A low-voltage lithium battery charging control system and method for an electric vehicle

Abstract

The application is named as a charging control system and method for low-voltage lithium battery of electric vehicle. It belongs to the technical field of low-voltage lithium battery management. It mainly solves the problem of fire phenomenon existing in the charging process or just after the charging process of the existing low-voltage lithium battery. Its main features are: including LBMS, VCU and DCDC which communicate with each other through bus; LBMS is used for collecting the voltage, temperature and current of the low-voltage lithium battery to calculate SOC, then sends the linear adjusted request charging voltage value to DCDC through SOC and MAP table combined with the low-voltage electrical load state of VCU; VCU is used for receiving the opening state of the whole vehicle low-voltage electrical appliances and the output power sent by DCDC to judge the low-voltage electrical load state is high, medium or low and send to LBMS; DCDC is used for output voltage and current to send the output power to VCU. The application has the characteristics of safe and fast charging of low-voltage lithium battery and reducing the energy consumption of the whole vehicle, and is mainly used for charging control of low-voltage lithium battery.

Description

Technical Field

[0001] This invention belongs to the field of low-voltage lithium battery management technology, and particularly relates to a charging control system and method for low-voltage lithium batteries in electric vehicles. Background Technology

[0002] With the increasing demands for lightweight vehicles and environmental protection, more and more cars are using low-voltage lithium batteries to replace lead-acid batteries. While lithium batteries offer many advantages, their safety is lower than that of lead-acid batteries, particularly the issue of battery fires, which raises concerns among consumers.

[0003] Most lithium battery fires currently occur during or immediately after charging, making battery charging safety crucial while also ensuring a smooth and fast charging experience. Low-voltage lithium batteries, charged via the vehicle's DC-DC converter, are primarily used during vehicle operation. Therefore, in addition to charging safety and speed, it's essential to prioritize a superior user experience and avoid interfering with the normal use of electrical appliances. Summary of the Invention

[0004] In view of this, it is necessary to provide a low-voltage lithium battery charging control system and method for electric vehicles to solve the problems of safety hazards, slow charging time and poor consumer experience during the charging process in the prior art.

[0005] The technical solution of the control system of the present invention is: a low-voltage lithium battery charging control system for electric vehicles, characterized in that: it includes a low-voltage lithium battery management system, a vehicle controller and a DC-DC converter that communicate with each other via a bus to realize bus communication; in, The low-voltage lithium battery management system is used to collect the voltage, temperature and current of the low-voltage lithium battery to calculate the state of charge of the low-voltage lithium battery. Then, it looks up the continuous charging current MAP table through the state of charge and temperature of the low-voltage lithium battery, and then sends a request for linear adjustment charging voltage value to the DC-DC converter in combination with the low-voltage electrical load status sent by the vehicle controller. The vehicle controller is used to receive the on-state of the low-voltage electrical appliances in the vehicle and the output power sent by the DC-DC converter, determine whether the low-voltage electrical load is high, medium or low, and then send the status to the low-voltage lithium battery management system. The DC-DC converter is used to output voltage and current to charge the low-voltage lithium battery and power the low-voltage electrical appliances in the vehicle, while also sending the output power to the vehicle controller.

[0006] The low-voltage lithium battery management system and vehicle controller described in the technical solution of the control system of this invention are also connected by a power line to realize the charging of the low-voltage lithium battery.

[0007] The technical solution of the control method of this invention is: a charging control method for low-voltage lithium batteries in electric vehicles, based on the above-mentioned charging control system for low-voltage lithium batteries in electric vehicles, characterized in that: based on the constant voltage output characteristics of a DC-DC converter, the charging request voltage V is linearly adjusted in real time by a low-voltage lithium battery management system. req ,include: Obtain the total voltage V of the low-voltage lithium battery batt Individual voltage V cell Current I batt and temperature T batt Calculate the state of charge of the low-voltage lithium battery, and then based on the temperature T batt By referring to the lithium battery continuous charging current MAP table based on the state of charge of the low-voltage lithium battery, the allowable charging current I of the low-voltage lithium battery at this time can be obtained. req0 ; Receive low-voltage electrical load status S from the vehicle controller lv1 According to the low-voltage electrical load state S lv1 The allowable charging current I is obtained by adjusting the MAP coefficient to high, medium, or low. req1 Then compare I batt and I req1 Real-time linear adjustment of charging request voltage V req ; If the low-voltage lithium battery has a state of charge of 100%, the low-voltage lithium battery management system should check the temperature T. batt - Requested voltage V reqT The table yields V. req ; If the low-voltage lithium battery management system detects a fault affecting charging in the low-voltage lithium battery system, the voltage level needs to be reduced according to the fault severity. req .

