A method for rapid and synchronous testing of battery maximum pulse current, peak power and DC internal resistance

Abstract

The present invention discloses a method for rapidly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery, comprising: a first step of calibrating the capacity of the battery for a preset number of times; a second step of discharging the battery that has passed the capacity calibration in the first step and has been fully charged until the battery SOC is equal to a pre-specified state of charge; a third step of discharging the battery at the pre-specified state of charge C TC In the fourth step, the initial voltage V0 of the battery is recorded, and the battery is discharged or charged in turn with multiple operating currents I, and the battery voltage value V is tested and recorded; the fourth step is to obtain the quantitative relationship between the operating current I and the battery voltage value V; the fifth step is to obtain the maximum pulse current value I of the battery under the pre-specified charge state max ; Step 6: Calculate the battery peak power P max The invention can efficiently, conveniently and reliably measure the maximum pulse current, peak power and DC internal resistance of the battery.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, in particular to a method for quickly and synchronously testing a battery's maximum pulse current, peak power and direct current internal resistance. Background Art

[0002] At present, new energy lithium-ion batteries are widely used in passenger cars, commercial vehicles and special-purpose vehicles. Therefore, in order to make better use of batteries, various car companies generally have clear requirements for the maximum pulse current, peak power and DC internal resistance (DCIR) value of power batteries when they are charged and discharged for different times at different temperatures and different SOCs (i.e., states of charge).

[0003] However, the HPPC (Hybrid Power Pulse Capability Characteristic) test method and the point-by-point test method are currently commonly used. Among them, the HPPC method uses a constant current method for testing, provides a maximum pulse current meter, and the test power value is generally too large; the point-by-point test method takes up too many test resources and time, and cannot perform synchronous testing of current, power, and DC internal resistance (DCIR) values. The test time far exceeds the time required by car manufacturers. Summary of the invention

[0004] The purpose of the present invention is to provide a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery in view of the technical defects in the prior art.

[0005] To this end, the present invention provides a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery, which comprises the following steps:

[0006] The first step is to calibrate the battery capacity for a preset number of times at a preset discharge current under a preset low temperature environment, and record the last capacity as C T ;

[0007] The preset number of times is greater than or equal to three times;

[0008] In the second step, the preset low temperature environment is maintained, and the battery that has passed the capacity calibration in the first step and has been fully charged is discharged with the preset discharge current in the first step until the battery state of charge SOC is equal to the pre-specified state of charge C TC ;

[0009] The third step is to set the charge state C TC After the battery is left to stand for a preset first time, an initial voltage V0 of the battery is recorded, and then a plurality of operating currents I of preset magnitudes are used, where the operating current I is a discharge current or a charge current, to sequentially discharge or charge the battery for a preset second time t, and during each discharge or charge operation, the battery voltage value V is tested and recorded in real time;

[0010] The fourth step is to establish a corresponding relationship between different operating currents I and battery voltage values ​​V: using the preset size of the operating current I as the horizontal coordinate and the battery voltage value V corresponding to each preset size of the operating current I as the vertical coordinate, a scatter plot of the operating current I of the battery and the battery voltage value V is drawn, and then the scatter plot is fitted to obtain a quantitative relationship between the operating current I of the battery and the battery voltage value V;

[0011] Step 5: Set the battery discharge termination voltage V min Or the charging termination voltage V max Substituting the quantitative relationship obtained in the fourth step into the formula, we can obtain the battery at the pre-specified state of charge C TC The maximum pulse current value I max ;

[0012] Step 6: According to the battery discharge termination voltage V min Or the charging termination voltage V max , and the maximum pulse current value I max , use the preset calculation formula to calculate the peak power P of the battery max and DC internal resistance.

[0013] Preferably, in the first step, the preset discharge current is 0.2-1C, where C is used to represent the ratio of the battery charge and discharge current, ie, the rate.

