Electric vehicle battery pack heating device applicable to low-temperature environment and its control method

Abstract

The present invention provides an electric vehicle battery pack heating device applicable to low-temperature environments, comprising a heater (2), a battery pack temperature sensor (3), an ambient temperature sensor (4), and a controller (5). The controller (5) controls the heater (2) to operate so as to heat the battery pack (1) to a target temperature. The present invention also provides a control method for the above heating device. When heating is required, the automatic control of the heater (2) is carried out in real time through three steps: calculating a first state parameter P1, a second state parameter P2, and a third state parameter P3, calculating a comprehensive state parameter P, and calculating a target temperature c, so as to heat the battery pack (1) to the target temperature c. The electric vehicle battery pack heating device and its control method of the present invention are simple to operate, have high versatility, low cost, and simple logic, and can better balance the power output capacity and heating energy consumption of electric vehicles in low-temperature environments, alleviating the range anxiety phenomenon of electric vehicle users in low-temperature driving environments.

Description

Technical Field

[0001] The present invention relates to the field of electric vehicles, and particularly to an electric vehicle battery pack heating device applicable to low-temperature environments and a control method thereof. Background Art

[0002] Electric vehicles are becoming increasingly popular due to their advantages such as being green, environmentally friendly, and comfortable. Currently, electric vehicles mainly use lithium-ion batteries to form a battery pack to provide power for the vehicle. The optimal operating temperature of lithium-ion batteries is usually 25°C to 35°C, and their performance is poor in low-temperature environments. The rate of charge and discharge ability deteriorates significantly, and it is very likely that sufficient electrical energy output cannot be provided for the vehicle. Generally below 20°C, the lower the temperature, the greater the performance degradation of the battery. Among the currently dominant lithium iron phosphate for vehicle power batteries, the charge and discharge performance in low-temperature environments is particularly poor. In the currently known technical means, in low-temperature environments, generally, heating means such as heat pumps and heating resistors are used to directly and / or indirectly heat the battery pack to raise the temperature of the battery pack, thereby meeting its performance at low temperatures. For example, Chinese Patent CN201921160899.8 discloses a PTC heating liquid cooling plate for power batteries, which heats the liquid in the liquid cooling plate through a PTC heating element, thereby indirectly raising the battery temperature.

[0003] However, during the driving process of an electric vehicle in a low-temperature environment, no matter what battery heating means is adopted, it is inevitable to consume a large amount of electrical energy of the battery pack itself to a large extent, thereby affecting the remaining driving range of the vehicle. In the currently known technical solutions for heating electric vehicle battery packs, no consideration has been specifically given to how to set a suitable heating temperature. From the perspective of battery performance, within a certain range (for example, on the premise of being lower than 20°C), the higher the battery temperature, the better the performance and the more abundant the power output ability; from the perspective of heat transfer, the driving force for heat dissipation of the battery pack mainly lies in the temperature difference between the battery temperature and the external environment temperature: when the external environment temperature remains unchanged, the higher the battery pack temperature, the greater the temperature difference between the battery pack and the external environment, and the higher the heating energy consumption required to maintain this high temperature. Therefore, it is necessary to consider the external environment temperature factor and set the maintenance temperature (referred to as the heating temperature) during the heating process of the battery pack within a more appropriate range: if the temperature is too high, although the power output ability is good, the energy consumption is also large; if the temperature is too low, although the energy consumption is small, the power output is poor.

[0004] Therefore, it is necessary to propose a new heating device and its control method according to the driving requirements of electric vehicles and the environmental temperature, fully considering the reasonable setting of the heating temperature, so as to better balance the power output ability and heating energy consumption of electric vehicles. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an electric vehicle battery pack heating device with simple operation, high versatility, low cost, and simple logic, and provides its control method to better balance the power output ability and heating energy consumption of electric vehicles in low-temperature environments.

[0006] According to one aspect of the present invention, there is provided an electric vehicle battery pack heating device applicable to low-temperature environments, including a heater for heating the battery pack, a battery pack temperature sensor placed inside the battery pack, an ambient temperature sensor placed outside the electric vehicle, and a controller. The controller is electrically connected to the heater, the battery pack temperature sensor, the ambient temperature sensor, and the electric vehicle driving computer and can control the heater to work to heat the battery pack to a target temperature. Figure 1 The connecting dotted lines inside represent communication signal connections.