[0008] The vehicle controller in the technical solution of the control method of this invention sends low-voltage load status S in real time. lv ,include: The vehicle controller determines the low-voltage electrical load status by detecting the activation frequency of low-voltage loads, including but not limited to multimedia, headlights, air conditioning blower, and windshield wipers. lv1 High, medium, or low; The vehicle controller receives the power output signal P from the DC-DC converter in real time. dcdc , will P dcdc With the rated power P of the DC-DC converter dcdc0 By comparison, the load state S of the DC-DC converter is obtained. lv2 High, medium, or low; Finally, the vehicle controller is compared with S. lv1 and S lv2 Level, S lvChoose the higher grade.

[0009] The low-voltage lithium battery management system described in the technical solution of the control method of this invention collects the total voltage V of the low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Information to determine if there is a charging-prohibited fault; in, If there is no charging failure, the low-voltage lithium battery can be charged, and proceed to the next charging judgment step. If a charging failure occurs, the low-voltage lithium battery cannot be charged. The low-voltage lithium battery management system disconnects the internal charging circuit of the low-voltage lithium battery and then requests V from the DC-DC converter. req =13.8V, please provide a fixed value to meet the low-voltage electrical load of the entire vehicle; Charging failures include, but are not limited to, the following: The lithium battery cell was severely over-voltage; The total voltage of the lithium battery is severely over-voltage; The lithium battery overheated severely; LBMS data acquisition failure.

[0010] The low-voltage lithium battery management system described in the technical solution of the control method of this invention collects the total voltage V of the low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Information to determine if there are any faults affecting charging power; in, If there is no fault affecting the charging power, the low-voltage lithium battery can be charged normally, and the process will proceed to the next charging judgment step. If a fault affects the charging power, the low-voltage lithium battery can only be charged with a small current. The low-voltage lithium battery management system requests V from the DC-DC converter. req =V batt +0.2V; Faults affecting charging power include, but are not limited to, the following: Slight overvoltage in a single lithium battery cell; The total voltage of the lithium battery is slightly over-voltage. The lithium battery experienced a slight overheating.

[0011] The low-voltage lithium battery management system described in the technical solution of the control method of the present invention determines whether the low-voltage lithium battery has experienced a full charge during the current power-on cycle, that is, whether the state of charge of the low-voltage lithium battery has reached 100%, and whether the current state of charge of the low-voltage lithium battery is greater than or equal to 90%. in, If so, then during this power-on cycle, the low-voltage lithium battery management system requests V from the DC-DC converter. req =13.8V, to avoid long-term high-voltage float charging of low-voltage lithium batteries, which would affect their lifespan; If not, then there are two possibilities. First, the low-voltage lithium battery has not been fully charged during this power-on cycle. The low-voltage lithium battery needs to continue charging to perform full-charge correction and ensure the accuracy of the low-voltage lithium battery's state of charge. Secondly, the low-voltage lithium battery experienced a full charge during this power cycle, but the low-voltage lithium battery management system requested V from the DC-DC converter. req =13.8V After the vehicle malfunctions, the battery continues to discharge until the low-voltage lithium battery's state of charge is less than 90%. To prevent the battery from continuing to discharge, the low-voltage lithium battery management system needs to perform normal charging.

[0012] The low-voltage lithium battery management system described in the technical solution of the control method of this invention determines the total voltage V of the low-voltage lithium battery collected. batt Individual voltage V cell Current I batt and temperature T batt Is it stable and reliable? Can the allowable charging current I be found from the lithium battery continuous charging current MAP table? req0 ; in, If so, the low-voltage lithium battery can be charged normally. Refer to the lithium battery continuous charging current MAP table to find the allowable charging current I at this time. req0 Proceed to the next charging determination step; If not, the low-voltage lithium battery management system requests V from the DC-DC converter. req =13.8V, please request a fixed value to meet the low-voltage electrical load of the whole vehicle.

