Description:
TECHNICAL FIELD
[0001] The present subject matter described herein generally relates to a battery pack for a vehicle. More specifically, the present disclosure relates to thermal management of the battery pack.
BACKGROUND
[0002] Typically, Lithium-ion battery pack is used as power source in electric vehicles and hybrid vehicles. The battery pack comprises of multiple cylindrical cells that are interconnected in series and parallel arrangement to meet current, voltage and capacity requirements. The charging and discharging of cells are being monitored and controlled by battery management system (BMS). Such series and parallel interconnections of multiple cells can present various problems. Due to high current charging and discharging, there may be excess heat generation causing melting of components and imbalance among cells, thereby leading to a fire in the battery pack. Since, Lithium is highly reactive component, Lithium ion is relatively unstable in nature that poses a safety challenge which requires for specialized handling and operational requirements.
[0003] In general, the battery device generates significant amount of the heat during functioning, because of which the battery temperature can rise significantly. Eventually, the temperature can rise to a value where the battery pack can go in to thermal runaway. A good battery pack design should be capable of preventing thermal runaway. The design can be applied to pouch or prismatic cell depending on other requirements like space, current, voltage, weight, cost etc.
[0004] Conventionally, to ensure thermal management for battery, thermal pads are used. Thermal Pad is a heat-discharging pad used to control the heat generated in a battery. Generally, it is located between the battery module and the heat sink of outside of the pack, it transfers heat generated inside to outside. With thermal pads, specialized substrates are provided separately for heat dissipation and insulation. Thermal pads are not advantageous for cylindrical cells as it cannot give proper contacts between the cells. Further, the thermal pads require different layer thickness at different spaces. Hence, the serviceability and assembling of the battery pack is cumbersome. Furthermore, the maximum temperature withstanding capability of the thermal pads is low.
[0005] The role of the battery thermal management system (BTMS) is to ensure the operation temperature of the battery pack in a normal safe range. Phase Change Materials (PCMs) can be used to absorb heat, the temperature of a battery pack could be kept within the normal operating range for a long time without using any external power. Under overheating conditions, due to the high thermal conductivity performance of phase change materials (PCMs) and the presence of cooling devices such as heat sinks and heat pipes in BTMS, the temperature of a battery pack could quickly return to the normal working range, thus effectively reducing the occurrence of thermal runaway (TR) or fire accidents. However, recently pure PCMs could not completely satisfy all the application requirements, because there are disadvantages such as supercooling, low thermal conductivity and chemical instability.

Summary
[0006] In the present invention, a battery pack includes a battery module, a battery cell assembly that is a component of the battery module, and a plurality of battery cells. The plurality of battery cells being disposed in the battery cell holder. A plurality of cell terminal connectors being configured to electrically assemble the plurality of battery cells. An outer casing being configured to protect a battery module form an external damage. A fire-retardant sheet being placed between the plurality of cell terminal connectors and the outer casing. Each of the plurality of battery cells being covered with a conduit and a fire suppression agent being disposed within the conduit.
[0007] The plurality of battery cells generate heat during operation. The damage due to increase in the temperature and heat in the battery pack is prevented due to the fire-retardant sheet and the fire suppression agent, thus improving safety and the range of the vehicle.

