Apparatus, System and Method for Calculating Battery Internal Resistance Using Time Delay Compensation

Abstract

The present invention relates to an apparatus, system, and method for precisely measuring the internal resistance of a battery. According to the present invention, while applying a step-shaped discharge current to the battery, the voltage and current of the battery are sampled and stored in a first period, and representative current values ​​and representative voltage values ​​are generated from the stored samples in a second period. At this time, the representative voltage value is generated based on voltage samples at a time point that is later than the time point corresponding to the representative current value by a preset time delay (td). Through this time delay correction, the time delay characteristics between the voltage channel and the current channel of the measurement system, time alignment errors in the sampling and data processing process, and the electrochemical response delay of the battery can be effectively compensated. By calculating the internal resistance as the ratio of the voltage change amount and the current change amount at the judgment time point using the generated representative current value and representative voltage value, the accuracy and reproducibility of the battery internal resistance measurement can be significantly improved.

Description

Technology Field

[0001] The present invention relates to a battery condition diagnosis technology, and more specifically, to a battery internal resistance calculation technology that can improve measurement accuracy and reproducibility by correcting the time delay between voltage samples and current samples when calculating the internal resistance by sampling the voltage and current of a battery while applying a step-type discharge current.

[0002] The present invention can be applied to an apparatus, system, and method for precisely calculating the internal resistance of a battery in electric vehicles (EVs), energy storage systems (ESS), industrial battery test equipment, battery management systems (BMS), and battery simulators. Background Technology

[0003] Battery internal resistance is one of the key indicators for assessing output characteristics, heat generation, efficiency, and degradation status. Accordingly, various methods have been proposed to accurately calculate battery internal resistance.

[0004] Among these, ICI (Instantaneous Current Interruption) or equivalent methods are widely used to calculate internal resistance by applying a change in current to the battery and analyzing the resulting change in terminal voltage. However, various problems exist in actual system environments.

[0005] Due to the electrochemical characteristics of the battery, electrode polarization, electrolyte ion migration, and response delays of sensors and measurement circuits, an inevitable time delay exists between the point at which a current change occurs and the point at which a voltage change is measured. Even if voltage and current are sampled in units of a few microseconds using a DSP, a problem arises where the voltage and current data are not aligned to the exact same time reference during subsequent processes such as representative value generation, packet transmission, and processing by external computing devices. If the representative voltage and current values, treated as the same point in time, actually reflect different physical time points, problems occur such as the internal resistance value being calculated as smaller than the actual value or the consistency of results degrading during repeated measurements.

[0006] In particular, under high-capacity battery or high-current conditions, this time delay problem is even more pronounced, as it takes several milliseconds for the current to rise to reach the target value. The problem to be solved

[0007] The problem that the present invention aims to solve is to provide a battery internal resistance calculation device and method that can improve the accuracy and reproducibility of internal resistance measurement by correcting the time discrepancy between the voltage measurement value and the current measurement value when measuring the internal resistance of a battery while applying a step-shaped discharge current to the battery.

[0008] More specifically, the present invention aims to solve the following problems.

[0009] 1) An apparatus and method for calculating battery internal resistance capable of compensating for the group delay difference of a measurement system and the electrochemical response delay of a battery by using voltage samples at a time point later than the time point corresponding to the current representative value by a preset time delay when generating the voltage representative value.

[0010] 2) To provide a battery internal resistance calculation device and method capable of providing consistent internal resistance measurement results under various battery types and measurement conditions by pre-calibrating the time delay inherent to the measurement system using a reference battery with a known internal resistance.

[0011] 3) To provide a battery internal resistance calculation device and method capable of calculating precise internal resistance by considering the transient period during which the step current rises to a target value in a high-current system, determining an appropriate judgment point, and, if necessary, through interpolation.

[0012] 4) Providing a battery internal resistance calculation system capable of determining the reliability of measurement results by evaluating the rise characteristics of the current step. means of solving the problem

[0013] To solve the above problem, the battery internal resistance calculation device according to the present invention is configured to calculate the internal resistance of the battery while applying a step-type discharge current that rises to a preset target current value to the battery. The device includes a data acquisition unit that samples and stores the voltage and current of the battery in a preset first period; a current representative value generation unit that generates a current representative value every second period based on current samples stored in the data acquisition unit; a voltage representative value generation unit that generates a voltage representative value every second period based on voltage samples stored in the data acquisition unit that are later than the time point corresponding to the current representative value by a preset time delay (td); and an internal resistance calculation unit that calculates the internal resistance of the battery at a judgment time point (tc) after the application of the discharge current using the current representative value and the voltage representative value.

[0014] According to one example, the representative current value may be a value generated by filtering a plurality of current samples acquired during the second period, and the representative voltage value may be a value generated by filtering a plurality of voltage samples acquired late by the time delay (td) during the second period.

[0015] According to another example, the current representative value may be the average value of a plurality of current samples acquired during the second period, and the voltage representative value may be the average value of a plurality of voltage samples acquired later by the time delay (td) during the second period.

[0016] According to another example, the internal resistance calculation unit can calculate the internal resistance as dV / dI based on the difference (dI) between the representative current value at the judgment point (tc) and the representative current value at the reference point (t0) corresponding to the application of the discharge current, and the difference (dV) between the representative voltage value at the judgment point (tc) and the representative voltage value at the reference point (t0).

[0017] According to another example, the judgment point (tc) may be determined as the point in time when the representative current value becomes greater than or equal to a preset ratio of the target current value.

[0018] According to another example, the above preset ratio may be 70% or more.

[0019] According to another example, the judgment point (tc) can be determined as a point corresponding to a preset ratio of the target current value through interpolation of the representative current values.

[0020] According to another example, the internal resistance calculation unit can calculate the internal resistance as dV / dI based on the difference (dI) between the preset ratio of the target current value and the representative current value at the reference point (t0) corresponding to the application of the discharge current, and the difference (dV) between the interpolated voltage value corresponding to the judgment point (tc) calculated through interpolation of the representative voltage values ​​and the representative voltage value at the reference point (t0).

[0021] According to another example, the time delay (td) may be a value calibrated using the same configuration as the data acquisition unit, the current representative value generation unit, the voltage representative value generation unit, and the internal resistance calculation unit for a reference battery with a known internal resistance value.

[0022] A battery internal resistance calculation system according to the present invention comprises a power converter configured to apply a step-type discharge current rising to a preset target current value to the battery, a signal processing device that samples the voltage and current of the battery while controlling the power converter and generates a representative current value and a representative voltage value based on the sampled voltage and current, and a calculation device that calculates the internal resistance of the battery using the representative current value and the representative voltage value, wherein the representative voltage value is generated based on voltage samples at a time point that is later than the time point corresponding to the representative current value by a preset time delay (td).

[0023] According to one example, the signal processing device may include a Digital Signal Processor (DSP) that samples the voltage and current of the battery in a first period and stores them in a buffer, and generates the representative current value and the representative voltage value of a second period from the samples stored in the buffer.

