharging process; a detected number counting process of detecting a battery cell having a biggest internal resistance value of the plurality of battery cells and count the detected number of the detected battery cell having the biggest internal resistance value for each battery cell by the BMS; and a defective battery cell determination process of determining the battery cell having the greatest number detected as the battery cell having the biggest internal resistance value by the BMS after repeatedly performing the discharging process, the internal resistance value calculation process, and the detected number counting process at a frequency of a predetermined time with predetermined repetition times.

The method may further include a defective battery cell alarm signal transmitting process of transmitting an alarm signal, which notifies presence of a defective battery cell, to the outside when the battery cell determined as the defective battery cell in the defective battery cell determination process is present.

The internal resistance calculated in the internal resistance value calculation process may be a DCIR value calculated by a DCIR calculation method.

The battery pack in accordance with the exemplary embodiment, which is a device for detecting the undervoltage defective battery cell, may detect the defective battery cell of the battery cells of the battery pack in the early stage.

Also, the exemplary embodiment may resolve a limitation of the reduction in output of the battery pack due to the defective battery cell by detecting the undervoltage defective battery cell in the early stage.

Also, the exemplary embodiment may detect the undervoltage defective battery cell in the early stage to prevent a situation in which as the defective battery cell is generated in one of the battery packs of the energy storage system (ESS), the output of the battery pack including the undervoltage defective battery cell may decrease, and the ESS may not be efficiently used.

Also, the exemplary embodiment may prevent the safety limitation and the ignition, which may be generated when the undervoltage defective battery cell is continuously charged or discharged, by detecting the undervoltage battery cell in the early stage.

A typically used method for detecting a defect of an undervoltage battery cell due to deterioration during usage determines a defect only when an undervoltage is substantially detected by measuring a voltage of a battery cell. That is, a state in which a defect is generated in a battery cell is detected after the undervoltage defective battery cell is already generated.

On the other hand, a battery cell, which has a high possibility to be a defective battery cell due to deterioration generated in the battery cell, etc., exhibits a feature in which an internal resistance value measured directly after charged is greater than that measured in a normal battery cell when the charging is performed for a predetermined time. Thus, in an exemplary embodiment, the undervoltage defective battery cell may be detected in an early state by repeating a process of charging a battery pack for a predetermined time, calculating an internal resistance value for each battery cell directly after charged, and detecting a battery cell having a biggest internal resistance value, thereby determining the battery cell, which has a greatest number detected as the battery cell having the biggest internal resistance value, as the undervoltage defective battery cell.

<FIG> is a flowchart representing a method for detecting the undervoltage defective battery cell when the battery pack is charged in accordance with an exemplary embodiment.

Hereinafter, the method for detecting the undervoltage defective battery cell when the battery pack is charged in accordance with an exemplary embodiment will be described with reference to <FIG>.

The method for detecting the undervoltage defective battery cell when the battery pack is charged in accordance with an exemplary embodiment may include: a charging process S110 of charging the battery pack for a predetermined time; an internal resistance value calculation process S120 of calculating an internal resistance value of each of the plurality of battery cells directly after the charging process S110; a detected number counting process S130 of detecting a battery cell having a biggest internal resistance value of the plurality of battery cells and counting the detected number as the battery cell having the biggest internal resistance value; and a defective battery cell determination process S150, S160, and S170 of determining a battery cell having a greatest number detected as the battery cell having the biggest internal resistance value in a battery management system (BMS) after a process S140 of repeating the charging process S110, the internal resistance value calculation process S120, and the detected number counting process S130 at a frequency of a predetermined time with a predetermined repeated number.

The internal resistance calculated in the internal resistance value calculation process may be a DCIR value measured by a direct current internal resistance (DCIR) method.

The DCIR value may be calculated for each battery cell by using a method of converting a voltage and current variation amount into a resistance value in the BMS. A technique of calculating the DCIR for each battery cell is a well-known method.

The defective battery cell determination process S150, S160, and S170 performs a process S180 of determining all battery cells of the battery pack as a normal state when a battery cell having the detected number, which is the number detected as the battery cell having the biggest internal resistance value, equal to or greater than a predetermined detected number, is not present.

