Method and system for measuring reference internal resistance of battery

Abstract

The invention provides a method and a system for measuring reference internal resistance of a battery. The method for measuring the reference internal resistance of the battery comprises the following steps of: (a) during a sensing period, sensing the battery voltage of the battery, the battery current flowing through the battery and the battery temperature of the battery so as to obtain a sensing result of the battery and further obtain the discharge depth; (b) in the step (a), the sensing result is compared with a preset threshold value, and whether the sensing result is accepted or not is determined; (c) when the sensing result is accepted, calculating the corresponding internal resistance of the battery according to the sensing result and the discharge depth; (d) performing regression analysis on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the discharge depth; and (e) obtaining a corresponding battery reference internal resistance according to the moving average battery internal resistance.

Description

Technical Field

[0001] The present invention relates to a method for measuring a battery reference internal resistance, and more particularly to a method for measuring a battery reference internal resistance by obtaining a moving average battery internal resistance through regression analysis. The present invention also relates to a system for measuring a battery reference internal resistance. Background Art

[0002] In the prior art methods and systems for determining the reference internal resistance of a battery, the reference internal resistance of the battery changes (usually increases) with the discharge current, temperature, and battery aging. This change in internal resistance has a significant impact on the accuracy of the estimation of the remaining capacity, discharge time, and state of health (SOH) of the battery. Therefore, in a battery management system, it is crucial to accurately estimate and predict the internal resistance of the battery.

[0003] Currently, the known battery internal resistance measurement method is usually performed when the battery discharge current is in a stable state with a fixed level. However, this method is difficult to apply to general applications such as laptop computers, because the discharge current of such devices may have large instantaneous changes. Therefore, the existing battery internal resistance measurement technology has limitations in practical applications and cannot effectively cope with the frequently changing discharge current conditions.

[0004] The main disadvantages of the battery internal resistance measurement method in the prior art include:

[0005] First, the response to instantaneous changes in battery internal resistance is insufficient: the existing technology cannot provide adequate response measures when the battery internal resistance changes with discharge current, temperature and aging, which leads to insufficient accuracy in battery internal resistance measurement.

[0006] Second, the application scope is limited: the existing battery internal resistance measurement technology usually requires the discharge current to be stable, which is difficult to achieve in most practical applications (such as laptops) because the current in these applications often changes. Therefore, this technology cannot be widely used in devices that require frequently changing current conditions.

[0007] Third, it affects the accuracy of estimation: Since the existing technology cannot accurately measure the internal resistance of the battery under changing current conditions, the estimation accuracy of the battery's remaining capacity, discharge time and health status is affected, which in turn affects the performance and reliability of the battery management system.

[0008] In summary, when facing actual application needs, the existing technology has the shortcomings of insufficient accuracy in measuring battery internal resistance, limited application scope, and affecting battery performance estimation. These problems urgently need to be solved through the development of new technologies.

[0009] In view of this, the present invention aims at the above-mentioned deficiencies of the prior art and proposes a method and system for measuring the reference internal resistance of a battery, which can not only improve the accuracy of battery internal resistance sensing, but also measure the reference internal resistance of the battery in an instant to improve the efficiency of battery reference internal resistance measurement. Summary of the invention

[0010] In one aspect, the present invention provides a method for determining a reference internal resistance of a battery, comprising: (a) during a sensing period, sensing a battery voltage, a battery current flowing through the battery, and a battery temperature of the battery to obtain a sensing result of the battery, thereby obtaining a depth of discharge (DOD); (b) in step (a), comparing the sensing result with a preset threshold to determine whether to accept the sensing result; (c) when the sensing result is accepted, calculating a corresponding battery internal resistance according to the sensing result and the depth of discharge; (d) performing a regression analysis on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the depth of discharge; and (e) calculating a corresponding battery reference internal resistance according to the moving average battery internal resistance.

[0011] In one embodiment, the method for determining a reference internal resistance of a battery further comprises: (f) selecting the sensing period during a discharge period, and determining whether the battery voltage is higher than an end of discharge voltage (EDV), and terminating the discharge period when the battery voltage is not higher than the end of discharge voltage.

[0012] In one embodiment, the method for determining a reference internal resistance of a battery further comprises: (g) in step (b), when the sensing result is not accepted and is discarded, step (a) is executed again during the next sensing period.

[0013] In one embodiment, the step (c) includes: calculating the battery internal resistance according to the battery voltage, the battery current and an open circuit voltage (OCV) corresponding to the discharge depth.