[0014] Preferably, in the fourth step, when the operating current I is a discharge current, the quantitative relationship between the operating current I of the battery and the battery voltage value V is an exponential relationship, which is as follows:

[0015] Formula (1): y = a1*e^(b1*x), where a1 and b1 are coefficients of the exponential function;

[0016] When the operating current I is the charging current, the quantitative relationship between the operating current I of the battery and the battery voltage value V is a logarithmic relationship, as follows:

[0017] Formula (2): y = a2ln(x) + b2, where a2 and b2 are logarithmic function coefficients;

[0018] y is the battery voltage value V, and x is the operating current I of the battery.

[0019] Preferably, in the sixth step, the peak power P of the battery max , including the peak discharge power P max放电 and peak charging power P max充电 ;

[0020] Among them, the peak discharge power P max放电 The calculation formula is:max放电 =V min *I max , formula (3);

[0021] Peak charging power P max充电 The calculation formula is: max充电 =V max *I max , formula (4).

[0022] Preferably, in the sixth step, the DC internal resistance (DCIR) of the battery includes the DC internal resistance during discharge and the DC internal resistance during charge;

[0023] The DC internal resistance (DCIR) calculation formula during discharge is: DCIR = (V0-V min ) / I max , formula (5);

[0024] The calculation formula of DC internal resistance (DCIR) during charging is: DCIR=(V max -V0) / I max , formula (6).

[0025] It can be seen from the technical solution provided by the present invention that, compared with the prior art, the present invention provides a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery. The method is scientifically designed and can efficiently, conveniently and reliably measure the maximum pulse current, peak power and DC internal resistance of the battery, which has great practical significance.

[0026] The invention provides a method for rapidly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery. Compared with traditional testing methods (such as point-by-point testing methods, etc.), the method saves testing time and testing resources and significantly improves testing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flow chart of a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery provided by the present invention;

[0028] Figure 2 A method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery provided by the present invention, in Example 1, a scatter plot (specifically a scatter plot with a smooth curve) between the operating current I and the battery voltage value V at 80% SOC discharge for 10s under -10°C conditions;

[0029] Figure 3The present invention provides a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery. In Example 1, a scatter plot (specifically a scatter plot with a smooth curve) is drawn between the operating current I and the battery voltage value V when charging for 30 seconds at 50% SOC at -20°C. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation modes.

[0031] See also Figures 1 to 3 The present invention provides a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery, comprising the following steps:

[0032] See also Figure 1 The present invention provides a method for accurately measuring the SOC-OCV curve of a power lithium-ion battery at low temperature, comprising the following steps:

[0033] The first step is to calibrate the battery capacity for a preset number of times at a preset low temperature environment (e.g. -25 to -15°C) with a preset discharge current, and record the last capacity as the discharge cut-off capacity C. T ;

[0034] The preset number of times is greater than or equal to three times;

[0035] In the first step, the preset discharge current is 0.2~1C, and C is used to represent the ratio of the battery charge and discharge current, that is, the rate.

[0036] It should be noted that the method for calibrating the capacity of the battery is a common method and will not be described here. For example, the method for calibrating the capacity of the battery can adopt the existing well-known national standard test method. It includes the following steps: a. charging the single battery according to the national standard method; b. charging the battery at room temperature at 1I i (a) discharge with electric current until the discharge termination voltage specified in the enterprise's technical conditions is reached; c. measure the discharge capacity (in Ah); d. repeat steps a to c 5 times. When the range of the test results for three consecutive times is less than 3% of the rated capacity, the test can be terminated in advance and the average of the last three test results can be taken.

[0037] It should be noted that the battery capacity should be measured at least three times, but it does not necessarily have to be three times. If the capacity difference is large in the first three times, it should be tested 4 or 5 times until the capacity difference is less than 3%. According to testing experience, the capacity difference of three times is generally less than 3%.

