A shunt current calibration method for battery formation or equalization equipment

Abstract

The application belongs to the technical field of current calibration, and specifically discloses a shunt current calibration method for battery formation or equalization equipment, which comprises the following steps: setting a calibration current value and controlling a constant current output by a step-up / down circuit; synchronously collecting a sampling current and a sampling temperature in a temperature rising stage and generating a current sequence and a temperature sequence respectively; stopping sampling to obtain multiple temperature sampling points and corresponding current sampling points when the temperature enters a stable state according to the temperature sequence; determining a correction coefficient corresponding to each temperature sampling point according to the ratio of each current sampling point to the calibration current value, and establishing a segmented linear interpolation relationship between the temperature and the correction coefficient with each temperature sampling point as an interval endpoint; and determining a current correction coefficient according to a current temperature when an actual current is output, and multiplying the sampling current by the current correction coefficient to obtain an actual current value. The application can ensure the current accuracy at different temperatures through only one current calibration.

Description

Technical Field

[0001] This application belongs to the field of current calibration technology, and more specifically, relates to a shunt current calibration method for battery formation or sizing equipment. Background Technology

[0002] Battery formation and capacity grading equipment requires high precision, and because it needs to operate continuously for extended periods, the performance of electronic components can deviate due to aging, necessitating periodic calibration. Current accuracy is a critical performance characteristic of this equipment, and two components are typically available for sampling current: Hall effect sensors and shunts (resistors). Shunts are often the preferred choice due to their simple manufacturing process and lower cost. However, shunts monitor current by generating voltage through current flow (U=I*R), and the power generated by the current flowing through the shunt (P=I*I*R) causes the shunt to heat up, resulting in temperature drift and sampling inaccuracies, requiring calibration.

[0003] Traditional calibration methods require separate calibrations for current and temperature. Current calibration involves acquiring the actual current using a multimeter, comparing it to the CPU's sampled value, and then fitting a proportionality coefficient k(I). 实际 =k*I 采样 +b) and offset b. Temperature calibration is performed by controlling the shunt temperature through a constant temperature chamber, collecting the relationship between temperature and sampled values, and fitting the temperature coefficient θ. T (The change in sampled value for every 0.5℃ change in temperature). However, this method suffers from high cost, long processing time, and poor flexibility: it requires additional high-precision temperature calibration equipment; temperature and current calibration must be performed in steps, and the calibration time for multi-channel equipment increases exponentially; the temperature sensor model is fixed, and changing the sensor requires recalibrating the temperature coefficient.

[0004] Therefore, how to ensure current accuracy at different temperatures through a single current calibration is a problem that urgently needs to be solved. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a shunt current calibration method for battery formation or capacity grading equipment, which can ensure current accuracy at different temperatures with only one current calibration.

[0006] To achieve the above objectives, in a first aspect, this application provides a shunt current calibration method for a battery formation or grading device, the device comprising a buck-boost circuit for charging and discharging the battery, a shunt for sampling the current flowing through the battery, and a temperature sensor for acquiring the temperature of the shunt, comprising the following steps: S10, Set the calibration current value and control the buck-boost circuit to output a constant current; S20, during the heating phase, the sampling current of the shunt and the sampling temperature of the temperature sensor are synchronously collected at a fixed sampling period to generate a current sequence and a temperature sequence, respectively. S30, when the temperature is determined to have entered a stable state according to the temperature sequence, sampling is stopped, and multiple temperature sampling points and current sampling points corresponding to each temperature sampling point are obtained. S40. Based on the ratio of the current sampling point corresponding to each temperature sampling point to the calibration current value, determine the correction coefficient corresponding to each temperature sampling point, and establish a piecewise linear interpolation relationship between temperature and correction coefficient in ascending order of temperature, with each temperature sampling point as the endpoint of the interval. S50: When the actual current is output, the current temperature is obtained, the current correction coefficient corresponding to the current temperature is determined according to the piecewise linear interpolation relationship, and the sampled current is multiplied by the current correction coefficient to obtain the actual current value.

