Battery charging current calculation method and device, medium and battery management system

Abstract

The invention relates to the technical field of batteries, in particular to a battery charging current calculation method and device, a medium and a battery management system. The method mainly comprises the steps of obtaining battery basic information and battery charging information; substituting the battery basic information and the charging information into a function that the battery temperature changes along with the charging current, and calculating the charging current; correcting the charging current based on the battery aging state SOH; and feeding back a closed-loop control charging current according to the temperature deviation. According to the invention, the feedforward charging current calculated based on the battery thermal model and the aging state can adapt to different environment temperatures and the aging state of the battery; by setting different charging target cut-off SOC values and target boundary temperature limit values and combining the deviation between the battery temperature and the target temperature limit value, the charging current and temperature rise of the battery can be controlled, so that the aging speed of the battery is controlled, and over-temperature charging or lithium precipitation is avoided.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a battery charging current calculation method, device, medium and battery management system. Background Art

[0002] As a complex electrochemical component, lithium-ion batteries are a complex system that is very sensitive to temperature. During high-rate charging in a high-temperature environment, the heat generated by the battery may accelerate the side reactions inside the battery, causing the battery life to decline faster and even cause safety issues. During high-rate charging in a low-temperature environment, the charge transfer kinetics of lithium ions inside the battery deteriorate, and the negative electrode potential is likely to reach the lithium plating potential threshold, causing lithium ions to directly undergo a reduction reaction on the surface of the negative electrode material to form lithium plating, which accelerates battery aging and capacity decay.

[0003] At present, for real-time calculations for vehicles, conventional BMS calculates the charging current by online table lookup based on the charging current table provided by the battery supplier. This charging method of table lookup to calculate the charging current has two obvious disadvantages. First, the charging current table is pre-calibrated by the battery supplier based on the prior knowledge of battery parameters, and cannot be adaptively adjusted as the charging capacity of the battery changes throughout its life cycle. Second, the OEM's requirements for charging time are becoming more and more stringent, and aggressive charging current will cause damage to the battery's life and safety. With the continuous improvement of the requirements of OEMs and end users for fast charging time, charging safety, and battery life, it is particularly critical and important to calculate the battery's charging current based on the battery thermal model to achieve safe and efficient fast charging from the perspective of charging current calculation and control. Summary of the invention

[0004] The invention discloses a battery charging current calculation method, device, medium and battery management system, which can calculate the battery charging current.

[0005] In order to achieve the above object, on the one hand, a method for calculating battery charging current is provided, characterized in that the specific method is as follows:

[0006] Get basic battery information and battery charging information;

[0007] Substitute the basic battery information and charging information into the function of battery temperature changing with charging current to calculate the charging current.

[0008] Furthermore, the battery charging information includes: ambient temperature, charging start temperature, charging target boundary temperature limit, charging time, charging start SOC and charging target cutoff SOC.

[0009] Optionally, the battery temperature varies with the charging current, and the specific formula is as follows:

[0010]

[0011] k env =h env A bat

[0012] k bat =m bat c p，bat

[0013] In the formula, I bat is the charging current, R bat is the internal resistance of the battery, h env is the air convection heat transfer coefficient, A bat is the battery surface area, T env is the ambient temperature, T bat，0 is the battery charging start temperature, m bat is the battery mass, c p，bat is the specific heat capacity of the battery, Q bat is the battery capacity parameter, SoC bat (t end ) is the charging target cut-off SOC, SoC bat (0) is the charging start SOC, T bat，des is the charging target boundary temperature limit, T bat，0 is the charging start temperature.