[0038] In the second step, the preset low temperature environment is maintained unchanged, and the battery that has passed the capacity calibration in the first step and is fully charged is discharged with the preset discharge current in the first step until the battery state of charge SOC (i.e., the battery capacity after discharging a preset proportion of capacity) is equal to the pre-specified state of charge C TC (e.g. 80% or 50% state of charge SOC);

[0039] It should be noted that, for the present invention, the third capacity or the capacity greater than the third capacity in the first step is C T , is the 100% SOC capacity of the battery from full charge to empty charge; the state of charge C pre-specified in the second step TC It is to calibrate the capacity to be tested, for example, 80% SOC. For the present invention, the capacity of 100% SOC in the first step is calibrated first, and then the capacity C of the pre-specified state of charge in the second step can be calculated. TC For example, if the battery is calibrated to 80% SOC, then the battery needs to release 20% SOC capacity after being fully charged. The subsequent processing steps are all based on the pre-specified state of charge C TC Tests performed below.

[0040] The third step is to set the charge state C TC After standing for a preset first time, record the initial voltage V0 of the battery at this time, and then use multiple (for example, 3 to 6) preset operating currents I, where the operating current I is a discharge current or a charge current, to sequentially discharge or charge the battery for a preset second time t (for example, 10 seconds or 30 seconds), and during each discharge or charge operation, test and record the battery voltage value V in real time;

[0041] In the present invention, in specific implementation, according to the battery rate data, multiple (for example, 3 to 6) preset operating currents I are selected within the tolerable range of the battery cell performance. Specifically, the data of 0.2C-10C at the specified temperature are tested on the battery, and the time taken for the discharge voltage to reach the lower limit voltage (i.e., the discharge termination voltage) or the charging to reach the upper limit voltage (i.e., the charging termination voltage), the discharge capacity, the discharge temperature rise and other data are selected, and whether it can be discharged to the termination voltage or charged to the termination voltage at the specified SOC to reach the required preset time. The rate data can be obtained according to the existing conventional testing methods.

[0042] In practical implementation, the specific operating current I is determined according to the pre-specified state of charge C. TC It varies depending on the magnification data and the range of the test equipment.

[0043] In the present invention, in a specific implementation, a first time duration is preset, indicating that the charge state C is set to a predetermined value. TCIn order to eliminate battery polarization, it is necessary to sleep for 30 minutes to 1 hour (national standard).

[0044] In the present invention, in a specific implementation, there is no fixed time for presetting the second duration t, and the test can be performed according to customer index requirements, generally including 2s, 5s, 10s, 15s, 18s, 30s and 60s.

[0045] The fourth step is to establish a corresponding relationship between different operating currents I and battery voltage values ​​V: with the preset size of the operating current I as the horizontal coordinate and the battery voltage value V corresponding to each preset size of the operating current I as the vertical coordinate, a scatter plot (specifically a scatter plot with a smooth curve) of the operating current I of the battery and the battery voltage value V is drawn, and then the quantitative relationship (i.e., a mathematical relationship model) between the operating current I of the battery and the battery voltage value V is obtained by fitting the scatter plot;

[0046] When the operating current I is the discharge current, the quantitative relationship between the operating current I of the battery and the battery voltage value V is an exponential relationship, which is as follows:

[0047] Formula (1): y = a1*e^(b1*x), a1 and b1 are exponential function coefficients, y is the battery voltage V, and x is the battery operating current I;

[0048] When the operating current I is the charging current, the quantitative relationship between the operating current I of the battery and the battery voltage value V is a logarithmic relationship, as follows:

[0049] Formula (2): y=a2ln(x)+b2, a2 ​​and b2 are logarithmic function coefficients, y is the battery voltage value V, and x is the battery operating current I.

[0050] In the above formula, the exponential function with e as the base, e = 2.718281828459..., is a natural constant. a1, b1, a2, b2 are constants, which can be directly obtained through the linear fitting function in the existing Excel software.

[0051] Step 5: Set the battery discharge termination voltage V min Or the charging termination voltage V max , substituting into the quantitative relationship (i.e. mathematical relationship model) obtained in the fourth step, we can obtain the battery at the pre-specified state of charge C TC The maximum pulse current value I max ;

[0052] Step 6: According to the battery discharge termination voltage V min Or the charging termination voltage V max , and the maximum pulse current value I max, use the preset calculation formula to calculate the peak power P of the battery max and DC internal resistance (DCIR).

