Adaptive fast charging method and system considering battery soh degradation

Abstract

The application provides an adaptive fast charging method and system considering battery SOH attenuation, comprising: obtaining and storing SOH of a battery to be charged; adjusting a maximum current value of allowed fast charging in real time according to a current SOH value of the battery to be charged; considering the maximum current value to perform fast charging on the battery to be charged; wherein the maximum current value is a product of the current SOH value of the battery to be charged and a first fast charging current value; the first fast charging current value is determined according to a current temperature and a SOC interval of the battery to be charged; SOH is battery health degree; and SOC is battery remaining capacity percentage. By calculating the SOH value in real time, the size of the fast charging current is adaptively controlled in different stages of battery life attenuation, so that the charging current size of the lithium ion battery is within a reasonable, efficient and safe range.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery charging, and particularly relates to an adaptive fast charging method and system considering battery SOH attenuation. BACKGROUND

[0002] The statements in this section merely provide background information related to the application and do not necessarily constitute prior art.

[0003] The installed capacity of lithium ion batteries is also increasing year by year. Lithium ion batteries have the advantages of high energy density, high charging and discharging rate, and long service life. In addition, due to the very active chemical properties of lithium, high and low temperatures have a great impact on lithium ion batteries. When overcharged and overdischarged, safety accidents such as fire and explosion are prone to occur.

[0004] In recent years, there have been many incidents of lithium ion electric vehicles catching fire and exploding, so the safety of battery vehicles has received widespread attention from society. Lithium ion batteries are particularly prone to over-temperature, explosion and other situations when charging with high-rate fast charging equipment. With the decline of SOH of lithium batteries after long-term use, such situations are more likely to occur.

[0005] The conventional method for lithium ion battery electric vehicles at present is to set the fast charging request current according to the two limiting conditions of temperature and SOC (or voltage), without considering the influence of battery SOH attenuation. In this case, due to the attenuation of battery SOH, if the charging current before the attenuation of battery SOH is still selected for charging during fast charging, it will lead to a situation where the charging current at this time does not match the SOH of the battery to be charged. Therefore, there is a safety risk of fire and explosion. SUMMARY

[0006] To solve the above problems, the application proposes an adaptive fast charging method considering battery SOH attenuation. The application adaptively performs safe fast charging according to the SOH attenuation of lithium ion batteries, which can avoid the safety risk of fire and explosion in the fast charging process.

[0007] According to some embodiments, the application adopts the following technical solution:

[0008] In a first aspect, an adaptive fast charging method considering battery SOH attenuation is disclosed, comprising:

[0009] acquiring and storing the SOH of the battery to be charged;

[0010] adjusting the maximum current value allowed for fast charging in real time according to the current SOH value of the battery to be charged;

[0011] considering the maximum current value to fast charge the battery to be charged;

[0012] The maximum current value is the product of the current SOH value of the battery to be charged and the first fast charging current value.

[0013] The first fast charging current value is determined according to the current temperature and the SOC interval of the battery to be charged, SOH is the battery health degree, and SOC is the battery remaining capacity percentage.

[0014] As a further technical solution, it further comprises an SOH calculation step of the charging battery, specifically:

[0015] The cycle number of the battery, the factory calendar time of the lithium ion battery, and the charging and discharging current of the lithium ion battery are obtained.

[0016] The SOH of the battery is calculated by using the following specific function:

[0017] The specific function is represented as:

[0018] X is the cycle number of the battery, Y is the factory calendar time of the battery, Z is the charging and discharging current of the battery, and abc are the coefficients of the above-mentioned factors, respectively. The above-mentioned charging and discharging current of the battery is the first fast charging current value.

[0019] As a further technical solution, the cycle number of the battery is calculated based on the cruising range of the vehicle, and one cycle is recorded when the cumulative NEDC cruising range is reached.