[0014] Preferably, when the battery has a battery thermal management system to adjust the battery temperature, the battery temperature variation function with the charging current also includes correcting the heating power or cooling power generated by the battery thermal management system. After correcting the heating power or cooling power generated by the battery thermal management system, the battery temperature variation function with the charging current is specifically formulated as follows:

[0015]

[0016] In the formula, is the heating power or cooling power generated by the battery thermal management system, I bat is the charging current, R bat is the internal resistance of the battery, h env is the air convection heat transfer coefficient, A bat is the battery surface area, T env is the ambient temperature, T bat，0 is the battery charging start temperature, m bat is the battery mass, c p，bat is the specific heat capacity of the battery, Q bat is the battery capacity parameter, SoC bat (t end ) is the charging target cut-off SOC, SoC bat(0) is the charging start SOC, T bat，des is the charging target boundary temperature limit, T bat，0 is the charging start temperature.

[0017] Optionally, the heating power or cooling power generated by the battery thermal management system is calculated as follows:

[0018] The heating power or cooling power generated by the battery thermal management system is equal to the maximum heating power or cooling power of the battery thermal management system multiplied by the heating or cooling coefficient;

[0019] When the battery thermal management system is in an active cooling state, the cooling coefficient is a constant greater than 0; when the battery thermal management system is in an active heating state, the heating coefficient is a constant less than 0; when the battery thermal management system is not working, the heating or cooling coefficient is 0.

[0020] Optionally, the heating power or cooling power generated by the battery thermal management system is calculated as follows:

[0021] The heating power or cooling power generated by the battery thermal management system is calculated based on the battery inlet coolant temperature, outlet coolant temperature and actual coolant flow rate.

[0022] Optionally, after the charging current is calculated, the battery aging state SOH correction is performed on the charging current, and the specific method is as follows:

[0023] The corrected charging current is equal to the current aging state of the battery multiplied by the charging current, and the current aging state of the battery ranges from 0 to 1.

[0024] Optionally, after the charging current is calculated, the battery aging state SOH correction is performed on the charging current, and the specific method is as follows:

[0025] According to the battery aging state SOH, piecewise linear interpolation is performed for correction.

[0026] Furthermore, if the battery temperature exceeds a threshold temperature and the SOC does not reach the charging target cut-off SOC, a feedback control algorithm is started according to the temperature deviation to adjust the charging current.

[0027] Furthermore, the feedback control algorithm is a PID closed-loop control algorithm.

[0028] In order to achieve the above object, on the other hand, a battery charging current calculation device is provided, comprising:

[0029] Information acquisition module, to obtain basic battery information and battery charging information;

[0030] The current calculation module substitutes the basic battery information and charging information into the battery temperature vs. charging current function to calculate the charging current.

[0031] In order to achieve the above object, on the other hand, a storage medium is provided, which stores a plurality of instructions, and a processor loads the plurality of instructions to execute the above battery charging current calculation method.

[0032] In order to achieve the above object, on the other hand, a battery management system is provided, which adopts the above battery charging current calculation device and / or the above storage medium.

[0033] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0034] 1. The charging current calculated based on the battery thermal model and aging status can adapt to different ambient temperatures and battery aging status

[0035] 2. By setting different charging target cutoff SOC values ​​and target boundary temperature limits, the charging depth and temperature rise of the battery can be controlled, thereby controlling the aging speed of the battery.

[0036] 3. Based on the deviation between the real-time measured battery temperature and the target boundary temperature limit, the charging current is adjusted in a closed loop to avoid excessive deviation of the feedforward charging current, which may lead to over-temperature charging or lithium deposition, thus ensuring the reliability of the charging process.

[0037] 4. Compared with the conventional BMS method of calculating the charging current based on the charging current table provided by the battery supplier, the present invention charges to the charging target cut-off SOC value under different ambient temperatures and different initial SOCs, which can effectively shorten the charging time.

[0038] It should be noted that the terms "first", "second" and similar terms used in this article are only for describing the various components in the technical solution, and do not constitute a limitation of the technical solution, nor can they be understood as an indication or suggestion of the importance of the corresponding elements; elements with "first", "second" and similar terms indicate that the corresponding technical solution contains at least one of the element. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solution of the present invention and facilitate further understanding of the technical effects, technical features and purposes of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings. The accompanying drawings constitute an essential part of the specification and are used together with the embodiments of the present invention to illustrate the technical solution of the present invention, but do not constitute a limitation to the present invention.

