A battery heating diagnostic system

Abstract

The present invention provides a battery heating diagnosis system, belonging to the technical field of power battery detection. When a battery heating film fails during operation, it may lead to problems such as battery explosion and combustion. The battery heating diagnosis system of the present invention includes a battery pack and a controller. The battery pack is composed of one or more battery series branches, and each battery series branch includes a plurality of series-connected single cells. A heating film is correspondingly arranged for each battery, and the heating films are connected in series to form a heating branch. A temperature sensor is arranged on each heating film, and the controller collects the temperature of the heating film through the temperature sensor. A current sensor is arranged on each heating branch, and the controller collects the current of the corresponding heating branch through the current sensor. The controller adopts a battery management system, which can judge whether there is a fault in the heating film according to the temperature of the heating film and the current of the heating branch, so as to improve the safety of the whole vehicle.

Description

Technical Field

[0001] The present invention relates to a battery heating diagnosis system, belonging to the technical field of power battery detection. Background Art

[0002] New energy vehicles have gradually become the mainstream products in the automotive market, and the automotive industry has basically achieved the transformation from fuel vehicles to electric vehicles. The electrification of vehicles is a major trend in the development of the automotive industry. Power batteries are an important link in the new energy vehicle industry chain. However, the poor low-temperature performance of power batteries has always been an important bottleneck restricting the development of the electric vehicle industry.

[0003] To solve the problem that the performance of lithium-ion batteries is poor at low temperatures, resulting in a short continuous driving range of the whole vehicle, the industry generally adopts the method of heating the power battery to ensure that the battery works in a suitable temperature range and improve the discharge capacity of the power battery. Due to the advantages of fast heating rate and relatively low cost of the heating film, the heating film is generally used in the industry to heat the power battery. However, the heating film belongs to a high-voltage electrical accessory and is closely attached to the power battery. If the heating film fails, it will cause a large safety hazard.

[0004] At present, the failure mode diagnosis of the heating film is not comprehensive and the treatment measures are incomplete. Major safety accidents caused by the failure of the heating film often occur. In 2020 alone, there were dozens of reported new energy vehicle fire accidents, most of which were caused by the failure of the heating film. The failure diagnosis of the heating film has become the key to ensuring the safety of new energy vehicles. Summary of the Invention

[0005] The purpose of the present invention is to provide a battery heating diagnosis system for solving the problem of difficult diagnosis of the failure of the heating film of the power battery.

[0006] To achieve the above purpose, the present invention provides a battery heating diagnosis system, including a battery pack and a controller. The battery pack includes at least one battery series branch. Each battery is correspondingly provided with a heating film. The heating films arranged on the same battery series branch are connected in series to form a heating branch. A temperature sensor is arranged on each heating film, and the controller is connected to the temperature sensor to obtain the temperature of the heating film. An current sensor is correspondingly arranged on each heating branch, and the controller is connected to the current sensor to obtain the current of the corresponding heating branch.

[0007] The battery heating diagnosis system of the present invention includes a battery pack and a controller. The battery pack is composed of one or more series-connected battery branches. Each battery series branch includes a plurality of series-connected single cells. A heating film is provided corresponding to each battery. The heating films are connected in series to form a heating branch. A temperature sensor is provided on each heating film. The controller collects the temperature of the heating film through the temperature sensor. An ammeter is provided on each heating branch. The controller collects the current of the corresponding heating branch through the ammeter. The controller uses a battery management system and can judge whether there is a fault in the heating film according to the temperature of the heating film and the current of the heating branch, so as to improve the safety of the whole vehicle.

[0008] Further, in the above system, when the heating branch starts to work, the controller starts timing. After a set time, the temperature of the heating film is collected, and the temperature rise rate of the heating film within the set time is calculated; the temperature rise rate of the heating film is the ratio of the change in the temperature of the heating film within the set time to the set time; if the temperature rise rate is greater than the first threshold, it is considered that the heating film has fallen off.

[0009] When the heating branch starts to work to heat the battery pack, the controller collects the temperature of the current heating film and starts timing. After a set time, the temperature of the heating film is collected again. According to the temperature of the heating film before and after the set time, the temperature difference is calculated. The temperature difference divided by the set time gives the temperature rise rate of the heating film. If the temperature rise rate exceeds the preset first threshold, it indicates that the heat of the heating film is not effectively transferred to the battery pack at this time, and it is considered that the heating film is not closely attached to the battery pack and the heating film has fallen off and failed.

[0010] Further, in the above system, the first threshold is 0.6 °C / min.