[0013] The lithium battery continuous charging current MAP table mentioned in the technical solution of the control method of this invention is as follows: .

[0014] The low-voltage lithium battery management system in the technical solution of the control method of this invention determines whether the low-voltage load state S of the vehicle controller can be obtained. lv ; in, If possible, the low-voltage lithium battery management system calculates the allowable charging current I in real time. req1 I req1 =X*I req0 ; When S lv When the value is high, X = 0.2; When S lv When the value is in the middle, X = 0.5; When S lv When the value is low, X=1; If not, the low-voltage lithium battery management system defaults to I. req1 =I req0 .

[0015] The low-pressure load state S described in the technical solution of the control method of this invention lv The acquisition includes: The VCU detects the activation status of each low-voltage load, calculates the ratio of the power consumption of the activated low-voltage loads to the total power consumption of the low-voltage loads, and checks the low-voltage electrical load status S. lv1 The MAP table yields S lv1 , The VCU receives the actual output power signal from the DC-DC converter, calculates the ratio of the actual output power to the rated power, and checks the DC-DC output power status S. lv2 The MAP table yields S lv2 ; VCU Comparison S lv1 and S lv2 Ultimately, low-pressure load state S lv Take S lv1 and S lv2 The higher level of both. The levels, from highest to lowest, are high, medium, and low.

[0016] The low-voltage electrical load state S described in the technical solution of the control method of this invention lv1 MAP is: .

[0017] The DC-DC output power state S described in the technical solution of the control method of this invention lv2 MAP is: .

[0018] The low-voltage lithium battery management system (LBMS) real-time comparison I described in the technical solution of the control method of this invention batt and I req1 Linearly adjust the charging request voltage V up or down req ; in, If 0.9*Ireq1≤I batt ≤1.1*I req1 V req Keep the current value unchanged; If I batt <0.9*I req1 V req It increases linearly in steps of 0.05V / s until it reaches 0.9*I. req1 ≤Ibatt ≤1.1*I req1 ; If I batt >1.1*I req1 V req Decrease linearly in steps of 0.1V / s until reaching 0.9*I. req1 ≤I batt ≤1.1*I req1 .

[0019] The low-voltage lithium battery management system described in the technical solution of the control method of this invention calculates the state of charge (SOC) of the low-voltage lithium battery in real time. When the SOC of the low-voltage lithium battery reaches 100%, V... req The voltage was linearly reduced to 13.8V in 0.1V / s increments and held.

[0020] This invention features the ability to safely and quickly charge low-voltage lithium batteries while reducing overall vehicle energy consumption and providing users with a better driving experience. It is mainly used for charging control of low-voltage lithium batteries. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an embodiment of the low-voltage lithium battery charging control system provided by the present invention.

[0022] Figure 2 and Figure 3 This is a flowchart of an embodiment of the low-voltage lithium battery charging control method provided by the present invention. Detailed Implementation

[0023] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0024] In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically defined.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] like Figure 1As shown, this invention discloses an embodiment of a low-voltage lithium battery charging control system for electric vehicles. The system includes a low-voltage lithium battery management system (LBMS), a vehicle controller (VCU), and a DC-DC converter (DCDC). The LBMS, VCU, and DCDC are connected via signal lines for bus communication. The low-voltage lithium battery system containing the LBMS and the DCDC are also connected via power lines to enable low-voltage lithium battery charging. The LBMS collects the voltage, temperature, and current of the low-voltage lithium battery to calculate its state of charge (SOC). It then looks up the continuous charging current map (MAP) using the SOC and temperature, and combines this with the low-voltage electrical load status sent by the VCU to send a linear adjustment request charging voltage value to the DCDC. The VCU receives the on / off status of low-voltage electrical appliances and the output power sent by the DCDC, determines the current low-voltage electrical load status (high, medium, or low), and then sends this status back to the LBMS. A DC-DC converter (DCDC) is used to output voltage and current to charge the low-voltage lithium battery and power the vehicle's low-voltage electrical appliances, while simultaneously supplying output power to the vehicle control unit (VCU). The low-voltage lithium battery management system (LBMS), VCU, and DC-DC converter are existing technologies; combining them for a new charging method requires software modifications to the existing infrastructure. The state of charge (SOC) of the low-voltage lithium battery is calculated using a complex formula, and this calculation method is also existing technology.

