Lithium battery temperature control method, lithium battery temperature control system and vehicle

Abstract

The invention provides a lithium battery temperature control method, a lithium battery temperature control system and a vehicle, and the method comprises the steps: obtaining a battery cell temperature value of a lithium battery cell and a state of charge of a lithium battery, and when the battery cell temperature value is smaller than a first temperature threshold value and the state of charge is larger than a preset state of charge, starting the lithium battery; heating the lithium battery by using a constant current until the temperature value of the battery core is greater than a first stop temperature; when the battery cell temperature value is smaller than a first temperature threshold value and the charge state is not larger than a preset charge state, pulse square wave voltage corresponding to the battery cell temperature value is used for heating the lithium battery; when the battery cell temperature value is smaller than the second temperature threshold value and not smaller than the first temperature threshold value, the pulse square wave current corresponding to the battery cell temperature value is used for heating the lithium battery. According to the method provided by the invention, corresponding working modes are selected under the condition of different temperatures and charge states, and the lithium battery is heated through constant current, pulse square wave voltage and pulse square wave current.

Description

Technical Field

[0001] The present application relates to the technical field of electric vehicles, and particularly to a method for controlling the temperature of a lithium battery, a lithium battery temperature control system, and a vehicle. Background Art

[0002] With the continuous development of modern technology, people's awareness of environmental protection has gradually increased. In order to better save energy and protect the environment, electric vehicles have emerged as the times require. The power supply system of an electric vehicle includes a high-voltage power supply system and a low-voltage power supply system. The high-voltage power supply system is mainly used to drive the motor to provide power, and the low-voltage power supply system generally supplies power to low-voltage vehicle-mounted devices, including: audio and lighting, etc.

[0003] Some low-voltage power supply systems of electric vehicles use lithium batteries as energy storage devices and power sources. However, the performance of lithium batteries is poor under low-temperature conditions. In this case, the lithium batteries of the low-voltage power supply system cannot be charged and discharged with a large current. The prior art provides heat to the lithium battery continuously by additionally setting up a heating system to maintain the temperature of the lithium battery at low temperature, and the additionally set heating system is powered by the high-voltage power supply system.

[0004] However, the method of providing heat to the lithium battery continuously by setting up an additional heating system has a high cost. How to improve the battery performance of lithium batteries under low-temperature conditions at a lower cost has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] Based on the above problems, the present application provides a method for controlling the temperature of a lithium battery, a lithium battery temperature control system, and a vehicle to reduce the cost of lithium battery temperature control.

[0006] The present application provides a method for controlling the temperature of a lithium battery, and the method includes the following steps:

[0007] Obtain the cell temperature value of the lithium battery cell and the state of charge of the lithium battery;

[0008] When the cell temperature value is less than the first temperature threshold and the state of charge is greater than the preset state of charge, heat the lithium battery with a constant current until the cell temperature value is greater than the first stop temperature;

[0009] When the cell temperature value is less than the first temperature threshold and the state of charge is not greater than the preset state of charge, heat the lithium battery with the pulse square wave voltage corresponding to the cell temperature value until the cell temperature value is not less than the first stop temperature, and the first temperature threshold is less than the first stop temperature;

[0010] When the cell temperature value is less than the second temperature threshold and the cell temperature value is not less than the first temperature threshold, use the pulsed square-wave current corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the second stop temperature.

[0011] In a possible implementation manner, the using a constant current to heat the lithium battery until the cell temperature value is greater than the first stop temperature includes:

[0012] The lithium battery discharges with a constant discharge current, and after discharging, uses a constant charging current to charge the lithium battery. The discharge current corresponds to the discharge capacity, the charging current corresponds to the charging capacity, and the charging capacity is greater than the discharge capacity;

[0013] Obtain the cell temperature value of the lithium battery cell after charging. If the cell temperature value of the lithium battery cell after charging is not greater than the first stop temperature, repeat the steps of discharging with a constant discharge current and then using a constant charging current to charge the lithium battery until the cell temperature value is greater than the first stop temperature.

[0014] In a possible implementation manner, the using the pulsed square-wave voltage corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the first stop temperature includes:

[0015] Output the first pulsed square-wave voltage within the first temperature range corresponding to the cell temperature value until the cell temperature value is greater than the upper limit of the first temperature range;

[0016] Output the second pulsed square-wave voltage within the second temperature range corresponding to the cell temperature value until the cell temperature value is not less than the first stop temperature. The highest voltage value of the first pulsed square-wave voltage is greater than the highest voltage value of the second pulsed square-wave voltage, and the lowest voltage value of the first pulsed square-wave voltage is greater than the lowest voltage value of the second pulsed square-wave voltage.