[0007] As a further preferred embodiment, in step S30, the condition for determining that the temperature has entered a stable state is: the difference ΔT between adjacent temperatures sampled N times consecutively. i All are not greater than the temperature stability threshold ΔT th The formula is: ΔT i =∣T i - T i-1 | ≤ ΔT th Among them, T i T represents the temperature of the i-th sampling; i-1 ΔT represents the (i-1)th sampling temperature; i is the sampling number; N is the number of consecutive stable samples; ΔT th The temperature stability threshold is set based on the accuracy of the temperature sensor.

[0008] As a further preferred embodiment, the number of consecutive stable cycles N is 5, and the temperature stability threshold is 0.1℃.

[0009] As a further preferred embodiment, in step S40, the correction coefficient is determined by dividing the current sampling point corresponding to each temperature sampling point by the calibration current value, and the resulting quotient is the correction coefficient corresponding to that temperature sampling point. The correction coefficient θ corresponding to the nth temperature sampling point n The formula for calculating θ is: n =I n / I cal , where I n For the current sampling point corresponding to the nth temperature sampling point, I cal The calibration current value is given.

[0010] As a further preferred embodiment, in step S40, in the piecewise linear interpolation relationship, for the nth interval [T] n ,T n+1 ], any temperature T∈[T n ,T n+1 The correction factor θ(T) is calculated according to the following formula: θ(T)=θ n + (θ n+1 - θ n ) / (T n+1 - T n )*(T - T n ) Where, θ n θ is the correction coefficient corresponding to the nth temperature sampling point; n+1 T is the correction coefficient corresponding to the (n+1)th temperature sampling point; n T represents the temperature value at the nth temperature sampling point. n+1 The temperature value is the (n+1)th temperature sampling point; T is the current temperature; n = 1, 2, ..., k-1, where k is the total number of temperature sampling points.

[0011] As a further preferred embodiment, step S50, determining the current correction coefficient corresponding to the current temperature based on the piecewise linear interpolation relationship, specifically includes: When the current temperature is equal to a certain temperature sampling point among the plurality of temperature sampling points, the correction coefficient corresponding to that temperature sampling point is used as the current correction coefficient. When the current temperature is between two adjacent temperature sampling points, the current correction coefficient is calculated according to the linear interpolation formula; When the current temperature is less than the minimum temperature value among the plurality of temperature sampling points or greater than the maximum temperature value among the plurality of temperature sampling points, the current correction coefficient is calculated according to the linear extrapolation formula.

[0012] As a further preferred embodiment, the current temperature is located at two adjacent temperature sampling points T. n With T n+1 When the interval is between, the linear interpolation formula is: θ(T current )=θ n + (θ n+1 -θ n ) / (T n+1 - T n ) * (T current - T n ) Among them, T current θ represents the current temperature. n θ is the correction coefficient corresponding to the nth temperature sampling point;n+1 T is the correction coefficient corresponding to the (n+1)th temperature sampling point; n T represents the temperature value at the nth temperature sampling point. n+1 This is the temperature value of the (n+1)th temperature sampling point.

[0013] As a further preferred embodiment, when the current temperature is less than the minimum temperature value T1, the linear extrapolation formula is: θ(T current )=θ1 + (θ2 -θ1) / (T2 - T1) * (T current - T1) The current temperature is greater than the maximum temperature value T. k When the linear extrapolation formula is: θ(T current )=θ k + (θ k -θ k-1 ) / (T k - T k-1 ) * (T current - T k ) Among them, T current T1 is the current temperature; T2 is the minimum temperature value; T3 is the second minimum temperature value; T4 is the current temperature. k This is the maximum temperature value; T k-1 θ1 is the correction factor corresponding to the minimum temperature value; θ2 is the correction factor corresponding to the second smallest temperature value; θ k θ is the correction factor corresponding to the maximum temperature value. k-1 This is the correction factor corresponding to the second largest temperature value.