[0007] For the above electric vehicle battery pack heating device, the controller controls the heating temperature of the battery pack by adjusting the on / off of the heater and / or the heating power of the heater.

[0008] Preferably, based on the battery pack temperature value feedback result obtained by the battery pack temperature sensor and compared with the target temperature, the heating of the heater is adjusted by any one or a combination of the following two methods:

[0009] Method 1: By dynamically changing the heating resistance value of the heater, thereby adjusting its heating power.

[0010] Method 2: By continuously turning on or off the heater and performing on / off control on it, thereby adjusting its actual heating effect.

[0011] For the above electric vehicle battery pack heating device, a navigation software is installed on the driving computer. When the user starts the navigation software, the controller can obtain the remaining distance to the destination in real time through the driving computer.

[0012] For the above electric vehicle battery pack heating device, the driving computer can provide the battery pack state of charge information to the controller in real time.

[0013] According to another aspect of the present invention, there is provided a control method applied to the above electric vehicle battery pack heating device. The method is that a first temperature a and a second temperature b are preset in the controller in advance and a < b; during the driving process of the electric vehicle, the controller obtains the battery pack temperature Tc, the ambient temperature Ta, the remaining distance L, and the state of charge SOC in real time and performs automatic control of the heater:

[0014] When Tc ≥ b or Ta ≥ b, the heater is turned off and does not work; otherwise, the heater is turned on and works to heat the battery pack to the target temperature c, where the value of the target temperature c is determined according to the following steps:

[0015] Step S1, calculate the first state parameter P1, the second state parameter P2, and the third state parameter P3 respectively:

[0016] P1 = min[(b - Ta) / b, 1] (1)

[0017] P2 = 1 - SOC (2)

[0018] P3 = min(L / L0, 1) (3)

[0019] Wherein, L0 in the formula is k times the nominal cruising range of the electric vehicle, k is a proportionality coefficient, and the min symbol represents taking the minimum value among all the values in the subsequent parentheses;

[0020] Step S2, calculate the comprehensive state parameter P according to the values of the first state parameter P1, the second state parameter P2, and the third state parameter P3: If any one of the values of P1, P2, and P3 is greater than the reference state parameter P0, then P = max(P1, P2, P3), and the max symbol represents taking the maximum value among all the values in the subsequent parentheses; otherwise P is equal to the average value of P1, P 2、 P3;

[0021] Step S3, calculate the target temperature c:

[0022] c = a + (1 - P)(b - a) (4)

[0023] Preferably, for the control method of the above-mentioned electric vehicle battery pack heating device, the first temperature a preset in the controller is between 0 and 15 °C, and the second temperature b is between 15 °C and 25 °C.

[0024] Preferably, for the control method of the above-mentioned electric vehicle battery pack heating device, the proportionality coefficient k is between 0.3 and 0.7.

[0025] Preferably, for the control method of the above-mentioned electric vehicle battery pack heating device, the reference state parameter P0 is between 0.7 and 0.9.

[0026] Preferably, for the control method of the above-mentioned electric vehicle battery pack heating device, the state of charge SOC of the battery pack is obtained by the ampere-hour integration method. That is, the initial SOC of the battery pack is calibrated in advance, and then the current value of the battery pack is continuously collected during the operation of the electric vehicle, and the integral of the current value is calculated to calculate the state of charge SOC of the battery pack.

[0027] The principle of the technical solution of the present invention is:

[0028] The present invention aims at the characteristic that the higher the heating temperature of the battery pack is during the driving process of the electric vehicle in a low-temperature environment, the greater the heating energy consumption is. The present invention comprehensively considers the three factors of the ambient temperature, the remaining distance and the charge state of the battery pack during the driving process of the electric vehicle, and reasonably sets the heating temperature of the battery pack, thereby achieving a balance between the power output capacity and the heating energy consumption of the electric vehicle:

[0029] The first state parameter P1 reflects the ambient temperature factor. The lower the ambient temperature Ta, the larger P1 is. Under the same conditions, the heating temperature of the battery pack should be relatively low to avoid excessive temperature difference and energy waste.