[0053] In the sixth step, the peak power P of the battery max , including the peak discharge power P max放电 and peak charging power P max充电 ;

[0054] Among them, the peak discharge power P max放电 The calculation formula is: max放电 =V min *I max , formula (3);

[0055] Peak charging power P max充电 The calculation formula is: max充电 =V max *I max , formula (4).

[0056] In the sixth step, the DC internal resistance (DCIR) of the battery includes the DC internal resistance during discharge and the DC internal resistance during charge;

[0057] The calculation formula of DC internal resistance (DCIR) during discharge is: DCIR=(V0-V min ) / I max , formula (5);

[0058] The calculation formula of DC internal resistance (DCIR) during charging is: DCIR=(V max -V0) / I max , formula (6).

[0059] In the above formula, the discharge termination voltage V min Or the charging termination voltage V max : Please refer to the provisions of Sections 3.16 and 3.17 of GB38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles".

[0060] Among them, the discharge termination voltage is the lowest voltage allowed to be reached when the battery cell is discharged normally; the charge termination voltage is the highest voltage allowed to be reached when the battery cell is charged normally; different systems (such as ternary and iron lithium) have different discharge and charge termination voltages. V0: obtained through the third step;

[0061] In order to more clearly understand the technical solution of the present invention, the technical solution of the present invention is described below through specific embodiments.

[0062] Example 1.

[0063] First, in a low temperature environment of -10℃, the capacity of the tested battery cell was calibrated three times with a current of 0.3C and the third capacity was taken as C T ;

[0064] Then, at a preset temperature (-10°C low temperature), the capacity is calibrated to 80% SOC state. After sufficient rest (e.g., 1 hour), the initial voltage V0 is measured to be 4.088V. Five current values ​​of 100A, 150A, 200A, 250A and 300A are taken to test the voltage value of the battery after discharging for 10 seconds respectively.

[0065] Then, establish the corresponding relationship between different currents I and voltages V, and draw a curve graph (scatter plot) of current I and voltage V, see Figure 2 , by fitting the curve, an exponential relationship model y=3.8516e^(-7E-04x) can be obtained; the exponential relationship model is obtained by fitting using Excel software.

[0066] Then, the discharge termination voltage V min =2.8V is brought into the exponential relationship model, and the maximum pulse current value I at 80% SOC can be obtained. max It is 456A; it should be noted that the discharge termination voltage of the ternary lithium-ion battery is 2.8V.

[0067] Peak discharge power P max放电 =V min *I max =2.8*456=1276.8W;

[0068] During discharge, the DC internal resistance DCIR=(V0-V min ) / I max =(4.088-2.8) / 456*1000=2.825mΩ.

[0069] Compared with the results of the existing point-by-point testing method, the difference is 0.08%.

[0070] Example 2.

[0071] First, in a low temperature environment of -20℃, the capacity of the tested battery cell was calibrated three times with a current of 0.2C and the third capacity was taken as C T ;

[0072] Then, at a preset temperature (-20°C), the capacity is calibrated to 50% SOC state. After sufficient rest (e.g., 1 hour), the initial voltage V0 is measured to be 3.791V. Five current values ​​of 10A, 15A, 20A, 25A, and 30A are taken to test the voltage value of the battery after charging for 30 seconds, and the corresponding relationship between different currents I and voltages V is established;

[0073] Then, draw a curve graph (scatter plot) of its current I and voltage V, see Figure 3 , by fitting the curve, we can get the logarithmic relationship model y=0.2567ln(x)+3.3772; the logarithmic relationship model is obtained by fitting through Excel software.

[0074] Then, the charge termination voltage V max =4.3V is brought into the exponential relationship model, and the maximum pulse current value I at 50% SOC can be obtained. max It is 36A; it should be noted that the charging termination voltage of the ternary high-voltage system battery is 4.3V.

[0075] Peak charging power P max充电 =V max *I max =4.3*36=154.8W;

[0076] When charging, the DC internal resistance DCIR=(V max -V0) / I max =(4.3-3.791) / 36*1000=14.139mΩ.

[0077] Compared with the results of the existing point-by-point testing method, the difference is 0.11%.