[0014] As a further preferred embodiment, the temperature range of the multiple temperature sampling points is divided into k-1 intervals, and the number of intervals k is determined according to the accuracy of the temperature sensor, the temperature coefficient of the shunt, and the current accuracy requirements of the device.

[0015] Secondly, this application provides a current calibration system for battery formation equipment or battery capacity grading equipment, which performs current calibration using the method described in any one of the above claims, including: A step-up / step-down circuit is used to output a constant current. A shunt is connected to the buck-boost circuit and is used to sample the current output by the buck-boost circuit. A temperature sensor is located near the shunt to collect the temperature of the shunt. An ADC (Analog-to-Digital Converter) is connected to the shunt and the temperature sensor, and is used to convert the sampling current of the shunt and the sampling temperature of the temperature sensor into digital quantities, respectively. The CPU processor is connected to the ADC analog-to-digital converter and the buck-boost circuit. It is used to control the buck-boost circuit to output a constant current, synchronously collect the sampling current and sampling temperature, establish a piecewise linear interpolation relationship, and determine the current correction coefficient based on the current temperature and multiply the sampling current by the current correction coefficient to obtain the actual current value when the actual current is output.

[0016] This application offers the following advantages: By collecting synchronous data on current and temperature and establishing a piecewise linear interpolation relationship, current accuracy at different temperatures can be guaranteed even with only current calibration performed. Specifically, since the piecewise linear interpolation relationship directly reflects the deviation between the sampled current and its actual value at different temperatures, it eliminates the need to pre-obtain the temperature coefficient to correct the sampled current at any temperature, thereby saving the independent temperature calibration step and reducing hardware costs and calibration time. Furthermore, because the establishment of this piecewise linear interpolation relationship does not depend on a fixed temperature coefficient, it can overcome the temperature range limitations imposed by the temperature coefficient and be used in a wider range of temperature environments. In addition, since it does not limit the use of a specific temperature sensor, different sensor models can be replaced at any time after the hardware design is completed or on-site, facilitating design and maintenance personnel. Attached Figure Description

[0017] Figure 1 This is a graph showing the change in the resistance of the shunt provided in this application as a function of ambient temperature. Figure 2 This is a flowchart of the current calibration method provided by this application; Figure 3 This is a structural block diagram of the current calibration system provided in the embodiments of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] It should be noted that battery formation or capacity grading equipment is used to charge and discharge batteries to achieve processes such as battery activation and capacity sorting. This equipment typically includes a power supply, a buck-boost circuit, a pulse width modulation module, a CPU processor, an analog-to-digital converter, a shunt, a temperature sensor, and the battery to be processed. The buck-boost circuit outputs charging and discharging current to the battery, the shunt is connected in series in this current loop to sample the current flowing through the battery, and the temperature sensor is placed near the shunt to collect the shunt's temperature. Figure 1As shown, the resistance of the shunt (resistor) changes with the environment, causing the sampling current of the shunt to deviate due to its own heating. Regular calibration is required to ensure the control accuracy of the charging and discharging current, thereby achieving accurate battery capacity sorting. However, existing calibration methods typically require separate current and temperature calibrations, which are costly, time-consuming, and inflexible. To address this, this application provides a shunt current calibration method that can guarantee current accuracy at different temperatures with only a single current calibration.

[0020] Specifically, such as Figure 2 As shown, the shunt current calibration method for battery formation or capacity grading equipment provided in this application includes steps S10 to S50, which are detailed below: Step S10: Set the calibration current value and control the buck-boost circuit to output a constant current. This step provides a known constant current reference value for subsequent calibration.

[0021] In step S20, during the heating phase, the sampling current of the shunt and the sampling temperature of the temperature sensor are synchronously collected at a fixed sampling period to generate current and temperature sequences, respectively. This step establishes a synchronous correspondence between current and temperature sampling in time, providing a data foundation for subsequent piecewise linear interpolation.

