A hybrid system for thermal management of battery pack with immersion and phase change techniques

Abstract

The present invention discloses a system for thermal management of battery packs using a hybrid of immersion and phase change techniques. The system comprises of battery enclosure having a dielectric fluid and battery cells at least partially immersed in the dielectric fluid. A FCS for circulating the dielectric fluid inside the battery enclosure to cool or heat the battery cells. A PCM heat sink attached to the battery enclosure to absorb heat from the dielectric fluid. An EAFS to cool the PCM by blowing cool air over the PCM. An IHS for heating the dielectric fluid during cold weather conditions. A microcontroller / processor to receive inputs from plurality of temperature sensors and accordingly operate the FCS, IHS and EAFS for thermal management of battery pack.

Description

A HYBRID SYSTEM FOR THERMAL MANAGEMENT OF BATTERY PACK WITH IMMERSION AND PHASE CHANGE TECHNIQUESFIELD OF THE INVENTION

[0001] The present disclosure generally relates to a system for thermal management of battery packs. More particularly, relates to a system for thermal management of battery packs using a hybrid of immersion and phase change techniques.BACKGROUND OF THE INVENTION

[0002] Batteries such as lithium-ion or sodium-ion batteries (or any other class of batteries) generate heat during discharging and recharging. Devices using electrical energy are directly influenced by the battery pack's performance having one or more battery cells that generate heat during discharging and recharging. Usually, the temperature of lithium-ion battery needs to be maintained between 25 to 50 °C during operation to ensure its ideal performance. If the heat is not managed, this can overheat the battery or lead to possible thermal runaway due to exothermic reaction and temperature rise above irreversible values. High battery temperatures can accelerate battery aging, battery-life degradation, thermal runaway and pose safety risks. Hence, the battery needs to be cooled to a predefined temperature to enhance efficiency and reliability of batteries. Whereas, low temperatures can lead to decreased battery capacity and weaker charging / discharging performance. Similarly, many battery users are unaware that consumer-grade lithium-ion batteries face problems when charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium occurs on the anode during a sub-freezing charge that leads to a permanent degradation in performance and safety. Hence, the battery needs to be heated to a predefined temperature to enhance efficiency and reliability of batteries. Thus, the battery system is provided with a BMS system that detects any degraded or failed battery cell due to overheating from the plurality of battery cells so that each battery cell will have maximum performance.

[0003] Different methods exist for liquid cooling batteries that use cooling fluids or refrigerants confined to pipes, tubes, or other flow channels where some portions of the individual battery cells are in contact with the fluid channel or have a path to reject heat to the channel, either through contact with a thermally conductive component (e.g., heat exchanger, heat sink, radiator, etc.) or through direct contact with other battery cells. These methodstypically have limited contact areas with individual battery cells. They have low-to-medium thermal conduction across their contact area. They have several components (pumps, fans, valves, expansion valves, compressors, coolant hoses, hydraulic connectors, etc.) through which heat from the battery cell must travel to reach the ultimate cooling fluid, thereby resulting in the limited ability to effectively remove heat. These measures introduce significant additional mass and volume to the battery pack that reduces the energy density and power density of the battery pack while increasing cost. Since most of the cooling plates in contact with the cells are metallic, they present challenges in terms of short-circuit protection. The uniformity of cell temperature across the battery system is also generally poor which leads to cycle-life degradation of the entire battery system. Also, these methods frequently do not offer significant mitigation of thermal runaway and propagation events.

[0004] Furthermore, said systems have several components in-between, through which the heat from the battery cells has to travel to reach the ultimate cooling fluid, thus resulting in the limited ability to remove the heat effectively. Moreover, conventional systems provide limited or insignificant protection against thermal runaway events.