[0024] According to another example, the first period may be 5 microseconds (μs) and the second period may be 1 millisecond (ms).

[0025] According to another example, the computing device is an external computing device configured to communicate with the signal processing device via a network, and the signal processing device can transmit the current representative value and the voltage representative value to the external computing device in packet units.

[0026] According to another example, the system may further include a current step suitability determination unit that determines the internal resistance calculation result as abnormal when the rising slope of the discharge current is below a preset threshold.

[0027] A method for calculating the internal resistance of a battery according to the present invention comprises the steps of: sampling and storing the voltage and current of the battery in a predetermined first period; generating a representative current value every second period based on the stored current samples; generating a representative voltage value every second period based on voltage samples at a time point that is later than the time point corresponding to the representative current value among the stored voltage samples by a predetermined time delay (td); determining a judgment time point (tc) after the application of the discharge current and a current value corresponding to the judgment time point (tc) using the representative current value; determining a voltage value corresponding to the judgment time point (tc) using the representative voltage value; and calculating the internal resistance of the battery based on the current value and the voltage value corresponding to the judgment time point (tc).

[0028] According to one example, the step of generating the current representative value includes the step of calculating the average value of a plurality of current samples acquired during the second period, and the step of generating the voltage representative value may include the step of calculating the average value of a plurality of voltage samples acquired late by the time delay (td) during the second period.

[0029] According to another example, the method may further include the step of calibrating the time delay (td) by generating the current representative value and the voltage representative value in the same manner for a reference battery with a known internal resistance value and calculating the internal resistance. Effects of the invention

[0030] According to the present invention, by generating a representative voltage value from voltage samples at a time point that is later than the time point corresponding to the representative current value by a preset time delay (td), the group delay difference between the voltage channel and the current channel of the measurement system, time alignment errors in the sampling and data processing process, and the electrochemical response delay of the battery can be effectively compensated. By correcting the time discrepancy between voltage and current, the accuracy of the measurement of the battery's internal resistance is improved, and consistent results can be obtained when repeating measurements are taken on the same battery, thereby significantly improving measurement reliability. Through a calibration method using a reference battery with known internal resistance, the time delay (td) inherent to the measurement system can be quantitatively determined, and by applying the td value, which has been calibrated once, to various battery types and measurement conditions, the measurement accuracy of the entire system can be uniformly improved.

[0031] By determining an appropriate decision point (tc) by considering the transient period during which the step current rises to a target value in a high-current system, and by using interpolation when necessary, precise internal resistance measurement is possible even in practical environments. By evaluating the slope of the rising current step to determine the reliability of the measurement results, errors under abnormal measurement conditions can be detected and excluded in advance, thereby improving the stability and reliability of battery testing.

[0032] Since real-time time delay correction can be performed in signal processing devices such as DSPs (Digital Signal Processors), it can be effectively utilized for online status diagnosis in manufacturing processes or Battery Management Systems (BMS) that require rapid inspection of a large number of battery cells. Brief explanation of the drawing

[0033] FIG. 1 is a schematic diagram of a battery internal resistance calculation device according to one embodiment of the present invention. FIG. 2 is an overall configuration diagram of a battery internal resistance calculation system according to one embodiment of the present invention. Figure 3 is a block diagram showing the internal configuration of the signal processing device illustrated in Figure 2. FIG. 4 is a timeline diagram showing the time delay (td) correction concept according to the present invention on the time axis. Figure 5 is a graph showing the current and voltage response characteristics and the concept of internal resistance calculation when a step-shaped discharge current is applied to the battery. FIG. 6 is a graph showing another embodiment for determining the judgment time point (tc). Figure 7 is a graph showing an example of precisely determining the decision time point (tc) through interpolation of representative current values. FIG. 8 is a flowchart illustrating a method for calculating battery internal resistance according to an embodiment of the present invention. FIG. 9 is a flowchart illustrating a time delay (td) calibration method according to one embodiment of the present invention. Specific details for implementing the invention

[0034] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression may include a plural expression unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this disclosure. Terms used in this disclosure that are defined in a general dictionary may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure are not to be interpreted to exclude the embodiments of this disclosure.

[0035] In this specification, "battery" refers to a rechargeable secondary battery and includes, but is not limited to, lithium-ion batteries, lithium polymer batteries, lithium iron phosphate batteries, etc. For example, supercapacitors may also be included in the batteries of this specification.

[0036] In this specification, "step-type discharge current" refers to a discharge current that rises rapidly from 0A or a low current value to a preset target current value. In actual high-current systems, due to physical constraints, it may take several milliseconds to tens of milliseconds to reach the target current value, and such cases are also included in the "step-type."

[0037] The "internal resistance" calculated in this specification is a value calculated based on the ratio of the change in voltage to the change in current at a specific judgment point after the application of a step-type discharge current, and may refer to the effective internal resistance that reflects not only the pure ohmic resistance of the battery but also some electrochemical polarization components. Accordingly, the internal resistance in this specification should be understood as a practical parameter defined according to the measurement time and conditions.

[0038] In this specification, "time delay (td)" refers to a time offset for acquiring voltage samples later than the point in time corresponding to the current representative value when generating the voltage representative value, and generally has a value of several milliseconds (ms) or less, and may be expressed in microseconds (µs).

[0039] When an element is described in this specification as being "connected" to another element, this includes not only cases where they are "directly connected" but also cases where they are "indirectly connected" with another element in between. When an element is described as "comprising" another element, this means that, unless specifically stated otherwise, it does not exclude other elements in addition to the other elements but may include additional elements.

[0040] Some embodiments may be described by functional block configurations and various processing steps. Some or all of these functional blocks may be implemented by various numbers of hardware and / or software configurations that perform specific functions. For example, the functional blocks of the present disclosure may be implemented by one or more microprocessors or by circuit configurations for a specific function. The functional blocks of the present disclosure may be implemented in various programming or scripting languages. The functional blocks of the present disclosure may be implemented as algorithms executed on one or more processors. The function performed by the functional block of the present disclosure may be performed by a plurality of functional blocks, or the functions performed by a plurality of functional blocks in the present disclosure may be performed by a single functional block.

[0041] In the following description of the present invention, detailed descriptions of components, such as prior art and known technology, that are deemed to unnecessarily obscure the essence of the invention may be omitted.

[0042] Hereinafter, various embodiments are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present disclosure. However, since the technical concept of the present disclosure can be modified and implemented in various forms, it is not limited to the embodiments described in this specification. Identical or similar components are given the same reference numerals, and redundant descriptions thereof are omitted.

[0044] FIG. 1 is a schematic diagram of a battery internal resistance calculation device according to one embodiment of the present invention.