[0040] The same reference numerals in the accompanying drawings represent the same components, specifically:

[0041] Figure 1 This is a schematic diagram of the overall process of Example 1.

[0042] Figure 2This is a schematic diagram of the overall process of calculating and feeding back the corrected charging current in Example 1. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described below are only for explaining the technical solutions of the present invention, rather than for limiting the present invention. In addition, the parts described in the embodiments or the accompanying drawings are only examples of the relevant parts of the present invention, rather than the whole of the present invention.

[0044] Embodiment 1:

[0045] A method for calculating battery charging current, such as Figure 1 As shown, the specific steps are as follows:

[0046] S1. Construct a function of battery temperature changing with charging current.

[0047] S11. Calculate the heating rate or cooling power of the battery under the active action of the battery thermal management system during charging

[0048]

[0049] Among them, P bat，max Indicates the maximum heating power or cooling power of the battery thermal management system, and α indicates the heating or cooling coefficient. When the battery thermal management system is in the active cooling state, that is, Batt_TM_State=Cooling, α is a constant greater than 0; when the battery thermal management system is in the active heating state, that is, Batt_TM_State=Heating, α is a constant less than 0; when the battery thermal management system is in the off and inactive state, that is, Batt_TM_State=InActive, α is a constant equal to 0.

[0050] In step S11, It can also be based on the battery inlet coolant temperature T bat，in , outlet coolant temperature T bat，out And the actual flow rate of coolant is calculated, the specific calculation is as follows:

[0051]

[0052] Among them, c p represents the specific heat capacity of coolant density, ρ c Indicates the coolant density, Indicates the actual coolant flow rate.

[0053] S12. Calculate the battery temperature change during the charging process:

[0054]

[0055] Among them, k bat =m bat c p，bat , k env =h env A bat , m bat Indicates the mass of the battery, c p，bat Represents the specific heat capacity of the battery, h env represents the air convection heat transfer coefficient, A bat represents the battery surface area, T bat Indicates the current battery temperature, dT bat / dt represents the battery temperature change rate, I bat Represents the battery charging current, R bat Represents the internal resistance of the battery, T env Indicates the ambient temperature.

[0056] The first term on the right side of formula (2) is I bat 2 R bat represents the heat generation rate during battery charging, and the second term k env (T bat -T env ) represents the heat exchange rate between the battery and the natural environment during the charging process; the second term Indicates the heating rate or cooling power of the battery due to the active action of the battery thermal management system during the charging process. It indicates the cooling power, and the battery thermal management system is in active cooling state; when It indicates the heating power and the battery thermal management system is in active heating state.

[0057] By solving the differential equation (2) above, it is possible to predict the battery temperature during charging as a function of the charging current I bat The changes are as follows:

[0058]

[0059] Among them, T bat，0 Indicates the starting temperature of the battery when charging.

[0060] S13, based on the ampere-hour integration algorithm, calculate the battery SOC during the charging process with the charging current I bat The changes are as follows:

[0061]

[0062] Among them, dSoC bat / dt represents the rate of change of battery SOC, Q bat Indicates the capacity parameter of the battery.

[0063] S14, calculating the charging time required from the battery charging start SOC value to the charging target end SOC value as follows:

[0064]

[0065] Among them, SoC bat (0) indicates the starting SOC value of charging, SoC bat (t end ) represents the charging target cut-off SOC value, that is, Figure 1 SoC bat，des , and its value range is 0 to 100.

[0066] S15, according to formula (3) and boundary conditions, when charging reaches the charging target cut-off SOC value SoC bat (t end ), the battery temperature reaches the target temperature limit T bat，des , thus we can get the following:

[0067]

[0068] In step S1, if the battery thermal management system does not work,

[0069] S2. Obtain basic battery information and battery charging information.