[0022] Step S30: When the temperature is determined to have reached a stable state based on the temperature sequence, sampling is stopped, resulting in multiple temperature sampling points and corresponding current sampling points. This step ensures that the collected data points cover the complete heating process of the shunt from its initial temperature to its thermal equilibrium temperature, providing reliable sample data for establishing subsequent interpolation relationships.

[0023] Step S40: Based on the ratio of the current sampling point to the calibration current value corresponding to each temperature sampling point, determine the correction coefficient corresponding to each temperature sampling point, and establish a piecewise linear interpolation relationship between temperature and correction coefficient in ascending order, with each temperature sampling point as the endpoint of the interval. This step can directly establish the correspondence between temperature and current correction coefficient without relying on the temperature coefficient, thereby supporting the correction of the sampling current at different temperatures.

[0024] Step S50: When the actual current is output, the current temperature is acquired, and the current correction coefficient corresponding to the current temperature is determined according to the piecewise linear interpolation relationship. The sampled current is multiplied by the current correction coefficient to obtain the actual current value. This step can dynamically correct the sampled current based on the real-time temperature during actual production to ensure current control accuracy across the entire temperature range.

[0025] This application offers the following advantages: By collecting synchronous data on current and temperature and establishing a piecewise linear interpolation relationship, current accuracy at different temperatures can be guaranteed even with only current calibration performed. Specifically, since the piecewise linear interpolation relationship directly reflects the deviation between the sampled current and its actual value at different temperatures, it eliminates the need to pre-obtain the temperature coefficient to correct the sampled current at any temperature, thereby saving the independent temperature calibration step and reducing hardware costs and calibration time. Furthermore, because the establishment of this piecewise linear interpolation relationship does not depend on a fixed temperature coefficient, it can overcome the temperature range limitations imposed by the temperature coefficient and be used in a wider range of temperature environments. In addition, since it does not limit the use of a specific temperature sensor, different sensor models can be replaced at any time after the hardware design is completed or on-site, facilitating design and maintenance personnel.

[0026] In one embodiment, the technical solution for achieving the above objective can be specifically as follows: Figure 3 As shown, this embodiment provides a current calibration system, which includes a power supply, a step-up / step-down circuit, a PWM pulse width modulation module, a CPU processor, an ADC analog-to-digital converter, a shunt (sampling resistor R), a temperature sensor (monitoring shunt temperature T), and a battery (the object under test).

[0027] Current sampling is achieved by converting the voltage U=I*R across the shunt into a digital quantity I via an ADC.

[0028] Temperature sampling is performed by acquiring the shunt temperature T through a temperature sensor (such as NTC or PT100), which is then converted into a digital value T by an ADC.

[0029] The CPU processor controls the output target current of the buck-boost circuit, synchronously acquires I-samples and T-samples, and generates data sets I. BUF (Current sequence) and T BUF (Temperature sequence); based on I BUF and T BUF Establish a piecewise linear interpolation relationship θ(T), and during production, adjust the interpolation based on the current temperature T. current Query θ(T) corrected current output, corrected current output (I) 实际 =θ(T current )*I 采样 ).

[0030] The calibration process provided in this embodiment is divided into a heating stage and a stabilization stage. The core is to capture the shunt temperature from the "initial temperature T0" to the "thermal equilibrium temperature T". max The current-temperature dynamic relationship.

[0031] (1) Sampling termination conditions (quantitative criteria) during the heating phase The buck-boost circuit outputs a constant current I. calThe CPU uses a fixed sampling period T s Synchronously collect current and temperature to generate I BUF ={I1,I2,...,I m} and T BUF ={T1,T2,...,T m}

[0032] When the following conditions are met, the temperature is considered to have reached a stable state, and sampling is stopped: ΔT i =∣T i - T i-1 | ≤ ΔT th (For N consecutive times, e.g., N=5, ΔT) th =0.1℃) Where, ΔT i ΔT represents the temperature difference between the i-th and (i-1)-th tests. th The temperature stabilization threshold is set according to the accuracy of the temperature sensor, such as ±0.1℃; N is the number of consecutive stabilization cycles (such as 5 cycles to ensure a stable temperature trend).