[0045] Referring to FIG. 1, the battery internal resistance calculation device (100) is configured to calculate the internal resistance of the battery (10) while applying a step-shaped discharge current to the battery (10) by means of a power converter (110). The battery internal resistance calculation device (100) of the present invention includes a sensor (120), a data acquisition unit (130), a current representative value generation unit (140), a voltage representative value generation unit (150), and an internal resistance calculation unit (160). In one embodiment, the battery internal resistance calculation device (100) may further include a power converter (110). In another embodiment, the battery internal resistance calculation device (100) may include only the sensor (120), the data acquisition unit (130), the current representative value generation unit (140), the voltage representative value generation unit (150), and the internal resistance calculation unit (160), excluding the power converter (110).

[0046] The power converter (110) applies a step-type discharge current to the battery (10) that rises to a preset target current value. The power converter (110) may be configured, for example, as an AC / DC converter, a DC / DC converter, or a combination thereof, and generates a discharge current by converting power supplied from an external power source into a form that the battery (10) can absorb. The target current value may be determined according to the capacity, rated current, and test conditions of the battery (10), and may be set, for example, to 50A, 100A, 200A, etc.

[0047] In actual high-current systems, due to the response characteristics of the power converter (110), the electrochemical characteristics of the battery (10), the inductance of the power path, and the constraints of the control algorithm, the discharge current does not reach the target current value from 0A instantaneously but rises in the form of an exponential rise over several milliseconds to tens of milliseconds. For example, for a target current of 100A, it may take about 10 milliseconds to reach 99A from 0A. In this specification, it should be understood that a discharge current having such realistic current rise characteristics is also included in the “step-type discharge current.”

[0048] The sensor (120) is configured to measure the current and voltage of the battery (10). The sensor (120) includes a current sensor (122) and a voltage sensor (124). The current sensor (122) is connected in series to the power path between the battery (10) and the power converter (110) to measure the current (i) flowing to the battery (10). The current sensor (122) can be implemented, for example, as a shunt resistor-based current sensor, a Hall effect sensor, a current transformer, etc. The voltage sensor (124) is connected to both ends of the battery (10) to measure the terminal voltage (v) of the battery (10). The voltage sensor (124) can be implemented, for example, as a voltage divider, an isolation amplifier, etc.

[0049] The current sensor (122) and the voltage sensor (124) may each include an independent signal conditioning circuit, and such signal conditioning circuit may include an amplifier, an analog filter (e.g., a low-pass filter), a buffer, etc. The signal path of the current sensor (122) and the signal path of the voltage sensor (124) may have different circuit configurations and filter characteristics, which may result in a group delay difference between the current measurement and the voltage measurement.

[0050] The data acquisition unit (130) samples and stores the voltage (v) and current (i) of the battery (10) from the current sensor (122) and the voltage sensor (124) at a predetermined first period. The first period may be, for example, 5 microseconds (μs), in which case 200,000 samples are generated per second. The data acquisition unit (130) includes a high-speed ADC (Analog-to-Digital Converter) and converts the analog signals output from the current sensor (122) and the voltage sensor (124) into digital values ​​and stores them in an internal buffer (memory).

[0051] The data acquisition unit (130) may include a current buffer for storing current samples and a voltage buffer for storing voltage samples. The size of the buffer may be determined according to the number of samples required in a subsequent processing step, for example, each of the current buffer and the voltage buffer may have a size capable of storing 200 or more samples. In one embodiment, if the time delay (td) is assumed to be less than or equal to the second period, the current buffer may have a size capable of storing approximately 400 samples and the voltage buffer may have a size capable of storing approximately 200 samples. The buffer may be implemented as a circular buffer or a First-In-First-Out (FIFO) structure.

[0052] The current representative value generation unit (140) generates a current representative value (I) for every second period based on current samples stored in the data acquisition unit (130). The second period is set to a longer time than the first period, for example, 1 millisecond (ms). If the first period is 5 microseconds and the second period is 1 millisecond, the second period corresponds to 200 first periods.

[0053] A representative current value (I) can be generated by filtering a plurality of current samples acquired during a second period. Filtering can be performed using methods such as, for example, average, moving average, low-pass filtering, and median filtering. In one embodiment, a representative current value generation unit (140) can generate a representative current value (I) by calculating the arithmetic mean of 200 current samples acquired during a second period. This filtering process has the effect of removing high-frequency noise and improving the signal-to-noise ratio (SNR) of the measurement signal.

[0054] The voltage representative value generation unit (150) generates a voltage representative value (V) every second period based on voltage samples at a time point that is later than the time point corresponding to the current representative value by a preset time delay (td) among the voltage samples stored in the data acquisition unit (130).

[0055] Specifically, when the current representative value generation unit (140) generates the current representative value I[t] at time point t, it uses current samples from time point (t - second period) to time point t, whereas the voltage representative value generation unit (150) generates the voltage representative value V[t] at time point t, it uses voltage samples from time point (t - second period + td) to time point (t + td). That is, the voltage sample interval for generating the voltage representative value is set later (shifted to the right) on the time axis by td compared to the current sample interval for generating the current representative value.

[0056] Time delay (td) is a parameter used to compensate for group delay differences between the voltage and current channels of the measurement system, time alignment errors during sampling and data processing, and electrochemical response delays of the battery. The value of time delay (td) is generally in the range of several hundred microseconds (µs), and can, for example, have a value between 300 microseconds and 800 microseconds. As a specific example, td can be set to 600 microseconds.

[0057] The time delay (td) can be pre-calibrated by performing the same representative value generation and internal resistance calculation procedures for a reference battery with a known internal resistance value. The calibration method is described in detail in Fig. 9 below. Once calibrated, the td value can be consistently applied to various batteries as long as the hardware configuration of the measurement system is not changed. In one embodiment, the time delay (td) can be used as a fixed value. In another embodiment, the time delay (td) may vary depending on the type of battery, state of charge (SOC), temperature, etc. In this case, optimized td values ​​for each battery type, SOC, and temperature are stored in memory in the form of a lookup table (LUT) and can be selectively applied according to measurement conditions. For example, NCM batteries and LFP batteries may have different td values ​​because their electrochemical characteristics differ, and even for the same battery, the optimal td value may differ at SOC 20% and SOC 80%.

[0058] A representative voltage value (V) can also be generated by filtering multiple voltage samples, just like a representative current value. In one embodiment, a representative voltage value generation unit (150) can generate a representative voltage value (V) by calculating the arithmetic mean of 200 voltage samples in a section shifted by a time delay (td).

[0059] The internal resistance calculation unit (160) calculates the internal resistance of the battery (10) at a determination point (tc) after applying the discharge current, using the representative current value (I) and the representative voltage value (V). The determination point (tc) can be determined as the point in time when the step discharge current rises above a preset ratio (e.g., 70% or 90%) of the target current value. This is to increase measurement reliability by measuring the internal resistance in a section where the current has risen sufficiently and stabilized.