[0020] As a further technical solution, when the maximum current value is used for fast charging of the battery to be charged, the maximum current value is compared with the current corresponding to the maximum output power of the fast charging post equipment, and the smaller value is taken as the charging current of the battery to be charged.

[0021] As a further technical solution, the size of the fast charging request current is continuously adjusted during the fast charging process according to the changes of the battery temperature and SOC, that is, the size of the first fast charging current value is continuously adjusted, and the SOH is calculated in real time according to the data.

[0022] In a second aspect, an adaptive fast charging system considering battery SOH decay is disclosed, comprising:

[0023] A data acquisition unit and a battery control unit;

[0024] The data acquisition unit is used to obtain the cycle number of the battery, the size of the charging current, and the factory calendar time, and to transmit the above-mentioned data to the battery control unit.

[0025] The battery control unit calculates the SOH value based on the received data, adjusts the maximum current value allowed for fast charging in real time according to the current SOH value, sends a maximum current value request instruction to the fast charging post equipment, and the fast charging post equipment outputs the maximum charging current according to the request current value.

[0026] As a further technical solution, the data acquisition unit comprises a wheel speed sensor, a temperature sensor and a current sensor.

[0027] The wheel speed data collected by the wheel speed sensor is used to calculate the NEDC range, and the battery cycle number is calculated based on the data.

[0028] The temperature sensor is used to measure the temperature data of the battery during operation, and the current sensor is used to collect the charging current during fast charging.

[0029] As a further technical solution, when the battery control unit calculates the SOH value based on the received data, the SOH value is updated at a set time interval.

[0030] As a further technical solution, the adaptive fast charging system considering the SOH decay of the battery is realized based on the battery management system (BMS), and when the fast charging is full or stopped, the BMS interacts with the fast charging pile device through fast charging CAN communication to end this fast charging.

[0031] In a third aspect, a vehicle is disclosed, the vehicle is an electric vehicle, and the electric vehicle comprises a battery management system (BMS), and the BMS uses the above method to fast charge the battery.

[0032] Compared with the prior art, the beneficial effects of the present application are:

[0033] The charging method disclosed in the present application considers the influence of SOH decay on the charging current during the charging process of the battery, and by calculating the SOH value in real time, the size of the fast charging current is adaptively controlled in different stages of the battery life decay, so that the size of the charging current of the lithium ion battery is within a reasonable, efficient and safe range.

[0034] The above method disclosed in the present application mainly involves real-time calculation of SOH value, and the overall charging algorithm is simple and easy to implement. By automatically adjusting the size of the fast charging current according to the decay of the SOH of the lithium battery, the lithium battery has a safe, stable and efficient fast charging effect during its life cycle, greatly reducing the probability of problems such as thermal runaway caused by using large current fast charging of the lithium battery.

[0035] The above method disclosed in the present application is based on the existing BMS software strategy, does not need to increase additional hardware devices, only needs to modify the fast charging request current program in the battery management system, and does not involve any hardware modification in the battery management system.

[0036] The advantages of the additional aspects of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by the practice of the present application.

[0037] In order to make the above objectives, characteristics and advantages of the present application more apparent, more comprehensible, hereinafter a preferred embodiment is specifically described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0038] The drawings constituting a part of this specification provide further understanding of the present application, the illustrative embodiments of the present application and its description serve the purpose of explaining the present application, and do not constitute an improper limitation of the present application.

[0039] Figure 1 The charging method flow chart of the present disclosure technical solution. DETAILED DESCRIPTION

[0040] The present application is further described below with reference to the drawings and embodiments.

[0041] It should be noted that the following detailed description is exemplary, and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0042] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form, and in addition, it should be understood that when the terms "comprise" and / or "include" are used in the specification, they indicate the presence of a feature, step, operation, device, component and / or combination thereof.

[0043] Term explanation:

[0044] SOH: state of health, battery health, which can be understood as the percentage of the current capacity of the battery and the factory capacity.

[0045] SOC: state of charge, which can be understood as the percentage of the remaining battery capacity.