[0011] The first threshold is set according to the national standard GB38031. Using the standard of 0.6 °C / min, if the temperature rise rate of the heating film is greater than 0.6 °C / min, it is considered that the heating film has fallen off.

[0012] Further, in the above system, the controller obtains the insulation resistance value of each heating branch. If the insulation resistance value of a certain heating branch is less than the second threshold, the heating film in the corresponding heating branch has insulation failure.

[0013] The controller detects the insulation resistance value of each heating branch or the total circuit after parallel connection of the heating branches. The method for detecting the insulation resistance value can refer to the method for testing the insulation resistance of the whole vehicle in GB18384. If the detected insulation resistance value is lower than the set second threshold, it is considered that the heating film has insulation failure.

[0014] Further, in the above system, the second threshold is 100 Ω / V to 500 Ω / V.

[0015] The second threshold is set according to the national standard GB18384, adopting the standard of 100 ohms / volt to 500 ohms / volt. If the detected insulation resistance is lower than 100 ohms / volt to 500 ohms / volt, it is considered that the heating film has insulation failure.

[0016] Further, in the above system, if there are two or more heating branches, after the heating branches are connected in parallel, they are connected in series with the total heating circuit; when the heating branch is working, if the current of each heating branch is detected to be 0, it is considered that each heating branch or the total heating circuit is open.

[0017] If there are two or more heating branches, and each heating branch is connected to the battery pack, but the current of each heating branch is detected to be 0 through the current sensor, it indicates that the heating film of each heating branch is open, or there is an open circuit fault in the heating circuit.

[0018] Further, in the above system, a heating positive relay and a heating negative relay are arranged on the total heating circuit. The heating positive relay is connected in series on the total heating circuit connected to the positive pole of the battery pack, and the heating negative relay is connected in series on the total heating circuit connected to the negative pole of the battery pack.

[0019] A heating positive relay and a heating negative relay are arranged on the above-mentioned total heating circuit. The heating positive relay is connected in series on the total heating circuit connected to the positive pole of the battery pack, and the heating negative relay is connected in series on the total heating circuit connected to the negative pole of the battery pack. The controller needs to close the heating positive relay and the heating negative relay so that the battery pack can supply power to each heating branch, thereby heating the battery pack.

[0020] Further, in the above system, if there are two or more heating branches, when the heating branch is working, if it is detected that the current of a heating branch is 0 and the current of a heating branch is not 0, there is an open circuit failure in the heating film on the heating branch with a current of 0.

[0021] If it is detected that the current of some heating branches is 0 but the current of some heating branches is not 0 when the heating branch is working, it indicates that there is an open circuit in the heating film on the heating branch with a current of 0.

[0022] Further, in the above system, when the heating branch is working, if it is detected that the current of a certain heating branch is greater than the third threshold, there is a heating film short-circuited on that heating branch.

[0023] When the heating branch is working, detect whether the current of the heating branch is greater than the set third threshold. The third threshold refers to the current calculated when all the heating films are normally connected in the heating branch. If it exceeds the third threshold, it indicates that the resistance of that heating branch is lower than normal, and it is considered that there is a heating film short-circuited.

[0024] Further, in the above system, when the heating branch is operating, if it is detected that the current of one heating branch is greater than that of the other heating branch and the difference is greater than the fourth threshold, then there is a short circuit in the heating film on the heating branch with the larger current.

[0025] When the heating branch is operating, detect the current of each heating branch, calculate the current difference of each heating branch, and determine whether the current difference is greater than the set fourth threshold. If the current difference is greater than the fourth threshold, it indicates that there is a short circuit in the heating film in the heating branch with the larger current. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the circuit structure in the system embodiment of the present invention;

[0027] Figure 2 is a flowchart of the power battery pack heating diagnosis method in the system embodiment of the present invention.

[0028] In the figure, 1 is the power battery pack, 10 is the first battery series branch, 101 is the power battery, 11 is the second battery series branch, 20 is the first heating branch, 201 is the heating film, 21 is the second heating branch, 3 is the heating positive relay, 4 is the heating negative relay, 50 is the first current sensor, and 51 is the second current sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] System Embodiment:

[0031] A battery heating diagnosis system according to this embodiment determines the heat transfer efficiency between the heating film and the power battery by detecting the temperature of the heating film, and further determines whether the heating film has fallen off. If there is a poor fit between the heating film and the power battery, a fault reminder is given to the driver; it also detects the current of the heating branch where the heating film is located to determine whether there is a problem of short circuit or open circuit in the heating film in the heating branch; it also detects the insulation resistance value of the circuit where the heating film is located to determine whether there is an insulation fault in the heating film.