[0030] The second state parameter P2 reflects the state of charge factor of the battery pack. The lower the state of charge, the larger P2 is. Under the same conditions, the heating temperature of the battery pack should be relatively low, which can fully save heating power consumption and use the remaining power for vehicle driving as much as possible.

[0031] The third state parameter P3 reflects the remaining driving distance factor required by the electric vehicle. The larger the remaining distance L, the larger P3. Under the same conditions, the heating temperature of the battery pack should be relatively low, fully saving heating power consumption and using the remaining power for vehicle driving as much as possible.

[0032] The calculation process truncates the first state parameter P1 and the third state parameter P3. If the value is greater than 1, it is truncated to 1 to ensure that both values ​​are between 0 and 1.

[0033] On this basis, the comprehensive state parameter P is calculated according to the values ​​of the first state parameter P1, the second state parameter P2 and the third state parameter P3: if a certain state parameter is particularly large, it means that some factors are more prominent and need special consideration, and the largest of the three state parameters is directly output as the comprehensive state parameter; otherwise, the average value of the three state parameters is output as the comprehensive state parameter P.

[0034] Finally, the target temperature c is set according to the comprehensive state parameter P: the larger the comprehensive state parameter P is, the closer the target temperature c is to the smaller first temperature a, the lower the battery pack heating temperature is, and energy saving is prioritized; the smaller the comprehensive state parameter P is, the closer the target temperature c is to the larger second temperature b, the higher the battery pack heating temperature is, and performance is prioritized.

[0035] According to the above principle description, it is not difficult to find the beneficial technical effects of the present invention:

[0036] 1. The heating device of the present invention only involves common components such as a heater, a temperature sensor and a controller, so it is convenient to modify on the basis of the existing electric vehicle design scheme, with high versatility and low cost.

[0037] 2. The control method of the present invention fully considers three factors: environmental temperature, remaining distance, and state of charge of the battery pack during the driving of the electric vehicle, reasonably sets the heating temperature of the battery pack, makes a good balance between the power output ability of the electric vehicle and the heating energy consumption, and the relevant calculation and control processes have simple operations and logics. Brief Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the composition of the electric vehicle battery pack heating device in the embodiment of the present invention. In the figure, 1 is the battery pack, 2 is the heater, 3 is the battery pack temperature sensor, 4 is the environmental temperature sensor, 5 is the controller, 6 is the vehicle computer, and 7 is the electronic switch.

[0039] Figure 2 It is a flowchart of the electric vehicle battery pack heating control method in the embodiment of the present invention. Detailed Embodiments

[0040] The present invention will be further described below in conjunction with the drawings and embodiments.

[0041] As Figure 1 shown, an electric vehicle battery pack heating device applicable to low-temperature environments includes a heater 2 for heating the battery pack 1, a battery pack temperature sensor 3 placed inside the battery pack 1, an environmental temperature sensor 4 placed outside the electric vehicle, and a controller 5. The controller 5 is electrically connected to the heater 2, the battery pack temperature sensor 3, the environmental temperature sensor 4, and the vehicle computer 6 of the electric vehicle and can control the heater 2 to work to heat the battery pack 1 to the target temperature. Figure 1 The connecting dotted lines inside represent communication signal connections.

[0042] The heater 2 is electrically connected to the battery pack 1 through an electronic switch 7 provided thereon and draws power from the battery pack 1. The electronic switch 7 is electrically connected to the controller 5.

[0043] For the above-mentioned electric vehicle battery pack heating device, the controller 5 can control the heating temperature of the battery pack by adjusting the on-off of the heater 2. That is, the controller 5 obtains the battery pack temperature value through the battery pack temperature sensor 3 and compares it with the target temperature. If the battery pack temperature value is lower than the target temperature, the electronic switch 7 closes and the heater 2 is powered on for heating; if the battery pack temperature value is greater than or equal to the target temperature, the electronic switch 7 disconnects and the heater 2 does not work.

[0044] For the above-mentioned electric vehicle battery pack heating device, a navigation software is installed on the vehicle computer 6. When the user starts the navigation software, the controller 5 can obtain the remaining distance L to the destination in real time through the vehicle computer 6.

[0045] For the above-mentioned electric vehicle battery pack heating device, the vehicle computer 6 can provide the state of charge information of the battery pack to the controller 5 in real time.

