A lithium battery self-heating control system and method

Abstract

The present invention discloses a lithium battery self-heating control system and method, which relate to the field of lithium batteries. The controller in the present invention is also used to control the lithium battery self-heating circuit to enter a first heating control mode or a second heating control mode when the lithium battery self-heating circuit is connected to an external AC power module, so that the lithium battery self-heating circuit enters a charging and discharging cyclic heating mode or a charging, discharging, and open-circuit cyclic heating mode. Therefore, the lithium battery self-heating circuit as a whole in the present invention realizes self-heating inside the battery during the discharge process of the lithium-ion battery, as well as cyclic self-heating of discharge and charging and cyclic self-heating of discharge, charging, and open-circuit, thereby solving the problems of slow heating speed, uneven temperature distribution inside the battery, and low energy utilization rate caused by the properties of external heating.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to a lithium battery self-heating control system and method. Background Art

[0002] Energy crises and environmental pressures have driven the rapid development of the electric vehicle industry. Lithium-ion batteries are the core energy component of electric vehicles, accounting for approximately 40% of the vehicle's total cost. However, low temperatures significantly degrade lithium-ion battery performance, increasing internal resistance and significantly reducing capacity, power, and service life. Charging in sub-zero temperatures, in particular, can trigger lithium deposition. The resulting lithium dendrites can even penetrate the separator, causing internal short circuits and potentially leading to safety accidents. Therefore, low-temperature battery heating technology is essential for improving the output power and usable capacity of low-temperature lithium-ion batteries.

[0003] Currently, the method used for low-temperature battery heating in commercial electric vehicles is still external heating. This method heats the battery from the outside using an external heat source. In addition to air heating and fluid heating, it also includes phase change material heating, resistance heating, heat pump heating, Peltier effect heating, and electric heating film heating. The external heating method is based on a mature battery management system and has a simple structure and relatively low implementation difficulty. However, due to its external heating properties, it results in slow heating speed, uneven temperature distribution within the battery, and low energy utilization. To overcome the limitations of the external heating method, the present invention proposes a lithium battery self-heating control system and method that utilizes the battery's internal resistance to generate heat. Summary of the Invention

[0004] In order to solve the problems of slow heating speed, uneven temperature distribution inside the battery, and low energy utilization caused by the properties of external heating, the present invention proposes a lithium battery self-heating control system, including:

[0005] Controller;

[0006] A lithium battery self-heating circuit includes a lithium-ion battery module, a discharge control module, a charge control module, and an external AC power supply module, wherein:

[0007] The discharge control module includes: a first N-channel MOS transistor and a first PWM controller; the discharge control module is connected to the lithium-ion battery module to form a discharge control loop; when the lithium battery self-heating circuit is not connected to the external AC power supply module, the controller controls the on and off of the first N-channel MOS transistor by controlling the high and low levels output by the first PWM controller to control the discharge and cut-off cycles of the lithium-ion battery module, thereby generating intermittent pulsed high current in the discharge control loop. During the process of discharging with the pulsed high current, the internal resistance temperature of the battery in the lithium-ion battery module increases, causing a large amount of ohmic heat to be generated inside the battery, thereby increasing the internal temperature of the battery;

[0008] The charging control module includes a second PWM controller, a second N-channel MOS transistor, and a first diode. The charging control module is connected to an external AC power supply module and to the lithium-ion battery module via the first diode, thereby forming a charging control loop. When the charging control module is connected to the external AC power supply module, the controller controls the second PWM controller to output high and low levels to control the on-off switching of the second N-channel MOS transistor, thereby controlling the cycle of charging and charging cutoff of the lithium-ion battery module by the external AC power supply module, thereby generating intermittent high-current pulses in the charging control loop. During the process of charging the batteries in the lithium-ion battery module with the high-current pulses, the internal resistance temperature of the batteries increases, causing a large amount of ohmic heat to be generated inside the batteries, thereby increasing the internal temperature of the batteries.