[0014] In one embodiment, the plurality of previous battery internal resistances include a plurality of battery internal resistances before the sensing period, or a plurality of moving average battery internal resistances before the sensing period.

[0015] In one embodiment, the regression analysis includes a linear regression analysis or a quadratic linear regression analysis.

[0016] In one embodiment, the step (e) includes: calculating the corresponding reference internal resistance of the battery according to the moving average internal resistance of the battery, the battery current and the battery temperature.

[0017] In one embodiment, the method for determining a reference internal resistance of a battery further comprises: (h) determining a next sensing period at the end of the sensing period according to the open circuit voltage and the discharge depth to repeat step (a) and further determine a sensing frequency, wherein the sensing frequency is inversely proportional to the sensing period.

[0018] In one embodiment, a time length of the next sensing period is negatively correlated to an absolute value of a slope between the open circuit voltage and the discharge depth.

[0019] In one embodiment, the sensing period does not exclude a transient condition.

[0020] In one embodiment, the step (b) includes: using the battery voltage as the sensing result and a corresponding open circuit voltage (OCV) as the preset threshold, and when the battery voltage is not higher than the corresponding open circuit voltage, deciding to accept the sensing result; and / or using the battery current as the sensing result and a current lower limit as the preset threshold, and when the battery current is not lower than the current lower limit, deciding to accept the sensing result.

[0021] In one embodiment, the lower current limit is 1 / 10 of the 1C discharge current of the battery.

[0022] In another aspect, the present invention provides a system for determining a reference internal resistance of a battery, comprising: a sensing unit for sensing a battery voltage, a battery current flowing through the battery, and a battery temperature of the battery during a sensing period to obtain a sensing result of the battery; and a control unit for comparing the sensing result with a preset threshold to determine whether to accept the sensing result, and when the sensing result is accepted, obtaining a depth of discharge (DOD) according to the sensing result, and then calculating a corresponding battery internal resistance, and performing a regression analysis on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the depth of discharge, and calculating a corresponding battery reference internal resistance based on the moving average battery internal resistance.

[0023] In one embodiment, the system for determining a battery reference internal resistance further comprises: a volatile memory unit for storing the battery internal resistance and the plurality of previous battery internal resistances; and a non-volatile memory unit for storing the battery reference internal resistance.

[0024] In one embodiment, the control unit selects the sensing period during a discharge period and determines whether the battery voltage is higher than an end of discharge voltage (EDV), and terminates the discharge period when the battery voltage is not higher than the end of discharge voltage.

[0025] In one embodiment, when the sensing result is not accepted and is rejected, the sensing unit re-senses the battery voltage, the battery current and the battery temperature during the next sensing period to obtain the next sensing result.

[0026] In one embodiment, the control unit calculates the battery internal resistance according to the battery voltage, the battery current and an open circuit voltage (OCV) corresponding to the discharge depth.

[0027] In one embodiment, the control unit calculates the corresponding battery reference internal resistance according to the moving average battery internal resistance, the battery current and the battery temperature.

[0028] In one embodiment, the control unit determines a next sensing period at the end of the sensing period according to the open circuit voltage and the discharge depth to repeat the sensing period, thereby determining a sensing frequency, wherein the sensing frequency is inversely proportional to the sensing period.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] First, accurate internal resistance measurement: This invention proposes a new method that can accurately detect the internal resistance of the battery by analyzing the data measured and stored in the memory through regression filtering, even when the discharge current changes. Unlike the prior art that requires a stable discharge current for accurate measurement, this invention overcomes this limitation and adapts to application scenarios with frequent current changes, such as laptops and other devices, thereby greatly improving the accuracy of internal resistance measurement.

[0031] Second, adaptive measurement time interval: The present invention provides an adaptive battery internal resistance measurement time interval, which aims to improve accuracy and save power. This means that the system can automatically adjust the measurement frequency according to actual needs to avoid unnecessary frequent measurements, thereby extending the battery life and improving energy efficiency; and increase the measurement frequency when the relevant parameters change drastically to improve measurement accuracy. This makes the present invention more practical and efficient in battery management systems, which is superior to existing technologies that can only perform measurements at fixed time intervals.

[0032] Combining the above advantages, the present invention can not only provide accurate battery internal resistance measurement under the condition of current fluctuation, but also effectively save power and improve accuracy through adaptive measurement time intervals, overcome the shortcomings of the existing technology in practical applications, and significantly improve the performance and reliability of the battery management system.

