Battery box structure
By combining lithium-ion and lead-acid batteries in the battery module and using a battery management system, phase change materials, and fire extinguisher materials, the thermal runaway risk and size and capacity limitations of lithium-ion and lead-acid batteries in electric vehicles have been solved, achieving efficient and safe power supply.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TVS MOTOR CO LTD
- Filing Date
- 2021-03-14
- Publication Date
- 2026-05-19
AI Technical Summary
In existing technologies, lithium-ion batteries and lead-acid batteries pose a risk of thermal runaway in electric vehicles, leading to safety hazards. At the same time, their size and capacity are limited, and their costs are high, making it difficult to effectively combine them to meet the needs of starting and long-term power supply.
Design a battery module that places lithium-ion and lead-acid batteries in the same battery box structure, combining a battery management system, phase change material, and fire extinguishing material. The battery pack is separated and managed by a partition, and the phase change material absorbs heat, while the fire extinguishing material suppresses fire, ensuring safety and flexibility.
It effectively reduces the weight and cost of the battery module, improves the maintainability and safety of the battery module, ensures timely heat release in the event of thermal runaway, avoids fire, and meets the power demand of electric vehicles.
Smart Images
Figure CN115315845B_ABST
Abstract
Description
Technical Field
[0001] This topic relates to battery packs. More specifically, this topic relates to battery packs that have multiple cell units stacked together. Background Technology
[0002] Essentially, unlike disposable batteries that cannot be recharged, rechargeable batteries can be charged and discharged. Typically, low-capacity batteries, where a single cell is packaged into a battery pack, can be used as a power source for various small portable electronic devices, such as mobile phones. In the case of high-capacity batteries, where several cells are connected in series or parallel, high-capacity batteries can be used in electrical devices such as power banks, laptops, or drive motors, such as electric scooters and hybrid vehicles.
[0003] Batteries are proposed as a clean, efficient, and environmentally responsible power source for electrical devices such as electric vehicles and a variety of other applications. Typically, a conventional battery module comprises multiple battery cells arranged in a stacked configuration and is electrically connected to the electrical device. Furthermore, each battery cell includes a cathode terminal and an anode terminal, which are electrically connected in a combination of series and parallel configurations to maximize the battery module's voltage output and runtime. In some designs, a battery cover must be placed on top of the stack of battery cells to isolate and protect the anode and cathode terminals of each cell. Attached Figure Description
[0004] The accompanying drawings are provided for detailed description. Throughout the drawings, the same reference numerals are used to denote features and components.
[0005] Figure 1 This is an assembly view of a battery box structure according to an embodiment of the present invention.
[0006] Figure 1a This is a rear view of a battery box structure according to an embodiment of the present invention.
[0007] Figure 1b This is a cross-sectional view of a battery box structure according to an embodiment of the present invention.
[0008] Figure 2 This is a cross-sectional view of a battery box structure having a battery module and a phase change material according to an embodiment of the present invention.
[0009] Figure 3 This is a graphical representation of an embodiment of the present invention.
[0010] Figure 4 This is a cross-sectional view of a battery box structure with fire extinguisher material according to an embodiment of the present invention.
[0011] Figure 4aThis is a cross-sectional view of a perforation according to an embodiment of the present invention. Detailed Implementation
[0012] In recent years, there has been a strong demand to reduce carbon dioxide emissions for environmental protection. In particular, the automotive industry has seen a surge in expectations for reducing carbon dioxide emissions through the introduction of electric or hybrid vehicles, and the battery industry is therefore continuously developing to meet the growing energy demands of the portable devices, transportation, and communications markets.
[0013] Batteries are generally classified into disposable batteries and rechargeable batteries. Disposable batteries, also known as single-use batteries, are primarily intended to be used until depleted, after which they are simply replaced by one or more other batteries. Rechargeable batteries, often called rechargeable batteries, can be repeatedly charged and reused, making them more economical and environmentally friendly in the long run compared to disposable batteries.
[0014] While rechargeable batteries offer many advantages over primary batteries, they also have some drawbacks due to the chemical properties of the batteries used, as these chemicals are less stable compared to primary batteries. Furthermore, because of these relatively unstable chemical properties, secondary batteries often require special handling during manufacturing.