[0017] In a possible implementation manner, the using the pulsed square-wave current corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the second stop temperature includes:

[0018] Output a first pulsed square-wave current within a third temperature range corresponding to the cell temperature value until the cell temperature value is greater than the upper limit value of the third temperature range. The maximum current value, maximum current duration, minimum current value, and minimum current - duration of the pulsed square-wave current corresponding to the third temperature range are obtained by difference using the maximum current value, maximum current duration, minimum current value, and minimum current - duration corresponding to the limit temperature values of the third temperature range. The limit temperature values include the upper limit temperature value and the lower limit temperature value of the third temperature range.

[0019] Output a second pulsed square-wave current within a fourth temperature range corresponding to the cell temperature value until the cell temperature value is not less than a second stop temperature. The maximum current value of the first pulsed square-wave current is less than the maximum current value of the second pulsed square-wave current, the absolute value of the minimum current value of the first pulsed square-wave current is less than the absolute value of the minimum current value of the second pulsed square-wave current, and the duration of the maximum current value of the first pulsed square-wave current is less than the duration of the maximum current value of the second pulsed square-wave current.

[0020] This application also provides a control system for the temperature of a lithium battery. The system includes:

[0021] A central processing unit, a lithium battery, an electrical load, a DC - DC converter, a lithium battery management module, and a switch;

[0022] The lithium battery management module is connected to the lithium battery. The lithium battery management module is used to obtain the cell temperature value of the lithium battery cell and the state of charge of the lithium battery, and the lithium battery supplies power to the electrical load;

[0023] The lithium battery management module is connected to the central processing unit. The lithium battery management module is used to send the cell temperature value and the state of charge of the lithium battery to the central processing unit;

[0024] The DC - DC converter is connected to the central processing unit through a switch. The central processing unit controls the DC - DC converter through the switch. The central processing unit controls the DC - DC converter to output a constant current, a pulsed square-wave voltage, or a pulsed square-wave current using the cell temperature value and the state of charge of the lithium battery obtained by the lithium battery management module.

[0025] This application also provides a control device for the temperature of a lithium battery. The device includes:

[0026] A lithium battery information acquisition module, used to acquire the cell temperature value of the lithium battery cell and the state of charge of the lithium battery;

[0027] The first heating module is used to heat the lithium battery with a constant current when the cell temperature value is less than the first temperature threshold and the state of charge is greater than the preset state of charge until the cell temperature value is greater than the first stop temperature;

[0028] The second heating module is used to heat the lithium battery with a pulse square wave voltage corresponding to the cell temperature value when the cell temperature value is less than the first temperature threshold and the state of charge is not greater than the preset state of charge until the cell temperature value is not less than the first stop temperature, and the first temperature threshold is less than the first stop temperature;

[0029] The third heating module is used to heat the lithium battery with a pulse square wave current corresponding to the cell temperature value when the cell temperature value is less than the second temperature threshold and the cell temperature value is not less than the first temperature threshold until the cell temperature value is not less than the second stop temperature.

[0030] In a possible implementation manner, the first heating module is specifically used for:

[0031] The lithium battery discharges with a constant discharge current, and after discharging, it is charged with a constant charging current. The discharge current corresponds to the discharge capacity, the charging current corresponds to the charging capacity, and the charging capacity is greater than the discharge capacity;

[0032] Obtain the cell temperature value of the lithium battery cell after charging. If the cell temperature value of the lithium battery cell after charging is not greater than the first stop temperature, repeat the steps of discharging the lithium battery with a constant discharge current and charging the lithium battery with a constant charging current after discharging until the cell temperature value is greater than the first stop temperature.

[0033] In a possible implementation manner, the second heating module is specifically used for:

[0034] Output the first pulse square wave voltage within the first temperature range corresponding to the cell temperature value until the cell temperature value is greater than the upper limit value of the first temperature range;

[0035] Output the second pulse square wave voltage within the second temperature range corresponding to the cell temperature value until the cell temperature value is not less than the first stop temperature. The highest voltage value of the first pulse square wave voltage is greater than the highest voltage value of the second pulse square wave voltage, and the lowest voltage value of the first pulse square wave voltage is greater than the lowest voltage value of the second pulse square wave voltage.

[0036] In a possible implementation manner, the third heating module is specifically used for:

[0037] Output a first pulsed square-wave current within a third temperature range corresponding to the cell temperature value until the cell temperature value is greater than the upper limit value of the third temperature range. The maximum current value, maximum current duration, minimum current value, and minimum current duration of the pulsed square-wave current corresponding to the third temperature range are obtained by differentiation using the maximum current value, maximum current duration, minimum current value, and minimum current duration corresponding to the limit temperature values of the third temperature range. The limit temperature values include the upper limit temperature value and the lower limit temperature value of the third temperature range.

[0038] Output a second pulsed square-wave current within a fourth temperature range corresponding to the cell temperature value until the cell temperature value is not less than a second stop temperature. The maximum current value of the first pulsed square-wave current is less than the maximum current value of the second pulsed square-wave current. The absolute value of the minimum current value of the first pulsed square-wave current is less than the absolute value of the minimum current value of the second pulsed square-wave current. The duration of the maximum current value of the first pulsed square-wave current is less than the duration of the maximum current value of the second pulsed square-wave current.