[0027] An embodiment of the present invention provides a low-voltage lithium battery charging control method for electric vehicles, based on the low-voltage lithium battery charging control system described above, comprising: a low-voltage lithium battery management system (LBMS) that linearly adjusts the charging request voltage V in real time based on the constant voltage output characteristics of a DC-DC converter (DCDC). req ,include: Obtain the total voltage V of the low-voltage lithium battery batt Individual voltage V cell Current I batt and temperature T batt Calculate the state of charge (SOC) of the low-voltage lithium battery, and then based on the temperature T. batt By referring to the lithium battery continuous charging current MAP table based on the state of charge (SOC) of the low-voltage lithium battery, the allowable charging current I at this time can be obtained. req0 ; Receive low-voltage electrical load status S from the vehicle control unit (VCU) lv1 According to the low-voltage electrical load state S lv1 The allowable charging current I is obtained by adjusting the MAP meter coefficient for high H, medium M, or low L.req1 Then compare I batt and I req1 Real-time linear adjustment of charging request voltage V req ; If the state of charge (SOC) of the low-voltage lithium battery is 100%, the low-voltage lithium battery management system (LBMS) should check the temperature T. batt - Requested voltage V reqT The table yields V. req ; If the low-voltage lithium battery management system (LBMS) detects a fault affecting charging in the low-voltage lithium battery system, the voltage level needs to be reduced according to the fault severity. req ; Among them, the vehicle controller (VCU) sends low-voltage load status S in real time. lv ,include: The vehicle control unit (VCU) determines the low-voltage electrical load status by detecting the activation frequency of low-voltage loads such as multimedia systems, headlights, air conditioning blowers, and windshield wipers. lv1 For H, medium M or low L; The vehicle control unit (VCU) receives the power output signal P from the DC-DC converter (DCDC) in real time. dcdc , will P dcdc With DC-DC converter DCDC rated power P dcdc0 By comparison, the load state S of the DC-DC converter is obtained. lv2 High H, medium M, or low L; Finally, the vehicle control unit (VCU) is compared with S. lv1 and S lv2 Grade (size), S lv Take the higher level (higher status value).

[0028] like Figure 2 and Figure 3 The diagram shows a flowchart of an embodiment of the low-voltage lithium battery charging control method provided by the present invention. Based on the low-voltage lithium battery charging control system described above, it includes: The first step is for the Low Voltage Lithium Battery Management System (LBMS) to collect the total voltage V of the low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Information such as these can be used to determine if there is a charging-prohibited fault. in, If there is no charging failure, the low-voltage lithium battery can be charged, and proceed to the next charging judgment step. If a charging failure occurs, the low-voltage lithium battery cannot be charged. The low-voltage lithium battery management system (LBMS) disconnects the internal charging circuit of the low-voltage lithium battery and then requests V from the DC-DC converter (DCDC).req =13.8V, please provide a fixed value to meet the low-voltage electrical load of the entire vehicle; Charging failures include, but are not limited to, the following: The lithium battery cell was severely over-voltage; The total voltage of the lithium battery is severely over-voltage; The lithium battery overheated severely; Low-voltage lithium battery management system (LBMS) data acquisition failure.

[0029] The second step is for the Low Voltage Lithium Battery Management System (LBMS) to collect the total voltage V of the low voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Information such as these can be used to determine if there are any faults affecting charging power. in, If there is no fault affecting the charging power, the low-voltage lithium battery can be charged normally, and the process will proceed to the next charging judgment step. If a fault affects the charging power, the low-voltage lithium battery can only be charged with a small current. The low-voltage lithium battery management system (LBMS) requests V from the DC-DC converter (DCDC). req =V batt +0.2V; Faults affecting charging power include, but are not limited to, the following: Slight overvoltage in a single lithium battery cell; The total voltage of the lithium battery is slightly over-voltage. The lithium battery experienced a slight overheating.

