Vehicle-mounted lithium battery system

Abstract

The utility model discloses a vehicle-mounted lithium battery system, which relates to the field of circuit devices or systems for power supply or power distribution, and comprises a plurality of lithium cells, a super capacitor bank, a positive pole of the super capacitor bank connected with a positive pole column of a battery, and a negative pole of the super capacitor bank connected with a negative pole column of the battery, along with the voltage fluctuation of the generator, the super capacitor bank charges and discharges to generate charge and discharge current. According to the utility model, the super capacitor group is connected in parallel on the lithium battery, and the super capacitor group is connected in parallel between the battery total positive electrode and the battery total negative electrode, so that the super capacitor group can charge and discharge along with the voltage fluctuation of the generator to generate corresponding charge and discharge current, and at the moment, the current sensor of the storage battery of the vehicle can detect normal current; and the storage battery fault is not reported.

Description

Technical Field

[0001] This utility model relates to the field of circuit devices or systems for power supply or distribution, specifically a vehicle-mounted lithium battery system. Background Technology

[0002] Lithium-ion batteries offer many advantages for automotive starting, such as low self-discharge, long storage time, and high instantaneous starting current. However, they also have disadvantages. For example, they cannot be charged below 0 degrees Celsius, as charging lithium-ion batteries at this temperature increases the risk of lithium plating within the cell. Lithium plating is a phenomenon where lithium ions abnormally deposit on the surface of the negative electrode during charging. At low temperatures, the risk of lithium plating increases significantly, making it easier for lithium dendrites to form on the negative electrode surface. The formation of lithium dendrites is mainly due to lithium ions escaping from the positive electrode and migrating to the negative electrode during charging, depositing on the negative electrode surface and forming dendritic metallic lithium, which affects the lifespan of the lithium battery.

[0003] Currently, most cars use lead-acid batteries as their starting power source. Lead-acid batteries have a relatively wide charging temperature range and can still charge normally at 0 degrees Celsius. However, when lithium batteries replace lead-acid batteries as the starting power source, the impact of sub-zero temperatures on lithium batteries must be considered. Therefore, charging lithium batteries is generally stopped below 0 degrees Celsius to prevent lithium plating. However, cars typically have a current sensor (usually located on the negative terminal) to monitor the battery current and transmit the data to the vehicle's computer. If an abnormal current is detected, the vehicle will display a battery fault indicator.

[0004] When the battery's BMS protection board activates its high-voltage protection or when charging of the lithium battery stops below 0 degrees Celsius, it means there is no current in the circuit. The current sensor's detection value will be low, and the vehicle will assume that the battery is damaged, causing the battery fault light to stay on, which may give the owner the false impression that the battery is damaged. Utility Model Content

[0005] The purpose of this invention is to provide an on-board lithium battery system to solve the technical problems mentioned in the background section.

[0006] To achieve the above objectives, this utility model provides the following technical solution: an on-board lithium battery system, comprising:

[0007] Multiple lithium battery cells, with the positive and negative electrodes of the multiple lithium battery cells welded together separately;

[0008] The supercapacitor bank has its positive terminal connected to the positive terminal of the battery and its negative terminal connected to the negative terminal. When the lithium battery charging is turned off, the supercapacitor bank will charge and discharge as the generator voltage fluctuates, generating charging and discharging current.

[0009] Preferably, it also includes a bracket, in which the plurality of lithium battery cells are encapsulated.

[0010] Preferably, a partition is also fixedly installed at the upper end of the bracket, and the supercapacitor group is fixedly installed on the upper side of the partition, the partition separating the supercapacitor group from the lithium battery cell.

[0011] Preferably, a capacitor box is fixedly installed directly above the partition, and the supercapacitor group is placed in the capacitor box.

[0012] Preferably, the supercapacitor bank is a structure consisting of multiple capacitors connected in series.

[0013] Preferably, the outer side of the plurality of lithium battery cells is provided with an outer shell, and heat insulation cotton is provided between the outer shell and the lithium battery cells.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] This invention connects a supercapacitor bank in parallel between the positive and negative terminals of the battery. As the generator voltage fluctuates, the supercapacitor bank will charge and discharge, generating corresponding charging and discharging currents. At this time, the vehicle's battery current sensor can detect the normal current and will not report a battery fault. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the bracket, partition, and capacitor box of this utility model;

[0017] Figure 2 This is a structural diagram of the bracket, partition, and capacitor of this utility model;

[0018] Figure 3 This is a structural diagram of the lithium battery cell and bracket of this utility model;

[0019] Figure 4 This is a structural diagram of the present invention;

[0020] Figure 5 This is a cross-sectional view of the heat insulation cotton and outer shell of this utility model;

[0021] Figure 6 This is a structural diagram of the heating control board of this utility model;

[0022] Figure 7 This is a structural diagram of the BMS protection board of this utility model.