[0039] The present application also provides a vehicle, which includes the control system for the lithium battery temperature described above and is controlled based on the control method for the lithium battery temperature described above.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] The method provided by the present application controls the temperature of the lithium battery in different ways when the cell temperature values of the lithium battery cells are different. When the cell temperature value is less than a first temperature threshold and the state of charge is greater than a preset state of charge, a constant current is used to heat the lithium battery. When the cell temperature value is less than a first temperature threshold and the state of charge is not greater than the preset state of charge, a pulsed square-wave voltage corresponding to the cell temperature value is used to heat the lithium battery. When the cell temperature value is less than a second temperature threshold and the cell temperature value is not less than the first temperature threshold, a pulsed square-wave current corresponding to the cell temperature value is used to heat the lithium battery. The lithium battery is heated by a constant current, a pulsed square-wave voltage, and a pulsed square-wave current, and the lithium battery heats up by its own heat generation. Compared with the prior art of providing heat to the lithium battery by setting an additional heating system externally, the cost is lower. Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 Flowchart of a method for controlling the temperature of a lithium battery provided by an embodiment of the present application;

[0044] Figure 2 Schematic diagram of a control system for the temperature of a lithium battery provided by an embodiment of the present application;

[0045] Figure 3 Schematic diagram of a working mode for controlling the temperature of a lithium battery provided by an embodiment of the present application;

[0046] Figure 4 Schematic diagram of a control device for the temperature of a lithium battery provided by an embodiment of the present application. Detailed implementation manners

[0047] As described above, some low-voltage power supply systems of electric vehicles use lithium batteries as energy storage devices and power sources. However, the lithium batteries in the low-voltage power supply system cannot be charged and discharged with large currents under low-temperature conditions. The lithium batteries used in the low-voltage power supply system, especially the lithium iron phosphate batteries, have poor positive electrode electronic conductivity and are prone to lithium battery polarization when operating in a low-temperature environment. Battery polarization will increase the viscosity of the lithium battery electrolyte, and the increase in the viscosity of the lithium battery electrolyte will increase the lithium ion migration impedance, which greatly affects the charging and discharging performance of the vehicle under low-temperature conditions.

[0048] In order to improve the charging and discharging performance of the vehicle under low-temperature conditions, the prior art continuously supplies heat to the lithium battery by additionally setting up a heating system, maintains the temperature of the lithium battery in a low-temperature environment through the heating system, and the additionally set heating system is powered by the high-voltage power supply system. Additionally setting up a heating system for the lithium battery will increase the hardware cost of the vehicle. In addition, the additionally set heating system is generally powered by the high-voltage power supply system, and using the high-voltage power supply system to power the heating system will consume the charge state of the high-voltage battery in the high-voltage power supply system.

[0049] To enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0050] It can be understood that the method provided by the present application can be applied to a processing device, and the processing device is a processing device that can obtain the core temperature value of the lithium battery cell, such as a terminal device that can heat the lithium battery with a constant current.

[0051] Figure 1A flowchart of a method for controlling the temperature of a lithium battery provided by this application. The method includes the following steps:

[0052] S101: Obtain the cell temperature value of the lithium battery cell and the state of charge of the lithium battery.

[0053] The lithium battery can be a lithium iron phosphate battery used in the low-voltage power supply system of an electric vehicle.

[0054] The terminal device can directly obtain the cell temperature value of the lithium battery cell and the state of charge of the lithium battery, or the terminal device can also obtain the cell temperature value of the lithium battery cell and the state of charge of the lithium battery through the lithium battery management module in the electric vehicle.

[0055] The state of charge (SOC) of the lithium battery. The state of charge is the ratio of the remaining capacity after the lithium battery has been used for a period of time or left unused for a long time to the capacity in the fully charged state.

[0056] S102: When the cell temperature value is less than the first temperature threshold and the state of charge is greater than the preset state of charge, heat the lithium battery with a constant current until the cell temperature value is greater than the first stop temperature.

[0057] The first temperature threshold is generally relatively low. In one possible implementation, the first temperature threshold can be -25°C.

[0058] The preset state of charge is generally low. In one possible implementation, the preset state of charge can be 30%. When the state of charge of the lithium battery is greater than 30%, heat the lithium battery with a constant current until the cell temperature value is greater than the first stop temperature. The first stop temperature is generally slightly higher than the first temperature threshold. In one possible implementation, the first temperature threshold can be -25°C and the first stop temperature can be -20°C.

[0059] In one possible implementation, the constant current includes a constant discharge current and a constant charge current. When the cell temperature value is less than the first temperature threshold, such as -35°C, and the state of charge of the lithium battery is greater than the preset state of charge, such as 40%, the lithium battery first discharges with a constant discharge current, stops discharging when the discharge cut-off condition is reached, and then charges the lithium battery with a constant charge current, and stops charging when the charge cut-off condition is reached. The discharge cut-off condition can be conditions such as discharging for a certain time or releasing a preset amount of electricity, and the charge cut-off condition can be conditions such as charging for a certain time or increasing a preset amount of electricity. The charge capacity is greater than the discharge capacity.