[0060] Internal resistance is basically calculated as the ratio of the voltage change amount (dV) and the current change amount (dI) according to Ohm's law. Specifically, the internal resistance calculation unit (160) can calculate the difference (dV) between the representative voltage value V[tc] at the judgment point (tc) and the representative voltage value V[t0] at the reference point (t0) corresponding to the step discharge current application point, and calculate the difference (dI) between the representative current value I[tc] at the judgment point (tc) and the representative current value I[t0] at the reference point (t0), and then calculate the internal resistance (Rint) using the following formula:

[0061] Rint = -dV / dI = -(V[tc] - V[t0]) / (I[tc] - I[t0])

[0062] Here, the negative sign (-) takes into account that the voltage decreases and the current increases during discharge. The reference point (t0) is a point in time corresponding to the point in time when the step discharge current is applied, for example, it may be a point in time immediately after the current starts to rise in a step form from 0A or the steady-state current.

[0063] In the present invention, since the representative voltage value V[tc] is generated by considering the time delay (td), a voltage value time-aligned with the representative current value I[tc] is used, enabling more accurate measurement of internal resistance.

[0064] The internal resistance calculation unit (160) may be implemented within the same physically identical device as the current representative value generation unit (140) and the voltage representative value generation unit (150), or it may be implemented in a separate device. For example, as shown in FIG. 2 described later, the data acquisition unit (130), the current representative value generation unit (140), and the voltage representative value generation unit (150) may be implemented in a DSP (Digital Signal Processor), and the internal resistance calculation unit (160) may be implemented in an external computing device (PC). Alternatively, the internal resistance calculation unit (160) may be implemented in an MCU (Micro Controller Unit).

[0065] With such a configuration, the battery internal resistance calculation device (100) of the present invention can measure the battery internal resistance more accurately and consistently by correcting the time discrepancy between the voltage measurement value and the current measurement value. In particular, it can significantly improve the accuracy and reproducibility of the internal resistance measurement by effectively compensating for the group delay difference of the measurement system, sampling error, and electrochemical response delay of the battery that may occur when performing battery testing in a high-current system.

[0067] FIG. 2 is an overall configuration diagram of a battery internal resistance calculation system according to one embodiment of the present invention.

[0068] Referring to FIG. 2, the battery internal resistance calculation system (1000) includes a measuring device (200) and a computing device (300). The measuring device (200) includes a hardware configuration for measuring the internal resistance of the battery (10) and may include a power converter (210), a sensor (220), a signal processing device (230), and an intermediate transmission device (240). The computing device (300) calculates the internal resistance of the battery (10) using data received from the measuring device (200).

[0069] The measuring device (200) includes a power converter (210), a sensor (220), a signal processing device (230), and an intermediate transmission device (240). In one embodiment, the measuring device (200) may include only the sensor (220), the signal processing device (230), and the intermediate transmission device (240), excluding the power converter (210).

[0070] The power converter (210) is configured to apply a step-type discharge current to the battery (10) that rises to a preset target current value under the control of the signal processing device (230). Specifically, when the power converter (210) receives a command to apply the discharge current from the signal processing device (230), it begins to apply the discharge current to the battery (10). The power converter (210) performs the same function as the power converter (110) shown in FIG. 1 and may be configured as an AC / DC converter, a DC / DC converter, or a combination thereof.

[0071] The sensor (220) is configured to measure the current and voltage of the battery (10). The sensor (220) includes a current sensor (222) and a voltage sensor (224). The current sensor (222) measures the current (i) flowing through the battery (10), and the voltage sensor (224) measures the terminal voltage (v) of the battery (10). The sensor (220) performs the same function as the sensor (120) shown in FIG. 1.

[0072] The signal processing unit (230) samples the voltage and current of the battery (10) while controlling the power converter (210), and generates a representative current value (I) and a representative voltage value (V) based on the sampled voltage and current. The signal processing unit (230) can be implemented, for example, as a Digital Signal Processor (DSP).

[0073] The signal processing device (230) may transmit a discharge current application command to the power converter (210) according to a command received from the computing device (300) or the intermediate transmission device (240). After transmitting the discharge current application command, the signal processing device (230) performs current and voltage sampling in a first period (e.g., 5 μs) only for a preset time (e.g., 3 seconds) and outputs representative current and voltage values ​​in a second period. Here, outputting representative current and voltage values ​​in a second period (e.g., 1 ms) is intended to accurately calculate the internal resistance of the battery (10). Meanwhile, before transmitting the discharge current application command or after the preset time has elapsed, the signal processing device (230) may output representative current and voltage values ​​in a period longer than the second period (e.g., 10 ms) or perform sampling in a period longer than the first period. This is intended to reduce power consumption of the system and lower the communication load.

[0074] The signal processing device (230) samples the voltage and current of the battery (10) in a first period (e.g., 5 μs) and stores them in a buffer, and generates a representative current value and a representative voltage value for a second period (e.g., 1 ms) from the samples stored in the buffer. The signal processing device (230) performs the functions of the data acquisition unit (130), the representative current value generation unit (140), and the representative voltage value generation unit (150) shown in FIG. 1. The internal configuration of the signal processing device (230) is described in detail in FIG. 3, which will be described later. In another embodiment, the signal processing device (230) may also perform the function of the internal resistance calculation unit (160) shown in FIG. 1.

[0075] The voltage representative value generated by the signal processing device (230) is generated based on voltage samples at a time point that is later than the time point corresponding to the current representative value by a preset time delay (td). This allows for compensation of the time delay characteristics between the voltage channel and the current channel of the measurement system.

[0076] The intermediate transmission device (240) receives representative current values ​​and representative voltage values ​​from the signal processing device (230) and transmits them to the computation device (300) in packet units. The intermediate transmission device (240) may be implemented, for example, as a Micro Controller Unit (MCU). The intermediate transmission device (240) may receive 10 representative current values ​​and 10 representative voltage values ​​from the signal processing device (230), for example, every 10 milliseconds, and configure them into packets to transmit to the computation device (300).

[0077] In one embodiment, the intermediate transmission device (240) may perform only the function of transmitting data. In another embodiment, the intermediate transmission device (240) may include the function of the internal resistance calculation unit (160) of FIG. 1 and may directly calculate the internal resistance of the battery (10) using the received representative current value and representative voltage value. In this case, the intermediate transmission device (240) may transmit the calculated internal resistance value to the calculation device (300) or output it to a separate display device or storage device.

[0078] The calculation device (300) calculates the internal resistance of the battery (10) using a representative current value and a representative voltage value. The calculation device (300) can be implemented, for example, as an external computing device (PC) and can be configured to communicate via a network with a signal processing device (230) or an intermediate transmission device (240). The calculation device (300) performs the function of the internal resistance calculation unit (160) shown in FIG. 1.

[0079] The computing device (300) receives a packet from the intermediate transmission device (240), analyzes the representative current values ​​included in the packet to detect the occurrence of a step current, determines a judgment time point (tc), and calculates the voltage change amount (dV) and current change amount (dI) at the judgment time point (tc) to calculate the internal resistance. The operation of the computing device (300) is described in detail in FIG. 8, which will be described later.