[0030] The third step is for the low-voltage lithium battery management system (LBMS) to determine whether the low-voltage lithium battery has experienced a full charge during this power-on cycle, i.e., whether the state of charge (SOC) of the low-voltage lithium battery has reached 100%, and whether the current state of charge (SOC) of the low-voltage lithium battery is greater than or equal to 90%. in, If so, then during this power-on cycle, the low-voltage lithium battery management system (LBMS) requests V from the DC-DC converter (DCDC). req =13.8V, to avoid long-term high-voltage float charging of low-voltage lithium batteries, which would affect their lifespan; If not, then there are two possibilities. First, the low-voltage lithium battery has not experienced a full charge during this power-on cycle. The low-voltage lithium battery needs to continue charging to perform a full charge correction and ensure the accuracy of the state of charge (SOC) of the low-voltage lithium battery. Secondly, the low-voltage lithium battery experienced a full charge during this power cycle, but the low-voltage lithium battery management system (LBMS) requested V from the DC-DC converter (DCDC). req=13.8V and abnormal vehicle conditions cause the battery to continue discharging until the state of charge (SOC) of the low-voltage lithium battery is less than 90%. To prevent the battery from continuing to discharge, the low-voltage lithium battery management system (LBMS) needs to perform normal charging.

[0031] The fourth step involves the Low Voltage Lithium Battery Management System (LBMS) determining the total voltage V of the collected low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Is it stable and reliable? Can the allowable charging current I be found from the lithium battery continuous charging current MAP table? req0 ; in, If so, the low-voltage lithium battery can be charged normally. Refer to the lithium battery continuous charging current MAP table to find the allowable charging current I at this time. req0 Proceed to the next charging determination step; If not, the low-voltage lithium battery management system (LBMS) requests V from the DC-DC converter (DCDC). req =13.8V, please request a fixed value to meet the low-voltage electrical load of the whole vehicle.

[0032] Step 5: The low-voltage lithium battery management system (LBMS) determines whether it can obtain the low-voltage load status S of the vehicle control unit (VCU). lv ; in, If possible, the low-voltage lithium battery management system (LBMS) can calculate the allowable charging current I in real time. req1 I req1 =X*I req0 ; When S lv When H is high, X = 0.2; When S lv When M is in the middle, X = 0.5; When S lv When L is low, X=1; If not, the default I for the low-voltage lithium battery management system (LBMS) req1 =I req0 .