[0070] In step S2, the battery charging information includes: ambient temperature, charging start temperature, charging target temperature limit, charging time, charging start SOC and charging target end SOC.

[0071] S3. Substitute the basic battery information and charging information into the function of battery temperature changing with charging current to calculate the charging current.

[0072] According to the above formula (6), the charging current I bat is the unknown quantity to be solved, so the following nonlinear equation can be obtained. By solving the numerical solution of the nonlinear equation, the charging current I during the charging process can be obtained: bat , which serves as the feedforward term of the charging current I bat，FF :

[0073]

[0074] S4. Considering the aging of the battery, the charging capacity of the battery gradually decreases with the aging of the whole life cycle. Based on the above (7) calculated to the feedforward charging current I bat，FF The battery aging state SOH needs to be corrected to adapt to the charging capacity of the battery throughout its life cycle, such as Figure 2As shown, a typical correction algorithm is as follows:

[0075] I bat，cor (t) = I bat，FF (t)*SoH bat (t) (8)

[0076] Among them, I bat，cor Indicates the charging current after battery aging correction, SoH bat Indicates the current aging status of the battery, and its value range is 0 to 1.

[0077] In step S4, the feedforward correction current I bat，cor (t) can also be corrected by piecewise linear interpolation according to the battery aging state SOH. The specific calculation method is as follows:

[0078] I bat，cor (t) = I bat，FF (t)*β (12)

[0079] Among them, β represents the correction coefficient, β 0 and β 1 It can be determined offline, and its value range is 0 to 1, β 1 ≤β 0 , as shown in the following table:

[0080] <![CDATA[SoH bat ]]> 100 80 0 β 1 <![CDATA[β 0 ]]> <![CDATA[β 1 ]]>

[0081] S5. Considering the battery thermal model, SoH bat The potential deviation of the value and the accuracy of the charging pile output current, once it is recognized that the battery temperature has exceeded the threshold T bat，FB However, when the charging target SOC has not been reached, the charging current feedback control algorithm needs to be started, that is, based on the current battery temperature T bat，act and the target temperature limit T bat，des Deviation T bat，err To close the loop to adjust the charging current, a typical PID-based closed-loop control algorithm is as follows:

[0082]

[0083] Among them, k P Represents the proportional gain coefficient, k I Indicates the integral gain coefficient, k D Represents the differential gain coefficient, which can be determined by offline calibration. bat，FB represents the feedback control activation threshold, represented by T bat，FB =T bat，des -T bat，diff The determination can be made by calibrating T at different ambient temperatures. bat，diffget.

[0084] When T bat，act ≤T bat，FB When ΔI bat，FB =0, that is, the charging current feedback control algorithm is not activated. bat，act >T bat，FB When the charging current feedback control algorithm is activated, ΔI bat，FB It is calculated by the above formula (9).

[0085] Based on the above equations (8) and (9), the final charging current I is calculated. bat，des The calculation of battery charging current in a wide temperature range is achieved as follows.

[0086] I bat，des (t) = I bat，cor (t)+ΔI bat，FB (t) (10)

[0087] Embodiment 2:

[0088] A battery charging current calculation device, comprising:

[0089] Information acquisition module, to obtain basic battery information and battery charging information;

[0090] The current calculation module substitutes the basic battery information and charging information into the battery temperature vs. charging current function to calculate the charging current.

[0091] It should be noted that the above embodiments are only for more clearly illustrating the technical solutions of the present invention. Those skilled in the art will understand that the implementation methods of the present invention are not limited to the above contents, and obvious changes, replacements or substitutions based on the above contents do not exceed the scope of the technical solutions of the present invention; other implementation methods will also fall within the scope of the present invention without departing from the concept of the present invention.

Claims

1. A method for calculating battery charging current, characterized in that: The specific method is as follows: Get basic battery information and battery charging information; Substitute the basic battery information and charging information into the function of battery temperature changing with charging current to calculate the charging current.