The predetermined detected number may be determined according to a predetermined number of repeating the charging process S110, the internal resistance value calculation process S120, and the detected number counting process S130, and each of the predetermined repetition times and the predetermined detected number may be a value that is differently set according to a capacity and a usage purpose of the battery cell.

For example, the predetermined detected number may be the number corresponding to approximately <NUM>% or more of the predetermined repetition times of repeating the charging process, the internal resistance value calculation process, and the detected number counting process.

In a particular embodiment, when first to fifth battery cells have the detected number, which is the number detected as the battery cell having the biggest internal resistance value, of <NUM> times, <NUM> times, four times, one times, and <NUM> times, respectively, in a process of charging the battery pack including the first to fifth battery cells at five times, since the third battery cell has the four detected number as the battery cell having the biggest internal resistance value, and this repetition number is approximately <NUM>% or more of the five repetition number, the third battery cell may be determined as a defective battery cell.

When the defective battery cell is detected in the defective battery cell determining process, an alarm signal transmitting process S170 of notifying presence of a defective battery cell to the outside may be further provided.

For example, the alarm signal transmitting process may notify the presence of the defective battery cell to the outside by using a light signal or a sound signal.

On the other hand, a battery cell, which has a high possibility to be a defective battery cell due to deterioration generated in the battery cell, etc., exhibits a feature in which a DCIR value measured directly after discharged is greater than an internal resistance value measured in a normal battery cell when the discharging is performed for a predetermined time. Thus, in another exemplary embodiment, the undervoltage defective battery cell may be detected in an early state by repeating a process of charging a battery pack for a predetermined time, calculating an internal resistance value for each battery cell directly after discharged, and detecting a battery cell having a biggest internal resistance value, thereby determining the battery cell, which has the greatest number detected as the battery cell having the biggest internal resistance value, as the undervoltage defective battery cell.

<FIG> is a flowchart representing a method for detecting the undervoltage defective battery cell when the battery pack is discharged in accordance with another exemplary embodiment.

Hereinafter, the method for detecting the undervoltage defective battery cell when the battery pack is discharged in accordance with another exemplary embodiment will be described with reference to <FIG>.

The method for detecting the undervoltage defective battery cell when the battery pack is discharged in accordance with another exemplary embodiment may include: a discharging process S210 of discharging the battery pack for a predetermined time; an internal resistance value calculation process S220 of calculating an internal resistance value of each of the plurality of battery cells directly after the discharging process S210; a detected number counting process S230 of detecting a battery cell having a biggest internal resistance value of the plurality of battery cells and counting the detected number as the battery cell having the biggest internal resistance value; and a defective battery cell determination process S250, S260, and S270 of determining a battery cell having the greatest detected number of the battery cell having the biggest internal resistance value in a BMS after a process S140 of repeating the discharging process S210, the internal resistance value calculation process S220, and the detected number counting process S230 at a frequency of a predetermined time with a predetermined repeated number.

The internal resistance calculated in the internal resistance value calculation process S220 may be a DCIR value calculated by the direct current internal resistance (DCIR) method.

The DCIR value may be calculated for each battery cell by using the method of converting a voltage and current variation amount into a resistance value in the BMS. The technique of calculating the DCIR for each battery cell is a well-known method.

The defective battery cell determination process S250, S260, and S270 performs a process S280 of determining all battery cells of the battery pack as a normal state when a battery cell, in which the detected number as the battery cell having the biggest internal resistance value is equal to or greater than a predetermined detected number, is not present.

The predetermined detected number may be determined according to a predetermined number of repeating the discharging process, the internal resistance value calculation process, and the detected number counting process, and each of the predetermined repetition times and the predetermined detected number may be a value that is differently set according to a capacity and a usage purpose of the battery cell.

For example, the predetermined detected number may be the number corresponding to approximately <NUM>% or more of the predetermined repetition times of repeating the discharging process, the internal resistance value calculation process, and the detected number counting process.