[0015] Furthermore, secondary batteries are divided into two parts: lithium-ion batteries and lead-acid batteries. Lead-acid batteries are the most common type of high-capacity rechargeable battery. Lead-acid batteries are made of many individual cells containing lead alloy plates immersed in an electrolyte, typically composed of sulfuric acid and water. Pure lead (Pb) is too soft to support itself, so small amounts of other metals are added to gain mechanical strength and improve electrical performance. The most common additives are antimony (Sb), calcium (Ca), tin (Sn), and selenium (Se). When sulfuric acid comes into contact with the lead plates, a chemical reaction occurs, generating energy. Lead-acid batteries perform well at low temperatures and are superior to lithium-ion batteries when operating below freezing.
[0016] Lithium-ion batteries are typically configured as rechargeable batteries, relying primarily on the movement of lithium ions (Li+) between the positive and negative electrodes to function. During charging and discharging, Li+ ions are inserted into the electrolyte and move between the two electrodes; Li+ ions exit from the positive electrode and are inserted into the negative electrode, which is then in a lithium-rich state. During charging, lithium-ion batteries generally use lithium-containing materials as electrodes and are representative of modern high-performance batteries.
[0017] Furthermore, lithium-ion batteries are manufactured in various ways; the most popular lithium-ion batteries, with the highest energy density, use cobalt or nickel-cobalt oxide anodes. These batteries also have drawbacks, such as a tendency to generate their own internal oxygen supply when overheated. More specifically, oxygen is released from the oxide material of the anode at high temperatures, which can occur due to various reasons such as internal short circuits, overcharging, or any other cause. Because both oxygen and fuel are available inside the battery, a fire can start within a single cell and may be difficult to extinguish using conventional methods, potentially posing a safety risk.
[0018] Furthermore, in current electric vehicles, lead-acid and lithium-ion batteries are used to provide power to the vehicle. The vehicle's tires are connected to a direct current (DC) motor, and the lead-acid and lithium-ion batteries provide DC power to the vehicle's DC motor.
[0019] Generally, during vehicle or electrical equipment startup, the DC motor requires a large current to generate sufficient torque to overcome the static friction during startup. A lead-acid battery can provide the current surge needed for starting the vehicle; thereafter, once the vehicle reaches a predefined speed, the lithium-ion battery takes over and supplies power to the DC motor. However, lithium-ion batteries cannot efficiently provide large currents during vehicle startup. For ion-based energy devices, the high current surge drawn during startup can often lead to wiring harness damage or other adverse effects. Therefore, a vehicle may not have a separate lithium-ion battery to power it and may also require a lead-acid battery to provide starting power.
[0020] Furthermore, secondary batteries (such as lithium-ion batteries) are more susceptible to thermal runaway than lead-acid batteries, and the primary cause of thermal runaway is when the internal reaction rate increases to the point that the rate of heat generation exceeds the rate of heat removal. Moreover, both the reaction rate and the exothermic reaction increase further over time. Therefore, the heat generated in the energy device can be sufficient to cause combustion or explosion of the battery and surrounding materials. The main causes of thermal runaway include internal short circuits, improper battery use, physical abuse, manufacturing defects, or exposure of the battery to excessively high external temperatures.
[0021] Thermal runaway is a significant problem because a single thermal runaway event can cause severe physical injury or damage, and in some cases, injury or death. When a battery is in a state of thermal runaway, it typically releases large amounts of smoke, jets of burning liquid electrolyte, and a significant amount of heat, causing surrounding components to burn and become damaged. Furthermore, if the battery pack has stacked cells, a single thermal runaway event will immediately lead to the thermal runaway of multiple cells, potentially causing extensive damage to the battery stack and surrounding components. Additionally, if the initial flame is not extinguished immediately, the flames resulting from the thermal runaway state will also increase the impact of property damage, regardless of whether the energy device consists of a single cell or multiple cells.
[0022] Consider thermal runaway in laptops or electric vehicles as an example. Thermal runaway in a laptop, where no human is attached, not only damages the laptop itself but also causes at least some damage to the surrounding environment, such as homes, offices, and cars. Furthermore, if the laptop battery is installed on an aircraft, the worst-case scenario is possible, as the smoke generated by thermal runaway could lead to a fatal emergency landing or, under more severe circumstances, an emergency landing. Similarly, in electric vehicles, thermal runaway of one or more batteries in a hybrid or electric vehicle's battery pack can not only damage the vehicle but also cause accidents and damage to the environment surrounding the vehicle's components.