[0033] (2) Establishing piecewise mathematical relationships (linear interpolation) After the steady-state phase ends, k temperature-current data points are obtained: (T1, I1), (T2, I2), ..., (T... k ,I k ), where T1 <T2<...<T k .

[0034] To simplify the calculation, piecewise linear interpolation is used to establish θ(T), where θ(T) represents the current correction factor at temperature T, i.e., I. 实际 =θ(T)×I 采样 .

[0035] For the nth interval [T] n ,T n+1 ], n=1,2,...,k-1, any temperature T∈[T n ,T n+1 The correction factor for ] is: θ(T)=θ n + (θ n+1 - θ n ) / (T n+1 - T n )*(T - T n ) Where, θ n Let θ be the correction coefficient for the nth sampling point. n =I n / I cal I calis the calibrated current setting value; θ n+1 is the correction coefficient of the (n+1)th sampling point; T n and T n+1 are the temperature values of the nth and (n+1)th sampling points respectively; T is the current temperature.

[0036] (3) Interval division and data point quantity determination Number of intervals k: determined according to the accuracy of the temperature sensor, the temperature coefficient of the shunt (e.g., 25ppm / ℃) and the current accuracy requirement (e.g., 0.02%FS). For example, if the accuracy of the temperature sensor is ±0.1℃, the maximum temperature drift of the shunt in the range of 0℃∼85℃ is 0.2125% (25ppm / ℃×85℃). To ensure the current accuracy of 0.02%FS, at least 10 intervals need to be divided, that is, the temperature change in each interval is ≤8.5℃.

[0037] Interval division principle: preferentially add sampling points in areas with large temperature gradients (such as low-temperature section or high-temperature section) to ensure interpolation accuracy. For example, if the temperature drift of the shunt is more significant in the range of 0℃∼40℃, more sampling points can be set in this interval (e.g., T1=0℃, T2=5℃, T3=10℃).

[0038] (4) Calling rules in normal production (including extrapolation mechanism) During production, the CPU queries θ(T) according to the current temperature T current , and processes in three cases.

[0039] Case 1, when T current is equal to a certain sampling point T n , directly use θ n of this point, that is, θ(T current )=θ n .

[0040] Case 2, T current is between two sampling points, that is, T n <T current <T n+1 , calculate by linear interpolation, the formula is θ(T current )=θ n + (θ n+1 -θ n ) / (T n+1 - T n ) * (T current - T n ).

[0041] Case 3, T current is beyond the sampling range, that is, T current <T1 or T current >T kwhen linear extrapolation is adopted, and the formula is: When T current < T1, the formula is θ(T current )=θ1 + (θ2 -θ1) / (T2 - T1) * (T current - T1); When T current > T k , the formula is θ(T current )=θ k + (θ k -θ k-1 ) / (T k - T k-1 ) * (T current - T k ).

[0042] The following is a specific embodiment of the present application: As shown in Table 1, a 0.5mΩ shunt (specification: ±0.5% accuracy, rated current 100A, temperature coefficient ±25ppm / ℃, range -55℃∼85℃) is taken as an example to verify the effectiveness of the method: Table 1

[0043] (1) Calibration process Set the calibration current I cal =100A, sampling period T s =1s, temperature stability threshold ΔT th =0.1℃, and the number of consecutive stability times N=5.

[0044] Data collection: 3 stable data points (example) are collected in the temperature rise stage: T1=25℃, I1=99.95A → θ1=99.95 / 100=0.9995; T2=45℃, I2=99.97A → θ2=99.97 / 100=0.9997; T3=65℃, I3=99.99A → θ3=99.99 / 100=0.9999.