[0009] The controller is further configured to control the lithium battery self-heating circuit to enter a first heating control mode or a second heating control mode when the lithium battery self-heating circuit is connected to an external AC power supply module. The first heating control mode is: adjusting the duty ratios output by the first PWM controller and the second PWM controller by the controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit enters a discharge and charge cycle heating mode;

[0010] The second heating control mode is as follows: the controller adjusts the duty cycle of the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit enters a cyclic heating mode of discharge, charge, and open circuit; the open circuit indicates that both the first N-channel MOS transistor and the second N-channel MOS transistor are in the off state.

[0011] Furthermore, the lithium-ion battery module includes:

[0012] A lithium-ion battery, a first resistor and a parasitic inductance inside the lithium-ion battery; one end of the first resistor is connected to the positive terminal of the lithium-ion battery, and the other end is connected to one end of the parasitic inductance.

[0013] Furthermore, the discharge control module further includes: a second resistor; the connection relationship between the components in the discharge control circuit is specifically as follows:

[0014] One end of the second resistor is connected to the negative terminal of the lithium-ion battery, and the other end is connected to the source terminal of the first N-channel MOS transistor; the gate of the first N-channel MOS transistor is connected to the first PWM controller; and the drain of the first N-channel MOS transistor is connected to the other end of the parasitic inductor.

[0015] Furthermore, the charging control module also includes: a third transistor and a third resistor; the emitter of the third transistor is grounded, the base is connected to the second PWM controller, and the collector is simultaneously connected to one end of the third resistor and the gate of the second N-channel MOS transistor; the source of the second N-channel MOS transistor is connected to the positive terminal of the first diode; the drain of the second N-channel MOS transistor is connected to the other end of the third resistor; and the negative terminal of the first diode is connected to the other end of the parasitic inductance in the lithium-ion battery module.

[0016] Furthermore, the external AC power supply module includes:

[0017] An AC power supply and a current processing module are connected to the AC power supply to output a DC power supply. The positive terminal of the DC power supply is connected to the connection terminal of the drain of the second N-channel MOS transistor and the third resistor to input DC power into the charging control loop. The negative terminal of the DC power supply is connected to the negative terminal of the lithium-ion battery. The current processing module is used to transform, rectify and filter the power output by the AC power supply to output a DC power supply.

[0018] Furthermore, the discharge control module also includes a second capacitor, a fourth resistor and a second diode; one end of the fourth resistor is connected to the positive terminal of the second diode and then connected to the connection line between the parasitic inductance and the drain of the first N-channel MOS transistor; the other end of the fourth resistor is connected to the negative terminal of the second diode and then connected to one end of the second capacitor; the other end of the second capacitor is connected to the connection line between the source of the first N-channel MOS transistor and the second resistor.

[0019] The present invention also proposes a lithium battery self-heating control method, comprising:

[0020] The controller determines whether an external AC power supply module is connected to the lithium battery self-heating circuit. If not, the controller controls the first PWM controller to output and adjusts the duty cycle of the first PWM controller output to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor, so that the first N-channel MOS transistor is cyclically turned on and off with a continuous preset on-time and preset off-time as a cycle, so that intermittent pulsed large current is generated in the discharge control loop. During the process of discharging with the pulsed large current, the temperature of the first resistor increases, thereby increasing the internal temperature of the lithium-ion battery; when in a period of the preset on-time, the first N-channel MOS transistor is in an on state; when in a period of the preset off-time, the first N-channel MOS transistor is in an off state;

[0021] If so, the controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit generates a bidirectional pulse current to achieve rapid self-heating of the battery.

[0022] Furthermore, the controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, specifically:

[0023] The controller adjusts the duty ratios output by the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the first N-channel MOS transistor and the second N-channel MOS transistor are cyclically switched on and off with a continuous preset discharge duration and a preset charge duration as one cycle; during the preset discharge duration, the first N-channel MOS transistor is in an on state and the second N-channel MOS transistor is in an off state; during the preset charge duration, the first N-channel MOS transistor is in an off state and the second N-channel MOS transistor is in a on state; or:

[0024] The controller adjusts the duty ratios output by the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the first N-channel MOS transistor and the second N-channel MOS transistor are cyclically switched on and off with a continuous preset discharge duration, a preset charge duration, and a preset open circuit duration as one cycle. During the preset discharge duration, the first N-channel MOS transistor is in an on state and the second N-channel MOS transistor is in an off state; during the preset charge duration, the first N-channel MOS transistor is in an off state and the second N-channel MOS transistor is in a on state; and during the preset open circuit duration, both the first N-channel MOS transistor and the second N-channel MOS transistor are in an off state.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) In the present invention, the discharge control module is connected to the lithium-ion battery module to form a discharge control loop. When there is no external power supply, the discharge control loop generates intermittent pulsed large current by controlling the discharge and discharge cut-off cycles of the lithium-ion battery module. In the process of discharging by the pulsed large current, the internal resistance temperature of the battery in the lithium-ion battery module increases, causing a large amount of ohmic heat to be generated inside the battery, thereby achieving battery temperature rise. It utilizes the internal resistance of the battery to generate heat during the discharge of the lithium-ion battery. In addition, in the present invention, the charging control module is connected to the external AC power module and is connected to the lithium-ion battery module through the first diode to form a charging control loop. When the charging control module is connected to the external AC power module, the external AC power module is controlled to charge the lithium-ion battery module and to cut off the charging cycle, thereby generating intermittent pulsed large current in the charging control loop. In the process of charging the batteries in the lithium-ion battery module by a pulsed large current, the internal resistance temperature of the battery increases, thereby increasing the internal temperature of the battery. The internal resistance of the battery is used to generate heat to achieve internal heating of the battery during the charging process of the lithium-ion battery. At the same time, the controller in the present invention is also used to control the lithium battery self-heating circuit to enter the first heating control mode or the second heating control mode when the lithium battery self-heating circuit is connected to the external AC power supply module, so that the lithium battery self-heating circuit enters the charging and discharging cyclic heating mode or the charging, discharging, and open-circuit cyclic heating mode. Therefore, the lithium battery self-heating circuit as a whole in the present invention realizes the self-heating of the battery during the discharge process of the lithium-ion battery, as well as the cyclic self-heating of discharging and charging and the cyclic self-heating of discharging, charging, and open-circuit, thereby solving the problems of slow heating speed, uneven temperature distribution inside the battery, and low energy utilization rate due to the properties of external heating.

[0027] (2) During the charge and discharge process, the present invention uses the corresponding PWM controller to generate intermittent pulsed large currents in the discharge control circuit and the charge control circuit, and performs charging or discharging through the intermittent pulsed large currents, which realizes pulse heating. Compared with DC continuous heating, pulse heating can provide longer heating performance before the battery voltage drops to the cut-off voltage. Secondly, under the same discharge voltage, the heating current of pulse heating can be designed to be higher than the heating current of DC continuous heating, and the heating process is faster and safer. The battery life of pulse heating is 2.2 times that of DC continuous heating. During DC continuous heating, the discharge voltage is lower and the polarization degree is higher, which can easily cause cracking of the electrode material;

[0028] (3) In the present invention, the controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit generates a bidirectional pulse current (controls the charging and discharging processes for cyclic switching), thereby achieving rapid self-heating of the battery and maintaining the battery SOC, thereby reducing the risk of battery aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the circuit diagram of lithium battery self-heating;

[0030] Figure 2 This is a discharge control circuit diagram corresponding to the first embodiment;

[0031] Figure 3 This is a charging control circuit diagram corresponding to the first embodiment;

[0032] Figure 4 This is the control timing diagram of the discharge control loop;

[0033] Figure 5 This is the charge and discharge control timing diagram under the first control mode;

[0034] Figure 6 This is the charge and discharge control timing diagram under the second control mode;

[0035] Figure 7 This is a charging control circuit diagram corresponding to the second embodiment;

[0036] Figure 8 This is the discharge control circuit diagram corresponding to the second embodiment. DETAILED DESCRIPTION

[0037] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0038] Example 1

[0039] In order to solve the problems of slow heating speed, uneven temperature distribution inside the battery, low energy utilization rate due to the properties of external heating, as well as low discharge voltage and high polarization degree during continuous DC heating, which easily cause cracking of electrode materials, such as Figure 1 As shown, the present invention proposes a lithium battery self-heating control system, comprising:

[0040] Controller;

[0041] A lithium battery self-heating circuit includes a lithium-ion battery module, a discharge control module, a charge control module, and an external AC power supply module, wherein:

[0042] The lithium-ion battery module comprises:

[0043] The lithium-ion battery E, the first resistor R1 (ie, the battery internal resistance), and the parasitic inductance L1 inside the lithium-ion battery; one end of the first resistor R1 is connected to the positive terminal of the lithium-ion battery E, and the other end is connected to one end of the parasitic inductance L1.