[0046] As Figure 2 shown, for the control method applied to the above-mentioned electric vehicle battery pack heating device, the first temperature a and the second temperature b are preset in advance in the controller 5, and a < b; during the driving process of the electric vehicle, the controller 5 obtains the battery pack temperature Tc, the ambient temperature Ta, the remaining distance L, and the state of charge SOC in real time and performs automatic control of the heater 2:

[0047] When Tc ≥ b or Ta ≥ b, the heater 2 is turned off and does not work; otherwise, the heater 2 is turned on and works to heat the battery pack 1 to the target temperature c, where the value of the target temperature c is determined according to the following steps:

[0048] Step S1: Calculate the first state parameter P1, the second state parameter P2, and the third state parameter P3 respectively:

[0049] P1 = min[(b - Ta) / b, 1] (1)

[0050] P2 = 1 - SOC (2)

[0051] P3 = min(L / L0, 1) (3)

[0052] Among them, L0 in the formula is k times the nominal cruising range of the electric vehicle, k is a proportionality coefficient, and the min symbol represents taking the minimum value among all the values in the subsequent parentheses;

[0053] Step S2: Calculate the comprehensive state parameter P according to the values of the first state parameter P1, the second state parameter P2, and the third state parameter P3: If any one of the values of P1, P2, and P3 is greater than the reference state parameter P0, then P = max(P1, P2, P3), and the max symbol represents taking the maximum value among all the values in the subsequent parentheses; otherwise, P is equal to the average value of P1, P 2、 P3;

[0054] Step S3: Calculate the target temperature c according to:

[0055] c = a + (1 - P)(b - a) (4)

[0056] For the above-mentioned control method of the electric vehicle battery pack heating device, the first temperature a preset in advance in the controller 5 is between 0 and 15 °C, and the second temperature b is between 15 °C and 25 °C.

[0057] For the above-mentioned control method of the electric vehicle battery pack heating device, the proportionality coefficient k is between 0.3 and 0.7.

[0058] For the above-mentioned control method of the electric vehicle battery pack heating device, the reference state parameter P0 is between 0.7 and 0.9.

[0059] The control method of the above-mentioned electric vehicle battery pack heating device, the state of charge SOC of the battery pack is obtained by the ampere-hour integration method. That is, the initial SOC of the battery pack is calibrated in advance, and then the current value of battery pack 1 is continuously collected during the operation of the electric vehicle, and the state of charge SOC of the battery pack is calculated by integrating the current value.

[0060] Embodiment

[0061] Please refer to Figure 1 and Figure 2 to understand this embodiment. The battery pack 1 of an electric vehicle is composed of lithium iron phosphate batteries, and the nominal cruising range is 300 km. According to the temperature characteristics of battery pack 1 and the actual situation of the vehicle, in this embodiment, the first temperature a = 5 °C, the second temperature b = 16 °C, the proportionality coefficient k = 0.5, the reference state parameter P0 = 0.8, and L0 = 0.5 * 300 = 150 km can be calculated.

[0062] In this embodiment, the form of the heater 2 is embodied as a resistance heating wire arranged on the surface of the battery, which directly provides heating for the battery; the controller performs temperature sampling once every 0.5 minutes and updates the calculated value of the target temperature c.

[0063] On a cold winter day, at a certain moment when the electric vehicle is running, the controller 5 obtains the battery pack temperature Tc = 6 °C, the ambient temperature Ta = 4 °C, the remaining distance L = 60 km, and the state of charge SOC = 0.7. Then Tc < b and Ta < b, so the first state parameter P1 = min[(b - Ta) / b, 1] = min[(16 - 4) / 16, 1] = 0.75, the second state parameter P2 = 1 - SOC = 0.3, and the third state parameter P3 = min(L / L0, 1) = min(60 / 150, 1) = 0.4 are calculated respectively.

[0064] Since P1, P2, and P3 are all less than the reference state parameter P0, the comprehensive state parameter P is:

[0065] P = (P1 + P2 + P3) / 3 = (0.75 + 0.3 + 0.4) / 3 = 0.48.

[0066] At this time, the target temperature c = a + (1 - P)(b - a) = 5 + (1 - 0.48)(16 - 5) = 10.72 °C is calculated.