[0005] In the case of thermal management of battery packs involving immersion cooling, present technologies involve a common heat exchanger for all battery modules. Hot cooling fluid from the batteries is pumped to this heat exchanger, where it is cooled and then sent back to battery packs for further service. Longer lengths of fluid flow paths reduce system efficiency (through frictional and viscous losses during fluid flow). These systems have high component count, higher costs and weight, complicated cooling system design, and inferior serviceability. Also, generally the cooling fluid is shared between the modules of a larger battery pack which results in thermal and fluid coupling of battery modules. If one battery module undergoes an overheating event, the cooling fluid will allow a medium for quick heat transfer to adjacent modules, thereby resulting in thermal propagation between battery modules. There is also a difficulty for the removal of individual battery modules, maintenance and swapping (it becomes necessary to drain the cooling fluid completely, whenever an individual battery-module pack is to be swapped / repaired / removed).

[0006] In the case of thermal management of battery packs involving solid-to-liquid phase change cooling, present technologies involve placing the battery cells or modules in the phase change material (PCM), and the battery is thermally managed by the heat absorbed and released when the PCM melts or solidifies. Although these methods provide good heat absorption at constant temperature (melting point of PCM), they provide challenges related to servicing the battery due to restricted access to cells and modules. In order to gain access tothe cells, it becomes necessary to melt the PCM by external heating. Non-uniform heating in such cases leads to battery overheating and damage to the cell, thereby reducing the cycle life. Also, due to the low thermal conductivity of PCMs, uniformity of cell temperature across the battery system is also poor. Generally, cells are only partially immersed in the PCM to keep the volume around the safety vents of the cells free from obstruction, which significantly limits the overall coverage and effectiveness of PCM cooling. These methods also add significant mass and cost to the battery system.

[0007] Hence, there is a need to overcome one or more limitations stated above and develop a system for thermal management of battery packs using a hybrid of immersion and phase change techniques.OBJECTS OF THE INVENTION

[0008] Main object of the present invention is to develop a system for thermal management of battery packs.

[0009] Another object of the present invention is to develop a system for thermal management of battery packs by combination of immersion cooling and phase change cooling.

[0010] Yet another object of the present invention is to develop a system for thermal management of battery packs having an immersed heating system for heating the battery cells.

[0011] Another object of the present invention is to develop a system for thermal management of battery packs having an external air flow system for cooling the battery pack.SUMMARY OF THE INVENTION

[0012] Before the present system for thermal management of battery packs is described, it is to be understood that this application is not limited to a particular a hybrid system for thermal management of battery packs with immersion and phase change techniques as there may be multiple possible embodiments, which are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular implementations, versions, or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a hybrid system for thermal management of battery packs with immersion and phase change techniques. This summary is not intended to identify essential features of theclaimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[0013] The present invention discloses a system for the thermal management of battery packs using a hybrid of immersion and phase change techniques. The system comprising of a battery enclosure for accommodating dielectric fluid and a plurality of battery cells wherein, the plurality of battery cells are at least partially immersed in a dielectric fluid to transfer heat from or to the battery cells and a fluid circulation system (FCS) having a circulation device (eg. Pump, fan, etc.) configured to circulate the dielectric fluid through flow-channels which may include spaces between the battery-cells and the enclosure or through ducts / pipes located inside the enclosure for uniform distribution of heat. The system comprises a cooling apparatus configured with a phase change material (PCM) integrated inside a heat sink attached to the battery enclosure to absorb heat from the dielectric fluid when the fluid is made to flow over the inner side of the PCM and heat sink. There is an external airflow system (EAFS) (e.g. fans, blowers, air pumps, etc.) to cool the PCM from outside when the PCM temperature exceeds a predetermined threshold value. Further, the system comprises of a heating device immersed in the dielectric fluid (Immersed Heating System (IHS)) to heat the dielectric fluid and transfer heat to the battery cells during cold weather conditions. Furthermore, the system comprises of a microcontroller / microprocessor to activate the FCS, EAFS and IHS on the temperature inputs provided by the battery cells, dielectric fluid, PCM and ambient temperature.STATEMENT OF INVENTION