[0044] The discharge control module includes: a first N-channel MOS transistor Q1 and a first PWM controller PWM1; the discharge control module is connected to the lithium-ion battery module to form a discharge control loop; when the lithium battery self-heating circuit is not connected to the external AC power supply module, the controller controls the first PWM controller PWM1 to output high and low levels to control the on and off of the first N-channel MOS transistor Q1, thereby controlling the discharge and cut-off cycles of the lithium-ion battery module, thereby generating intermittent pulsed high current in the discharge control loop. During the process of discharging with the pulsed high current, the internal resistance temperature of the battery in the lithium-ion battery module increases, causing a large amount of ohmic heat to be generated inside the battery, thereby increasing the internal temperature of the battery;

[0045] like Figure 2 As shown, the discharge control module further includes: a second resistor R2; the connection relationship of the components in the discharge control circuit is specifically as follows:

[0046] One end of the second resistor R2 is connected to the negative terminal of the lithium-ion battery E, and the other end is connected to the source terminal of the first N-channel MOS transistor Q1; the gate of the first N-channel MOS transistor Q1 is connected to the first PWM controller PWM1; and the drain of the first N-channel MOS transistor Q1 is connected to the other end of the parasitic inductor L1.

[0047] It should be noted that the second resistor R2 is a balancing resistor, and its function is to prevent safety problems caused by the battery terminal voltage being too low.

[0048] like Figure 8 As shown, the discharge control module further includes a second capacitor C2, a fourth resistor R4, and a second diode D2; one end of the fourth resistor R4 is connected to the positive terminal of the second diode D2 and then connected to the connection line between the parasitic inductor L1 and the drain of the first N-channel MOS transistor Q1; the other end of the fourth resistor R4 is connected to the negative terminal of the second diode D2 and then connected to one end of the second capacitor C2; the other end of the second capacitor C2 is connected to the connection line between the source of the first N-channel MOS transistor Q1 and the second resistor R2.

[0049] Figure 8This is a discharge control circuit diagram corresponding to the second embodiment, which aims to ensure that the voltage across the first N-channel MOS transistor Q1 remains within the safe operating area. A second diode D2 is connected in parallel across the fourth resistor R4, a damping element, to provide freewheeling for the parasitic inductance L1 of the current storage element when the first N-channel MOS transistor Q1 is turned off. The fourth resistor R4, the second diode D2, and the second capacitor C2 form an absorption circuit, which is used to reduce the rate of current drop in the discharge control circuit when the first N-channel MOS transistor Q1 is turned off. When the first N-channel MOS transistor Q1 is turned off, the induced voltage across the parasitic inductance L1 forces the second diode D2 to turn on, allowing freewheeling to occur, thereby ensuring that the voltage across the first N-channel MOS transistor Q1 remains within the safe operating area. When the first N-channel MOS transistor Q1 turns on again, the energy stored in the second capacitor C2 of the charge storage element can be dissipated by the fourth resistor R4, a damping element.

[0050] The charging control module includes a second PWM controller PWM2, a second N-channel MOS transistor Q2, and a first diode D1. The charging control module is connected to an external AC power supply module and to the lithium-ion battery module via the first diode D1, forming a charging control loop. When the charging control module is connected to the external AC power supply module, the controller controls the second PWM controller PWM2 to output high and low levels to control the on-off switching of the second N-channel MOS transistor Q2, thereby controlling the cycle of charging and charging cutoff of the lithium-ion battery module by the external AC power supply module. This generates intermittent high-current pulses in the charging control loop. During the process of charging the batteries in the lithium-ion battery module with the high-current pulses, the internal resistance temperature of the batteries increases, generating a large amount of ohmic heat inside the batteries, thereby increasing the internal temperature of the batteries.