BRIEF DESCRIPTION OF DRAWINGS
[0008] The detailed description of the present subject matter is described with reference to the accompanying figures. Same reference signs are used throughout the drawings to reference like features and components.
[0009] Figure 1 illustrates an exploded view of a conventional battery pack, in accordance with existing art.
[00010] Figure 2 illustrates an internal cell arrangement of a battery pack and placement of fire-retardant sheet, in accordance with an embodiment of the disclosure.
[00011] Figure 3 illustrates an individual cell having a conduit and its arrangement, in accordance with an embodiment of the disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[00012] The demand for electrochemical power cells such as lithium-ion batteries is growing in automotive industry due to the emergence of electric vehicles and grid storage systems. Further, multi-cell battery applications such as electric bicycles, uninterruptible power battery systems and lead-acid battery replacement batteries are increasing day by day. Hence, high energy and power density are a requirement with low manufacturing costs and increased safety to enable widespread commercial adoption of electric vehicles.
[00013] This invention relates to thermal management in such battery power supply systems. The word “battery” here is meant to include various forms of electrochemical power generation which have in common that chemical energy, in the form of one or more chemical reactants stored in a confined space, react with each other or with an external reactant in an electrochemical reaction, so as to produce electric power when desired.
[00014] Various uses of battery power supplies have been well established. For example, the packaging together of a plurality of cells in a parallel or series configuration to form a battery module or pack for use as a power supply for personal electronic devices such as cell phones, lap top computers, camcorders or the like have become well-known and common. In addition, desirable properties or characteristics of battery power supplies including, for example, the capability of certain battery power supplies to be recharged makes such battery power supplies potential power sources for vehicle propulsion, i.e., electric vehicles (EV). Recently, the concept as well as the application of battery power has been extended to include “fuel batteries” or “fuel cell batteries”, in which a fuel cell reaction is used to generate electric power similarly as in a conventional rechargeable battery, but in which one of the reactants (the fuel) must be replenished from time to time.
[00015] In various such applications, it is common that a number of cells be packed together in a preselected configuration (e.g., in parallel or in series) to form a battery module. A number of such battery modules may, in turn, be combined or joined to form various battery packs such as are known in the art. During operation and discharge, such cells, battery modules or battery packs commonly produce or generate quantities of heat which can significantly impact the performance resulting therefrom. Thus, in order to maintain desired or optimal performance by such cells or resulting battery modules or battery packs, it is generally important to maintain temperature of such cells, battery module or battery packs within fairly narrow prescribed ranges.
[00016] In practice, temperature variations between individual cells can result from one or more of a variety of different factors including, for example changes in ambient temperature; unequal impedance distribution among cells and differences in heat transfer efficiencies among cells.
[00017] Differences in heat transfer efficiencies among cells can typically primarily be attributed to the cell pack configuration. For example, cell elements at the centre of a cell pack configuration may tend to accumulate heat while those cell elements at the periphery of a cell pack configuration will generally tend to be more easily or freely cooled as a result of heat transfer to the surrounding environment. Further, such variation in heat transfer efficiencies may lead to further differences in impedance such as may serve to amplify capacity differences among the cells. Such capacity imbalances can cause or result in some cells being over-charged or over-discharged which in turn may result in premature failure of the cell pack or specific cell elements thereof. In particular, such failures may take the form of thermal runaway or accelerating capacity fading.
[00018] Thermal management systems based on the use of active cooling (e.g., such as based on forced circulation of air, liquid or other selected cooling medium) have been proposed for use in conjunction with such battery power supply systems. However, the incorporation and use of such active cooling regimes may introduce a level of complexity in either or both power supply design and operation such as may hinder or prevent the more widespread use of such power supplies.
[00019] Further, the required or desired size of a battery power supply is generally dependent on the specific application thereof. Thus, certain contemplated or envisioned applications for such power supplies, such as to power electric vehicles, for example, may necessitate the use of such power supplies which have or are of significantly larger physical dimensions that those commonly used or available. As will be appreciated by those skilled in the art, thermal management in power supply systems can become even more critical or significant as the size of such cell, battery module, or battery pack is increased.
[00020] Typically, the Lithium-ion battery construction consists of an outer metal casing and a plastic cell holder in which cells are placed. The battery pack generally consists of plurality of cells. The plurality of battery cells are placed on a cell holder. Depending on the electrical requirement in the vehicle the number of battery cells in the battery pack may be increased or decreased.
[00021] The lithium-ion battery packs are equipped with battery management system to prevent the malfunctioning caused inside the cells and to ensure that the series and parallel connected cells are operated in desired current, voltage and temperature range. However, in an unfortunate turn of events, wherein the BMS fails to protect the lithium-ion cells, the cells may undergo thermal runaway causing fire and explosion. Also, in the event of a single cell undergoing failure in a series-parallel arrangement of plurality of cell, this may lead to a cascading failure on other cells. The conventional battery construction is not equipped to protect these failures.
[00022] The thermal management for Lithium-ion battery packs is important to avoid thermal runaway. The increased temperature inside the battery pack can cause safety issues and decreases the life of battery pack. To ensure effective thermal management for Lithium-ion battery packs, a fire-retardant sheet is provided inside the battery pack.