[0046] NEDC: New European Driving Cycle, Chinese: New European Driving Cycle, which can also be called: New European Cycle Test.

[0047] BMS: battery management system.

[0048] Embodiment one:

[0049] In this embodiment, the charging method is illustrated by taking the lithium ion battery of an electric vehicle as an example, but it does not mean that the charging method provided by the present application can only be applied to the lithium ion battery of an electric vehicle. According to the different charging objects, it can also be applied to the fast charging of the battery of other devices.

[0050] In this embodiment, an adaptive fast charging method considering battery SOH attenuation is disclosed, see FIG. 8 Figure 1 As shown, comprising:

[0051] Step one: record the total mileage of the vehicle according to the wheel speed sensor, and the VCU transmits the total mileage to the battery management system through the vehicle CAN communication after receiving the data of the wheel speed sensor, and the battery management system records and stores the SOH in combination with the cycle number of the lithium ion battery, the factory calendar time, the charging current size, etc.

[0052] The above-mentioned battery cycle number is calculated based on the NEDC endurance mileage of the electric vehicle, and one cycle is recorded when the cumulative NEDC endurance mileage reaches one.

[0053] In this step, when calculating the SOH value:

[0054] The stored SOH is inversely proportional to the cycle number of the lithium ion battery, the factory calendar time, and the charging and discharging current size, and the specific function can be represented as:

[0055]

[0056] Where X is the cycle number of the lithium ion battery, Y is the factory calendar time of the lithium ion battery, and Z is the charging and discharging current size of the lithium ion battery. Here, Z can be the current I1, and abc are the coefficients of each factor.

[0057] The selection range of abc data is 0-1, and the specific value can be determined by experience or experiment.

[0058] Step two: the lithium ion battery electric vehicle and the fast charging pile equipment establish connection and interaction through fast charging CAN communication.

[0059] Step three: the battery management system determines the size of the fast charging request current I1 according to the current temperature and SOC interval of the lithium ion battery. This table is developed according to the performance of the lithium ion battery at the time of factory shipment, and the current is obtained by collecting the temperature and SOC data of the lithium ion battery and corresponding to the table.

[0060] The current battery temperature and SOC interval are two limiting conditions in the fast charging request current two-dimensional map.

[0061] Regarding the SOC calculation method:

[0062] When the BMS is in dynamic mode, the Ah integral method is used to calculate the SOC in the charging and discharging overcharge, formula: SOC = 1-∫Idt / Q, I is the charging and discharging current, and Q is the rated capacity of the battery;

[0063] After the BMS is in static mode for a period of time (e.g., 1 hour), the OCV-SOC table is queried, the SOC value corresponding to the present voltage and temperature is obtained according to the OCV curve, and then the SOC is corrected at the next loading time, with the ampere-hour integral being corrected to the target value at a certain rate.

[0064] Since there is a certain error in calculating the SOC by the ampere-hour integral method, the error accumulates and becomes larger over time, so the ampere-hour integral and OCV-SOC table correction are combined to calculate the SOC.

[0065] For example, the fast charging current table at 25℃ is shown in Table 1. It should be noted that the data in the table is not the same for different types of batteries.

[0066] Table 1

[0067]

[0068] The fast charging request current I1 is a fast charging current value formulated in the battery management system at SOH = 100% according to the performance of the lithium ion battery.

[0069] Step four: The battery management system reads the stored SOH value, combines the size of the current I1, and obtains the fast charging request current value I2 through function operation;

[0070] The fast charging request current value I2 is a function value composed of I1 and SOH. In this embodiment, I2 = I1*SOH.

[0071] In addition, according to the different types of batteries, the function of I2 with I1 and SOH can be one of a linear function, a curve function, or a discrete function, which needs to be determined according to the simulation experiment.