[0051] The controller is further configured to control the lithium battery self-heating circuit to enter a first heating control mode or a second heating control mode when the lithium battery self-heating circuit is connected to an external AC power module. The first heating control mode is: adjusting the duty ratio of the outputs of the first PWM controller and the second PWM controller by the controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit enters a discharge and charge cyclic heating mode; specifically:

[0052] The controller adjusts the duty ratios of the outputs of the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the first N-channel MOS transistor and the second N-channel MOS transistor are cyclically switched on and off with a continuous preset discharge duration and a preset charge duration as one cycle, thereby entering a discharge and charge cyclic heating mode; during the preset discharge duration, the first N-channel MOS transistor is in an on state and the second N-channel MOS transistor is in an off state; during the preset charge duration, the first N-channel MOS transistor is in an off state and the second N-channel MOS transistor is in a on state;

[0053] The second heating control mode is as follows: the controller adjusts the duty ratio of the outputs of the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit enters a cyclic heating mode of discharge, charge, and open circuit; the open circuit means that the first N-channel MOS transistor and the second N-channel MOS transistor are both in the off state; specifically:

[0054] The controller adjusts the duty ratios of the outputs of the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the first N-channel MOS transistor and the second N-channel MOS transistor are cyclically switched on and off with a continuous preset discharge duration, a preset charge duration, and a preset open circuit duration as a cycle, thereby entering a cyclic heating mode of discharge, charge, and open circuit. During the preset discharge duration, the first N-channel MOS transistor is in an on state and the second N-channel MOS transistor is in an off state; during the preset charge duration, the first N-channel MOS transistor is in an off state and the second N-channel MOS transistor is in a on state; during the preset open circuit duration, the first N-channel MOS transistor is in an off state and the second N-channel MOS transistor is in a on state; and during the preset open circuit duration, both the first N-channel MOS transistor and the second N-channel MOS transistor are in an off state.

[0055] like Figure 3 As shown, the charging control module further includes: a third transistor Q3 and a third resistor R3; the emitter of the third transistor Q3 is grounded, the base is connected to the second PWM controller PWM2, and the collector is connected to one end of the third resistor R3 and the gate of the second N-channel MOS transistor Q2; the source of the second N-channel MOS transistor Q2 is connected to the positive terminal of the first diode D1; the drain of the second N-channel MOS transistor Q2 is connected to the other end of the third resistor R3; and the cathode of the first diode D1 is connected to the other end of the parasitic inductor L1 in the lithium-ion battery module.

[0056] Specifically, when an external AC power module is connected, the controller controls the high and low levels of PWM2 to control the on and off of Q3, thereby controlling the on and off of Q2. When the output of PWM2 is high, Q3 is on, the gate voltage of Q2 is close to 0, and Q2 is off. When the output of PWM2 is low, Q3 is off, and the pull-up resistor R3 pulls up the gate voltage of Q2, turning Q2 on. Current flows through Q2, D1, L1, and R1 to charge the lithium-ion battery E.

[0057] The charging control module of the present invention also includes another embodiment, which is connected to an external AC power supply module and connected to the lithium-ion battery module through a first diode D1 to form a charging control circuit. Figure 7 .

[0058] Figure 7 In the figure, Q4 is a P-channel MOS tube. When the output of PWM2 is low, Q4 is turned on. The controller controls the on and off of Q4 by controlling PWM2 to perform intermittent high-current pulse charging.

[0059] The external AC power supply module includes:

[0060] An AC power supply U and a current processing module are connected to the current processing module to output a DC power supply. The positive terminal V+ of the DC power supply is connected to the drain of the second N-channel MOS transistor Q2 and the connection terminal of the third resistor R3 to input DC power into the charging control loop; the negative terminal V- of the DC power supply is connected to the negative terminal of the lithium-ion battery E. The current processing module is used to transform, rectify, and filter the power output by the AC power supply to output a DC power supply.