[0033] The following will be described in detail through specific embodiments to make it easier to understand the purpose, technical content, characteristics and effects achieved by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a module block diagram of a method for determining a reference internal resistance of a battery in one embodiment of the present invention.

[0035] Figure 2 It is an operational flow chart of a method for determining a reference internal resistance of a battery in one embodiment of the present invention.

[0036] Figure 3A and Figure 3B It is an operational flow chart of a method for determining a reference internal resistance of a battery in another embodiment of the present invention.

[0037] Figure 4A FIG. 4 is a schematic diagram showing a table lookup relationship between OCV and DOD in one embodiment of the present invention.

[0038] Figure 4B In one embodiment of the present invention, the corresponding Figure 4A Schematic diagram of the relationship between the local OCV and DOD lookup table relationship and the battery internal resistance calculated during multiple sensing periods.

[0039] Figure 4C A schematic diagram showing a regression analysis performed on a battery internal resistance and a plurality of previous battery internal resistances in one embodiment of the present invention is shown.

[0040] Figure 4D A schematic diagram showing the relationship between the old battery reference internal resistance and the updated battery reference internal resistance corresponding to the DOD before and after measuring the battery reference internal resistance in one embodiment of the present invention.

[0041] Explanation of symbols in the figure

[0042] 1: System for determining the reference internal resistance of batteries

[0043] 2: Battery Pack

[0044] 11: Sensing unit

[0045] 12: Control unit

[0046] 13: Volatile memory cell

[0047] 14: Non-volatile memory unit

[0048] 15: Charge / discharge drive unit

[0049] 111: Voltage sensing circuit

[0050] 112: Current sensing circuit

[0051] 113: Temperature Sensing Circuit

[0052] Bat1, Bat2, Bat3: Batteries

[0053] Ib: Battery current

[0054] R: Battery internal resistance

[0055] Rs: sensing resistor

[0056] Rstd: Battery reference internal resistance

[0057] S100-S140, S200~S280, S211: Steps

[0058] SR: Sensing result

[0059] SWC, SWD: Power Switch

[0060] Tc: Temperature sensitive element

[0061] tsp1-tsp8: sensing period

[0062] Vb1, Vb2, Vb3: battery voltage

[0063] Vb1', Vb2', Vb3': battery voltage sensing signals

[0064] Vb11'-Vb18': Battery voltage sensing signal

[0065] Vs: Battery current sensing signal

[0066] Vt: Battery temperature sensing signal

[0067] ΔV: Voltage difference DETAILED DESCRIPTION

[0068] The drawings in the present invention are all schematic, and are mainly intended to show the coupling relationship between various circuits and the relationship between various signal waveforms. The circuits, signal waveforms and frequencies are not drawn according to scale.

[0069] Please refer to Figure 1 , Figure 1 FIG. 1 is a block diagram of a system 1 for determining a reference internal resistance of a battery in one embodiment of the present invention. Figure 1As shown, the system 1 for determining the reference internal resistance of the battery includes a sensing unit 11 and a control unit 12. In the present embodiment, the system 1 for determining the reference internal resistance of the battery further includes a volatile memory unit 13, a non-volatile memory unit 14 and a charge / discharge drive unit 15. The sensing unit 11 includes, for example, a voltage sensing circuit 111, a current sensing circuit 112 and a temperature sensing circuit 113. It should be noted that the reference internal resistance refers to the internal resistance of the battery under certain temperature and load conditions, which will be stored in the non-volatile memory unit 14 and can be updated to be used as a reference for calculations related to battery characteristic parameters such as relative state of charge (RSOC) or full charge capacity (FCC).

[0070] In the present embodiment, the voltage sensing circuit 111 is coupled to a battery pack 2 and is used to sense the battery voltage Vb1, Vb2, Vb3 of each battery of a plurality of batteries Bat1, Bat2, Bat3 connected in series in the battery pack 2, and generate battery voltage sensing signals Vb1', Vb2', Vb3' accordingly. The battery voltage sensing signals Vb1', Vb2', Vb3' can be stored in a volatile memory unit 13 for calculation or transmission, and the battery current sensing signal and battery temperature sensing signal described later can also be stored in the volatile memory unit 13, which will not be described in detail. In some embodiments, the voltage sensing circuit 111 includes, for example but not limited to, an analog-to-digital converter (ADC) and a multiplexer (MUX) to realize the function of sensing voltage, wherein the structure and function of the analog-to-digital converter and the multiplexer are well known to those skilled in the art, and thus will not be described in detail.

