Battery pack temperature equalization system and active control method

Abstract

In order to reduce the internal friction and efficiency attenuation caused by the temperature difference in the battery pack, the present invention provides a power battery pack cooling system and an active temperature balancing control method. During the battery pack cooling process, the average temperature and the maximum temperature difference of each sensor in the battery pack are determined in real time, each cooling circuit is opened and closed, and the speed of the fan and the water pump is adjusted to achieve a step-by-step slow increase and decrease in the temperature of the coolant flow at the inlet of the battery pack, reduce the drastic temperature fluctuation caused by the large temperature difference heat exchange between the inlet coolant and the high-temperature battery pack, and improve the temperature consistency, working efficiency and thermal safety between the internal single cells.

Description

Technical Field

[0001] The present invention belongs to the field of thermal management of electric vehicles and power batteries, and in particular relates to a temperature balancing control method for a power battery pack. Background Art

[0002] Power batteries are key components of electric vehicles, directly affecting the performance and range of electric vehicles. Battery electrochemical reactions are extremely sensitive to temperature. Harsh and changeable driving conditions and high-temperature environments can cause the battery temperature to be too high, greatly affecting the battery capacity, service life and safety. Liquid media have stronger heat exchange capabilities than air media, which is more conducive to achieving two-way thermal control of cold and warm and building integrated thermal management for the entire vehicle. For large-capacity and high-power power battery packs, liquid thermal management technology has become an important research and application direction.

[0003] At the same time, during the battery cooling process, when the initial battery temperature is significantly different from the coolant flow temperature, the battery pack temperature fluctuates violently, causing the temperature difference of each single battery to expand rapidly, and even cold shock and micro-damage may occur, thereby causing the differences in internal resistance, voltage, SOC and other parameters to increase sharply, directly leading to the rapid attenuation of battery pack efficiency and life, increasing the internal consumption of the battery pack and the probability of thermal runaway, and even causing safety problems such as leakage and explosion under harsh working conditions and high cycle working times.

[0004] Therefore, it is particularly important to carry out timely and effective active temperature balance control on the power battery pack. To this end, the present invention provides a power battery pack cooling system and an active temperature balance control method to ensure the step-by-step ramp-up and ramp-down of the coolant flow temperature at the inlet of the battery pack, reduce the drastic temperature fluctuations in the battery pack, and the resulting deterioration of temperature consistency and working efficiency between single cells, thereby reducing the risk of thermal runaway. Summary of the invention

[0005] The present invention provides a power battery pack cooling system and an active temperature balancing control method. During the battery pack cooling process, the average temperature and maximum temperature difference of each sensor in the battery pack are determined in real time, each cooling circuit is opened and closed, and the rotation speed of the fan and the water pump is adjusted to achieve a step-by-step slow increase and decrease in the temperature of the coolant flow at the inlet of the battery pack, reduce the drastic temperature fluctuation caused by the large temperature difference heat exchange between the inlet coolant and the high-temperature battery pack, and improve the temperature consistency, working efficiency and thermal safety between the internal single batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 Schematic diagram of battery pack liquid flow cooling system.

[0007] Figure 1 The numbers and corresponding names of the components are as follows:

[0008] 1 battery pack, 2 controller, 3 radiator, 4 radiator fan, 5 circulating fluid pump, V1-V2 control valve, T1-T4 temperature sensor, S1-S2 three-way valve.

[0009] Figure 2 Battery pack cooling temperature balance control process DETAILED DESCRIPTION

[0010] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0011] As attached Figure 1 As shown, the battery pack liquid flow cooling system includes a battery pack 1, a controller 2, a radiator 3, a radiator fan 4, a circulating liquid pump 5, a first control valve V1, a second control valve V2, a first temperature sensor T1, a second temperature sensor T2, a third temperature sensor T3, a fourth temperature sensor T4, a first three-way valve S1, and a second three-way valve S2, characterized in that the controller 2 receives temperature signals through temperature sensors T1-T4 to regulate the first control valve V1, the second control valve V2, the circulating liquid pump 5, and the radiator fan 4; the circulating liquid pump 5 controls the flow of circulating liquid in the system; the radiator fan 4 introduces ambient air into the radiator 3 for heat exchange with the cooling liquid flow; the first solenoid valve V1 controls the opening and closing of the circulating liquid flow entering the battery radiator 3; the second solenoid valve V2 controls the opening and closing of another cooling liquid flow of the system; the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3, and the fourth temperature sensor T4 respectively measure the battery temperatures at different positions in the battery pack.