[0080] In one embodiment, the measuring device (200) includes a signal processing device (230) and an intermediate transmission device (240), but may not include an internal resistance calculation function. In this case, the measuring device (200) generates a representative current value and a representative voltage value and transmits them to a calculation device (300), and the calculation device (300) calculates the internal resistance.

[0081] In another embodiment, the measuring device (200) may include an internal resistance calculation function in the intermediate transmission device (240), and the measuring device (200) alone may perform all the functions of the battery internal resistance calculation device (100) of FIG. 1. In this case, the calculation device (300) is optionally configured, and the measuring device (200) can independently measure the internal resistance of the battery (10) and output the result.

[0082] That is, the configuration and functional distribution of the measuring device (200) can be implemented in various ways according to system design requirements, and various combinations including a power converter (210), a sensor (220), a signal processing device (230), an intermediate transmission device (240), and optionally a computing device (300) are possible.

[0083] In this embodiment, the representative voltage value is generated based on voltage samples at a time point that is delayed by a preset time delay (td) compared to the time point corresponding to the representative current value, thereby compensating for the time delay characteristics of the measurement system and enabling accurate internal resistance measurement.

[0084] With this configuration, the battery internal resistance calculation system (1000) of the present invention has its functions distributed among a signal processing device (230), an intermediate transmission device (240), and a computation device (300), thereby distributing the processing burden of each device, while also enabling accurate and consistent measurement of battery internal resistance through time delay (td) correction.

[0085] In one embodiment, the system (1000) may further include a current step suitability determination unit that evaluates the rising slope of the discharge current to determine the reliability of the measurement result. The current step suitability determination unit may be implemented in a computing device (300), and in other embodiments, it may be implemented in an intermediate transmission device (240) or a signal processing device (230). The specific operation of the current step suitability determination unit is described in detail in FIG. 8, which is described later.

[0087] FIG. 3 is a block diagram showing the internal configuration of the signal processing device (230) illustrated in FIG. 2.

[0088] Referring to FIG. 3, the signal processing device (230) includes a power converter control unit (231), a sampling unit (232), a current representative value generation unit (233), a voltage representative value generation unit (234), and an output unit (235).

[0089] The power converter control unit (231) controls the power converter (210) to apply a step-shaped discharge current to the battery (10). The power converter control unit (231) may transmit a discharge current application command to the power converter (210) according to a command received from the computing device (300) or the intermediate transmission device (240). When the discharge current application command is transmitted, the power converter (210) starts applying the discharge current to the battery (10).

[0090] The sampling unit (232) samples the voltage (v) and current (i) of the battery (10) in a first period (e.g., 5 μs) and stores them in an internal buffer. The sampling unit (232) may perform current and voltage sampling in the first period only for a preset time (e.g., 3 seconds) after a discharge current application command is transmitted. Before transmitting the discharge current application command or after the preset time has elapsed, the sampling unit (232) may perform sampling in a period longer than the first period. This is intended to reduce the power consumption of the system.

[0091] The current representative value generation unit (233) generates a current representative value (I) for a second period (e.g., 1 ms) from current samples stored in the buffer of the sampling unit (232). The current representative value (I) can be generated by filtering (e.g., averaging) a plurality of current samples acquired during the second period. For example, if the first period is 5 microseconds and the second period is 1 millisecond, the current representative value generation unit (233) can generate the current representative value (I) by calculating the average value of 200 current samples.

[0092] The voltage representative value generation unit (234) generates a voltage representative value (V) of the second period from voltage samples stored in the buffer of the sampling unit (232) that are at a time point later than the time point corresponding to the current representative value by a time delay (td). The voltage representative value (V) can also be generated by filtering (e.g., averaging) multiple voltage samples, just like the current representative value. However, there is a difference in that the acquisition interval of the voltage samples is set later than the acquisition interval of the current samples by a time delay (td, e.g., 600 microseconds). Through this time delay correction, the group delay difference between the voltage channel and the current channel of the measurement system, the time alignment error in the sampling and data processing process, and the electrochemical response delay of the battery can be effectively compensated.

[0093] The output unit (235) outputs the generated current representative value (I) and voltage representative value (V) to the intermediate transmission device (240). The output unit (235) may output the current and voltage representative values ​​in a second cycle only for a preset time (e.g., 3 seconds) after the discharge current application command is transmitted. The output unit (235) may transmit 10 current representative values ​​and 10 voltage representative values ​​to the intermediate transmission device (240) every 10 milliseconds.

[0094] Before transmitting a discharge current application command or after a preset time has elapsed, the output unit (235) may output representative current and voltage values ​​at a period longer than the second period (e.g., 10 ms). At this time, the output unit (235) may transmit one representative current value and one representative voltage value to the intermediate transmission device (240) every 10 milliseconds. This is intended to reduce the communication load.

[0095] With this configuration, the signal processing device (230) can generate a representative value while performing time delay (td) correction in real time, and can improve the power efficiency and communication efficiency of the system by performing high-speed sampling and output only in the section where the internal resistance of the battery needs to be measured.

[0097] FIG. 4 is a timeline diagram showing the time delay (td) correction concept according to the present invention on the time axis.

[0098] Referring to Fig. 4, the time axis proceeds in units of the first period (T1, e.g., 5 microseconds), and the second period (T2, e.g., 1 millisecond) corresponds to 200 × T1. The time delay (td) is a parameter of the time concept, and Td represents a natural number obtained by converting td into units of the first period (T1). For example, if td = 600 μs and T1 = 5 μs, then Td = 120.

[0099] The buffer size of the data acquisition unit (130) can be appropriately set according to the td value. In one embodiment, when td is less than or equal to the second period (T2), the voltage buffer may have a size capable of storing approximately 200 samples corresponding to the second period, and the current buffer may have a size capable of storing approximately 400 samples corresponding to the interval of the second period plus the time delay (td). In another embodiment, when td is determined, the current buffer may have a size capable of storing the number of samples corresponding to T2+td, and the voltage buffer may have a size capable of storing the number of samples corresponding to T2.

[0100] Current samples sampled for each first period are sequentially stored in the current buffer, such as i0, i1, i2, ..., i(Td-1), i(Td), i(Td+1), ..., i198, i199, i200, i201, ..., i(Td+199), i(Td+200), ..., i398, i399.

[0101] Voltage samples sampled for each first period are also sequentially stored in the voltage buffer, such as v0, v1, v2, ..., v(Td-1), v(Td), v(Td+1), ..., v198, v199, v200, v201, ..., v(Td+199), v(Td+200), ..., v398, v399.

[0102] According to the present invention, the sample intervals used when generating the current representative value and the voltage representative value are set differently. The current representative value I[1] at time t=T2 (1 millisecond) is generated by filtering (e.g., averaging) 200 samples from samples i0 to i199. That is, I[1] can be expressed as filter(i0, i1, ..., i199).