[0032] The battery heating diagnosis system of this embodiment adopts the circuit structure as shown in Figure 1 and includes a power battery pack 1, a battery management system BMS, and a battery heating system. The power battery pack 1 is also connected to the vehicle drive and high-voltage accessory system. Specifically, the power battery pack 1 is connected to the battery management system BMS, the vehicle drive and high-voltage accessory system, which can realize the power supply and control of the power battery pack 1 for the vehicle drive and high-voltage accessory system. The power battery pack 1 is also connected to the battery heating system to supply power to the battery heating system, and the battery heating system performs heating to raise the temperature of the power battery pack 1.

[0033] The power battery pack 1 is composed of a number of power batteries connected in series and parallel. In this embodiment, the power battery pack 1 includes two battery series branches connected in parallel, namely the first battery series branch 10 and the second battery series branch 11. The first battery series branch includes 3 power batteries 101. Correspondingly, the second battery series branch also includes three power batteries. A total of 6 power batteries are first connected in series and then in parallel to form the power battery pack 1. The total voltage of the power battery pack 1 is 600V. The positive electrode of the power battery pack 1 is connected in series with a fuse, which can disconnect the power supply to other circuits or loads in time when an overcurrent fault occurs in the power battery pack 1, ensuring the safety of the whole vehicle.

[0034] The battery management system BMS (Battery management system) mainly monitors the state of the power batteries on the vehicle, such as temperature, voltage, state of charge, etc., to realize functions such as the safety control of power batteries, battery state analysis, and fault diagnosis, and communicates with the whole vehicle to report the faults of the power batteries in time, so as to realize the safety management and control of the whole vehicle. In this embodiment, the battery management system BMS mainly detects and controls the battery heating system to realize the heating failure diagnosis of the power battery pack 1.

[0035]

[0034] The battery heating system includes a first heating branch 20, a second heating branch 21, a heating positive relay 3, a heating negative relay 4, a first current sensor 51, and a second current sensor 52. The first heating branch 20 corresponds to the first battery series branch 10, and the second heating branch 21 corresponds to the second battery series branch 11. The first heating branch 20 and the second heating branch 21 are connected in parallel to form a heating main branch. The heating main branch is connected to the positive electrode of the power battery pack 1 through the heating positive relay 3 and is also connected to the negative electrode of the power battery pack 1 through the heating negative relay 4. A manual control switch MSD is also provided on the heating main line where the heating positive relay 3 is connected to the positive electrode of the power battery pack 1, and a manual control switch MSD is also provided on the heating main line where the heating negative relay 4 is connected to the negative electrode of the power battery pack 1. The manual control switch MSD is used to be controlled by the staff during vehicle maintenance to prevent safety hazards during the maintenance process.

[0036] The first heating branch 20 and the second heating branch 21 both include a plurality of heating films, and the heating films are arranged corresponding to the batteries. In this embodiment, the first heating branch 20 includes three heating films 201. Correspondingly, the second heating branch 21 also includes three heating films, a total of six heating films. Each heating film corresponds to one power battery in the power battery pack 1 and is closely attached to the power battery. For example, the heating film 201 corresponds to the power battery 101 and is attached to the outer shell of the power battery 101. The heating film is a resistive device with a certain resistance value. When current passes through, it can generate a large amount of heat. In this embodiment, the resistance value of each heating film is 20 ohms.

[0037] In this embodiment, according to the number of power batteries in the power battery pack 1, the same number of heating films are selected and arranged in a matching manner with the power batteries. Those skilled in the art can perform other series-parallel combinations of power batteries according to the actual situation when designing the power battery pack of the vehicle, and the heating films also adopt corresponding series-parallel settings.

[0038] The battery management system BMS is connected to the control terminals of the heating positive relay 3 and the heating negative relay 4, and is used to control the power supply of the power battery pack 1 to the first heating branch 20 and the second heating branch 21. When the heating positive relay 3 and the heating negative relay 4 are both closed, the first heating branch 20 and the second heating branch 21 are powered on, the temperature of the heating film rises, and the temperature of the power battery pack 1 is increased by means of heat transfer, so that its temperature is in a suitable working range, thereby improving its charge and discharge efficiency.

[0039] A temperature sensor (not shown in the figure) is provided on each heating film. The battery management system BMS is connected to the temperature sensor. When the battery heating system is powered on, the temperature of the heating film gradually rises. At this time, the battery management system BMS can obtain the temperature of the corresponding heating film through the temperature sensor, so as to judge the battery heating system to determine whether the heating film is closely attached to the battery pack.