[0014] Accordingly, the present invention discloses a hybrid system for thermal management of battery packs with immersion and phase change techniques comprising at least one battery enclosure, at least one battery cell configured to be at least partially immersed within a dielectric fluid in the battery enclosure, at least one fluid circulation system (FCS) configured to circulate the dielectric fluid inside the battery enclosure to facilitate uniform cooling of each of the battery cells, at least one heat sink integrated with at least one phase change material (PCM) configured be mounted on or be an integral-part of the battery enclosure, at least one immersed heating system (IHS) configured for heating the dielectric fluid, at least one external air flow system (EAFS) configured to be mounted at proximity of the external side of the battery enclosure for cooling the heat sink externally, plurality of temperature sensors to sense the temperature of battery cell, dielectric fluid, PCM, ambient air and aprocessor configured to operate the FCS, IHS and EAFS based on the inputs received from the temperature sensors.

[0015] The present invention also discloses the FCS is configured with a fluid circulation device, at least partially submerged in the dielectric fluid for suction of fluid through at least one flow channel and an outflow of said dielectric fluid from said fluid circulation device is configured through at least one outflow-channel, over the inner surface of the PCM heat sinks. The heat sink is configured with an internal surface, an external surface and PCM sealed / enclosed between the said surfaces. The internal surface is configured to receive heat from the dielectric fluid to transfer heat to the PCM. The PCM is configured to absorb heat from the internal surface and transfer heat to the external surface for effective cooling of dielectric fluid. The PCM is configured to change state from solid to liquid at a predefined temperature by receiving heat from the dielectric fluid and change state from liquid to solid by releasing heat to the surrounding. The internal surface of heat sink is configured with a thermally conductive material constituted in the form of fins, pin-fins, dimples, extrusions, etc. for uniform conductive heat transfer and temperature distribution inside the PCM for maximum heat storage capabilities. The external surface of heat sink is configured with a thermally conductive material constituted in the form of rectangular fins, parabolic fins, pin- fins, dimples, skived fins, tube-fins, louver fins, extrusions, etc. for convective and radiative heat transfer to the surrounding air. The internal surface and external surface are integrated with the PCM or modularly attached by means of either of, or a combination of fasteners, rivets, structural / thermal adhesives, etc. The processor constitutes of microcontroller or microprocessor. The processor is configured to turn ON the EAFS based on temperature of PCM Heat Sink exceeding above a predetermined threshold value or based on the ambient temperature dropping below a predetermined threshold value to convert the state of PCM from liquid to solid. The IHS is configured with at least one heating element immersed in the dielectric fluid to heat the dielectric fluid in cold weather conditions. The processor is configured to turn ON the IHS based on the temperature of battery cells dropping below a predetermined threshold value. The processor is configured to turn ON the FCS based on the temperature of at least one battery cell exceeding above a predetermined threshold value or based on the difference between the maximum and minimum temperature of different battery cells exceeding above a predetermined threshold value. The battery pack is configured with a drain port mounted at the bottom of the battery enclosure for removal of the dielectric fluid and an inlet port mounted on a battery enclosure lid for refilling of new dielectric fluid. The battery pack is configured with at least one pressure relief vent mounted on top of the batteryenclosure lid to release all the gases generated inside the battery pack during thermal runaway events. The fluid circulation device constitutes of pumps, fans etc. The heating element constitute of resistance wire-types, ceramic and semiconductor types, thick films (NTC / PTC) or polymer PTC types heaters. The PCM is configured from any one of paraffin waxes, non-paraffin organics, hydrated salts or metallic. The dielectric fluid is configured from one of the synthetic dielectric esters, Naphthenic based and Paraffinic based oils or Silicone Oils. The EAFS constitute of fans, blowers, air-pumps, etc. The FCS and IHS are configured to be operated by the battery pack or external power supply. The flow channel constitutes of spaces between battery-cells and enclosure, ducts, tubes, etc. and said outflow channel constitutes of orifices, nozzles, etc.BRIEF DESCRIPTION OF DRAWINGS

[0016] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present subject matter, an example of construction of the present subject matter is provided as figures; however, the present subject matter is not limited to the specific a hybrid system for thermal management of battery packs with immersion and phase change techniques disclosed in the document and the figures.

[0017] The present subject matter is described in detail with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer various features of the present subject matter.