[0071] The current sensing circuit 112 is coupled to the sensing resistor Rs connected in series with the battery pack 2 to sense the battery current Ib flowing through the batteries Bat1, Bat2, and Bat3, and to generate a battery current sensing signal Vs. The temperature sensing circuit 113 is coupled to the temperature-sensitive element Tc to sense the battery temperature and to generate a battery temperature sensing signal Vt. The battery voltage sensing signals Vb1', Vb2', and Vb3', the battery current sensing signal Vs, and the battery temperature sensing signal Vt form a sensing result SR.

[0072] In the present embodiment, the sensing unit 11 is used to sense the battery voltage Vb1, Vb2, Vb3 of each battery Bat1, Bat2, Bat3, sense the battery current Ib flowing through the battery Bat1, Bat2, Bat3, and the battery temperature of the battery Bat1, Bat2, Bat3 during the sensing period, so as to obtain the sensing result SR of the battery Bat1, Bat2, Bat3. It should be noted that in the present embodiment, each sensing result SR only corresponds to a single battery Bat1, Bat2 or Bat3, and the subsequent corresponding battery internal resistance and standard battery internal resistance also correspond to a single battery Bat1, Bat2 or Bat3; that is, each battery Bat1, Bat2 or Bat3 has its own corresponding battery internal resistance and standard battery internal resistance, and also has its own corresponding open circuit voltage (OCV) corresponding to the depth of discharge (DOD) look-up table relationship.

[0073] The control unit 12 is used to compare the sensing result SR with a preset threshold value to determine whether to accept the sensing result SR. When the sensing result SR is accepted, the corresponding depth of discharge (DOD) is obtained according to the sensing result SR, and the corresponding battery internal resistance is calculated. A regression analysis is performed on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the depth of discharge, and a corresponding battery reference internal resistance is calculated according to the moving average battery internal resistance.

[0074] In one embodiment, the battery voltage Vb1, Vb2, Vb3 (or the corresponding battery voltage sensing signal Vb1', Vb2', Vb3') is used as the sensing result SR, and the corresponding open circuit voltage (OCV) is used as the preset threshold value, and the control unit 12 decides to accept the sensing result SR when the battery voltage Vb1, Vb2, Vb3 is not higher than the corresponding open circuit voltage; and / or the battery current Ib is used as the sensing result SR, and the current lower limit is used as the preset threshold value, and when the battery current Ib is not lower than the current lower limit, it decides to accept the sensing result. In other words, according to the present invention, the sensing results of the battery voltage being higher than the corresponding open circuit voltage (representing the unreasonable phenomenon that the battery current is negative current) and / or the battery current being lower than the current lower limit (representing that the battery current is too low) can be excluded.

[0075] In one embodiment, the lower current limit is 1 / 10 of the 1C discharge current of the battery Bat1, Bat2 or Bat3. It should be noted that the 1C discharge current refers to the current corresponding to the battery at 1C discharge. When the rated capacity of the battery can be fully discharged in 1 hour, it is called 1C discharge. For example, for a battery with a rated capacity of 200mAh, the 1C discharge current is 200mA, which is well known to those skilled in the art and will not be elaborated here.

[0076] In one embodiment, when the sensing result SR is accepted, the control unit 12 uses the comparison table and / or built-in function stored in the non-volatile memory unit 14 to look up the battery voltage sensing signal Vb1', the battery current sensing signal Vs and / or the battery temperature sensing signal Vt to obtain the corresponding depth of discharge (DOD); and then obtains the corresponding open circuit voltage (OCV) according to the comparison table of open circuit voltage (OCV) and depth of discharge (DOD) stored in the non-volatile memory unit 14. Then, for example, the voltage difference between the open circuit voltage (OCV) and the battery voltage Vb1 is divided by the battery current Ib to calculate the battery internal resistance.

[0077] The volatile memory unit 13 is coupled to the control unit 12 to store the battery internal resistance and a plurality of previous battery internal resistances. The non-volatile memory unit 14 is coupled to the control unit 12 to store the battery reference internal resistance. The non-volatile memory unit 14 can also store the aforementioned comparison table, built-in function, open circuit voltage (OCV) and depth of discharge (DOD) comparison table, etc. The charge / discharge drive unit 15 is coupled between the control unit 12 and the power switches SWC, SWD to drive and operate the power switches SWC, SWD according to the operation signal of the control unit 12 to charge / discharge the battery pack 2, which is well known to those skilled in the art and will not be described in detail here.