[0040] A first current sensor 50 is provided on the first heating branch 20, and a second current sensor 51 is provided on the second heating branch 21. The battery management system BMS is connected to the first current sensor 50 and is used to collect the heating current I1 of the first heating branch 20. It is also connected to the second current sensor 51 and is used to collect the heating current I2 of the second heating branch 21. The battery management system BMS can perform fault detection on the battery heating system through I1 and I2 to determine whether a corresponding heating branch has a fault.

[0041] The following combines Figure 2 , and introduces the battery heating diagnosis system of this embodiment, including the following steps:

[0042] When the vehicle is in a low-temperature state, the charge and discharge capacity of the power battery pack 1 is greatly reduced. At this time, it is necessary to start the battery heating system to raise the temperature of the power battery pack 1, ensure that it works in a reasonable temperature range, and improve the working efficiency. At this time, the battery management system BMS closes the heating positive relay 3 and the heating negative relay 4, and the power battery pack 1 supplies power to the first heating branch 20 and the second heating branch 21. The heating film corresponding to the power battery is energized and generates a large amount of heat, and its temperature is raised by means of heat transfer.

[0043] 1) Diagnosis of heating film detachment failure. The battery management system BMS collects the temperature of the corresponding heating film through the temperature sensor set on the heating film, and calculates the actual temperature rise rate of the heating film. In this embodiment, the total voltage of the power battery pack 1 is 600V, and the resistance value of a single heating film is 20 ohms. The theoretical temperature rise rate of the corresponding heating film can be calculated as T, and T is 0.6 °C / min in this embodiment. The battery management system obtains the temperature of the heating film at the start of heating and the temperature of the heating film after the heating set time, calculates the actual temperature rise rate of the heating film, compares the actual temperature rise rate and the theoretical temperature rise rate of the corresponding heating film. If the actual temperature rise rate is greater than 0.6 °C / min, it is considered that the fit between the heating film and the power battery is not tight, resulting in the heat generated by the heating film not being effectively transferred to the corresponding power battery, and local overheating occurs. Therefore, it can be judged that the heating film set on the power battery has fallen off and failed. At this time, the battery management system BMS promptly sends a fault to the whole vehicle for alarm.

[0044] 2) Diagnosis of heating film open circuit failure. The battery management system BMS obtains the heating current I1 of the first heating branch 20 through the first current sensor 50, and obtains the heating current I2 of the second heating branch 21 through the second current sensor 51. If both the heating current I1 and the heating current I2 are 0, it is considered that there is an open circuit in the power supply line connecting the power battery pack 1 and the heating main branch and / or the heating main branch; if the heating current I1 is 0 and the heating current I2 is not 0, it is considered that there is an open circuit in the first heating branch 20; if the heating current I1 is not 0 and the heating current I2 is 0, it is considered that there is an open circuit in the second heating branch 21. At this time, the battery management system BMS sends a fault to the whole vehicle for alarm.

[0045] 3) Diagnosis of short - circuit failure of the heating film. The battery management system BMS also determines whether there is a local short - circuit in the first heating branch 20 or the second heating branch 21 based on the heating current I1 and the heating current I2. If both the heating current I1 and the heating current I2 are 10A, it is considered that there is no local short - circuit in both the first heating branch 20 and the second heating branch 21; if the heating current I1 and / or the heating current I2 is 15A, it is considered that there is a short - circuit in one of the heating films in the first heating branch 20 and / or the second heating branch 21, which reduces the total resistance in the first heating branch 20 and / or the second heating branch 21 to 40 ohms, and the corresponding heating current increases, exceeding the heating current during normal operation; if the heating current I1 and / or the heating current I2 is 30A, it is considered that there are short - circuits in two of the heating films in the first heating branch 20 and / or the second heating branch 21, which reduces the total resistance in the first heating branch 20 and / or the second heating branch 21 to 20 ohms, and the corresponding heating current increases; at this time, the battery management system BMS sends a fault alarm to the whole vehicle.