[0103] On the other hand, when generating the representative voltage value V[1] at time t=T2 (1 millisecond), voltage samples from a time delay (td) are used instead of the same interval (i0~i199) as the representative current value. Specifically, V[1] can be expressed as V[1] = filter(v(Td), v(Td+1), ..., v(Td+199)). That is, the voltage sample interval is set from v(Td) to v(Td+199), and is shifted to the right (acquired later) by td on the time axis compared to the current sample interval.

[0104] At any given time point t, the representative current value (I[t]) and the representative voltage value (V[t]) can be expressed as I[t] = filter(i_(t-T2), ..., i_t) and V[t] = filter(v_(t-T2+td), ..., v_(t+td)), respectively.

[0105] In this way, by generating the representative voltage value from samples at a time point td later than the representative current value, the difference in group delay between the voltage channel and the current channel of the measurement system, time alignment errors in the sampling and data processing process, and the electrochemical response delay of the battery are effectively corrected, thereby enabling accurate measurement of internal resistance.

[0107] Figure 5 is a graph showing the current and voltage response characteristics and the concept of internal resistance calculation when a step-shaped discharge current is applied to the battery.

[0108] Referring to FIG. 5, the graph includes a curve representing the temporal change of a representative current value (I) and a curve representing the temporal change of a representative voltage value (V). The horizontal axis represents time (in milliseconds), the left vertical axis represents voltage (V), and the right vertical axis represents current (A).

[0109] When a step discharge current is applied, the current increases exponentially from around 0A to a target current value (approx. 100A). In actual high-current systems, due to the response characteristics of the power converter, the electrochemical characteristics of the battery, the inductance of the power path, and constraints of the control algorithm, the discharge current does not reach the target value instantaneously but rises over a period of several milliseconds to tens of milliseconds. In this embodiment, it can be seen that it takes about 10 milliseconds for the current to rise from 0A to approximately 100A.

[0110] The judgment point (tc) is determined as the point when the representative current value reaches a preset ratio (e.g., 70%) of the target current value. In Figure 5, since the target current value is approximately 100A, the 70% point corresponds to approximately 70A, and the point t6, when the representative current value reaches this value, is determined as the judgment point (tc). At this point, the current is considered to have risen sufficiently, and measurement reliability can be improved by measuring the internal resistance at this point.

[0111] The voltage drops sharply with the application of step current and then decreases gradually. The initial sharp voltage drop is mainly due to the ohmic resistance component of the battery, and the subsequent gradual decrease reflects the electrochemical polarization and diffusion components.

[0112] Internal resistance (Rint) is calculated as the ratio of the change in voltage (dV) and the change in current (dI) between the judgment time point (tc) and the reference time point (t0):

[0113] Rint = -dV / dI = -(V[tc] - V[t0]) / (I[tc] - I[t0])

[0114] Here, t0 is the reference point immediately after the step current is applied, tc is t6, and the negative sign (-) takes into account that the voltage decreases and the current increases during discharge. In Figure 5, the voltage change amount (dV) and current change amount (dI) at time t6 are indicated by arrows, and the internal resistance is calculated based on their ratio.

[0115] In the present invention, by applying a time delay (td) correction when generating the representative voltage value V[tc], dV is measured more accurately, thereby improving the accuracy of the calculation of internal resistance.

[0117] FIG. 6 is a graph showing another embodiment for determining the judgment time point (tc).

[0118] Referring to FIG. 6, in this embodiment, the point (ts) at which the step discharge current reaches 90% or more of the target current value is first identified. The point t11, at which the representative current value exceeds the 90% point (approx. 90A) indicated by the dotted line in the graph, is determined as ts.

[0119] Next, the average value (I_avg) of a predetermined number (e.g., 5) of representative current values ​​(e.g., I[t7], I[t8], I[t9], I[t10], I[t11]) prior to time point ts is calculated. Then, among these representative current values, the time point that has the value closest (approximate) to I_avg is selected as the judgment time point (tc). In FIG. 6, time point t9 is determined as the judgment time point (tc).

[0120] For example, if I[t9] is closest to I_avg, tc = t9 is determined, and in some cases, I[t10] may be selected. This method can increase measurement reliability by calculating the internal resistance in a region where the current is sufficiently close to the target value and stabilized.

[0121] In this embodiment as well, the internal resistance is calculated as Rint = -dV / dI = -(V[tc] - V[t0]) / (I[tc] - I[t0]), and a time delay (td) correction is applied when generating the representative voltage value. In FIG. 6, the judgment time point (tc=t9) and ts (t11) are distinguished and displayed, and the voltage change amount (dV) and current change amount (dI) at time point tc are clearly indicated by arrows.

[0123] Figure 7 is a graph showing an example of precisely determining the decision time point (tc) through interpolation of representative current values.

[0124] Referring to FIG. 7, the present embodiment calculates a point in time that exactly corresponds to a preset ratio (e.g., 70%) of the target current value through interpolation. Since the current representative values ​​are generated only at discrete points in time, the point in time corresponding to exactly 70% of the target current value may not coincide with the point in time when the representative values ​​are generated. In this case, the exact tc can be determined by using methods such as linear interpolation or spline interpolation between two current representative values ​​around the 70% value.

[0125] For example, when the representative current value I[t5] at time point t5 is 65A and the representative current value I[t6] at time point t6 is 75A, the exact time point tc corresponding to 70A, which is 70% of the target current value of 100A, can be calculated by linear interpolation as follows:

[0126] tc = t5 + (t6 - t5) × (70 - 65) / (75 - 65) = t5 + 0.5 × (t6 - t5)

[0127] The current value at tc determined in this way becomes exactly 70% of the target current value. Similarly, the voltage value can be calculated by interpolating the representative voltage values ​​to obtain the interpolated voltage value corresponding to time tc.

[0128] The internal resistance is calculated as follows:

[0129] Rint = -dV / dI = -(V_interpolated[tc] - V[t0]) / (70A - I[t0])

[0130] Here, V_interpolated[tc] is the interpolated voltage value at time tc calculated through interpolation of the voltage representative values.

[0131] This interpolation method minimizes the inaccuracy of the judgment timing caused by the discrete nature of the current representative value, thereby enabling more precise internal resistance measurement. In this embodiment as well, time delay (td) correction is applied when generating the voltage representative value, so that the time alignment between the voltage value and the current value at the judgment time (tc) is optimized.

[0133] FIG. 8 is a flowchart illustrating a method for calculating battery internal resistance according to an embodiment of the present invention.

[0134] Referring to Fig. 8, a computing device (e.g., a PC) calculates the internal resistance of the battery in the following order.

[0135] First, the computing device receives a packet containing a current representative value and a voltage representative value from an intermediate transmission device (S31). The packet may be received every, for example, 50 milliseconds, and each packet may contain 50 current representative values ​​and 50 voltage representative values. These representative values ​​are generated every second period (e.g., 1 millisecond) from data sampled in a first period (e.g., 5 microseconds) by a signal processing device, and the voltage representative values ​​are generated from voltage samples at a time point that is later than the time point corresponding to the current representative values ​​by a time delay (td).