[0033] It should be added that, Figure 3 The VCU obtains low-voltage load state S lv Methods; in, The VCU detects the activation status of each low-voltage load, calculates the ratio of the power consumption of the activated low-voltage loads to the total power consumption of the low-voltage loads, and obtains S by looking up a table. lv1 , ; The VCU receives the actual output power signal from the DC-DC converter, calculates the ratio of the actual output power to the rated power, and then looks up the S value in a table. lv2 , ; VCU Comparison S lv1 and S lv2 Ultimately, low-pressure load state S lv Take S lv1 and S lv2 The higher levels of both. The levels, from highest to lowest, are High (H), Medium (M), and Low (L). Step 6: Real-time comparison of the low-voltage lithium battery management system (LBMS) with I batt and I req1 Linearly adjust the charging request voltage V up or down req ; in, If 0.9*Ireq1≤I batt ≤1.1*I req1 V req Keep the current value unchanged; If I batt <0.9*I req1 V req It increases linearly in steps of 0.05V / s until it reaches 0.9*I. req1 ≤I batt ≤1.1*I req1 ; If I batt >1.1*I req1 V req Decrease linearly in steps of 0.1V / s until reaching 0.9*I. req1 ≤I batt ≤1.1*I req1 ; Step 7: The low-voltage lithium battery management system (LBMS) calculates the state of charge (SOC) of the low-voltage lithium battery in real time. When the SOC reaches 100%, V... req The voltage was linearly reduced to 13.8V in 0.1V / s increments and held.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the charging of a low-voltage lithium battery in an electric vehicle, comprising a low-voltage lithium battery management system (LBMS), a vehicle control unit (VCU), and a DC-DC converter (DCDC) communicating with each other via a bus, characterized in that: Based on the constant voltage output characteristics of the DC-DC converter (DCDC), the charging request voltage V is linearly adjusted in real time through the low-voltage lithium battery management system (LBMS). req ,include: The low-voltage lithium battery management system (LBMS) obtains the total voltage V of the low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Calculate the state of charge (SOC) of the low-voltage lithium battery, and then based on the temperature T batt By referring to the lithium battery's state of charge (SOC) table and the continuous charging current MAP table, the allowable charging current I of the low-voltage lithium battery at this time can be obtained. req0 ; The low-voltage lithium battery management system (LBMS) receives the low-voltage load status S sent by the vehicle control unit (VCU). lv According to the low-pressure load condition S lv The allowable charging current I is obtained by adjusting the MAP coefficient to high, medium, or low. req1 Then compare I batt and I req1 Real-time linear adjustment of charging request voltage V req Send a linearly regulated charging request voltage V to the DC-DC converter (DCDC). req ; Low-voltage load status S sent by the vehicle control unit (VCU) lv include: The vehicle control unit (VCU) determines the low-voltage electrical load status by detecting the frequency of low-voltage load activation, including multimedia, headlights, air conditioning blower, and windshield wipers. lv1 High, medium, or low; The vehicle control unit (VCU) receives the power output signal P from the DC-DC converter (DCDC) in real time. dcdc , will P dcdc With DC-DC converter (DCDC) rated power P dcdc0 By comparison, the load state S of the DC-DC converter (DCDC) is obtained. lv2 High, medium, or low; Finally, the vehicle control unit (VCU) compares the low-voltage electrical load state S. lv1 and DC-DC converter (DCDC) load state S lv2 Level, S lv Choose the higher grade; The low-voltage lithium battery management system (LBMS) determines whether the low-voltage load state S of the vehicle control unit (VCU) can be obtained. lv ; in, If possible, the low-voltage lithium battery management system (LBMS) calculates the allowable charging current I in real time. req1 I req1 =X*I req0 ; When S lv When the value is high, X = 0.2; When S lv When the value is in the middle, X = 0.5; When S lv When the value is low, X=1; If not, the low-voltage lithium battery management system (LBMS) defaults to I. req1 =I req0 ; If the state of charge (SOC) of the low-voltage lithium battery is 100%, check the temperature T in the low-voltage lithium battery management system (LBMS). batt - Requested voltage V req The table yields V. req ; If the low-voltage lithium battery management system (LBMS) detects a fault affecting charging in the low-voltage lithium battery system, the voltage level needs to be reduced according to the fault severity. req .

2. The charging control method for a low-voltage lithium battery in an electric vehicle according to claim 1, characterized in that: The low-voltage lithium battery management system (LBMS) collects the total voltage V of the low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Information to determine if there is a charging-prohibited fault; in, If there is no charging failure, the low-voltage lithium battery can be charged, and proceed to the next charging judgment step. If a charging failure occurs, the low-voltage lithium battery cannot be charged. The low-voltage lithium battery management system (LBMS) disconnects the internal charging circuit of the low-voltage lithium battery and then requests V from the DC-DC converter (DCDC). req =13.8V, please provide a fixed value to meet the low-voltage electrical load of the entire vehicle; Charging not allowed faults include the following: The lithium battery cell was severely over-voltage; The total voltage of the lithium battery is severely over-voltage; The lithium battery overheated severely; Low-voltage lithium battery management system (LBMS) acquisition failure.

3. A charging control method for a low-voltage lithium battery in an electric vehicle according to claim 1 or 2, characterized in that: The low-voltage lithium battery management system (LBMS) collects the total voltage V of the low-voltage lithium battery. batt Individual voltage V cell Current I batt and temperature T batt Information to determine if there are any faults affecting charging power; in, If there is no fault affecting the charging power, the low-voltage lithium battery can be charged normally, and the process will proceed to the next charging judgment step. If a fault affects charging power, the low-voltage lithium battery can only be charged with a small current. The low-voltage lithium battery management system (LBMS) requests V from the DC-DC converter (DCDC). req =V batt +0.2V; Faults affecting charging power include the following: Slight overvoltage in a single lithium battery cell; The total voltage of the lithium battery is slightly over-voltage. The lithium battery experienced a slight overheating.