[0072] Step five: The battery management system sends the request current value I2 to the fast charging pile device end, and the fast charging pile device outputs a fast charging current not greater than I2 according to the size of its maximum output power;

[0073] Specifically, the fast charging pile device will output the maximum charging current according to the request current value, and the fast charging pile end will compare the request current size of the battery management system (BMS) with the output power capability of itself, and take the smaller one.

[0074] Step six: During the fast charging process, the battery management system continuously adjusts the size of the fast charging request current in real time according to the changes of the battery temperature and the SOC;

[0075] Step seven: When the fast charging is completed or the user stops charging, the BMS ends this fast charging through the fast charging CAN communication and message interaction with the fast charging pile device.

[0076] The principle of the technical solution of the embodiment is: after the lithium battery is used for a long time, the internal active material will gradually become less active with time, and the electrochemical performance and capacity will gradually decrease, and the SOH will gradually decrease. At this time, the size of the charging rate needs to be adjusted according to the SOH of the lithium battery, so that the lithium battery can achieve a safe and efficient fast charging state in the later use process.

[0077] In the embodiment, a new SOH attenuation adaptive safe fast charging strategy for electric vehicle lithium ion batteries is designed based on the existing BMS software strategy. Specifically, the adaptive fast charging method considering the attenuation of the SOH of the battery is used to complete the fast charging of the lithium battery, which can protect the lithium ion battery and fully utilize the fast charging capacity of the lithium ion battery, and avoid the safety hazards of the lithium ion battery caused by excessive current in the fast charging process.

[0078] Embodiment two:

[0079] Based on the method of embodiment one, the adaptive fast charging system considering the attenuation of the SOH of the battery is disclosed, which comprises:

[0080] a data acquisition unit and a battery control unit;

[0081] The data acquisition unit is used to obtain the cycle number of the battery, the size of the charging current, and the factory calendar time, and to transmit the above data to the battery control unit;

[0082] The battery control unit calculates the SOH value based on the received data, adjusts the maximum current value of the allowed fast charging in real time according to the current SOH value, sends a maximum current value request instruction to the fast charging pile device, and the fast charging pile device outputs the maximum charging current according to the request current value.

[0083] In the embodiment, the data acquisition unit comprises a wheel speed sensor, a temperature sensor and a current sensor;

[0084] The wheel speed sensor collects vehicle wheel speed data for calculating the NEDC range.

[0085] The temperature sensor is used to measure the temperature data of the battery during operation, and the current sensor is used to collect the charging current during fast charging.

[0086] When the battery control unit calculates the SOH value based on the received data, the SOH value is updated at a set time interval. The above set time can be set according to the type of battery and the actual charging accuracy requirement.

[0087] The adaptive fast charging system considering the attenuation of the SOH of the battery is realized based on the battery management system BMS. When the fast charging is completed or stopped, the BMS exchanges messages with the fast charging pile device through the fast charging CAN communication, and ends this fast charging.

[0088] Further comprising a battery acquisition unit BMU for acquiring battery-related internal temperature, voltage and other related data, and transmitting to the battery control unit for monitoring the state of the battery itself.

[0089] The method for adjusting the maximum current allowed for fast charging in real time according to the characteristics of lithium battery SOH decay is as follows: judging the current temperature and SOC interval of the lithium battery, obtaining the fast charging request current size I1 according to the temperature and SOC, reading the stored SOH value, and then sending the fast charging request current value I2 to the fast charging pile end, I2 being a function value composed of I1 and SOH, and the fast charging pile end outputting current according to the final request I2.

[0090] With the increase of the number of charging and discharging of lithium ion batteries, the performance of the lithium ion batteries continuously decays, and the actual fast charging capacity of the lithium ion batteries cannot meet the size of the current I1 previously formulated, and it is necessary to combine the current actual performance of the battery to perform function operation to obtain the current I2. The advantage of the prior art is that the SOH can be calculated in real time according to the daily charging and discharging current size and the driving mileage in the embodiment, which is more in line with the actual performance of the battery, has high precision and self-adaptability.