[0018] Figure 1 shows an illustrative exploded view of Battery pack.

[0019] Figure 2 shows an illustrative exploded view of Battery pack.

[0020] Figure 3 shows an illustrative complete assembly of the battery pack.

[0021] Figure 4 shows an illustrative exploded view of Battery pack.

[0022] Figure 5 shows an illustrative view of stacked battery cells and Fluid Circulation System.

[0023] Figure 6 shows an illustrative view of subsystems in each Battery pack.

[0024] Figure 7 shows an illustrative view of fluid circulation system.

[0025] Figure 8 shows an illustrative view of Phase Change Material Matrix and External Air Flow.

[0026] Figure 9 shows an illustrative sectional top-view of Battery pack.

[0027] Figure 10 shows a flow chart for flow of heat energy through the system during cooling.

[0028] Figure 11 shows a flow chart for flow of heat energy through the system during heating.

[0029] Figure 12 shows a flow chart for cooling system operation.

[0030] Figure 13 shows a flow chart for heating system operation.DETAILED DESCRIPTION

[0031] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any a hybrid system for thermal management of battery packs with immersion and phase change techniques and, similar or equivalent to those described herein may be used in the practice or testing of embodiments of the present disclosure, the exemplary, a hybrid system for thermal management of battery packs with immersion and phase change techniques is now described.

[0032] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments described but is to be accorded the widest scope consist in this regard, in a generic sense.

[0033] The present invention envisages a method, system, and apparatus for active (or passive) thermal management and mitigation of thermal runaway and propagation for battery packs. The methods and system disclosed herein provide a system for thermal management of battery packs using a hybrid of Immersion and Phase Change techniques. In particular, thedisclosed system employs direct fluid immersion that puts nearly the entire surface area of the battery cells in direct thermal contact with the cooling or heating medium. Referring to figures 1 and 2, the system for battery thermal management of battery packs comprises of at least one battery enclosure (2), plurality of batteries (4) at least partially immersed within a heat transfer fluid (28) contained in the battery enclosure (2) and at least one fluid circulation device (26) to circulate the heat transfer fluid (28) through the enclosure (2) containing the batteries. The system comprises of at least one heat sink containing Phase Change Material (PCM) (30) attached to the enclosure (2), at least one heating element (16) that is at least partially immersed in the fluid (28) inside the enclosure (2). The system comprises of at least one External Air Flow device mounted on / external to the battery enclosure. The system comprises of at least one temperature sensor (8) at least partially submerged within the heat transfer fluid (28) for determining the temperature of one or more batteries (4), at least one temperature sensor at least partially submerged within the fluid (28) for determining the temperature of the heat transfer fluid (28), at least one temperature sensor placed on the exterior or within the PCM (30) for determining the temperature of PCM heat sink (38), at least one temperature sensors placed external to the battery enclosure for determining the ambient temperature. The system comprises of a microcontroller / processor (18) to read data from all temperature sensors in the system. The microcontroller / processor (18) is configured to turn on and off the fluid circulation devices (26) when the temperature of at least one battery from the one or more batteries (4) exceeds or drops below a predetermined threshold value or when the difference between the maximum and minimum temperature inside the battery exceeds or drops below a predetermined threshold value. The microcontroller / processor (18) is configured to turn on and off the external Air Flow devices when PCM Heat Sink (38) temperature exceeds or drops below predetermined threshold value or when ambient temperature exceeds or drops below predetermined threshold value. The heat from the batteries (4) contained in the enclosure (2) is transferred to the fluid (28). The fluid (28) may be circulated by the fluid circulation devices (26) and heat from the fluid (28) contained in the fluid (28) is transferred to the PCM Heat Sinks (38). The heat from the PCM Heat Sinks (38) is transferred to the atmosphere though natural convection or forced air convection from Air Flow Devices over the PCM Heat Sinks (38). The microcontroller / processor (18) is configured to turn on and off the immersed heating devices (16) when battery temperature drops below or exceeds predetermined threshold value.