[0078] In one embodiment, the control unit 12 selects the sensing period during the discharge period and determines whether the battery voltage is higher than the end of discharge voltage (EDV). When the battery voltage is not higher than the end of discharge voltage, the discharge period is terminated, and the sensing period is also terminated to stop measuring the battery reference internal resistance. In one embodiment, the steps performed during the sensing period are all performed during the discharge period of the battery.

[0079] In one embodiment, when the sensing result SR is rejected because it is not accepted, the sensing unit 11 waits for the end of the sensing period and re-senses the battery voltages Vb1, Vb2, Vb3, the battery current Ib and the battery temperature in the next sensing period to obtain the next sensing result SR.

[0080] In one embodiment, the control unit 12 calculates the battery internal resistance according to the battery voltages Vb1, Vb2, Vb3, the battery current Ib, and the open circuit voltage (OCV) corresponding to the depth of discharge (DOD).

[0081] In one embodiment, the plurality of previous battery internal resistances include a plurality of previous battery internal resistances before the sensing period, or a plurality of previous moving average battery internal resistances before the sensing period.

[0082] In one embodiment, the regression analysis includes a linear regression analysis or a quadratic linear regression analysis.

[0083] In one embodiment, the control unit 12 calculates the corresponding battery reference internal resistance according to the moving average battery internal resistance, the battery current Ib and the battery temperature. It should be noted that in this embodiment, the battery reference internal resistance refers to the battery internal resistance at 25 degrees Celsius without load (when the battery is open circuit).

[0084] In one embodiment, the control unit determines the next sensing period according to the open circuit voltage and the discharge depth at the end of the sensing period to repeat the sensing period and further determine the sensing frequency, wherein the sensing frequency is inversely proportional to the sensing period.

[0085] In one embodiment, the length of a sensing period is negatively correlated to the absolute value of a slope between the open circuit voltage and the depth of discharge. That is, according to the present invention, the greater the absolute value of the slope between the open circuit voltage (OCV) and the depth of discharge (DOD), the greater the change in the open circuit voltage. The smaller the adaptive battery internal resistance measurement time interval (i.e., sensing period) according to the present invention is, the purpose is to improve accuracy and save energy. For example, the length of the sensing period is inversely proportional to the absolute value of the slope between the open circuit voltage and the depth of discharge. This means that the system can automatically adjust the measurement frequency according to the change in the open circuit voltage to the depth of discharge, avoid unnecessary frequent measurements, thereby extending the battery life and improving energy efficiency; and increase the sensing frequency when the open circuit voltage changes drastically to improve the accuracy of the battery reference internal resistance.

[0086] In one embodiment, a transient condition is not excluded during the sensing period. That is, according to the present invention, even when the discharge current (battery current in the discharge state) changes relatively drastically, the data measured and stored in the memory can be analyzed by regression filtering to accurately detect the battery internal resistance and calculate a more accurate battery reference internal resistance without deliberately avoiding the transient condition, thereby improving the efficiency and accuracy of determining the battery reference internal resistance.

[0087] Please refer to Figure 2 , Figure 2FIG. 1 is an operational flow chart of a method for determining a reference internal resistance of a battery in one embodiment of the present invention. Figure 2 As shown, the method for determining the reference internal resistance of a battery comprises:

[0088] Step S100: During a sensing period, a battery voltage of a battery, a battery current flowing through the battery, and a battery temperature of the battery are sensed to obtain a sensing result of the battery, thereby obtaining a depth of discharge (DOD);

[0089] Step S110: Continuing from step S100, comparing the sensing result with a preset threshold value to determine whether to accept the sensing result;

[0090] Step S120: Continuing from step S110, when the sensing result is accepted, the corresponding battery internal resistance is calculated according to the sensing result;

[0091] Step S130: Continuing from step S120, performing regression analysis on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the discharge depth; and

[0092] Step S140: Continuing from step S130, a corresponding battery reference internal resistance is obtained according to the moving average battery internal resistance.

[0093] Please refer to Figure 3A and Figure 3B , Figure 3A and Figure 3B FIG. 1 is an operation flow chart of a method for determining a reference internal resistance of a battery in another embodiment of the present invention. Figure 3A and Figure 3B As shown, the method for determining the reference internal resistance of a battery comprises:

[0094] Step S200: During the sensing period, a battery voltage of the battery, a battery current flowing through the battery, and a battery temperature of the battery are sensed to obtain a sensing result of the battery, thereby obtaining a depth of discharge (DOD);

[0095] Step S210: Select a sensing period during the discharge period and determine whether the battery voltage is higher than the discharge termination voltage. If so, execute step S220; if not, execute step S211;

[0096] Step S211: When the sensing result is not accepted and is rejected, the discharge period is terminated, and the sensing period is also terminated and the determination of the battery reference internal resistance is stopped.