4. A charging control method for a low-voltage lithium battery in an electric vehicle according to claim 1 or 2, characterized in that: The low-voltage lithium battery management system (LBMS) determines whether the low-voltage lithium battery has experienced a full charge during the current power-on cycle, i.e., whether the state of charge (SOC) of the low-voltage lithium battery has reached 100%, and whether the current state of charge (SOC) of the low-voltage lithium battery is greater than or equal to 90%. in, If so, then during this power-on cycle, the low-voltage lithium battery management system (LBMS) requests V from the DC-DC converter (DCDC). req =13.8V, to avoid long-term high-voltage float charging of low-voltage lithium batteries, which would affect their lifespan; If not, then there are two possibilities. First, the low-voltage lithium battery has not been fully charged during this power-on cycle. The low-voltage lithium battery needs to continue charging to perform full-charge correction and ensure the accuracy of the state of charge (SOC) of the low-voltage lithium battery. Secondly, during this power cycle, the low-voltage lithium battery experienced a full charge, but the low-voltage lithium battery management system (LBMS) requested V from the DC-DC converter (DCDC). req =13.8V and abnormal vehicle conditions cause the battery to continue discharging until the low-voltage lithium battery state of charge (SOC) is <90%. To prevent the battery from continuing to discharge, the low-voltage lithium battery management system (LBMS) needs to perform normal charging.

5. A charging control method for a low-voltage lithium battery in an electric vehicle according to claim 1 or 2, characterized in that: The low-voltage lithium battery management system (LBMS) determines the total voltage V of the low-voltage lithium battery collected. batt Individual voltage V cell Current I batt and temperature T batt Is it stable and reliable? Can the allowable charging current I be found from the lithium battery continuous charging current MAP table? req0 ; in, If so, the low-voltage lithium battery can be charged normally. Refer to the lithium battery continuous charging current MAP table to find the allowable charging current I at this time. req0 Proceed to the next charging determination step; If not, the low-voltage lithium battery management system (LBMS) requests V from the DC-DC converter (DCDC). req =13.8V, please request a fixed value to meet the low-voltage electrical load of the whole vehicle.

6. A charging control method for a low-voltage lithium battery in an electric vehicle according to claim 1 or 2, characterized in that: The low-voltage lithium battery management system (LBMS) real-time comparison I batt and I req1 Linearly adjust the charging request voltage V up or down req ; in, If 0.9*I req1 ≤I batt ≤1.1*I req1 V req Keep the current value unchanged; If I batt <0.9*I req1 V req It increases linearly in steps of 0.05V / s until it reaches 0.9*I. req1 ≤I batt ≤1.1*I req1 ; If I batt >1.1*I req1 V req Decrease linearly in steps of 0.1V / s until reaching 0.9*I. req1 ≤I batt ≤1.1*I req1 ; The low-voltage lithium battery management system (LBMS) calculates the state of charge (SOC) of the low-voltage lithium battery in real time. When the SOC of the low-voltage lithium battery reaches 100%, V... req The voltage was linearly reduced to 13.8V in 0.1V / s increments and held.

7. A charging control system for a low-voltage lithium battery in an electric vehicle, employing the charging control method for a low-voltage lithium battery in an electric vehicle as described in claim 1, characterized in that: This includes a low-voltage lithium battery management system (LBMS), a vehicle control unit (VCU), and a DC-DC converter (DCDC) that communicate with each other via a bus. in, The low-voltage lithium battery management system (LBMS) is used to collect the voltage, temperature, and current of the low-voltage lithium battery to calculate the state of charge (SOC). Then, it looks up the continuous charging current MAP table using the SOC and temperature, and combines this with the low-voltage load status SOC sent by the vehicle control unit (VCU). lv Sends a linearly regulated charging request voltage value to the DC-DC converter (DCDC); The vehicle control unit (VCU) receives the on / off status of low-voltage electrical appliances in the vehicle and the output power sent by the DC-DC converter (DCDC), and determines the low-voltage load status S at this time. lv It is high, medium, or low, and then the status is sent to the low-voltage lithium battery management system (LBMS). The DC-DC converter is used to output voltage and current to charge the low-voltage lithium battery and power the low-voltage electrical appliances in the vehicle, while also sending the output power to the vehicle control unit (VCU).

8. The electric vehicle low-voltage lithium battery charging control system according to claim 7, characterized in that: The low-voltage lithium battery management system (LBMS) and the vehicle control unit (VCU) are also connected by a power line to enable low-voltage lithium battery charging.

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