[0061] In the present invention, the discharge control module is connected to the lithium-ion battery module to form a discharge control loop. When there is no external power supply, the discharge control loop generates intermittent large pulse currents by controlling the discharge and discharge cut-off cycles of the lithium-ion battery module. In the process of discharging through the pulsed large current, the internal resistance temperature of the battery in the lithium-ion battery module increases, causing a large amount of ohmic heat to be generated inside the battery, thereby achieving battery temperature rise. It utilizes the internal resistance of the battery to generate heat to achieve internal heating of the battery during the discharge process of the lithium-ion battery. In addition, in the present invention, the charging control module is connected to the external AC power module and is connected to the lithium-ion battery module through a first diode to form a charging control loop. When the charging control module is connected to the external AC power module, the external AC power module is controlled to charge the lithium-ion battery module and to cut off the charging cycle, so that the charging control loop generates intermittent large pulse currents. During the process of charging the batteries in the lithium-ion battery module with a large pulse current, the internal resistance temperature of the battery increases, thereby increasing the internal temperature of the battery. The internal resistance of the battery is used to generate heat to achieve internal heating of the battery during the charging process of the lithium-ion battery. At the same time, the controller in the present invention is also used to control the lithium battery self-heating circuit to enter the first heating control mode or the second heating control mode when the lithium battery self-heating circuit is connected to the external AC power supply module, so that the lithium battery self-heating circuit enters the charging and discharging cyclic heating mode or the charging, discharging, and open-circuit cyclic heating mode. Therefore, the lithium battery self-heating circuit as a whole in the present invention realizes self-heating of the battery during the discharge process of the lithium-ion battery, as well as the charging and discharging cyclic self-heating and the charging, discharging, and open-circuit cyclic self-heating, thereby solving the problems of slow heating speed, uneven temperature distribution inside the battery, and low energy utilization rate due to the properties of external heating.

[0062] Example 2

[0063] The present invention also proposes a lithium battery self-heating control method, comprising:

[0064] The controller determines whether the lithium battery self-heating circuit is connected to an external AC power module. If not, the controller controls the first PWM controller to output and adjusts the duty cycle of the first PWM controller output to adjust the on-off frequency and on-off timing of the first N-channel MOS tube Q1. Figure 4(as shown) the first N-channel MOS transistor Q1 is cyclically turned on and off with a continuous preset on-time and a preset off-time as a cycle, so that intermittent pulse large current is generated in the discharge control loop. During the discharge process using the pulse large current, the temperature of the first resistor increases, thereby increasing the internal temperature of the lithium-ion battery; when in the period of the preset on-time, the first N-channel MOS transistor Q1 is in the on state; when in the period of the preset off-time, the first N-channel MOS transistor Q1 is in the off state;

[0065] Figure 4 In the embodiment, the discharge time is the preset turn-on time of the first N-channel MOS tube. During discharge, Q1 is turned on and Q2 remains off. The cut-off time is the preset cut-off time of the first N-channel MOS tube. During cut-off discharge, Q1 is cut-off and Q2 remains off.

[0066] If so, the controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2, so that the lithium battery self-heating circuit generates a bidirectional pulse current to achieve rapid self-heating of the battery.

[0067] During the charge and discharge process, the present invention uses the corresponding PWM controller to generate intermittent pulsed large currents in the discharge control circuit and the charge control circuit, and performs charging or discharging through the intermittent pulsed large currents, which realizes pulse heating. Compared with DC continuous heating, pulse heating can provide longer heating performance before the battery voltage drops to the cut-off voltage. Secondly, under the same discharge voltage, the heating current of pulse heating can be designed to be higher than the heating current of DC continuous heating, and the heating process is faster and safer. The battery life of pulse heating is 2.2 times that of DC continuous heating. During DC continuous heating, the discharge voltage is lower and the degree of polarization is higher, which can easily cause cracking of the electrode material.

[0068] The controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2, specifically:

[0069] The controller adjusts the duty cycle of the first PWM controller and the second PWM controller outputs to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2 (such as Figure 5(as shown) the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2 are cyclically switched on and off with a continuous preset discharge duration and a preset charge duration as one cycle; during the preset discharge duration, the first N-channel MOS transistor Q1 is in the on state and the second N-channel MOS transistor Q2 is in the off state; during the preset charge duration, the first N-channel MOS transistor Q1 is in the off state and the second N-channel MOS transistor Q2 is in the on state;

[0070] Figure 5 In the figure, the discharge time is the preset discharge time. During discharge, Q1 is turned on and Q2 is turned off. The charge time is the preset charge time. During charge, Q1 is turned off and Q2 is turned on.