[0023] Furthermore, in known technologies, the size and capacity of lead-acid and lithium-ion batteries that can be used are fixed. The dimensions of the compartments housing lead-acid and lithium-ion batteries are also fixed, thus limiting their size and capacity. Additionally, to generate a fixed voltage, a greater number of lead-acid batteries are required compared to lithium-ion batteries. Moreover, the separate use of lithium-ion batteries increases the overall cost of the vehicle because, besides being difficult to effectively cool and handle the generated heat and gases, and being difficult to manufacture and maintain, lithium-ion batteries are also expensive. Therefore, in known technologies, lead-acid and lithium-ion batteries are used separately, and the greater combined effect of lead-acid and lithium-ion batteries remains untapped.
[0024] In addition, in known technologies, different types of mechanisms are used to prevent thermal runaway, namely, control charging mechanisms to ultimately avoid high temperatures, battery management systems, step charging, pulse charging, or the addition of cooling systems such as heat sinks. This requires additional manual intervention in case of malfunctions, such as faults in the BMS (Battery Management System) circuit.
[0025] Therefore, there is a challenge in designing efficient battery modules without requiring any major changes to the design and manufacturing setup of the vehicle.
[0026] Therefore, there is a need for an improved battery module that overcomes all the aforementioned problems and other issues with known technologies.
[0027] This invention provides a solution to the above-mentioned problems, while meeting the requirement of minimal modification to electrical equipment (e.g., electric vehicles) in a low-cost and easy-to-manufacture manner.
[0028] In view of the above objectives, the present invention relates to battery modules, and more particularly to an improved configuration of a battery module in which lead-acid batteries and lithium-ion batteries are placed together, and thermal runaway is also overcome, thereby making it cost-effective, increasing maintainability, and ensuring rider safety.
[0029] According to one aspect of the invention, a battery box structure includes four walls, a base plate, and a cover, wherein the cover is detachably attached to allow access to the interior of the box structure. Access to the interior of the box structure is for placing or removing lead-acid and lithium-ion batteries from the box structure. The box structure also includes a plurality of recesses that can accommodate separators. The separators divide the interior of the box structure into one or more compartments. The size of the compartments can be changed by altering the position of the separators in the assigned recesses. Due to the presence of multiple recesses within the box structure, the separators can be secured at different positions within the box structure.
[0030] According to one aspect of the invention, one or more compartments are formed by partitions, one compartment housing at least one battery and another compartment housing at least one lithium-ion battery. Furthermore, the housing includes a battery management system disposed between a stack of lithium-ion batteries and lead-acid batteries, the battery management system managing a combination of at least one lead-acid battery and at least one lithium-ion battery to provide power to the device, and more particularly, to a DC motor.
[0031] According to one aspect of the invention, the battery module is also protected by a phase change material (PCM) disposed adjacent to the battery module. Furthermore, according to one aspect of the invention, when the temperature of the battery module exceeds the melting point of the PCM, the PCM changes from a solid to a liquid state, preventing a rapid increase in battery temperature and thus increasing the battery module's lifespan and durability. Furthermore, according to one aspect of the invention, when the temperature around the PCM decreases, the generated heat is released to the atmosphere through vents provided in the PCM, and then the PCM returns to a solid state. Furthermore, according to one embodiment of the invention, the PCM has two walls, an inner wall and an outer wall, wherein the inner wall, having a predetermined thickness "A", is separated from the other wall (i.e., the outer wall of the battery module). The inner wall of the PCM is made of plastic. A wall thickness greater than or less than the predetermined thickness will affect the effective heat release of the PCM, which will adversely affect the release of heat from the PCM into the atmosphere.
[0032] Furthermore, according to one embodiment of the invention, the battery box structure further includes a fire extinguishing material, such as a dry chemical powder. Additionally, according to one aspect of the invention, the fire extinguishing material has portions that connect to perforations present in the battery module. The perforations are filled with a self-fluxing material, such as silicon. When the temperature of the battery module reaches a predetermined limit, for example, 100°C to 120°C, the self-fluxing material present in the grooves of the perforations in the battery module dissolves, which further causes the fire extinguishing material to come into contact with the battery module, thereby suppressing any fire from the battery module. Therefore, any irreparable damage or fire hazard is avoided, and the safety of the battery module and its surrounding components is greatly enhanced. According to one aspect of this embodiment, the fire extinguisher is activated to suppress fire when the phase change material and the phase change material wall made of plastic dissolve.
[0033] Furthermore, according to another embodiment of the invention, the thickness 'A' of the phase change material wall is less than the outer thickness 'B' of the phase change material wall, such that the phase change material should exchange energy with the battery module rather than with the atmosphere, because there is more heat transfer between the battery module and the phase change material than between the phase change material and the atmosphere.