[0067] That is, at the current moment, the controller 5 dynamically adjusts the heater 2 to keep the temperature of the battery pack 1 at 10.72 °C.

[0068] It should be noted that in the above technical solution, the controller 5 obtains the information of the remaining distance L from the vehicle computer 6. If the user does not turn on the navigation software, there is no remaining distance value in the vehicle computer 6. At this time, the controller 5 can set the third state parameter P3 to its preset default value, and the size of the default value can be between 0.3 and 0.7.

[0069] The heating device in the embodiment of the present invention only involves general components such as the heater 2, the temperature sensor, and the controller 5, so it is convenient to be modified on the basis of the existing electric vehicle design scheme, with high versatility and low cost; the control method in the embodiment of the present invention fully considers the three aspects of environmental temperature, remaining distance, and battery pack state of charge during the driving process of the electric vehicle, reasonably sets the heating temperature of the battery pack, and makes a good balance between the power output ability and heating energy consumption of the electric vehicle. The relevant calculation and control processes are simple in operation and logic.

Claims

1. A control method for a battery pack heating device for an electric vehicle suitable for a low temperature environment, characterized in that: The control method is based on a battery pack heating device. The heating device includes a heater (2) for heating the battery pack (1), a battery pack temperature sensor (3) placed inside the battery pack (1), an ambient temperature sensor (4) placed outside the electric vehicle, and a controller (5). The controller (5) is electrically connected to the heater (2), the battery pack temperature sensor (3), the ambient temperature sensor (4), and the on-board computer (6) of the electric vehicle and can control the heater (2) to operate so as to heat the battery pack (1) to a target temperature; The control method is as follows: a first temperature a and a second temperature b are preset in the controller (5) in advance and a < b; during the driving of the electric vehicle, the controller (5) obtains the temperature Tc of the battery pack (1), the ambient temperature Ta, the remaining distance L, and the state of charge SOC in real time and performs automatic control of the heater (2): When Tc ≥ b or Ta ≥ b, the heater (2) is turned off and does not work; otherwise, the heater (2) is turned on and works to heat the battery pack (1) to the target temperature c, where the value of the target temperature c is determined according to the following steps: Step S1: Calculate the first state parameter P1, the second state parameter P2, and the third state parameter P3 respectively: P1 = min[(b - Ta) / b, 1] (1) P2 = 1 - SOC (2) P3 = min(L / L0, 1) (3) Where, L0 in the formula is k times the nominal cruising range of the electric vehicle, k is a proportionality coefficient, and the min symbol represents taking the minimum value among all the values in the subsequent parentheses; Step S2, calculate the comprehensive state parameter P according to the values ​​of the first state parameter P1, the second state parameter P2 and the third state parameter P3: if any one of the values ​​of P1, P2 and P3 is greater than the reference state parameter P0, then P = max(P1, P2, P3), where the max symbol indicates the maximum of all the values ​​in the brackets; otherwise, P is equal to P1, P2, P3. 2、 P3 is the average of the three; Step S3: Calculate the target temperature c: c = a + (1 - P)(b - a) (4).

2. The control method of the electric vehicle battery pack heating device according to claim 1, characterized in that: The controller (5) realizes the control of the heating temperature of the battery pack (1) by adjusting the on / off of the heater (2) and / or the heating power of the heater (2).

3. The control method of the electric vehicle battery pack heating device according to claim 1, characterized in that: The on-board computer (6) is equipped with navigation software. When the user starts the navigation software, the controller (5) can obtain the remaining distance to the destination in real time through the on-board computer (6).

4. The control method of the electric vehicle battery pack heating device according to claim 1, characterized in that: The on-board computer (6) can provide the state of charge information of the battery pack (1) to the controller (5) in real time.

5. The control method of the electric vehicle battery pack heating device according to claim 1, characterized in that: The first temperature a preset in the controller (5) in advance is between 0 and 15 °C, and the second temperature b is between 15 °C and 25 °C.

6. The control method of the electric vehicle battery pack heating device according to claim 1, characterized in that: The proportionality coefficient k is between 0.3 and 0.

7.

7. The control method of the electric vehicle battery pack heating device according to claim 1, characterized in that: The reference state parameter P0 is between 0.7 and 0.9.

Images