[0091] Embodiment three:

[0092] In this embodiment, a vehicle is disclosed, which can be an electric vehicle, and the electric vehicle comprises a battery management system BMS, and the battery management system BMS uses the above method to fast charge the battery.

[0093] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0094] The above describes the specific embodiments of the present application in combination with the drawings, but is not a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications or changes made on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. An adaptive fast charging method considering battery SOH degradation, characterized in that, The method comprises the following steps: acquiring and storing SOH of the battery to be charged; adjusting the maximum current value allowing fast charging in real time according to the current SOH value of the battery to be charged; fast charging the battery to be charged considering the maximum current value; wherein the maximum current value is the product of the current SOH value of the battery to be charged and the first fast charging current value; the first fast charging current value is determined according to the current temperature and SOC interval of the battery to be charged, SOH is the battery health degree, and SOC is the battery remaining capacity percentage; the SOH calculation step of the battery, specifically comprising the following steps: acquiring the battery cycle number, the lithium ion battery factory calendar time and the lithium ion battery charging and discharging current; calculating the SOH of the battery by using the following specific function: The specific function is represented as: X is the battery cycle number, Y is the battery factory calendar time, Z is the battery charging and discharging current, and abc are the coefficients of the above-mentioned factors, and the above-mentioned battery charging and discharging current is the first fast charging current value.

2. The adaptive fast charging method considering battery SOH degradation according to claim 1, wherein, The battery cycle number is calculated based on the vehicle's cruising range. One cycle is recorded when the cumulative NEDC cruising range is reached. 3.The adaptive fast charging method considering battery SOH degradation of claim 1, wherein, When fast charging the battery to be charged considering the maximum current value, the maximum current value is compared with the current corresponding to the maximum output power of the fast charging pile equipment, and the smaller one is taken as the charging current of the battery to be charged. 4.The adaptive fast charging method considering battery SOH degradation of claim 1, wherein, The size of the fast charging request current is continuously adjusted according to the changes of the battery temperature and SOC during the fast charging process, that is, the size of the first fast charging current value is continuously adjusted, and the SOH is calculated in real time according to the data.

5. A system implementing the adaptive fast charging method taking into account the battery SOH degradation according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: a data acquisition unit and a battery control unit; the data acquisition unit is used to acquire the battery cycle number, the charging current size and the factory calendar time, and the above-mentioned data is transmitted to the battery control unit; the battery control unit calculates the SOH value based on the received data, adjusts the maximum current value allowing fast charging in real time according to the current SOH value, sends the maximum current value request instruction to the fast charging pile equipment, and the fast charging pile equipment outputs the maximum charging current according to the request current value. 6.The system of claim 5, wherein the method comprises: determining a battery state of health (SOH) of the battery; and determining a battery charging rate based on the battery SOH. The data acquisition unit comprises a wheel speed sensor, a temperature sensor and a current sensor; the wheel speed data collected by the wheel speed sensor is used to calculate the NEDC cruising range, and the battery cycle number is calculated based on the data; the temperature sensor is used to measure the temperature data of the battery during operation, and the current sensor is used to collect the charging current during fast charging. 7.The system of claim 5, wherein the battery SOH decay is considered in the adaptive fast charging method. When the battery control unit calculates the SOH value based on the received data, the SOH value is updated at a set time interval. 8.The system of claim 5, wherein the battery SOH decay is considered in the adaptive fast charging method. The adaptive fast charging system considering the battery SOH attenuation is realized based on the battery management system BMS. When the fast charging is completed or stopped, the BMS exchanges messages with the fast charging pile equipment through the fast charging CAN communication, and the fast charging is ended.

9. A vehicle, which is an electric automobile, characterized by The electric vehicle comprises a battery management system BMS, and the battery management system BMS fast charges the battery by using the adaptive fast charging method considering the battery SOH attenuation according to any one of claims 1-4.

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