[0034] Various other features of the invention are described in detail below with reference to the accompanying drawings. In the drawings, the same reference numerals generally denote the same, functionally similar, and / or structurally similar elements. The first appearance of an element in the drawing is indicated by the leftmost numeral of the corresponding reference numeral. Referring to the drawings, the same reference numerals will be used to identify the same or similar elements in all several views. Furthermore, the subject matter can be implemented at the two terminals of a cylindrical battery.
[0035] Figure 1 This is an assembled view of the battery box structure (100). According to one embodiment of the invention, the battery box structure (100) consists of four walls (105), namely a pair of side walls (105b, 105d), a front wall (105a), and a rear wall (105c), and has a base plate (not shown) and a cover (103), wherein the base plate supports the four walls (105) of the battery box structure (100). In addition, the battery box structure (100) also includes at least a pair of retainers (106) fixed to the outside of the battery box structure (100) (e.g., Figure 1aAs shown), the battery box structure (100) is attached to an electrical device (e.g., a vehicle). At least one wall (105c) includes one or more retainers (106) to attach the battery box structure (100) to the vehicle. Furthermore, the battery box structure (100) includes one or more handles (101) for gripping the battery box structure, ensuring easy movement. Additionally, according to one embodiment of the invention, the cover (103) of the battery box structure includes one or more holes (102) for establishing a connection between the terminals of the battery module and the wiring harness in the vehicle, and these holes serve as drainage paths in case of any pressure generated in the battery module, ensuring the drainage of generated pressure and heat. Furthermore, the cover (103) is closed and locked by a locking mechanism (104) to ensure rigid packaging of the battery module and also to ensure easy access.
[0036] Furthermore, the battery box structure (100) is divided into one or more compartments due to one or more separators (108) used to house the stacked lithium-ion and lead-acid batteries, which also improves the accessibility of the battery module. Additionally, one or more separators are attached to the battery box structure (100) via recesses (107) (e.g., Figure 1b (As shown).
[0037] Furthermore, for example, let's consider that to achieve voltages above 50 volts, 40% lead-acid batteries and 60% lithium-ion batteries are required, resulting in a 48% weight reduction in the combined battery module compared to using only lead-acid batteries. Additionally, the cost of the battery module is reduced by 32% compared to using only lithium-ion batteries. This flexible configuration ensures that the synergistic effect of using lithium-ion and lead-acid batteries leads to weight and cost reductions, while maintaining the required starting energy or power supply for motors, etc. Moreover, this configuration ensures that designers can prioritize the flexibility of balancing energy sources between lead-acid and lithium-ion battery modules to overcome the conflicting challenges of meeting high energy supply requirements under starting and / or low-speed conditions and meeting long-range / long-duration power supply requirements during extended quasi-steady-state operation of motors or electrical equipment.
[0038] Figure 2 This is an assembled view of the battery module (205) in the battery box structure. According to one embodiment of the invention, the battery module (205) is further divided into one or more compartments by a separator (108). Figure 1bAs shown), one compartment contains a stack of one or more lithium-ion batteries (201), and another compartment contains a stack of one or more lead-acid batteries (203). Furthermore, a battery management system (BMS) (202) is disposed in the compartment formed between the stacks of lithium-ion batteries (201) and lead-acid batteries (203). Moreover, since lead-acid and lithium-ion batteries have different nominal voltages, operating windows, charge-discharge currents, and cycle counts, the battery management system is constructed and configured for optimized use and calibration to meet the predetermined requirements of the electrical equipment. For example, a lead-acid battery has a nominal voltage of 2 volts, while a lithium-ion battery has a nominal voltage of 4 volts. Furthermore, to compensate for a lithium-ion battery with a nominal voltage of 4 volts, two lead-acid batteries with a nominal voltage of 2 volts are required. Additionally, the battery management system protects the batteries from operating outside their safe operating area, thus preventing overcharging or over-discharging.
[0039] Furthermore, the battery module manages the power demand of the power-consuming unit / device. Additionally, the battery module (205), together with the BMS, can engage a lead-acid battery (203) disposed within a compartment to provide energy to the power-consuming unit during startup, and can engage a lithium-ion battery (201) housed within the compartment to provide energy to the power-consuming unit when the motor of the power-consuming device reaches a predetermined speed. Furthermore, according to another embodiment, the battery module (205) can engage a combination of lead-acid battery (203) and lithium-ion battery (201) to provide energy to the power-consuming unit at a ratio R, where R is the load rate on each of the batteries, ranging from 0 to 100%. Furthermore, the charging of at least one lead-acid battery (203) and one lithium-ion battery (201) is managed by a battery management system (202). The battery management system (202), present in the battery module, prevents the lead-acid and lithium-ion batteries from being overcharged by preventing charging current from flowing to them when they are fully charged.