[0071] In the present invention, a controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2, so that the lithium battery self-heating circuit generates a bidirectional pulse current (controls the charging and discharging processes for cyclic switching), thereby achieving rapid self-heating of the battery, maintaining the battery SOC, and reducing the risk of battery aging.

[0072] or:

[0073] The controller adjusts the duty cycle of the first PWM controller and the second PWM controller outputs to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2 (such as Figure 6 (as shown in the figure) causes the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2 to be cyclically switched on and off with a continuous preset discharge duration, a preset charge duration, and a preset open circuit duration as one cycle; during the preset discharge duration, the first N-channel MOS transistor Q1 is in the on state and the second N-channel MOS transistor Q2 is in the off state; during the preset charge duration, the first N-channel MOS transistor Q1 is in the off state and the second N-channel MOS transistor Q2 is in the on state; during the preset open circuit duration, both the first N-channel MOS transistor Q1 and the second N-channel MOS transistor Q2 are in the off state.

[0074] Figure 6 In the cut-off time, the cut-off time is the preset open circuit time. When the cut-off time comes, both Q1 and Q2 are in the cut-off state.

[0075] The present invention controls the outputs of PWM1 and PWM2 by a controller to adjust the on-off frequency and on-off timing of Q1 and Q2 so that the lithium-ion battery can be cyclically switched between the three states of charge / discharge / open circuit, thereby achieving rapid heating inside the battery.

[0076] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0077] In addition, in the present invention, descriptions such as "first," "second," and "one" are for descriptive purposes only and should not be understood to indicate or imply their relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0078] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0079] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A lithium battery self-heating control system, characterized in that: include: Controller; A lithium battery self-heating circuit includes a lithium-ion battery module, a discharge control module, a charge control module, and an external AC power supply module, wherein: The discharge control module includes: a first N-channel MOS transistor and a first PWM controller; the discharge control module is connected to the lithium-ion battery module to form a discharge control loop; when the lithium battery self-heating circuit is not connected to the external AC power supply module, the controller controls the on and off of the first N-channel MOS transistor by controlling the high and low levels output by the first PWM controller to control the discharge and cut-off cycles of the lithium-ion battery module, thereby generating intermittent pulsed high current in the discharge control loop. During the process of discharging with the pulsed high current, the internal resistance temperature of the battery in the lithium-ion battery module increases, causing a large amount of ohmic heat to be generated inside the battery, thereby increasing the internal temperature of the battery; The charging control module includes a second PWM controller, a second N-channel MOS transistor, and a first diode. The charging control module is connected to an external AC power supply module and to the lithium-ion battery module via the first diode, thereby forming a charging control loop. When the charging control module is connected to the external AC power supply module, the controller controls the second PWM controller to output high and low levels to control the on-off switching of the second N-channel MOS transistor, thereby controlling the cycle of charging and charging cutoff of the lithium-ion battery module by the external AC power supply module, thereby generating intermittent high-current pulses in the charging control loop. During the process of charging the batteries in the lithium-ion battery module with the high-current pulses, the internal resistance temperature of the batteries increases, causing a large amount of ohmic heat to be generated inside the batteries, thereby increasing the internal temperature of the batteries. The controller is further configured to control the lithium battery self-heating circuit to enter a first heating control mode or a second heating control mode when the lithium battery self-heating circuit is connected to an external AC power module. The first heating control mode is: adjusting the duty ratios output by the first PWM controller and the second PWM controller by the controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit enters a charging and discharging cyclic heating mode; The second heating control mode is as follows: the controller adjusts the duty ratio of the outputs of the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit enters a cyclic heating mode of charging, discharging, and open circuit; the open circuit indicates that both the first N-channel MOS transistor and the second N-channel MOS transistor are in the off state.

2. A lithium battery self-heating control system according to claim 1, characterized in that: The lithium-ion battery module comprises: A lithium-ion battery, a first resistor and a parasitic inductance inside the lithium-ion battery; one end of the first resistor is connected to the positive terminal of the lithium-ion battery, and the other end is connected to one end of the parasitic inductance.