[0136] Next, the occurrence of a step current is detected by analyzing the received representative current values ​​(S32). Since the step current appears as a pattern in which the current value rapidly increases from 0A or a low value to a target current value (e.g., 100A), the occurrence of the step current can be detected by comparing the consecutive representative current values ​​to detect the rapid increase section.

[0137] When a step current is detected, the reliability of the measurement result can be determined by evaluating the slope of the discharge current rise. Specifically, the slope of the discharge current rise is determined based on the time taken for the step discharge current to increase from 10% to 90% of the target current value. For example, the slope of the discharge current rise can be determined based on the time difference between the time immediately before exceeding 10% of the target current value and the time immediately after exceeding 90%, as well as the difference in current values ​​at these times, and this can be compared with a preset threshold value. More precisely, the time at exactly 10% and 90% of the target current value can be determined by applying interpolation to representative current values. If the slope of the discharge current rise is below the preset threshold value, it is determined that the current rise is too gradual to accurately measure internal resistance, and the internal resistance calculation result can be judged as abnormal and excluded. This function can be performed by the current step suitability judgment unit.

[0138] When the step current is detected normally and the rising slope of the discharge current is suitable, a judgment point (tc) is determined (S33). The judgment point (tc) can be determined as the point in time when the representative current value becomes greater than or equal to a preset ratio (e.g., 70% or 90%) of the target current value. In one embodiment, the point in time with the representative current value closest to 70% of the target current value can be directly selected as tc (see FIG. 5). In another embodiment, the average value (I_avg) of the representative current values ​​prior to the point in time (ts) when 90% or more of the target current value is reached is calculated, and the point in time with the representative current value closest to this average value can be selected as tc (see FIG. 6). In yet another embodiment, the point in time that exactly corresponds to the preset ratio of the target current value can be calculated as tc through interpolation of the representative current values ​​(see FIG. 7).

[0139] When a judgment time point (tc) is determined, a current value and a voltage value corresponding to the judgment time point (tc) are determined (S34). The representative current value I[tc] and the representative voltage value V[tc] at the judgment time point (tc) are checked, and the representative current value I[t0] and the representative voltage value V[t0] at the reference time point (t0) immediately after the step current is applied are also checked. If interpolation is used, the interpolated current value and the interpolated voltage value at time point tc can be calculated through interpolation of the representative current values ​​and the representative voltage values.

[0140] Finally, the internal resistance of the battery is calculated based on the current and voltage values ​​corresponding to the judgment time point (tc) (S35). The internal resistance (Rint) is calculated using the following formula:

[0141] Rint = -dV / dI = -(V[tc] - V[t0]) / (I[tc] - I[t0])

[0142] Here, dV is the amount of voltage change between the judgment time point (tc) and the reference time point (t0), dI is the amount of current change, and the negative sign (-) takes into account that the voltage decreases and the current increases during discharge.

[0143] The internal resistance calculated in this specification is a value calculated based on the ratio of the change in voltage and the change in current at a specific judgment point after the point of application of a step-type discharge current, and may mean the effective internal resistance that reflects not only the pure ohmic resistance of the battery but also some electrochemical polarization components.

[0144] In this method, since the representative voltage value is generated from voltage samples at a time point delayed by a time delay (td) compared to the time point corresponding to the representative current value, the time delay characteristics of the measurement system are corrected, enabling accurate internal resistance measurement.

[0145] By the method illustrated in FIG. 8, the present invention can accurately calculate the internal resistance of a battery using representative values ​​of voltage and current with time delay (td) correction applied, and can improve the reliability of the measurement by detecting and excluding errors in abnormal measurement conditions in advance through current step suitability judgment.

[0147] FIG. 9 is a flowchart illustrating a time delay (td) calibration method according to one embodiment of the present invention.

[0148] Referring to FIG. 9, a calibration method for determining the optimal time delay (td) value to be used in a measurement system is performed in the following order.

[0149] First, a reference battery with an accurately known internal resistance value is prepared (S41). The reference battery may be, for example, a battery whose internal resistance has been confirmed to be 0.5Ω using precision measuring equipment. It is desirable for the reference battery to have a similar type and capacity to the battery to be measured in the measurement system being calibrated.

[0150] Next, candidate values ​​for time delay to be used in the measurement system are set (S42). For example, candidate values ​​such as td = 0 microseconds, 200 microseconds, 400 microseconds, 600 microseconds, and 800 microseconds can be set. The range and interval of the candidate values ​​can be appropriately selected by considering the characteristics of the measurement system, the sampling period, and the expected delay characteristics.

[0151] Next, the internal resistance is calculated for the reference battery in the same way by applying each time delay candidate value (S43). Specifically, for each td candidate value, a voltage representative value is generated using voltage samples shifted by the corresponding td when generating the voltage representative value, and the internal resistance is calculated using the same configuration and method as the data acquisition unit (130), current representative value generation unit (140), voltage representative value generation unit (150), and internal resistance calculation unit (160) illustrated in FIG. 1. This process is repeated for all time delay candidate values.

[0152] Next, among the calculated internal resistance values, an internal resistance value having the minimum error with respect to the known internal resistance value of the reference battery is selected (S44). For example, if the known internal resistance of the reference battery is 0.5Ω, and the internal resistance calculated at td=0 microseconds is 0.42Ω (error: 0.08Ω), at td=200 microseconds is 0.45Ω (error: 0.05Ω), at td=400 microseconds is 0.48Ω (error: 0.02Ω), at td=600 microseconds is 0.502Ω (error: 0.002Ω), and at td=800 microseconds is 0.55Ω (error: 0.05Ω), then the internal resistance value (0.502Ω) corresponding to td=600 microseconds having the minimum error is selected.

[0153] Finally, a time delay candidate value corresponding to the selected internal resistance calculation value is determined as the time delay value (td) of the measurement system (S45). In the above example, td = 600 microseconds is determined as the time delay value of the measurement system. The td value determined in this way is subsequently consistently applied to generate a representative voltage value when measuring the internal resistance of various batteries, thereby compensating for the time delay characteristics of the measurement system.

[0154] In one embodiment, calibration can be performed by battery type (e.g., NCM, LFP), state of charge (SOC), or temperature, respectively, and in this case, optimal td values ​​corresponding to each condition are stored in the form of a lookup table and can be selectively applied according to measurement conditions.

[0155] Through this calibration method, the time delay (td) inherent to the measurement system can be quantitatively determined, and the measurement accuracy of the entire system can be uniformly improved by applying the calibrated td value to various battery types and measurement conditions.

[0157] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention.

[0158] For example, the present specification mainly describes cases where the first period is 5 microseconds and the second period is 1 millisecond, but these periods may be varied depending on the performance of the system, the characteristics of the battery, the required measurement accuracy, etc.