[0034] The present invention describes a ‘Battery Pack’ comprising of the following subsystems which work together.1. Fluid Circulation System (FCS) (6)2. Phase Change Material Matrix (PCM) (38)3. External Air Flow System (EAFS)4. Immersed Heating System (IHS) (not shown in figure).The subsystems are further described in detail:

[0035] Fluid Circulation System (FCS) (6):In an embodiment, the chemistries that are used as heat transfer fluids are from among fully synthetic dielectric esters, Naphthenic based and Paraffinic based oils and Silicone Oils and can also be used up with a proper additive package. Referring to figures 1, 2 and 7, the heat transfer fluid is a dielectric fluid (28), with sufficiently low electrical conductivity and ability to absorb, carry and transfer heat. An appropriate dielectric fluid (28) with sufficiently high flash point and auto-ignition temperature is selected as heat transfer fluid. Through direct contact with cells (4) and busbars inside the battery module, the present invention helps in minimizing thermal resistance from cells (4) and busbars to dielectric fluid, and in the elimination of internal parts (conductive cooling plates, conductive flow channels, etc.) typically found in other liquid-cooled systems.The fluid (28) may be circulated internally by circulation devices (26) (e.g. pumps, fans, etc.). The fluid (28) transfers heat to or from the batteries and may be made to flow through one or more internal flow-channels (e.g. spaces between the battery-cells and the enclosure or through ducts / pipes etc.) by the fluid circulation devices. Thereafter, it may be made to flow through outflow-channels (e.g. Orifices, nozzles, etc.) present on the flow-channels, at suitable velocity over the inner surface of the Phase Change Material Heat Sinks (30). The internal circulation increases the rate of convective heat transfer between cells (4) to fluid (28) and between fluid (28) to PCM Heat Sink (30). The temperature of fluid (28) decreases as it flows over the Heat sinks (30), and is then recirculated back to the batteries for further heat transfer. The internal circulation of fluid (28) internally also results in extended battery life due to greater uniformity and control on battery pack temperature distribution in a narrow range (typically 25 to 50 deg C for Lithium-ion Batteries). The fluid forms an encapsulation around the battery-cells and therefore helps in cutoff of oxygen supply to battery cells (4) which helps in increased safety with no propagation of thermal runaway. This results in firesuppression in case of fires caused by short-circuits, thermal runaways, overvoltage, overcurrent or any other faults. The FCS (6) may be powered by the battery pack itself or through external power-supply.

[0036] Phase Change Material Heat Sink (38):In an embodiment, the Phase Change Material (PCM) (30) is chosen from among Paraffin Waxes, Non-paraffin Organics, Hydrated Salts or Metallics. Referring to figure 1 and 2, a solid-to-liquid PCM (30) with appropriate melting temperature and sufficiently high Latent Heat is chosen for maximizing thermal performance of the system. The Phase Change Material (PCM) (30) integrated within the Heat sinks (38) helps in better thermal damping. Heavy, continuous or transient thermal loads can be absorbed easily by the PCM (30) mass due to high latent heat, thereby maintaining nearly constant temperature within the normal operating temperature window of the battery. Appropriate quantity of PCM (30) mass is taken based on specific requirements of application-areas of the invention.The PCM Matrix (38) may have internal heat transfer surfaces (12) made of materials having good thermal conductivity (e.g.: fins, pin-fins, dimples, extrusions, etc.) which help in uniform conductive heat transfer and temperature distribution inside the PCM (30) mass for maximum heat storage capabilities. These internal heat transfer surfaces (12) may be integrated with the PCM (30) or modularly attached by means of either of, or a combination of fasteners, rivets, structural / thermal adhesives, etc.The heat transferred to the PCM (30) by the internal fluid results in sensible heating (increase in temperature and Entropy) and latent heating (increase in Entropy with nearly constant temperature). The state of PCM (30) may change from solid to liquid by accepting heat from the fluid (28). The PCM Heat Sinks (38) comprise of extended-surface elements (14) made of materials having good thermal conductivity, which improve the convective and radiative heat transfer rate to surrounding air such as fins (rectangular, parabolic, etc.), pin-fins, dimples, skived fins, tube-fins, louver fins, extrusions, etc. The extended-surface elements (14) are integrated with the PCM (30) or modularly attached by means of either of, or a combination of fasteners, rivets, structural / thermal adhesives, etc.In an embodiment, The PCM (30) is not in direct contact with the battery-cells (4), but rather loaded in a modular housing (PCM Heat sink) which may be then attached to the enclosure by means of either of, or a combination of fasteners, rivets, structural / thermal adhesives, etc. The PCM Heat sinks (38) can thus be manufactured separately and assembled on each individual battery pack.In another embodiment, the PCM Heat Sink may also be an Integral Part of the Battery enclosure.