[0046] As another implementation, the method for the battery management system BMS to determine whether there is a short - circuit in the first heating branch 20 or the second heating branch 21 based on the heating current I1 and the heating current I2 is: if the value of the heating current I1 is a and the value of the heating current I2 is b, if |a - b| is greater than or equal to a preset current, it is considered that there is a local short - circuit in the first heating branch 20 or the second heating branch 21. Specifically, if a > b and |a - b| is greater than or equal to the preset current, it is considered that there is a local short - circuit in the heating film in the first heating circuit 20, resulting in a decrease in the total resistance of the first heating branch 20, so that the difference between the heating current I1 and the heating current I2 is greater than the preset current; if a < b and |a - b| is greater than or equal to the preset current, it is considered that there is a local short - circuit in the heating film in the second heating circuit 21, resulting in a decrease in the total resistance of the second heating branch 21, so that the difference between the heating current I2 and the heating current I1 is greater than the preset current. Considering the error of the current sensor, the value of the preset current in this embodiment is 2A.

[0047] 4) Diagnosis of heating film insulation failure. When both the first heating branch 20 and the second heating branch 21 are working properly, that is, the heating currents I1 and I2 are both 20 A, and the actual temperature rise rate is equal to 0.6 °C / min. At this time, the battery management system BMS detects the insulation resistance value of the battery heating system and compares it with the preset insulation resistance value to determine whether there is an insulation failure in the battery heating system. If the insulation resistance value of the heating system is greater than the preset insulation resistance value, the insulation of the battery heating system is normal; if the insulation resistance value of the heating system is less than the preset insulation resistance value, there is an insulation failure in the battery heating system, and the insulation failure of the battery heating system is mainly caused by the insulation failure of the first heating branch 20 and / or the second heating branch 21. Therefore, it is considered that there is an insulation failure in the heating film of the first heating branch 20 and / or the second heating branch 21. At this time, the battery management system BMS sends a fault to the whole vehicle for alarm.

[0048] The preset insulation resistance value is set according to GB18384. GB18384 stipulates that in the maximum working voltage, the insulation resistance of the DC circuit should not be less than 100 ohms / volt, the insulation resistance of the AC circuit should not be less than 500 ohms / volt, and the insulation resistance of the combined circuit should not be less than 100 ohms / volt. To ensure the safety of the whole vehicle, in this embodiment, the preset insulation resistance value is designed to be 500 ohms / volt.

Claims

1. A battery heating diagnosis system, characterized in that, It includes a battery pack and a controller. The battery pack includes at least one battery series branch, and a heating film is correspondingly arranged for each battery. The heating films arranged on the same battery series branch are connected in series to form a heating branch. A temperature sensor is arranged on each heating film, and the controller is connected to the temperature sensor to obtain the temperature of the heating film; a current sensor is correspondingly arranged on each heating branch, and the controller is connected to the current sensor to obtain the current of the corresponding heating branch; when the heating branch starts to work, the controller starts timing, collects the temperature of the heating film after a set time, and calculates the temperature rise rate of the heating film within the set time; the temperature rise rate of the heating film is the ratio of the change in the temperature of the heating film within the set time to the set time; if the temperature rise rate is greater than the first threshold, it is considered that the heating film has fallen off.

2. The battery heating diagnosis system according to claim 1, wherein The first threshold is 0.6 °C / min.

3. The battery heating diagnosis system according to claim 1, wherein The controller obtains the insulation resistance values of each heating branch. If the insulation resistance value of a certain heating branch is less than the second threshold, there is an insulation failure in the heating film of the corresponding heating branch.

4. The battery heating diagnosis system according to claim 3, wherein The second threshold is 100 ohms / volt to 500 ohms / volt.

5. The battery heating diagnosis system according to claim 1, characterized in that If there are two or more heating branches, after the heating branches are connected in parallel, they are connected in series with the total heating circuit; when the heating branch is working, if it is detected that the current of each heating branch is 0, it is considered that each heating branch or the total heating circuit is open.

6. The battery heating diagnosis system according to claim 5, wherein, A heating positive relay and a heating negative relay are arranged on the total heating circuit. The heating positive relay is connected in series to the total heating circuit connected to the positive electrode of the battery pack, and the heating negative relay is connected in series to the total heating circuit connected to the negative electrode of the battery pack.

7. The battery heating diagnosis system according to claim 1, characterized in that, If there are two or more heating branches, when the heating branch is working, if it is detected that the current of a heating branch is 0 and the current of a heating branch is not 0, there is an open failure in the heating film on the heating branch with a current of 0.

8. The battery heating diagnosis system according to claim 1, wherein When the heating branch is working, if it is detected that the current of a certain heating branch is greater than the third threshold, there is a heating film short-circuited on that heating branch.

9. The battery heating diagnosis system according to claim 1, wherein When the heating branch is working, if it is detected that the current of a heating branch is greater than the current of another heating branch and the difference is greater than the fourth threshold, there is a heating film short-circuited on the heating branch with a larger current.

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