[0097] Step S220: When the sensing result is accepted, a corresponding depth of discharge (DOD) is obtained according to the sensing result;

[0098] Step S230: Compare the sensing result with a preset threshold to determine whether to accept the sensing result. If yes, execute step S240; if no, execute step S200;

[0099] Step S240: Calculate the battery internal resistance according to the battery voltage, battery current and OCV corresponding to the discharge depth;

[0100] Step S250: Continuing from step S240, performing regression analysis on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the discharge depth;

[0101] Step S260: Continuing from step S250, calculating the corresponding battery reference internal resistance according to the moving average battery internal resistance;

[0102] Step S270: Continuing from step S260, storing the updated battery reference internal resistance in a non-volatile memory unit;

[0103] Step S280: Continuing from step S270, the next sensing period is determined according to the open circuit voltage and the discharge depth, and the process returns to step S200 to further determine a sensing frequency, wherein the sensing frequency is inversely proportional to the sensing period.

[0104] Figure 4A A schematic diagram showing the relationship between OCV and DOD in an embodiment of the present invention is shown. Figure 4A As shown, the horizontal axis is the discharge depth (DOD), and the vertical axis is the open circuit voltage (OCV). The OCV corresponds to the DOD lookup table relationship, for example, stored in the non-volatile memory unit 140. During the sensing period, the control unit 12 obtains the corresponding DOD according to the sensing result SR and the lookup table relationship or built-in function corresponding to the sensing result stored in the non-volatile memory unit 140; then, according to Figure 4A The OCV-DOD lookup table relationship shown above determines the interval to be calculated, such as Figure 4A The dotted ellipse box in the figure shows the schematic diagram.

[0105] In addition, it should be noted that Figure 4A The multiple dotted straight lines in the figure indicate the absolute value relationship of the slope of OCV corresponding to DOD, which is used to indicate the sensing frequency, that is, the inverse relationship of the sensing period corresponding to DOD; when the multiple dotted straight lines are denser, it means that the absolute value of the slope of OCV corresponding to DOD is larger, and the change of OCV corresponding to DOD is larger, indicating that the adaptive adjustment increases the number of times the battery reference internal resistance is measured to improve the accuracy of the battery reference internal resistance; when the multiple dotted straight lines are sparser, it means that the absolute value of the slope of OCV corresponding to DOD is smaller, and the change of OCV corresponding to DOD is smaller, indicating that the adaptive adjustment reduces the number of times the battery reference internal resistance is measured to save energy.

[0106] Figure 4B In one embodiment of the present invention, the corresponding Figure 4A Local (i.e. Figure 4A Schematic diagram of the relationship between the OCV corresponding to the DOD lookup table relationship and the battery internal resistance calculated during multiple sensing periods. Figure 4B As shown, in the plurality of sensing periods tsp1-tsp8, the corresponding depth of discharge (DOD) is obtained according to each sensing result SR in each sensing period tsp1-tsp8, and then compared with the battery voltage in each sensing period tsp1-tsp8 (such as Figure 4B The corresponding battery internal resistance is calculated based on the battery voltage sensing signals Vb11'-Vb18' indicated by the solid circles in the middle, for example, the voltage difference ΔV between the open circuit voltage (OCV) and the battery voltage (indicated by the battery voltage sensing signals Vb11'-Vb18') is divided by the battery current Ib to calculate the corresponding battery internal resistance.

[0107] Continue reading Figure 4B Since the battery voltage indicated by the battery voltage sensing signal Vb13' is higher than the corresponding open circuit voltage, it means that the battery current Ib is an unreasonable negative current, and the battery current indicated by the battery voltage sensing signal Vb15' is lower than the current lower limit, the sensing results of the sensing periods tsp3 and tsp5 are excluded.