[0060] When the terminal device controls the lithium battery to discharge once using the discharge current, and then charges the lithium battery with a constant charging current. After charging, the cell temperature value of the charged lithium battery cell is obtained. If the cell temperature value of the charged lithium battery cell is not greater than the first stop temperature, at this time, the terminal device controls the lithium battery to discharge once again using the discharge current and charges the lithium battery with a constant charging current. Repeat the above process until the cell temperature value is greater than the first stop temperature.

[0061] In a possible implementation, the first temperature threshold is -25 °C, the preset state of charge is 30%, and the first stop temperature is -20 °C. The cell temperature value obtained by the terminal device is -35 °C, and the state of charge of the lithium battery is 40%. At this time, the terminal device controls the lithium battery to discharge using a constant current I 1 with a discharge capacity of Ah 1 , and then the terminal device charges the lithium battery with a constant charging current I 2 with a charging capacity of Ah 2 , and Ah 2 is greater than Ah 1 . After charging, the terminal device obtains the cell temperature value again. At this time, the cell temperature value is -27 °C, and -27 °C is less than the first stop temperature. At this time, the terminal device controls the lithium battery to discharge using a constant current I 1 with a discharge capacity of Ah 1 , and then the terminal device charges the lithium battery with a constant charging current I 2 with a charging capacity of Ah 2 , and Ah 2 is greater than Ah 1 . After the second charging, the terminal device obtains the cell temperature value again. At this time, the cell temperature value is -17 °C, and -17 °C is greater than -20 °C. At this time, the cell temperature value of -17 °C obtained by the terminal device is greater than the first stop temperature of -20 °C, and no third charge and discharge is performed after two charge and discharges.

[0062] S103: When the cell temperature value is less than the first temperature threshold and the state of charge is not greater than the preset state of charge, use the pulse square wave voltage corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the first stop temperature.

[0063] The preset state of charge is generally low. In a possible implementation, the preset state of charge can be 30%. When the state of charge of the lithium battery is not greater than 30%, use the pulse square wave voltage corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the first stop temperature.

[0064] In a possible implementation, the first temperature threshold is -25°C, the preset state of charge is 30%, the first stop temperature is -20°C, the first temperature range is -30°C to -25°C (including -30°C, excluding -25°C), and the second temperature range is -25°C to -20°C (including -25°C, excluding -20°C). The cell temperature value obtained by the terminal device is -27°C, and the state of charge of the lithium battery is 15%. At this time, the cell temperature value is within the first temperature range, and the terminal device can release the first pulse square wave voltage corresponding to the first temperature range. The first pulse square wave voltage can charge the lithium battery and can also heat the lithium battery. The highest voltage value of the first pulse square wave voltage can be 13.0V, the duration of the highest voltage value can be 3 seconds, the highest low voltage value of the first pulse square wave voltage can be 12.8V, and the duration of the lowest voltage value can be 3 seconds.

[0065] Use the first pulse square wave voltage to continuously heat the lithium battery until the cell temperature value is greater than the upper limit value of the first temperature range, that is, until the cell temperature value is greater than -25°C. When the cell temperature value is greater than -25°C, the cell temperature value enters the second temperature range. At this time, the terminal device can output the second pulse square wave voltage corresponding to the second temperature range. The second pulse square wave voltage can charge the lithium battery and can also heat the lithium battery. The highest voltage value of the second pulse square wave voltage can be 12.9V, the duration of the highest voltage value can be 3 seconds, the lowest voltage value of the second pulse square wave voltage can be 12.7V, and the duration of the lowest voltage value can be 3 seconds. When the cell temperature value is not less than the first stop temperature of -20°C, the terminal device stops using the second pulse square wave voltage to heat the lithium battery.

[0066] In a possible implementation, the correspondence between the pulse square wave voltage output by the terminal device and the temperature range can be as shown in Table 1.

[0067] Table 1

[0068]

[0069]

[0070] T in Table 1 is the cell temperature value.

[0071] S104: When the cell temperature value is less than the second temperature threshold and the cell temperature value is not less than the first temperature threshold, use the pulse square wave current corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the second stop temperature.

[0072] When the cell temperature value obtained by the terminal device is less than the second temperature threshold and not less than the first temperature threshold, the terminal device outputs a pulsed square-wave current corresponding to the cell temperature value, and uses the pulsed square-wave current corresponding to the cell temperature value to heat the lithium battery until the cell temperature value is not less than the second stop temperature.