[0012] Combined with Figure 1-2 The working principle of the present invention is described as follows:

[0013] Each temperature sensor T1-T4 is sampled in real time and fed back to the controller 2 for judgment. When the average temperature T of the temperature sensors T1-T4 in the battery pack 1 is greater than 45°C, the controller 2 commands the control valve V1 to open and closes the control valve V2, so that the circulating fluid flows through the first three-way valve S1 into the radiator 3; the circulating fluid pump 5 is turned on and its speed is adjusted to the maximum; at the same time, the radiator fan 4 is turned on and its speed is adjusted to the maximum. The circulating fluid in the battery thermal management system exchanges heat with the ambient air through the radiator 3 to achieve rapid temperature reduction of the battery pack. Return to the controller 2 and sample and judge the temperature sensor T1-T4 signals in real time.

[0014] When the average temperature T of each temperature measuring point is less than 45°C and the maximum temperature difference between each temperature measuring point is greater than 5°C, the controller (2) commands the control valve (V1) to be closed and the control valve (V2) to be opened, so that the circulating fluid flows through the first three-way valve (S1) and directly enters the second three-way valve (S2); the radiator fan (4) is closed, the circulating fluid pump (5) is opened, the rotation speed thereof is increased by a fixed preset value Δrp, and maintained for a fixed preset value Δt time, while the radiator fan (4) is kept closed, the rotation speed of the fan (4) is increased by a fixed preset value Δrp, and maintained for a fixed preset value Δt time; the radiator fan (4) is kept closed, the rotation speed of the circulating fluid pump (5) is increased by a fixed preset value Δrp again, and maintained for a fixed preset value Δt time; the radiator fan (4) is kept closed, the rotation speed of the circulating fluid pump (5) is increased by a fixed preset value Δrp for a third time, and maintained for a fixed preset value Δt time; the controller (2) is returned and the temperature sensor (T1)-(T4) signals are sampled and judged in real time. By increasing the speed of the water pump and the coolant flow rate in the above step-by-step manner, the temperature difference of the coolant flow at the inlet and outlet of the battery pack (1) can be reduced. At the same time, after the second three-way valve (S2) branch is opened, the coolant does not flow through the radiator to dissipate heat and cool down, thereby reducing the temperature difference between the coolant flow and the battery pack (1), thereby further reducing the maximum temperature difference in the battery pack (1) and improving the temperature consistency between battery cells.

[0015] When the average temperature T of each temperature measuring point is less than 45°C, the maximum temperature difference between each temperature measuring point is less than 2°C, and the temperature consistency of the battery pack (1) is good, in order to ensure that the operating temperature of the battery pack (1) can be maintained within the optimal operating temperature range, it is necessary to open the radiator branch to improve the cooling capacity. At the same time, in order to minimize the impact on the temperature consistency in the battery pack (1), the speed of the radiator fan (4) is increased in a step-by-step manner. The specific control method is: the controller (2) commands the control valve (V1) to open, and the control valve (V2) to open; the circulating liquid pump (5) is kept turned on, and its speed is reduced by a fixed preset value Δrp1, and the fixed preset value Δt1 time is maintained, and the radiator fan (4) is turned on at the same time. ), increase the fan speed by a fixed preset value Δrp1 and maintain the fixed preset value for Δt1 time; reduce the circulating liquid pump (5) speed by a fixed preset value Δrp1 again, and maintain the fixed preset value for Δt1 time, while increasing the radiator fan (4) speed by a fixed preset value Δrp1 and maintain the fixed preset value for Δt1 time; reduce the circulating liquid pump (5) speed by a fixed preset value Δrp1 for a third time, and maintain the fixed preset value for Δt1 time, while increasing the radiator fan (4) speed by a fixed preset value Δrp1 and maintain the fixed preset value for Δt1 time; return to the controller (2) and perform real-time sampling and judgment on the temperature sensor (T1)-(T4) signals.