3. A lithium battery self-heating control system according to claim 2, characterized in that: The discharge control module further includes: a second resistor; the connection relationship between the components in the discharge control circuit is specifically as follows: One end of the second resistor is connected to the negative terminal of the lithium-ion battery, and the other end is connected to the source terminal of the first N-channel MOS transistor; the gate of the first N-channel MOS transistor is connected to the first PWM controller; and the drain of the first N-channel MOS transistor is connected to the other end of the parasitic inductor.

4. A lithium battery self-heating control system according to claim 3, characterized in that: The charging control module further includes: a third transistor and a third resistor; the emitter of the third transistor is grounded, the base is connected to the second PWM controller, and the collector is simultaneously connected to one end of the third resistor and the gate of a second N-channel MOS transistor; the source of the second N-channel MOS transistor is connected to the positive terminal of the first diode; the drain of the second N-channel MOS transistor is connected to the other end of the third resistor; and the negative terminal of the first diode is connected to the other end of the parasitic inductance in the lithium-ion battery module.

5. A lithium battery self-heating control system according to claim 4, characterized in that: The external AC power supply module includes: An AC power supply and a current processing module are connected to the AC power supply to output a DC power supply. The positive terminal of the DC power supply is connected to the connection terminal of the drain of the second N-channel MOS transistor and the third resistor to input DC power into the charging control loop. The negative terminal of the DC power supply is connected to the negative terminal of the lithium-ion battery. The current processing module is used to transform, rectify and filter the power output by the AC power supply to output a DC power supply.

6. A lithium battery self-heating control system according to claim 5, characterized in that: The discharge control module also includes a second capacitor, a fourth resistor, and a second diode; one end of the fourth resistor is connected to the positive terminal of the second diode and then connected to the connection line between the parasitic inductance and the drain of the first N-channel MOS transistor; the other end of the fourth resistor is connected to the negative terminal of the second diode and then connected to one end of the second capacitor; the other end of the second capacitor is connected to the connection line between the source of the first N-channel MOS transistor and the second resistor.

7. A lithium battery self-heating control method, characterized in that: include: The controller determines whether an external AC power supply module is connected to the lithium battery self-heating circuit. If not, the controller controls the first PWM controller to output and adjusts the duty cycle of the first PWM controller output to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor, so that the first N-channel MOS transistor is cyclically turned on and off with a continuous preset on-time and preset off-time as a cycle, so that intermittent pulsed large current is generated in the discharge control loop. During the process of discharging with the pulsed large current, the temperature of the first resistor increases, thereby increasing the internal temperature of the lithium-ion battery; when in a period of the preset on-time, the first N-channel MOS transistor is in an on state; when in a period of the preset off-time, the first N-channel MOS transistor is in an off state; If so, the controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the lithium battery self-heating circuit generates a bidirectional pulse current to achieve rapid self-heating of the battery.

8. A lithium battery self-heating control method according to claim 7, characterized in that: The controller controls the outputs of the first PWM controller and the second PWM controller to control the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, specifically: The controller adjusts the duty ratios output by the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the first N-channel MOS transistor and the second N-channel MOS transistor are cyclically switched on and off with a continuous preset discharge duration and a preset charge duration as one cycle; during the preset discharge duration, the first N-channel MOS transistor is in an on state and the second N-channel MOS transistor is in an off state; during the preset charge duration, the first N-channel MOS transistor is in an off state and the second N-channel MOS transistor is in a on state; or: The controller adjusts the duty ratios of the outputs of the first PWM controller and the second PWM controller to adjust the on-off frequency and on-off timing of the first N-channel MOS transistor and the second N-channel MOS transistor, so that the first N-channel MOS transistor and the second N-channel MOS transistor are cyclically switched on and off with a continuous preset discharge duration, a preset charge duration, and a preset open circuit duration as one cycle; during the preset discharge duration, the first N-channel MOS transistor is in an on state and the second N-channel MOS transistor is in an off state; During a preset charging time period, the first N-channel MOS transistor is in a cut-off state and the second N-channel MOS transistor is in a conducting state; during a preset open circuit time period, both the first N-channel MOS transistor and the second N-channel MOS transistor are in a cut-off state.

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