[0073] In a possible implementation, the first temperature threshold is -25 °C, the second temperature threshold is 0 °C, the second stop temperature is 0 °C, the second temperature range is -25 °C to -20 °C (including -25 °C, excluding -20 °C), the third temperature range is -20 °C to -10 °C (including -20 °C, excluding -10 °C), and the fourth temperature range is -10 °C to 0 °C (including -10 °C, excluding 0 °C). The cell temperature value obtained by the terminal device is -16 °C, which is within the third temperature range. At this time, the terminal device can output the first pulsed square-wave current corresponding to the third temperature range and use the first pulsed square-wave current to heat the lithium battery. The maximum current value of the first pulsed square-wave current can be obtained by differentiating the maximum current values corresponding to the upper and lower limits of the third temperature range, and the duration of the maximum current value can be obtained by differentiating the maximum current durations corresponding to the upper and lower limits of the third temperature range. The minimum current value of the first pulsed square-wave current can be obtained by differentiating the minimum current values corresponding to the upper and lower limits of the third temperature range, and the duration of the minimum current value can be obtained by differentiating the minimum current durations corresponding to the upper and lower limits of the third temperature range.

[0074] When the terminal device detects that the cell temperature value is greater than the upper limit of the third temperature range, -10 °C, for example, the terminal device detects that the cell temperature value is -7 °C, and -7 °C corresponds to the fourth temperature range. The terminal device then outputs the second pulsed square-wave current corresponding to the fourth temperature range and uses the second pulsed square-wave current to heat the lithium battery. The maximum current value of the second pulsed square-wave current can be obtained by differentiating the maximum current values corresponding to the upper and lower limits of the fourth temperature range, and the duration of the maximum current value can be obtained by differentiating the maximum current durations corresponding to the upper and lower limits of the fourth temperature range. The minimum current value of the second pulsed square-wave current can be obtained by differentiating the minimum current values corresponding to the upper and lower limits of the fourth temperature range, and the duration of the minimum current value can be obtained by differentiating the minimum current durations corresponding to the upper and lower limits of the fourth temperature range. When the cell temperature value obtained by the terminal device is greater than the second stop temperature of 0 °C, heating the lithium battery using the pulsed square-wave current stops.

[0075] In a possible implementation, the correspondence between the pulsed square-wave current output by the terminal device and the temperature range can be as shown in Table 2.

[0076] Table 2

[0077]

[0078] The T in Table 2 is the cell temperature value. T = -25°C, T = -20°C, T = -10°C, and T = 0°C in Table 2 are the limit values of each temperature range. When -25°C < T < -20°C, the maximum current value is obtained by the difference between 0.2C and 0.5C, the duration of the maximum current value is obtained by the difference between 3s and 5s, the minimum current value is obtained by the difference between -0.2C and -0.5C, the duration of the minimum current is obtained by the difference between 3s and 5s. The maximum current value, the maximum current duration, the minimum current value, and the minimum current duration of the remaining temperature ranges are all obtained by the difference using the upper limit value and the lower limit value of the temperature range.

[0079] In a possible implementation, the temperature value of the battery cell is not less than the second temperature threshold. At this time, the terminal device can control the temperature of the lithium battery using the lithium battery management strategy and charge and discharge logic under normal working conditions.

[0080] The method provided in this application uses different methods to control the temperature of the lithium battery when the temperature value of the lithium battery cell is different. When the temperature value of the battery cell is less than the first temperature threshold and the state of charge is greater than the preset state of charge, a constant current is used to heat the lithium battery. The constant current can heat the lithium battery while charging the lithium battery. In this case, since the charge of the battery is relatively high, using a constant current can enable the lithium battery to charge and discharge quickly, and the heating efficiency using a constant current is higher. When the temperature value of the battery cell is less than the first temperature threshold and the state of charge is not greater than the preset state of charge, a pulse square wave voltage corresponding to the temperature value of the battery cell is used to heat the lithium battery. The pulse square wave voltage can not only charge the lithium battery but also heat the lithium battery. In this case, since the charge of the lithium battery is relatively low, large-scale discharging may affect the starting performance of the vehicle. The pulse square wave heating method can avoid the influence of large-scale discharging on the starting performance of the whole vehicle. When the temperature value of the battery cell is less than the second temperature threshold and the temperature value of the battery cell is not less than the first temperature threshold, a pulse square wave current corresponding to the temperature value of the battery cell is used to heat the lithium battery. The lithium battery generates heat through the constant current, the pulse square wave voltage, and the pulse square wave current, and the lithium battery heats up by its own heat generation. Compared with the prior art of using an additional external heating system to supply heat to the lithium battery, the cost is lower. The present invention is based on the temperature value of the lithium battery cell, and the lithium battery is excited to generate heat by energy flows such as voltage and current, so that the lithium battery heats up without the aid of an external heating system, reducing the usage amount of electric vehicle electronic devices, and effectively ensuring the state and power supply capacity of the low-voltage lithium battery of the electric vehicle under low-temperature environments while taking into account the cost, weight, and power consumption of the electric vehicle.