[00023] In the present invention, a battery pack includes a battery module, a battery cell assembly that is a component of the battery module, and a plurality of battery cells. The plurality of battery cells being disposed in the battery cell holder. A plurality of cell terminal connectors being configured to electrically assemble the plurality of battery cells. An outer casing being configured to protect a battery module form an external damage. A fire-retardant sheet being placed between the plurality of cell terminal connectors and the outer casing. Each of the plurality of battery cells being covered with a conduit and a fire suppression agent being disposed within the conduit.
[00024] The plurality of battery cells generate heat during operation. The damage due to increase in the temperature and heat in the battery pack is prevented due to the fire-retardant sheet and the fire suppression agent, thus improving safety and the range of the vehicle.
[00025] As per an aspect of present invention, the fire-retardant sheet being placed over a positive terminal of each of the plurality of battery cells.
[00026] As per an aspect of present invention, the fire-retardant sheet being placed over a negative terminal of each of the plurality of battery cells.
[00027] As per another aspect of present invention, the fire suppression agent being one of a clean fire extinguishing agent or a powder based extinguishing agent.
[00028] As per yet another aspect of present invention, the fire-retardant sheet having a thickness being in a range of 1 mm to 10 mm.
[00029] As per another aspect of present invention, the fire-retardant sheet being made up of one of silicon oxide, calcium oxide and aluminium oxide.
[00030] As per yet another aspect of present invention, the conduit being a tubular structure being spirally wrapped around each of the plurality of battery cells.
[00031] As per another aspect of present invention, tubular structure having a diameter being in a range of 1mm-5mm, the tubular structure being made of a polymer.
[00032] The present invention prevents the battery pack from a damage due to excessive heat and temperature generated due to thermal runaway. Further, the fire-retardant sheet is made up of composite materials by incorporating several silicate materials which can withstand high temperature. Furthermore, the design protects the neighbouring battery cells from cell-to-cell propagation of fire with the help of spirally wrapped conduit around each of plurality of battery cells. The conduit is made up of a rubber or polymer material which melts at high temperature. The conduit ejects fire suppressant agent, which prevent the spreading of the flame to the neighbouring cells. The battery pack disclosed in present invention enhances performance due to increase in range of operating temperature, further durability of the battery pack also increases. Further, the battery pack disclosed in present invention is easy to assemble and manufacture. Furthermore, the present invention provides a solution for thermal management and fire suppression also. Further, fire retardant sheet and fire suppression agent together prevents thermal runaway.
[00033] Summary provided above explains the basic features of the invention and does not limit the scope of the invention. The nature and further characteristic features of the present subject matter will be made clearer from the following descriptions made with reference to the accompanying drawings.
[00034] Exemplary embodiments detailing features of the retrofittable assembly for the battery pack and its construction, in accordance with the present subject matter will be described hereunder with reference to the accompanying drawings. Various aspects of different embodiments of the present subject matter will become discernible from the following description set out hereunder. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the present subject matter. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
[00035] The present subject matter along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00036] Figure.1 illustrates a conventional battery pack 100. Typically, a battery pack 100 comprises of a top cover 101, a bottom cover 104, an aluminium outer casing 103. A battery pack 100 comprises of a battery module 102, and an aluminium outer casing 103. The battery module 102 comprises of a plurality of battery cells, interconnectors, interconnector dampers, with plastic cell holder.
[00037] Figure.2 illustrates an internal cell arrangement of a battery pack and placement of a fire-retardant sheet, in accordance with an existing art. The fire-retardant sheet 201 is placed at a top portion and a bottom portion of a battery cell holder. More specifically, the fire-retardant sheet 201 is placed over a plurality of cell terminal connectors. Further, the fire-retardant sheet 201 is placed inside an outer casing 103. The plurality of battery cells 301 being disposed in the battery cell holder. A plurality of cell terminal connectors being configured to electrically assemble the plurality of battery cells 301. An outer casing 103 being configured to protect a battery module form an external damage. Each of the plurality of battery cells 301 being covered with a conduit and a fire suppression agent being disposed within the conduit.
[00038] The plurality of battery cells 301 generate heat during operation. The damage due to increase in the temperature and heat in the battery pack is prevented due to the fire-retardant sheet 201 and the fire suppression agent, thus improving safety and the range of the vehicle.
[00039] Figure.3 illustrates an individual cell having a conduit and its arrangement, in accordance with an existing art. The conduit 202 covers each of the plurality of battery cells 301. The conduit 202 is a tubular structure which is spirally wrapped around each of the plurality of battery cells 301. The design of conduit 202 is such that it prevents the neighbouring battery cells from cell-to-cell propagation of fire. The conduit 202 is made up of a rubber or polymer material which melts at high temperature. After the melting of outer cover of the conduit 202, there is an ejection of fire suppressant agent, which prevent the spreading of the flame to the neighbouring cells.
[00040] The fire suppression agent inside a conduit, aids in preventing the spread of fire starting from a localized area of the cell. This prevents the spread of fire in the neighbouring cells leading to catastrophic failure of the battery module. Further, the fire-retardant sheet prevents the fire to spread outside the battery module. The claimed steps as discussed above are not routine, conventional, or well understood in the art, as the claimed steps enable the following solutions to the existing problems in conventional technologies.
[00041] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.