Claims

1. A method for actively controlling battery pack temperature balance, characterized in that: The battery cooling system is composed of a battery pack, a controller, a radiator, a radiator fan, a circulating liquid pump, a first control valve V1, a second control valve V2, a first temperature sensor T1, a second temperature sensor T2, a third temperature sensor T3, a fourth temperature sensor T4, a first three-way valve S1, and a second three-way valve S2; the controller receives temperature signals from the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3, and the fourth temperature sensor T4 to regulate the first control valve V1, the second control valve V2, the circulating liquid pump, and the radiator fan; the circulating liquid pump controls the flow of circulating liquid in the system; the radiator fan introduces ambient air into the radiator for heat exchange with the coolant flow; the first control valve V1 controls the opening and closing of the circulating liquid flow entering the battery radiator; the second control valve V2 controls the opening and closing of another coolant flow of the system; the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3, and the fourth temperature sensor T4 respectively measure the battery temperatures at different positions in the battery pack; The controller samples and judges the signals of the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3, and the fourth temperature sensor T4 in real time. When the average temperature T of each temperature measurement point is greater than 45°C, the controller commands the first control valve V1 to open and the second control valve V2 to close, so that the circulating fluid flows through the first three-way valve S1 into the radiator; the circulating fluid pump is turned on and its speed is adjusted to the maximum, and the radiator fan is turned on and its speed is adjusted to the maximum; the circulating fluid flow in the battery thermal management system exchanges heat with the ambient air through the radiator to achieve rapid cooling of the battery pack; The controller samples and judges the signals of the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3 and the fourth temperature sensor T4 in real time. When the average temperature T of each temperature measuring point is less than 45°C and the maximum temperature difference between each temperature measuring point is greater than 5°C, the controller commands the first control valve V1 to be closed and the second control valve V2 to be opened, so that the circulating fluid flows through the first three-way valve S1 and directly enters the second three-way valve S2; the radiator fan is turned off, the circulating fluid pump is turned on, and its speed is increased by a fixed preset value Δrp, and maintained for a fixed preset value Δt time; the radiator fan is kept off, and the speed of the circulating fluid pump is increased by a fixed preset value Δrp again, and maintained for a fixed preset value Δt time; the radiator fan is kept off, and the speed of the circulating fluid pump is increased by a fixed preset value Δrp for the third time, and maintained for a fixed preset value Δt time; the controller is returned to and samples and judges the signals of the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3 and the fourth temperature sensor T4 in real time; The controller samples and judges the signals of the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3 and the fourth temperature sensor T4 in real time. When the average temperature T of each temperature measuring point is less than 45°C and the maximum temperature difference between each temperature measuring point is less than 2°C, the controller commands the first control valve V1 to open and the second control valve V2 to open; keeps the circulating liquid pump on, reduces its speed by a fixed preset value Δrp1, and maintains the fixed preset value Δt1 time; at the same time, turns on the radiator fan, increases the fan speed by a fixed preset value Δrp1 and maintains the fixed preset value Δt1 time; and again turns on the circulating liquid pump, reduces its speed by a fixed preset value Δrp1, and maintains the fixed preset value Δt1 time. The circulating liquid pump speed is reduced by a fixed preset value Δrp1 and maintained for a fixed preset value Δt1 time, while the radiator fan speed is increased by a fixed preset value Δrp1 and maintained for a fixed preset value Δt1 time; the circulating liquid pump speed is reduced by a fixed preset value Δrp1 for the third time and maintained for a fixed preset value Δt1 time, while the radiator fan speed is increased by a fixed preset value Δrp1 and maintained for a fixed preset value Δt1 time; the controller is returned to and the signals of the first temperature sensor T1, the second temperature sensor T2, the third temperature sensor T3 and the fourth temperature sensor T4 are sampled and judged in real time.

Images