[0081] This application also provides a method as Figure 2Schematic diagram of the control system for the temperature of a lithium battery. The system includes a central processing unit 201, a lithium battery 202, an electrical load 203, a DC-DC converter 204, a lithium battery management module 205, and a switch 206.

[0082] Figure 2 The central processing unit 201 in it is used to execute the above-mentioned control method for the temperature of the lithium battery. The lithium battery management module 205 is connected to the lithium battery 202. The lithium battery management module 205 is used to obtain the cell temperature value of the lithium battery 202 cells. The lithium battery management module 205 can also obtain the state of charge of the lithium battery 202 through detection and calculation. The lithium battery management module 205 can also be used to obtain the voltage, current, and state of health (SOH) of the lithium battery 202. The lithium battery 202 supplies power to the electrical load 203.

[0083] The lithium battery management module 205 can send the obtained information to the central processing unit 201. When the central processing unit 201 determines that the cell temperature value is less than the first temperature threshold and the state of charge is greater than the preset state of charge, the central processing unit turns on the switch 206. The central processing unit 201 controls the DC-DC converter 204 (HVDCDC) to output voltage. The central processing unit 201 monitors the DC-DC converter 204 to output a constant current, and closes the loop to regulate the voltage based on the current state output by the DC-DC converter 204.

[0084] When the central processing unit 201 determines that the cell temperature value is less than the first temperature threshold and the state of charge is not greater than the preset state of charge, the central processing unit 201 turns on the switch 206. The central processing unit 201 controls the DC-DC converter 204 to output a pulse square wave voltage corresponding to the cell temperature value.

[0085] When the central processing unit 201 determines that the cell temperature value is less than the second temperature threshold and the cell temperature value is not less than the first temperature threshold, the central processing unit 201 turns on the switch 206. The central processing unit 201 controls the DC-DC converter 204 to output a pulse square wave current corresponding to the cell temperature value.

[0086] This application also provides a Figure 3 Schematic diagram of the working mode of lithium battery temperature control as shown. The abscissa in the figure is the cell temperature value of the lithium battery, and the ordinate is the state of charge of the low-voltage lithium battery. The corresponding working modes are used under different cell temperature values and states of charge. Mode 1 corresponds to the working mode of controlling the lithium battery temperature through a constant current. Mode 2 corresponds to the working mode of controlling the lithium battery temperature through a pulse square wave voltage. Mode 3 corresponds to the working mode of controlling the lithium battery temperature through a pulse square wave current. Mode 4 corresponds to the normal working mode of the lithium battery.

[0087] The present application also provides a schematic diagram of a control device for the temperature of a lithium battery as shown in Figure 4 The control device 400 for the temperature of the lithium battery includes the following modules:

[0088] A lithium battery information acquisition module 401, configured to acquire the cell temperature value of the lithium battery cell and the state of charge of the lithium battery;

[0089] A first heating module 402, configured to heat the lithium battery with a constant current until the cell temperature value is greater than a first stop temperature when the cell temperature value is less than a first temperature threshold and the state of charge is greater than a preset state of charge;

[0090] A second heating module 403, configured to heat the lithium battery with a pulse square wave voltage corresponding to the cell temperature value until the cell temperature value is not less than the first stop temperature when the cell temperature value is less than the first temperature threshold and the state of charge is not greater than the preset state of charge, and the first temperature threshold is less than the first stop temperature;

[0091] A third heating module 404, configured to heat the lithium battery with a pulse square wave current corresponding to the cell temperature value until the cell temperature value is not less than a second stop temperature when the cell temperature value is less than a second temperature threshold and the cell temperature value is not less than the first temperature threshold.

[0092] In a possible implementation manner, the first heating module is specifically configured to:

[0093] The lithium battery discharges with a constant discharge current, and after discharging, the lithium battery is charged with a constant charging current. The discharge current corresponds to the discharge capacity, the charging current corresponds to the charging capacity, and the charging capacity is greater than the discharge capacity;

[0094] Acquire the cell temperature value of the lithium battery cell after charging. If the cell temperature value of the lithium battery cell after charging is not greater than the first stop temperature, repeat the steps of discharging the lithium battery with a constant discharge current and charging the lithium battery with a constant charging current after discharging until the cell temperature value is greater than the first stop temperature.

[0095] In a possible implementation manner, the second heating module is specifically configured to:

[0096] Output a first pulse square wave voltage within a first temperature range corresponding to the cell temperature value until the cell temperature value is greater than the upper limit value of the first temperature range;

[0097] Output a second pulse square wave voltage within a second temperature range corresponding to the cell temperature value until the cell temperature value is not less than a first stop temperature, where the highest voltage value of the first pulse square wave voltage is greater than the highest voltage value of the second pulse square wave voltage, and the lowest voltage value of the first pulse square wave voltage is greater than the lowest voltage value of the second pulse square wave voltage.