[0023] In the diagram: 1. Lithium battery cell; 2. Supercapacitor pack; 3. Bracket; 31. Base; 32. Side plate; 4. Separator; 5. Capacitor box; 6. Lithium battery cover; 7. Insulation cotton. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] Please see Figure 1-7 This embodiment provides an on-board lithium battery system, including multiple lithium battery cells 1 and a bracket 3. The bracket 3 is located outside the multiple lithium battery cells 1 and encapsulates the lithium battery cells inside the bracket 3. The positive electrodes of the multiple lithium battery cells 1 are welded together and extend upward to form a total positive electrode, and the negative electrodes are also welded together and extend upward to form a total negative electrode.

[0026] The bracket 3 includes a base 31, with side plates 32 fixedly mounted on both sides of the base 31 by bolts 32. Bolt holes are provided at the bottom of the side plates 32, allowing the bracket and lithium battery to be fixed together to the vehicle frame using bolts. Multiple lithium battery cells 1 are placed side-by-side on the base 31, positioned on the two side plates 32. A partition 4 is also bolted to the upper side of the two side plates 22. Through holes are provided in the partition 4, through which the total positive and total negative terminals of the lithium battery cells extend to the upper side of the partition 4.

[0027] A capacitor box 5 is fixedly installed on the upper side of the partition 4. The supercapacitor pack 2 is placed inside the capacitor box 5. The partition 4 separates the lithium battery cell 1 from the supercapacitor pack 2, placing them in different chambers for enhanced safety during lithium battery operation. The supercapacitor pack 2 consists of multiple supercapacitors connected in series, such as... Figure 1 As shown, supercapacitor group 2 consists of six supercapacitors connected in series. The supercapacitors used are 16.2V with capacitance values ​​ranging from 6F to 85F. The number and capacitance values ​​of the supercapacitors can also be other types, depending on the specific product.

[0028] In this embodiment, the lithium battery is also covered by an outer shell, which encloses the lithium battery cell inside. The top of the outer shell is fixedly connected to the lithium battery cover 6. A positive terminal and a negative terminal are fixedly installed on the battery cover 6. The positive terminal of the supercapacitor group 2 is connected to the positive terminal, and the negative terminal of the supercapacitor group 2 is connected to the negative terminal.

[0029] In this embodiment, a BMS battery protection board is also fixedly installed on the upper side of the separator 4. The BMS battery protection board is located between the separator 4 and the lithium battery cover 6. The positive terminal of the lithium battery cover 6 is connected to the total positive terminal of the lithium battery cell, and the total negative terminal of the lithium battery cell is connected to the negative terminal of the BMS battery protection board. The total negative terminal of the BMS battery protection board is connected to the negative terminal of the lithium battery cover 6. The BMS battery protection board is prior art and will not be described in detail here.

[0030] Heating elements are fixedly installed on the outer side and bottom of multiple lithium battery cells 1. The heating elements can be connected to the side wall of the lithium battery cell 1 by adhesive bonding. The heating elements wrap around the lithium battery cell, which can improve the heating effect of the lithium battery cell.

[0031] A heating control board is also fixedly installed on partition 4. The main controller of the heating control board uses an STM32F103C8T6 microcontroller, which is existing technology and will not be described in detail here. The positive terminal of the heating control board is connected to the positive terminal of the lithium battery cover 6, and the negative terminal is connected to the negative terminal of the cover. The heating control board is used to control the heating of the heating element. The operating temperature of the heating element is set to 0 degrees Celsius. When the temperature is below 0 degrees Celsius, the heating element is energized to heat the lithium battery. Two relays are also installed on the heating control board, namely relay one and relay two. The normally closed terminal of relay one is connected to the charging MOSFET control terminal pad on the BMS protection board, and the normally open terminal of relay two is connected to the power supply line of the heating element.

[0032] Relay 1 and Relay 2 are normally powered on but not conducting by default. When NTC temperature sensor 2 is detected to be below or equal to the set temperature value (default 0 degrees Celsius) or above the set voltage value (default 14V), the switches of Relay 1 and Relay 2 are turned on. When NTC temperature sensor 2 is detected to be above the set temperature value (1 degree Celsius), the switches of Relay 1 and Relay 2 are turned off.

[0033] When the temperature is below 0 degrees Celsius and the voltage is above 14V, the combinational logic confirms that the ambient temperature is below 0 degrees Celsius and the car's alternator is working with current output, indicating the battery is in charging mode. Once these conditions are met, the heating control board will activate two relay switches. Relay one, with its normally closed terminal controlling the charging MOSFET of the battery protection board, opens when relay one is activated, turning off the charging MOSFET and stopping battery charging. Relay two, with its normally open terminal controlling the power supply to the heating element, closes when relay two is activated, energizing the heating element and initiating heating.