In a particular embodiment, when first to fifth battery cells have the detected number, which is the number detected as the battery cell having the biggest internal resistance value, of <NUM> times, <NUM> times, four times, one times, and <NUM> times, respectively, in a process of discharging the battery pack including the first to fifth battery cells at five times, since the third battery cell has the four detected number as the battery cell having the biggest internal resistance value, and this repetition number is approximately <NUM>% or more of the five repetition number, the third battery cell may be determined as a defective battery cell.

When a battery cell determined as a defective battery cell is present in the defective battery cell determining process, an alarm signal transmitting process S270 of notifying presence of a defective battery cell to the outside may be further provided.

<FIG> is a view showing a configuration of a battery pack in accordance with an exemplary embodiment.

Hereinafter, the battery pack in accordance with an exemplary embodiment will be described with reference to <FIG>.

A battery pack <NUM> in accordance with an exemplary embodiment may be applied with the above-described method for detecting a defective battery cell in accordance with an exemplary embodiment and the method for detecting a defective battery cell in accordance with another exemplary embodiment.

A battery pack in accordance with another exemplary embodiment may include a battery management system (BMS) <NUM> controlling a plurality of battery cells and the battery pack.

Particularly, the BMS <NUM> may include: an internal resistance value calculation module <NUM> calculating an internal resistance value for each battery cell directly after the battery pack is charged or discharged for a predetermined time; a maximum internal resistance valued battery cell detection module <NUM> detecting a battery cell having a maximum internal resistance value of the calculated internal resistance values for each battery cell; and a defective battery cell determination module <NUM> determining a defective battery cell on the basis of the detected number as the battery cell having the maximum internal resistance value.

Here, the internal resistance value calculation module <NUM> may perform the process of calculating the internal resistance value directly after the battery pack is charged or discharged for the predetermined time whenever the battery pack is charged or discharged.

In other words, the internal resistance value calculation module <NUM> may calculate the internal resistance value one times when the battery pack is charged one times and calculate the internal resistance value five times when the battery pack is charged five times.

Also, the maximum internal resistance valued battery cell detection module <NUM> may detect the battery cell having the maximum internal resistance value of the calculated internal resistance values directly after the battery pack is charged or discharged for a predetermined time and count the detected number of the battery cell detected as the battery cell having the maximum internal resistance value.

Also, when the defective battery cell determination module <NUM> may determine a battery cell having the detected number, which is the number detected as the battery cell having the maximum internal resistance value, equal to or greater than a predetermined detected number is present directly after the battery pack is charged or discharged, the battery cell having the detected number, which is the number detected as the battery cell having the maximum internal resistance value, equal to or greater than the predetermined detected number may be determined as a defective battery cell.

In a particular embodiment, when first to fifth battery cells have the detected number, which is the number detected as the battery cell having the biggest internal resistance value, of <NUM> times, <NUM> times, four times, one times, and <NUM> times, respectively, in a process of charging the battery pack including the first to fifth battery cells at five times, since the third battery cell has the four detected number as the battery cell having the biggest internal resistance value, and this repetition number is approximately <NUM>% or more of the five repetition number, the third battery cell may be determined as the defective battery cell.

Here, the battery pack may further include an alarm part <NUM> transmitting an alarm signal to the outside when a battery cell determined as the defective battery cell in the defective battery cell determination module <NUM> is present.

Claim 1:
A battery pack comprising a plurality of battery cells, the battery pack comprising a battery management system, BMS, (<NUM>) configured to control the battery pack,
wherein the BMS comprises:
an internal resistance value calculation module (<NUM>) configured to calculate an internal resistance value for each battery cell directly after the battery pack is charged or discharged for a predetermined time whenever the battery pack is charged or discharged;
a maximum internal resistance valued battery cell detection module (<NUM>) configured to detect a battery cell having the biggest internal resistance value of the calculated internal resistance values and count a detected number being a number of times a respective battery cell is detected as having the biggest internal resistance value; and
a defective battery cell determination module (<NUM>) configured to determine a defective battery cell as the battery cell having the greatest detected number after the charging or discharging process of the battery pack is repeatedly performed at a frequency of a predetermined time with a predetermined repetition time.