[0098] In a possible implementation, the third heating module is specifically configured to:

[0099] Output a first pulse square wave current within a third temperature range corresponding to the cell temperature value until the cell temperature value is greater than the upper limit value of the third temperature range. The highest current value, highest current duration, lowest current value, and lowest current duration of the pulse square wave current corresponding to the third temperature range are obtained by difference using the highest current value, highest current duration, lowest current value, and lowest current duration corresponding to the limit temperature values of the third temperature range. The limit temperature values include the upper limit temperature value and the lower limit temperature value of the third temperature range;

[0100] Output a second pulse square wave current within a fourth temperature range corresponding to the cell temperature value until the cell temperature value is not less than a second stop temperature, where the highest current value of the first pulse square wave current is less than the highest current value of the second pulse square wave current, the absolute value of the lowest current value of the first pulse square wave current is less than the absolute value of the lowest current value of the second pulse square wave current, and the duration of the highest current value of the first pulse square wave current is less than the duration of the highest current value of the second pulse square wave current.

[0101] The embodiment of the present application further provides a vehicle. In a possible implementation, the vehicle is equipped with Figure 2 a control system for the corresponding lithium battery temperature and uses Figure 1 the corresponding control method for the lithium battery temperature for control.

[0102] The embodiment of the present application further provides a control device for the lithium battery temperature. Among them, the device includes a memory and a processor. The memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the steps of the control method for the lithium battery temperature according to any embodiment of the present application.

[0103] In practical applications, the computer-readable storage medium may adopt any combination of one or more computer-readable media. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium.

[0104] A computer-readable storage medium may, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples (a non-exhaustive list) of the computer-readable storage medium include: an electrical connection with one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this embodiment, the computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0105] A computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, which carries computer-readable program code. Such a propagated data signal may take many forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0106] The program code contained on the computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the above.

[0107] The computer program code for performing the operations of the present invention may be written in one or more programming languages or combinations thereof. The programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code may execute entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0108] It should be noted that the various embodiments in this specification are described in a progressive manner. For the same or similar parts among the various embodiments, reference can be made to each other, and the key point of each embodiment is to illustrate the differences from other embodiments. In particular, for the apparatus embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for the relevant parts, reference can be made to the corresponding parts in the method embodiments. The apparatus embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components referred to as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative efforts.

[0109] As described above, it is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for controlling the temperature of a lithium battery, characterized in that: include: Obtaining a cell temperature value of a lithium battery cell and a state of charge of the lithium battery; When the battery cell temperature value is less than a first temperature threshold and the state of charge is greater than a preset state of charge, heating the lithium battery using a constant current until the battery cell temperature value is greater than a first stop temperature; When the battery cell temperature value is less than a first temperature threshold and the state of charge is not greater than a preset state of charge, the lithium battery is heated using a pulse square wave voltage corresponding to the battery cell temperature value until the battery cell temperature value is not less than a first stop temperature and the first temperature threshold is less than the first stop temperature; When the battery cell temperature value is less than a second temperature threshold and the battery cell temperature value is not less than the first temperature threshold, the lithium battery is heated using a pulse square wave current corresponding to the battery cell temperature value until the battery cell temperature value is not less than a second stop temperature.

2. The method according to claim 1, characterized in that The step of heating the lithium battery using a constant current until the battery core temperature value is greater than a first stop temperature comprises: The lithium battery is discharged at a constant discharge current, and after discharge, the lithium battery is charged with a constant charge current, the discharge current corresponds to the discharge capacity, the charge current corresponds to the charge capacity, and the charge capacity is greater than the discharge capacity; Obtain the cell temperature value of the lithium battery cell after charging. If the cell temperature value of the lithium battery cell after charging is not greater than the first stop temperature, repeat the steps of discharging with a constant discharge current and charging the lithium battery with a constant charging current after discharging until the cell temperature value is greater than the first stop temperature.

3. The method according to claim 1, characterized in that The step of heating the lithium battery by using a pulse square wave voltage corresponding to the battery core temperature value until the battery core temperature value is not less than a first stop temperature includes: Outputting a first pulse square wave voltage within a first temperature range corresponding to the battery core temperature value until the battery core temperature value is greater than an upper limit value of the first temperature range; Output a second pulse square wave voltage within a second temperature range corresponding to the battery cell temperature value until the battery cell temperature value is not less than the first stop temperature, the maximum voltage value of the first pulse square wave voltage is greater than the maximum voltage value of the second pulse square wave voltage, and the minimum voltage value of the first pulse square wave voltage is greater than the minimum voltage value of the second pulse square wave voltage.