[0040] Furthermore, according to one embodiment of the invention, the battery module (205) is also covered by a phase change material (204) layer, wherein the phase change material (204) comprises two walls, namely an inner wall (204b) and an outer wall (204a). The inner wall (204b) is made of plastic and configured to have a predetermined thickness A, wherein the thickness A is in a predetermined range of 0.5 to 2 mm. A thickness less than 0.5 mm will adversely affect the strength of the inner wall of the phase change material, because the strength will decrease if the thickness is less than 0.5 mm, while a thickness greater than 2 mm will adversely affect the heat transfer efficiency of the phase change material, which in turn affects the heat absorption performance of the phase change material. In addition, when the temperature in the battery module (205) rises due to potential thermal runaway conditions, the heat energy thus released is absorbed by the phase change material (204), causing the phase change material (204) to change from a solid to a liquid or semi-solid state, while still being firmly held between the inner wall (204b) and the outer wall (204a). Furthermore, the phase change material (204) releases less heat, and this is achieved through vent holes (403) provided on the outer wall (204a) (as shown in the image). Figure 4 The phase change material (204) is released into the atmosphere to ensure a predetermined temperature or ambient temperature in the battery module (205). The thickness B of the outer wall of the phase change material is in a predetermined range of 2 mm to 5 mm, wherein the thickness B is equal to or greater than the thickness A, ensuring a higher rate of heat absorption from the battery module (204) by the phase change material (204), which increases the service life and durability of the battery cell.
[0041] Figure 3 This is a graphical representation of the charging and discharging of battery modules (205) with and without phase change materials. According to one embodiment of the invention, during battery charging, it can be clearly seen from graphical representation G1 that the peak charging temperature of the battery module (302) with phase change materials is lower than that of the battery module (301) without phase change materials, demonstrating the advantageously lower operating temperature of the battery module with phase change materials. This reduces the capacity loss over the lifespan of the battery module with phase change materials by up to 50% compared to the capacity loss over the lifespan of the battery module without phase change materials. Furthermore, according to one embodiment of the invention, during battery discharging, it can be clearly seen from graphical representation G2 that the peak discharge temperature of the battery module with phase change materials (304) is lower than that of the battery module without phase change materials (303). This indicates that the use of phase change materials significantly reduces the battery temperature, thereby improving the lifespan and durability of the battery module.
[0042] Figure 4This is an assembled view of the battery module in which the fire extinguisher is disposed. According to one embodiment of the invention, a perforation (401) is provided in the inner wall (204b) of the phase change material (204). And the fire extinguisher material (402) is disposed around the outer periphery of the PCM. The perforation (401) includes one or more openings (404) (e.g., ...). Figure 4a As shown), the opening is filled with a self-fluxing material, such as silicon. When the temperature suddenly rises, for example, above 100 degrees Celsius, causing the PCM to change from a solid to a liquid state, the self-fluxing material changes its state from solid to liquid, which allows the fire extinguishing material (402) to come into physical contact with the battery module (205), thereby suppressing the fire in the battery module (205) and ensuring the safety of the energy unit. Furthermore, according to one embodiment, the required weight ratio of the phase change material to the fire extinguisher is a predetermined ratio of 1:2.5, so that the safest result can be obtained for different load rates R between the lead-acid module and the lithium-ion module.
[0043] This invention helps overcome problems such as increased weight, increased cost, and heat release due to thermal runaway, increases the accessibility of the battery module, and ensures the safety of surrounding components of the battery module.
[0044] Advantageously, embodiments of the invention describe potential modifications in the assembly of a battery module comprising at least one lithium-ion battery and a lead-acid battery, as well as a phase change material and a fire extinguishing material. Such a configuration overcomes the limitations of lead-acid and lithium-ion technologies while effectively combining the two technologies in a synergistic manner and overcoming the new challenges arising from their integration. The invention facilitates the simple and easy release of heat accumulated in the battery module under thermal runaway conditions, effectively increasing the accessibility and safety of components surrounding the battery module.
[0045] Many other improvements and modifications (such as the use of elastic devices with different stiffness) can be incorporated herein without departing from the scope of the invention.