[0108] For example, after excluding the sensing results of the sensing periods tsp3 and tsp5, the battery internal resistance corresponding to each depth of discharge (DOD) is calculated using the battery voltage sensing signals Vb11', Vb12', Vb14', Vb16'-Vb18' in each sensing result SR in the sensing periods tsp1, tsp2, tsp4, tsp6-tsp8 and the open circuit voltage (OCV) corresponding to the depth of discharge (DOD). Then, a regression analysis is performed on the battery internal resistance in these corresponding sensing periods tsp1, tsp2, tsp4, tsp6-tsp8 to obtain the moving average battery internal resistance of the depth of discharge in the corresponding sensing period tsp8, and then the battery reference internal resistance of the depth of discharge in the corresponding sensing period tsp8 is calculated using the obtained moving average battery internal resistance in the corresponding sensing period tsp8, and then the battery reference internal resistance is stored in the non-volatile memory unit 13 to update the old battery reference internal resistance.

[0109] Figure 4C A schematic diagram showing a regression analysis of a battery internal resistance and a plurality of previous battery internal resistances in one embodiment of the present invention is shown. Figure 4CAs shown, after obtaining multiple battery internal resistances R corresponding to different DODs, regression analysis is performed on these battery internal resistances R, for example, a linear regression analysis is performed, and a linear relationship between the battery internal resistance R and the DOD is obtained, such as Figure 4C The black solid line in the middle is shown, and the moving average battery internal resistance corresponding to DOD will be shown later. Figure 4C As shown in the hollow circle, the function of the battery reference internal resistance is substituted into the function, and the battery reference internal resistance corresponding to the DOD is calculated.

[0110] Figure 4D A schematic diagram showing the relationship between the old battery reference internal resistance Rstd and the updated battery reference internal resistance Rstd corresponding to the DOD before and after the battery reference internal resistance Rstd is measured in one embodiment of the present invention. With the discharge current, temperature and battery aging, the battery reference internal resistance Rstd will increase. The battery reference internal resistance Rstd before the battery reference internal resistance Rstd is measured is as follows: Figure 4D The multiple solid rectangles in FIG. 1 are schematically shown, and the battery reference internal resistance Rstd after the battery reference internal resistance Rstd is measured according to the present invention is as follows: Figure 4D According to the present invention, not only can accurate battery internal resistance measurement be provided under current fluctuation conditions, but also power can be effectively saved and accuracy can be improved through adaptive measurement time intervals, thus overcoming the shortcomings of the prior art in practical applications and significantly improving the performance and reliability of the battery management system.

[0111] The present invention has been described above with respect to the preferred embodiment, but the above description is only to make it easy for those skilled in the art to understand the content of the present invention, and is not used to limit the scope of rights of the present invention. The various embodiments described are not limited to individual applications, but can also be used in combination. For example, two or more embodiments can be used in combination, and part of the components in one embodiment can also be used to replace the corresponding components in another embodiment. In addition, under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations. For example, the present invention refers to "processing or calculating or generating an output result according to a certain signal", which is not limited to the signal itself, but also includes, when necessary, converting the signal to voltage and current, current and voltage, and / or ratio conversion, and then processing or calculating according to the converted signal to generate an output result. It can be seen that under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations, and there are many combinations, which are not listed one by one here. Therefore, the scope of the present invention should cover the above and all other equivalent changes.

Claims

1. A method for determining a reference internal resistance of a battery, comprising: (a) sensing a battery voltage of a battery, a battery current flowing through the battery and a battery temperature of the battery during a sensing period to obtain a sensing result of the battery and further obtain a depth of discharge; (b) in step (a), comparing the sensing result with a preset threshold to determine whether to accept the sensing result; (c) when the sensing result is accepted, calculating a corresponding battery internal resistance according to the sensing result and the discharge depth; (d) performing a regression analysis on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the discharge depth; as well as (e) Calculate a corresponding battery reference internal resistance based on the moving average battery internal resistance.

2. The method for determining the reference internal resistance of a battery according to claim 1, wherein: Also includes: (f) selecting the sensing period during a discharge period, and determining whether the battery voltage is higher than a discharge termination voltage, and terminating the discharge period when the battery voltage is not higher than the discharge termination voltage.

3. The method for determining the reference internal resistance of a battery as claimed in claim 1, wherein: Also includes: (g) In step (b), when the sensing result is not accepted and is discarded, step (a) is executed again during the next sensing period.

4. The method for determining the reference internal resistance of a battery as claimed in claim 1, wherein: The step (c) includes: calculating the internal resistance of the battery according to the battery voltage, the battery current and an open circuit voltage corresponding to the discharge depth.

5. The method for determining the reference internal resistance of a battery as claimed in claim 1, wherein: The plurality of previous battery internal resistances include a plurality of battery internal resistances before the sensing period, or a plurality of moving average battery internal resistances before the sensing period.