[0034] The applicant's first purpose in setting up the supercapacitor bank is to address the issue that when the ambient temperature is below 0 degrees Celsius and the heating function is activated, the charging MOSFETs on the BMS protection board will be shut off. However, due to this brief shutdown of the charging function, vehicles equipped with battery current detection capabilities may report a battery fault because they cannot detect the battery current. By connecting a supercapacitor bank in parallel between the battery's positive and negative terminals, the supercapacitor bank will charge and discharge with the alternator voltage fluctuations, generating corresponding charging and discharging currents. At this time, the vehicle's battery current sensor can detect normal current, thus preventing a battery fault report. This solution addresses the problem of the vehicle reporting a battery damage fault light when there is no current after lithium battery protection.

[0035] Objective Two: To ensure safety, lithium batteries require strict control over their maximum charging voltage. Lithium batteries must be protected against overcharging using a Battery Management System (BMS) to control the maximum voltage. Under certain vehicle operating conditions, the alternator voltage may occasionally exceed the lithium battery's maximum charging voltage. When this voltage exceeds the limit, the BMS protection board will actively shut down the charging MOSFETs, cutting off the charging current. Therefore, in this protected state, the alternator output cannot reach the battery, causing voltage fluctuations. The vehicle system will then report a fault because it cannot detect the charging current. Therefore, adding a supercapacitor at the front end of the protection board can prevent voltage fluctuations and system faults caused by BMS protection. When the alternator voltage drops back to normal, the charging MOSFETs will automatically turn on to conduct the charging current.

[0036] During the protection period, due to the brief shutdown of the charging function, vehicles equipped with battery current detection capabilities may report a battery fault because they cannot detect the battery current. However, by connecting a supercapacitor bank in parallel between the battery's positive and negative terminals, the supercapacitor bank will charge and discharge with the alternator voltage fluctuations, generating corresponding charging and discharging currents. At this time, the vehicle's battery current sensor can detect normal current, and therefore will not report a battery fault.

[0037] Additionally, when the lithium battery cannot be charged after the charging protection is activated, the surge caused by the generator voltage being higher than the lithium battery voltage can cause the instrument lights to flash. Here, the supercapacitor bank also plays a role in voltage stabilization. Utilizing the rapid charging and discharging characteristics of supercapacitors, when used in conjunction with batteries, can extend battery life and enhance instantaneous pulse power, thereby improving vehicle performance.

[0038] During actual testing of the lithium battery, the applicant discovered that in summer, due to prolonged exposure to the sun, the temperature inside the car's engine compartment became excessively high. This heat was transferred to the battery's interior, triggering the over-temperature protection function of the BMS battery protection board. The BMS overheat protection shut down, causing the battery to disconnect. However, the temporarily stored charge and current within the added supercapacitor pack could be detected by the car's computer system, preventing an alarm for battery disconnection. To avoid triggering the over-temperature protection function due to heat, the applicant filled a layer of heat-insulating cotton 7 between the outer casing and the lithium battery cell 1. Figure 5 As shown, the heat insulation cotton is made of fiberglass. In hot summer weather, the cotton can insulate against high external temperatures, preventing heat from being transferred to the lithium battery. The applicant's experiments showed that while lithium batteries do generate heat in summer, the amount of heat generated is far less than the temperature transferred from direct sunlight. Therefore, adding the heat insulation cotton does not affect the normal operation of the lithium battery, and there is no need to worry about its self-heating. Furthermore, lithium batteries heat up relatively slowly; the applicant conducted continuous vehicle tests for 6-8 hours, and the temperature rise of the lithium battery was significantly lower than the temperature in the engine compartment. Additionally, in cold weather, the heat insulation cotton also has a heat preservation function.

[0039] Besides fiberglass, thermal insulation can also be made of aluminosilicate ceramic fiber. Aluminosilicate needled blanket ceramic fiber has better fire resistance and higher safety performance.

[0040] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A vehicle-mounted lithium battery system, characterized in that, include: Multiple lithium battery cells (1), with the positive and negative electrodes of the multiple lithium battery cells welded together respectively; It also includes a bracket (3), in which the plurality of lithium battery cells (1) are encapsulated inside the bracket (3), and a partition (4) is fixedly installed on the upper end of the bracket (3). The supercapacitor group (2) is fixedly installed on the upper side of the partition (4). The partition (4) separates the supercapacitor group (2) from the lithium battery cell (1). The positive terminal of the supercapacitor group (2) is connected to the positive terminal of the battery, and the negative terminal is connected to the negative terminal of the battery. When the charging of the lithium battery is turned off, the supercapacitor group will charge and discharge as the voltage of the generator fluctuates, generating a charging and discharging current. The battery current sensor of the vehicle can detect the normal current. The outer side of the plurality of lithium battery cells (1) is provided with an outer shell, and heat insulation cotton (7) is provided between the outer shell and the lithium battery cells.

2. The on-board lithium battery system according to claim 1, characterized in that: A capacitor box (5) is fixedly installed directly above the partition (4), and the supercapacitor group (2) is placed in the capacitor box.

3. The on-board lithium battery system according to claim 2, characterized in that: The supercapacitor bank (2) is a structure consisting of multiple capacitors connected in series.

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