[0046] List of reference numerals in the attached diagram:
[0047] Figure 1 ：
[0048] 100: Battery box structure
[0049] 101: A pair of handles
[0050] 102: Kong
[0051] 103: Lid
[0052] 104: Locking mechanism
[0053] 105 (105a, 105b, 105c, 105d): Four walls
[0054] 106: Holder
[0055] 107: Groove
[0056] 108: Partition
[0057] Figure 2 ：
[0058] A: The thickness of the inner wall of the phase change material
[0059] 201: Lithium-ion battery stacking
[0060] 202: Battery Management System
[0061] 203: Lead-acid battery stacking
[0062] 204: Phase Change Materials
[0063] 204a: Outer wall of phase change material
[0064] 204b: Inner wall of phase change material
[0065] B: Thickness of the outer wall of the phase change material
[0066] Figure 3 ：
[0067] 301: Charging without phase change materials
[0068] 302: Charging in the presence of phase change materials
[0069] 303: Discharge without phase change material
[0070] 304: Discharge in the presence of phase change materials
[0071] Figure 4 ：
[0072] 401: Perforation
[0073] 402: Fire extinguisher materials
[0074] 403: Vent
[0075] 404: slot.
Claims
1. A battery case structure (100), the battery case structure (100) comprising: A cover (103) is detachably attached to allow access to the interior of the battery compartment structure (100); in: The battery module (205) includes a plurality of recesses (107) configured to hold one or more separators (108), wherein the battery module (205) includes a stack of lithium-ion batteries (201) and a stack of lead-acid batteries (203); A phase change material (204) detachably attached to the battery module (205) of the battery housing structure (100), wherein the battery module (205) is configured with a perforation (401), wherein the perforation (401) includes one or more openings (404) filled with a self-fluxing material; and Fire extinguisher material (402) detachably attached to the phase change material (204) of the battery box structure (100) and the battery module (205), wherein the fire extinguisher material (402) has a portion connected to the perforation (401) present in the battery module (205) and a portion disposed around the outer periphery of the phase change material (204).
2. The battery box structure (100) according to claim 1 includes a battery management system (202) configured to manage a combination of stacks of lithium-ion batteries (201) and stacks of lead-acid batteries (203), and disposed in a compartment between the stacks of lithium-ion batteries and the stacks of lead-acid batteries (203), wherein the battery management system (202) provides energy to the power consumption unit at a ratio R.
3. The battery box structure (100) according to claim 2, wherein the ratio R is the load rate on each of the batteries, ranging from 0 to 100%.
4. The battery box structure (100) according to claim 1, wherein the battery box structure has four walls (105).
5. The battery box structure (100) according to claim 4, wherein the four walls (105) include a pair of side walls (105b, 105d), a front wall (105a) and a rear wall (105c).
6. The battery box structure (100) according to claim 1, wherein the cover (103) includes one or more holes (102) to establish a terminal connection between the battery module (205) and an electrical connector in the vehicle.
7. The battery box structure (100) according to claim 5, wherein the rear wall (105c) includes one or more retainers (106) for attaching the battery box structure (100) to the vehicle.
8. The battery box structure (100) according to claim 5, wherein the pair of sidewalls (105b, 105d) includes one or more holes (102) to guide airflow to the outside of the battery box structure (100).
9. The battery box structure (100) according to claim 1, wherein the phase change material (204) comprises two walls: an inner wall (204b) and an outer wall (204a).
10. The battery box structure (100) according to claim 9, wherein the inner wall (204b) has a predetermined thickness (A).
11. The battery box structure (100) according to claim 10, wherein the thickness (A) of the inner wall (204b) is in a predetermined range of 0.5 mm to 2 mm.
12. The battery box structure (100) according to claim 9, wherein the outer wall (204a) has a predetermined thickness (B).
13. The battery box structure (100) according to claim 12, wherein the thickness (B) of the outer wall (204a) is in a predetermined range of 2 to 5 mm.
14. The battery box structure (100) according to claim 12, wherein the thickness (B) of the outer wall (204a) is greater than the thickness (A) of the inner wall (204b) of the phase change material (204).
15. The battery box structure (100) according to claim 1, wherein the phase change material (204) is configured with one or more vents (403) to release the heat absorbed by the phase change material (204).
16. The battery box structure (100) according to claim 1, wherein the one or more partitions (108) divide the battery box structure (100) into two or more compartments, one compartment accommodating a stack of lithium-ion batteries (201) and another compartment accommodating a stack of lead-acid batteries (203).