LIST OF REFERENCE NUMERALS
100- A Battery Pack
101- Top cover
102- Battery Module
103- Outer casing
104- Botom Cover
201- Fire-retardant sheet
202- Conduit
301- Battery cell
, Claims:I/We claim:

1. A battery pack (100) comprising:
a battery module (102), said battery module comprising,
a battery cell holder (103),
a plurality of battery cells (301), said a plurality of battery cells (301) being disposed in said battery cell holder (103),
a plurality of cell terminal connectors, said plurality of cell terminal connectors being configured to be electrically connected with said plurality of battery cells (301),
an outer casing (103), said outer casing (103) being configured to protect said battery module (102) from an external damage,
wherein
a fire-retardant sheet (201) being placed over said plurality of cell terminal connectors, said fire-retardant sheet (201) being placed inside said outer casing (103),
wherein each of said plurality of battery cells (301) being annularly covered with a conduit (202), and wherein a fire suppression agent being disposed within said conduit (202).

2. The battery pack (100) as claimed in claim 1, wherein said fire-retardant sheet (201) being placed over a positive terminal of each of said plurality of battery cells (301).

3. The battery pack (100) as claimed in claim 1, wherein said fire-retardant sheet (201) being placed over a negative terminal of each of said plurality of battery cells (301).

4. The battery pack (100) as claimed in claim 1, wherein said fire suppression agent being one of a clean fire extinguishing agent or a powder based extinguishing agent.

5. The battery pack (100) as claimed in claim 1, wherein said fire-retardant sheet (201) having a thickness being in a range of 1 mm to 10 mm.

6. The battery pack (100) as claimed in claim 1, wherein said fire-retardant sheet (201) being made up of one of silicon oxide, calcium oxide and aluminum oxide.

7. The battery pack (100) as claimed in claim 1, wherein said conduit (202) being a tubular structure being spirally wrapped around each of said plurality of battery cells (301).

8. The battery pack (100) as claimed in claim 6, wherein said tubular structure having a diameter being in a range of 1mm-5mm, said tubular structure being made of a polymer.