6. The method for determining the reference internal resistance of a battery as claimed in claim 1, wherein: The regression analysis includes a linear regression analysis or a quadratic linear regression analysis.

7. The method for determining the reference internal resistance of a battery as claimed in claim 1, wherein: The step (e) includes: calculating the corresponding reference internal resistance of the battery according to the moving average internal resistance of the battery, the battery current and the battery temperature.

8. The method for determining the reference internal resistance of a battery as claimed in claim 4, wherein: Also includes: (h) At the end of the sensing period, a next sensing period is determined according to the open circuit voltage and the discharge depth to repeat step (a) to determine a sensing frequency, wherein the sensing frequency is inversely proportional to the sensing period.

9. The method for determining the reference internal resistance of a battery as claimed in claim 8, wherein: A time length of the next sensing period is negatively correlated to an absolute value of a slope between the open circuit voltage and the discharge depth.

10. The method for determining the reference internal resistance of a battery according to claim 1, wherein: The sensing period does not exclude a transient state.

11. The method for determining a reference internal resistance of a battery according to claim 1, wherein: The step (b) includes: using the battery voltage as the sensing result and a corresponding open circuit voltage as the preset threshold, and deciding to accept the sensing result when the battery voltage is not higher than the corresponding open circuit voltage; and / or using the battery current as the sensing result and a current lower limit as the preset threshold, and deciding to accept the sensing result when the battery current is not lower than the current lower limit.

12. The method for determining a reference internal resistance of a battery according to claim 11, wherein: The lower current limit is 1 / 10 of the 1C discharge current of the battery.

13. A system for measuring a reference internal resistance of a battery, comprising: a sensing unit for sensing a battery voltage of a battery, a battery current flowing through the battery, and a battery temperature of the battery during a sensing period to obtain a sensing result of the battery; and A control unit is used to compare the sensing result with a preset threshold value to determine whether to accept the sensing result, and when the sensing result is accepted, a discharge depth is obtained according to the sensing result, and a corresponding battery internal resistance is calculated, and a regression analysis is performed on the battery internal resistance and a plurality of previous battery internal resistances to obtain a moving average battery internal resistance corresponding to the discharge depth, and a corresponding battery reference internal resistance is calculated according to the moving average battery internal resistance.

14. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: Also includes: a volatile memory unit for storing the battery internal resistance and the plurality of previous battery internal resistances; and A non-volatile memory unit is used to store the reference internal resistance of the battery.

15. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The control unit selects the sensing period during a discharge period, and determines whether the battery voltage is higher than a discharge termination voltage, and terminates the discharge period when the battery voltage is not higher than the discharge termination voltage.

16. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: When the sensing result is not accepted and is rejected, the sensing unit re-senses the battery voltage, the battery current and the battery temperature during the next sensing period to obtain the next sensing result.

17. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The control unit calculates the battery internal resistance according to the battery voltage, the battery current and an open circuit voltage corresponding to the discharge depth.

18. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The plurality of previous battery internal resistances include a plurality of battery internal resistances before the sensing period, or a plurality of moving average battery internal resistances before the sensing period.

19. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The regression analysis includes a linear regression analysis or a quadratic linear regression analysis.

20. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The control unit calculates the corresponding reference internal resistance of the battery according to the moving average internal resistance of the battery, the battery current and the battery temperature.

21. The system for determining a reference internal resistance of a battery as claimed in claim 17, wherein: The control unit determines the next sensing period at the end of the sensing period according to the open circuit voltage and the discharge depth to repeat the sensing period, thereby determining a sensing frequency, wherein the sensing frequency is inversely proportional to the sensing period.

22. The system for determining a reference internal resistance of a battery as claimed in claim 21, wherein: A time length of the next sensing period is negatively correlated to an absolute value of a slope between the open circuit voltage and the discharge depth.

23. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The sensing period does not exclude a transient state.

24. The system for determining a reference internal resistance of a battery as claimed in claim 13, wherein: The battery voltage is used as the sensing result, and a corresponding open circuit voltage is used as the preset threshold value, and the control unit decides to accept the sensing result when the battery voltage is not higher than the corresponding open circuit voltage; and / or the battery current is used as the sensing result, and a current lower limit is used as the preset threshold value, and the control unit decides to accept the sensing result when the battery current is not lower than the current lower limit.

25. The system for determining a reference internal resistance of a battery as claimed in claim 24, wherein: The lower current limit is 1 / 10 of the 1C discharge current of the battery.

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