[0078] Compared with the existing point-by-point testing method and other methods, the existing point-by-point testing method tests the maximum pulse current, peak power, and DC internal resistance of each SOC state point by point. After inspection, it is found that the total time required is about 24 hours. The method provided by the present invention provides a method for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery, which can be tested simultaneously and the total time required is about 8 hours, which can save 3 times of time, thereby significantly saving test time and improving test efficiency.

[0079] To sum up, compared with the prior art, the method provided by the present invention for quickly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery is scientifically designed, and can efficiently, conveniently and reliably measure the maximum pulse current, peak power and DC internal resistance of the battery, which has great practical significance.

[0080] The invention provides a method for rapidly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery. Compared with traditional testing methods (such as point-by-point testing methods, etc.), the method saves testing time and testing resources and significantly improves testing efficiency.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for rapidly and synchronously testing the maximum pulse current, peak power and DC internal resistance of a battery, characterized in that: The following steps are involved: The first step is to calibrate the battery capacity for a preset number of times at a preset discharge current under a preset low temperature environment, and record the last capacity as C T ; The preset number of times is greater than or equal to three times; In the second step, the preset low temperature environment is maintained, and the battery that has passed the capacity calibration in the first step and has been fully charged is discharged with the preset discharge current in the first step until the battery state of charge SOC is equal to the pre-specified state of charge C TC ; The third step is to set the charge state C TC After the battery is left to stand for a preset first time, an initial voltage V0 of the battery is recorded, and then a plurality of operating currents I of preset magnitudes are used, where the operating current I is a discharge current or a charge current, to sequentially discharge or charge the battery for a preset second time t, and during each discharge or charge operation, the battery voltage value V is tested and recorded in real time; The fourth step is to establish a corresponding relationship between different operating currents I and battery voltage values ​​V: using the preset size of the operating current I as the horizontal coordinate and the battery voltage value V corresponding to each preset size of the operating current I as the vertical coordinate, a scatter plot of the operating current I of the battery and the battery voltage value V is drawn, and then the scatter plot is fitted to obtain a quantitative relationship between the operating current I of the battery and the battery voltage value V; Step 5: Set the battery discharge termination voltage V min Or the charging termination voltage V max Substituting the quantitative relationship obtained in the fourth step into the formula, we can obtain the battery at the pre-specified state of charge C TC The maximum pulse current value I max ; Step 6: According to the battery discharge termination voltage V min Or the charging termination voltage V max , and the maximum pulse current value I max , use the preset calculation formula to calculate the peak power P of the battery max and DC internal resistance.

2. The method according to claim 1, characterized in that In the first step, the preset discharge current is 0.2~1C, and C is used to represent the ratio of the battery charge and discharge current, that is, the rate.

3. The method according to claim 1, characterized in that In the fourth step, when the operating current I is a discharge current, the quantitative relationship between the operating current I of the battery and the battery voltage value V is an exponential relationship, which is as follows: Formula (1): y = a1*e^(b1*x), where a1 and b1 are coefficients of the exponential function; When the operating current I is the charging current, the quantitative relationship between the operating current I of the battery and the battery voltage value V is a logarithmic relationship, as follows: Formula (2): y = a2ln(x) + b2, where a2 and b2 are logarithmic function coefficients; y is the battery voltage value V, and x is the operating current I of the battery.

4. The method according to any one of claims 1 to 3, characterized in that In the sixth step, the peak power P of the battery max , including the peak discharge power P max放电 and peak charging power P max充电 ; Among them, the peak discharge power P max放电 The calculation formula is: max放电 =V min *I max , formula (3); Peak charging power P max充电 The calculation formula is: max充电 =V max *I max , formula (4).

5. The method according to any one of claims 1 to 3, characterized in that In the sixth step, the DC internal resistance DCIR of the battery includes the DC internal resistance during discharge and the DC internal resistance during charge; The calculation formula of DC internal resistance DCIR during discharge is: DCIR=(V0-V min ) / I max , formula (5); The calculation formula of DC internal resistance DCIR during charging is: DCIR=(V max -V0) / I max , formula (6).

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