[0159] In addition, although the present specification describes the case where the time delay (td) is 600 microseconds as an example, the actual td value may vary depending on the hardware configuration of the measurement system, sensor characteristics, filter settings, battery type, etc., and can be determined as a value optimized for each system through calibration.

[0160] In addition, although the average has been primarily described in this specification as a filtering method for generating representative current and voltage values, various filtering methods such as moving averages, low-pass filters, and median filters may be used.

[0161] In addition, although the present specification mainly describes cases where the signal processing device is implemented as a DSP and the intermediate transmission device is implemented as an MCU, these functions can be implemented in various forms of hardware, such as a single processor or FPGA, and can also be implemented in software.

[0162] In addition, although the present specification presents various methods for determining the judgment point (tc), various other methods utilizing the stabilization of the current change rate (dI / dt), the characteristics of the voltage change rate (dV / dt), or combinations thereof may also be applied. Explanation of the symbols

[0164] 10: Battery 100: Battery Internal Resistance Calculation Device 110: Power converter 120: Sensor 122: Current sensor 124: Voltage sensor 130: Data Acquisition Unit 140: Current Representative Value Generation Unit 150: Voltage Representative Value Generation Unit 160: Internal resistance calculation section 200: Measuring device 210: Power converter 220: Sensor 222: Current sensor 224: Voltage sensor 230: Signal processing unit 231: Power converter control unit 232: Sampling section 233: Current Representative Value Generation Unit 234: Voltage Representative Value Generation Unit 235: Output section 240: Intermediate transmission device 300: Arithmetic Unit 1000: Battery Internal Resistance Calculation System

Claims

Claim 1 A battery internal resistance calculation system comprising: a power converter configured to apply a step-type discharge current rising to a preset target current value to the battery; a signal processing device that samples the voltage and current of the battery while controlling the power converter and generates a representative current value and a representative voltage value based on the sampled voltage and current; and a calculation device that calculates the internal resistance of the battery using the representative current value and the representative voltage value, wherein the representative voltage value is generated based on voltage samples at a time point that is later than the time point corresponding to the representative current value by a preset time delay (td). Claim 2 A battery internal resistance calculation system according to claim 1, wherein the signal processing device comprises a Digital Signal Processor (DSP) that samples the voltage and current of the battery in a first period and stores them in a buffer, and generates the representative current value and the representative voltage value of a second period from the samples stored in the buffer. Claim 3 A battery internal resistance calculation system according to claim 2, characterized in that the first period is 5 microseconds (μs) and the second period is 1 millisecond (ms). Claim 4 A battery internal resistance calculation system according to claim 1, wherein the computing device is an external computing device configured to communicate with the signal processing device via a network, and the signal processing device transmits the current representative value and the voltage representative value to the external computing device in packet units. Claim 5 A battery internal resistance calculation system according to claim 1, wherein the system further comprises a current step suitability determination unit that determines the internal resistance calculation result to be abnormal when the rising slope of the discharge current is below a preset threshold value. Claim 6 A battery internal resistance calculation system according to claim 1, wherein the signal processing device comprises: a data acquisition unit that samples and stores the voltage and current of the battery at a predetermined first period; a current representative value generation unit that generates a current representative value every second period based on current samples stored in the data acquisition unit; and a voltage representative value generation unit that generates a voltage representative value every second period based on voltage samples at a time point that is later than the time point corresponding to the current representative value among voltage samples stored in the data acquisition unit by a predetermined time delay (td); and wherein the computing device comprises an internal resistance calculation unit that calculates the internal resistance of the battery at a judgment time point (tc) after the application of the discharge current using the current representative value and the voltage representative value. Claim 7 A battery internal resistance calculation system according to claim 6, wherein the current representative value is a value generated by filtering a plurality of current samples acquired during the second period, and the voltage representative value is a value generated by filtering a plurality of voltage samples acquired late by the time delay (td) during the second period. Claim 8 A battery internal resistance calculation system according to claim 6, wherein the current representative value is the average value of a plurality of current samples acquired during the second period, and the voltage representative value is the average value of a plurality of voltage samples acquired late by the time delay (td) during the second period. Claim 9 A battery internal resistance calculation system according to claim 6, wherein the internal resistance calculation unit calculates the internal resistance as dV / dI based on the difference (dI) between the representative current value at the judgment point (tc) and the representative current value at the reference point (t0) corresponding to the application of the discharge current, and the difference (dV) between the representative voltage value at the judgment point (tc) and the representative voltage value at the reference point (t0). Claim 10 A battery internal resistance calculation system according to claim 6, characterized in that the judgment point (tc) is determined as the point in time when the representative current value becomes greater than or equal to a preset ratio of the target current value. Claim 11 A battery internal resistance calculation system according to claim 10, characterized in that the preset ratio is 70% or more. Claim 12 A battery internal resistance calculation system according to claim 6, characterized in that the judgment time point (tc) is determined as a time point corresponding to a preset ratio of the target current value through interpolation of the representative current values. Claim 13 A battery internal resistance calculation system according to claim 12, wherein the internal resistance calculation unit calculates the internal resistance as dV / dI based on the difference (dI) between the preset ratio of the target current value and the representative current value at a reference point (t0) corresponding to the application of the discharge current, and the difference (dV) between the interpolated voltage value corresponding to the judgment point (tc) calculated through interpolation of the representative voltage values ​​and the representative voltage value at the reference point (t0). Claim 14 A battery internal resistance calculation system according to claim 6, wherein the time delay (td) is a value calibrated using the same configuration as the data acquisition unit, the current representative value generation unit, the voltage representative value generation unit, and the internal resistance calculation unit for a reference battery with a known internal resistance value. Claim 15 A battery internal resistance calculation system according to claim 1, wherein the signal processing device is configured to sample and store the voltage and current of the battery in a predetermined first period, generate a representative current value every second period based on the stored current samples, and generate a representative voltage value every second period based on voltage samples at a time point later than the time point corresponding to the representative current value among the stored voltage samples by a predetermined time delay (td); and the computing device is configured to determine a judgment time point (tc) after the application of the discharge current and a current value corresponding to the judgment time point (tc) using the representative current value, determine a voltage value corresponding to the judgment time point (tc) using the representative voltage value, and calculate the internal resistance of the battery based on the current value and the voltage value corresponding to the judgment time point (tc). Claim 16 A battery internal resistance calculation system according to claim 15, wherein the signal processing device is configured to generate the current representative value by calculating the average value of a plurality of current samples acquired during the second period, and to generate the voltage representative value by calculating the average value of a plurality of voltage samples acquired late by the time delay (td) during the second period. Claim 17 A battery internal resistance calculation system according to claim 1, further comprising a control unit that calibrates the time delay (td) by generating the current representative value and the voltage representative value in the same manner for a reference battery with a known internal resistance value and calculating the internal resistance.

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