4. The method according to claim 1, characterized in that: The step of heating the lithium battery by using a pulse square wave current corresponding to the battery core temperature value until the battery core temperature value is not less than a second stop temperature includes: Outputting a first pulse square wave current within a third temperature interval corresponding to the battery core temperature value until the battery core temperature value is greater than an upper limit value of the third temperature interval, wherein the maximum current value, the maximum current duration, the minimum current value and the minimum current-duration time corresponding to the pulse square wave current in the third temperature interval are obtained by difference using the maximum current value, the maximum current duration, the minimum current value and the minimum current duration time corresponding to the limit temperature value of the third temperature interval, and the limit temperature value includes an upper limit temperature value of the third temperature interval and a lower limit temperature value of the third temperature interval; Output a second pulse square wave current within a fourth temperature range corresponding to the battery cell temperature value until the battery cell temperature value is not less than a second stop temperature, the maximum current value of the first pulse square wave current is less than the maximum current value of the second pulse square wave current, the absolute value of the minimum current value of the first pulse square wave current is less than the absolute value of the minimum current value of the second pulse square wave current, and the duration of the maximum current value of the first pulse square wave current is less than the duration of the maximum current value of the second pulse square wave current.

5. A lithium battery temperature control system, characterized in that: include: CPU, lithium battery, electrical load, DC-DC converter, lithium battery management module and switch; The lithium battery management module is connected to the lithium battery, and is used to obtain the cell temperature value of the lithium battery cell and the charge state of the lithium battery, and the lithium battery supplies power to the electrical load; The lithium battery management module is connected to the central processing unit, and the lithium battery management module is used to send the battery core temperature value and the charge state of the lithium battery to the central processing unit; The DC-DC converter is connected to the central processing unit via a switch, and the central processing unit controls the DC-DC converter via the switch. The central processing unit uses the battery cell temperature value and the charge state of the lithium battery obtained by the lithium battery management module to control the DC-DC converter to output a constant current, a pulsed square wave voltage, or a pulsed square wave current.

6. A lithium battery temperature control device, characterized in that: include: A lithium battery information acquisition module, used to obtain the cell temperature value of the lithium battery cell and the charge state of the lithium battery; A first heating module is used to heat the lithium battery using a constant current when the battery cell temperature value is less than a first temperature threshold and the state of charge is greater than a preset state of charge until the battery cell temperature value is greater than a first stop temperature; a second heating module, configured to heat the lithium battery using a pulse square wave voltage corresponding to the battery cell temperature value when the battery cell temperature value is less than a first temperature threshold and the state of charge is not greater than a preset state of charge, until the battery cell temperature value is not less than a first stop temperature and the first temperature threshold is less than the first stop temperature; The third heating module is used to heat the lithium battery using a pulse square wave current corresponding to the battery cell temperature value when the battery cell temperature value is less than a second temperature threshold and the battery cell temperature value is not less than the first temperature threshold, until the battery cell temperature value is not less than a second stop temperature.

7. The device according to claim 6, characterized in that The first heating module is specifically used for: The lithium battery is discharged at a constant discharge current, and after discharge, the lithium battery is charged with a constant charge current, the discharge current corresponds to the discharge capacity, the charge current corresponds to the charge capacity, and the charge capacity is greater than the discharge capacity; Obtain the cell temperature value of the lithium battery cell after charging. If the cell temperature value of the lithium battery cell after charging is not greater than the first stop temperature, repeat the steps of discharging with a constant discharge current and charging the lithium battery with a constant charging current after discharging until the cell temperature value is greater than the first stop temperature.

8. The device according to claim 6, characterized in that The second heating module is specifically used for: Outputting a first pulse square wave voltage within a first temperature range corresponding to the battery core temperature value until the battery core temperature value is greater than an upper limit value of the first temperature range; Output a second pulse square wave voltage within a second temperature range corresponding to the battery cell temperature value until the battery cell temperature value is not less than the first stop temperature, the maximum voltage value of the first pulse square wave voltage is greater than the maximum voltage value of the second pulse square wave voltage, and the minimum voltage value of the first pulse square wave voltage is greater than the minimum voltage value of the second pulse square wave voltage.

9. The device according to claim 6, characterized in that The third heating module is specifically used for: Outputting a first pulse square wave current within a third temperature interval corresponding to the battery core temperature value until the battery core temperature value is greater than an upper limit value of the third temperature interval, wherein the maximum current value, the maximum current duration, the minimum current value and the minimum current duration corresponding to the pulse square wave current in the third temperature interval are obtained by difference using the maximum current value, the maximum current duration, the minimum current value and the minimum current duration corresponding to the limit temperature value of the third temperature interval, and the limit temperature value includes an upper limit temperature value of the third temperature interval and a lower limit temperature value of the third temperature interval; Output a second pulse square wave current within a fourth temperature range corresponding to the battery cell temperature value until the battery cell temperature value is not less than a second stop temperature, the maximum current value of the first pulse square wave current is less than the maximum current value of the second pulse square wave current, the absolute value of the minimum current value of the first pulse square wave current is less than the absolute value of the minimum current value of the second pulse square wave current, and the duration of the maximum current value of the first pulse square wave current is less than the duration of the maximum current value of the second pulse square wave current.

10. A vehicle, characterized in that: It includes a lithium battery temperature control system as described in claim 5, and is controlled based on a lithium battery temperature control method as described in any one of claims 1-4.

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