2. The battery charging current calculation method according to claim 1, characterized in that: The battery charging information includes: ambient temperature, charging start temperature, charging target boundary temperature limit, charging time, charging start SOC and charging target end SOC.

3. The battery charging current calculation method according to claim 2, characterized in that: The battery temperature changes with the charging current function. The specific formula is as follows: k env =h env A bat k bat =m bat c p,bat In the formula, I bat is the charging current, R bat is the internal resistance of the battery, h env is the air convection heat transfer coefficient, A bat is the battery surface area, T env is the ambient temperature, T bat，0 is the battery charging start temperature, m bat is the battery mass, c p,bat is the specific heat capacity of the battery, Q bat is the battery capacity parameter, SoC bat (t end ) is the charging target cut-off SOC, SoC bat (0) is the charging start SOC, T bat,des is the charging target boundary temperature limit, T bat，0 is the charging start temperature.

4. The battery charging current calculation method according to claim 2, characterized in that: When the battery has a battery thermal management system to adjust the battery temperature, the battery temperature change function with the charging current also includes correcting the heating power or cooling power generated by the battery thermal management system. After correcting the heating power or cooling power generated by the battery thermal management system, the battery temperature change function with the charging current is as follows: In the formula, is the heating power or cooling power generated by the battery thermal management system, I bat is the charging current, R bat is the internal resistance of the battery, h env is the air convection heat transfer coefficient, A bat is the battery surface area, T env is the ambient temperature, T bat，0 is the battery charging start temperature, m bat is the battery mass, c p,bat is the specific heat capacity of the battery, Q bat is the battery capacity parameter, SoC bat (t end ) is the charging target cut-off SOC, SoC bat (0) is the charging start SOC, T bat,des is the charging target boundary temperature limit, T bat，0 is the charging start temperature.

5. The battery charging current calculation method according to claim 4, characterized in that: The heating power or cooling power generated by the battery thermal management system is calculated as follows: The heating power or cooling power generated by the battery thermal management system is equal to the maximum heating power or cooling power of the battery thermal management system multiplied by the heating or cooling coefficient; When the battery thermal management system is in an active cooling state, the cooling coefficient is a constant greater than 0; when the battery thermal management system is in an active heating state, the heating coefficient is a constant less than 0; when the battery thermal management system is not working, the heating or cooling coefficient is 0.

6. The battery charging current calculation method according to claim 4, characterized in that: The heating power or cooling power generated by the battery thermal management system is calculated as follows: The heating power or cooling power generated by the battery thermal management system is calculated based on the battery inlet coolant temperature, outlet coolant temperature and actual coolant flow rate.

7. The battery charging current calculation method according to claim 1, characterized in that: After calculating the charging current, the battery aging state SOH correction is performed on the charging current. The specific method is as follows: The corrected charging current is equal to the current aging state of the battery multiplied by the charging current, and the current aging state of the battery ranges from 0 to 1.

8. The battery charging current calculation method according to claim 1, characterized in that: After calculating the charging current, the battery aging state SOH correction is performed on the charging current. The specific method is as follows: According to the battery aging state SOH, piecewise linear interpolation is performed for correction.

9. The battery charging current calculation method according to claim 1, characterized in that: If the battery temperature exceeds the threshold temperature and the SOC does not reach the charging target cut-off SOC, the feedback control algorithm is started to adjust the charging current according to the temperature deviation.

10. The battery charging current calculation method according to claim 9, characterized in that: The feedback control algorithm is a PID closed-loop control algorithm.

11. A battery charging current calculation device, characterized in that: include: Information acquisition module, to obtain basic battery information and battery charging information; The current calculation module substitutes the basic battery information and charging information into the battery temperature vs. charging current function to calculate the charging current.

12. A storage medium, characterized in that: A plurality of instructions are stored, and a processor loads the plurality of instructions to execute the battery charging current calculation method according to any one of claims 1 to 10.

13. A battery management system, characterized in that: Use the battery charging current calculation device described in claim 11 and / or the storage medium described in claim 12.

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