[0045] (2) Calling in normal production (example) Scenario 1: Current temperature T current =45℃ (equal to T2), then θ(45℃)=θ2=0.9997, actual current I 实际 =0.9997×I 采样 。

[0046] Scenario 2: Current temperature T current=35℃ (between T1 and T2), then: θ(35℃)=0.9995+(0.9997-0.9995) / (45-25)*(35-25)=0.9995+0.0001=0.9996.

[0047] Scenario 3: Current temperature T current =85℃ (greater than T3), then: θ(85℃)=0.9999+(0.9999-0.9997) / (65-45)*(85-65)=0.9999+0.0002=1.0001.

[0048] (3) Comparison of accuracy between this application and existing methods (as shown in Table 2) Table 2

[0049] The current calibration method in this scheme has the following advantages: 1. This calibration method can eliminate the need for temperature calibration equipment, saving hardware costs and operational complexity, while also reducing calibration time, as only the current parameter needs to be calibrated.

[0050] 2. Since this calibration method does not require the use of a temperature coefficient, it can break through the operating temperature range limited by the temperature coefficient and can be used in a wider range of temperature environments.

[0051] 3. This calibration method is not limited to using a specific temperature sensor. Different models of sensors can be replaced at any time after the hardware design is completed or on the production site, which greatly facilitates design and maintenance personnel.

[0052] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for calibrating the current of a shunt in a battery formation or grading device, the device comprising a buck-boost circuit for charging and discharging the battery, a shunt for sampling the current flowing through the battery, and a temperature sensor for acquiring the temperature of the shunt, characterized in that, Includes the following steps: S10, Set the calibration current value and control the buck-boost circuit to output a constant current; S20, during the heating phase, the sampling current of the shunt and the sampling temperature of the temperature sensor are synchronously collected at a fixed sampling period to generate a current sequence and a temperature sequence, respectively. S30, when the temperature is determined to have entered a stable state according to the temperature sequence, sampling is stopped, and multiple temperature sampling points and current sampling points corresponding to each temperature sampling point are obtained. S40. Based on the ratio of the current sampling point corresponding to each temperature sampling point to the calibration current value, determine the correction coefficient corresponding to each temperature sampling point, and establish a piecewise linear interpolation relationship between temperature and correction coefficient in ascending order of temperature, with each temperature sampling point as the endpoint of the interval. S50: When the actual current is output, the current temperature is obtained, the current correction coefficient corresponding to the current temperature is determined according to the piecewise linear interpolation relationship, and the sampled current is multiplied by the current correction coefficient to obtain the actual current value.

2. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 1, characterized in that, In step S30, the condition for determining that the temperature has entered a stable state is: the difference ΔT between adjacent temperatures sampled N times consecutively. i All are not greater than the temperature stability threshold ΔT th The formula is: ΔT i =∣T i - T i-1 ∣ ≤ ΔT th Among them, T i T represents the temperature of the i-th sampling; i-1 ΔT represents the (i-1)th sampling temperature; i is the sampling number; N is the number of consecutive stable samples; ΔT th The temperature stability threshold is set based on the accuracy of the temperature sensor.

3. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 2, characterized in that, The number of consecutive stable cycles N is 5, and the temperature stability threshold is 0.1℃.

4. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 1, characterized in that, In step S40, the correction coefficient is determined by dividing the current sampling point corresponding to each temperature sampling point by the calibration current value, and the resulting quotient is the correction coefficient corresponding to that temperature sampling point. The correction coefficient θ corresponding to the nth temperature sampling point n The formula for calculating θ is: n =I n / I cal , where I n For the current sampling point corresponding to the nth temperature sampling point, I cal The calibration current value is given.

5. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 4, characterized in that, In step S40, in the piecewise linear interpolation relationship, for the nth interval [T] n ,T n+1 ], any temperature T∈[T n ,T n+1 The correction factor θ(T) is calculated according to the following formula: θ(T)=θ n + (θ n+1 - i n ) / (T n+1 - T n )*(T - T n ) Where, θ n θ is the correction coefficient corresponding to the nth temperature sampling point; n+1 T is the correction coefficient corresponding to the (n+1)th temperature sampling point; n T represents the temperature value at the nth temperature sampling point. n+1 The temperature value is the (n+1)th temperature sampling point; T is the current temperature; n = 1, 2, ..., k-1, where k is the total number of temperature sampling points.

6. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 1, characterized in that, In step S50, determining the current correction coefficient corresponding to the current temperature based on the piecewise linear interpolation relationship specifically includes: When the current temperature is equal to a certain temperature sampling point among the plurality of temperature sampling points, the correction coefficient corresponding to that temperature sampling point is used as the current correction coefficient. When the current temperature is between two adjacent temperature sampling points, the current correction coefficient is calculated according to the linear interpolation formula; When the current temperature is less than the minimum temperature value among the plurality of temperature sampling points or greater than the maximum temperature value among the plurality of temperature sampling points, the current correction coefficient is calculated according to the linear extrapolation formula.

7. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 6, characterized in that, The current temperature is located at two adjacent temperature sampling points T. n With T n+1 When the interval is between, the linear interpolation formula is: θ(T current )=θ n + (θ n+1 -θ n ) / (T n+1 - T n ) * (T current - T n ) Among them, T current θ represents the current temperature. n θ is the correction coefficient corresponding to the nth temperature sampling point; n+1 T is the correction coefficient corresponding to the (n+1)th temperature sampling point; n T represents the temperature value at the nth temperature sampling point. n+1 This is the temperature value of the (n+1)th temperature sampling point.

8. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 6, characterized in that, When the current temperature is less than the minimum temperature value T1, the linear extrapolation formula is: θ(T current )=θ1 + (θ2 -θ1) / (T2 - T1) * (T current - T1) The current temperature is greater than the maximum temperature value T. k When the linear extrapolation formula is: θ(T current )=θ k + (θ k -θ k-1 ) / (T k - T k-1 ) * (T current - T k ) Among them, T current T1 is the current temperature; T2 is the minimum temperature value; T3 is the second minimum temperature value; T4 is the current temperature. k This is the maximum temperature value; T k-1 θ1 is the correction factor corresponding to the minimum temperature value; θ2 is the correction factor corresponding to the second smallest temperature value; θ k θ is the correction factor corresponding to the maximum temperature value. k-1 This is the correction factor corresponding to the second largest temperature value.

9. The shunt current calibration method for battery formation or capacity grading equipment as described in claim 1, characterized in that, The temperature range of the multiple temperature sampling points is divided into k-1 intervals, and the number of intervals k is determined according to the accuracy of the temperature sensor, the temperature coefficient of the shunt, and the current accuracy requirements of the device.

10. A current calibration system for battery formation equipment or battery capacity testing equipment, wherein current calibration is performed using the method described in any one of claims 1 to 9, characterized in that, include: A step-up / step-down circuit is used to output a constant current. A shunt is connected to the buck-boost circuit and is used to sample the current output by the buck-boost circuit. A temperature sensor is located near the shunt to collect the temperature of the shunt. An ADC (Analog-to-Digital Converter) is connected to the shunt and the temperature sensor, and is used to convert the sampling current of the shunt and the sampling temperature of the temperature sensor into digital quantities, respectively. The CPU processor is connected to the ADC analog-to-digital converter and the buck-boost circuit. It is used to control the buck-boost circuit to output a constant current, synchronously collect the sampling current and sampling temperature, establish a piecewise linear interpolation relationship, and determine the current correction coefficient based on the current temperature and multiply the sampling current by the current correction coefficient to obtain the actual current value when the actual current is output.

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