[0037] External Air Flow System (EAFS):Referring to figures 1, 2 and 8, once the PCM (30) mass in the battery pack completely changes its state from solid to liquid through latent heating, it offers significantly lesser capability to store further heat energy. The EAFS helps in increasing the rate of heat transfer from the PCM (30) to atmospheric air, which helps in PCM -regeneration (phase change from liquid to solid). External air (at lower temperature than PCM Heat sink) is made to flow over the PCM Heat sink (38) at a suitable velocity. The EAFS may be switched on or off when PCM (30) temperature exceeds or drops below predetermined threshold value. The switching of EAFS is controlled by the microcontroller / processor (18). The EAFS comprises of appropriately selected air flow generating devices from among fans, blowers, air-pumps, etc.

[0038] Immersed Heating System (IHS) (not shown in figure):Referring to figures 1 and 2, one or more heating devices (16) are at least partially immersed in the dielectric fluid (28). The heating devices (16) may be suitably chosen from among Resistance Wire-types, Ceramic and Semiconductor types, Thick Films (NTC / PTC) or Polymer PTC types. The heat generated by the immersed heating elements (16) is convectively transferred to the fluid (28) and thereafter from the fluid (28) to the batteries (4). The fluid (28) is circulated internally by circulation devices (26) (eg: pumps, fans, etc.) which helps in uniform heating of all battery-cells (4) and uniform temperature distribution. The IHS may be powered by the battery pack itself or through external power-supply. The IHS is switched on or off when battery temperature drops below or exceeds predetermined threshold value. The switching of IHS is controlled by the microcontroller / processor (18)

[0039] The system comprises of a pressure relief vent (24) to release all the gases generated inside the battery pack, in case of venting of gases from battery-cells during thermal runaway events. In case of swap / repair / replacement / removal, any individual module in a battery pack can be serviced without the need to drain the coolant / refrigerant (28) of the entire battery pack. The safety during swap / repair / replacement / removal is ensured through easy electrical disconnection of the module from the rest of the battery pack. In case of replacement / removal of the heat transfer fluid (28) in one individual battery pack, the fluid (28) can be completely drained from the Drain-port (22) located at the bottom of the enclosure (2) and new fluid can be introduced through the Inlet Port (20) on the enclosure lid (10). In the case of replacement / removal of PCM (30) in one individual battery-module, the entire modular PCM Heat sink (38) can be detached from the enclosure (2) and serviced separately. The new PCM Heat sink (38) can be directly attached to the battery enclosure (2).

[0040] Cooling fluid (28) is not shared between the battery modules of a larger battery pack which results in total thermal and fluid decoupling of battery modules. If one battery module undergoes an overheating thermal event, there is no path for quick heat transfer to adjacent modules, thereby mitigating thermal propagation between battery modules in a pack. In the case of a Vehicle / Energy Storage System Application, individual modules can be distributed based on space availability. Since modules are only electrically connected and Thermal Management System is independent for each battery module, it results in better flexibility in system Design and Packaging.

[0041] Since only dielectric fluid is in contact with cells, there is no hindrance to escaping gases in the event of venting of cells; the gases can escape through the fluid (28) to one or more safety pressure-relief valve / pressure release valves (24) on the enclosure lid (10) of each pack.

[0042] The invention may be directly applied to the following areas: Battery Packs used in Electric Vehicles, Battery Packs used in Heavy Equipment Electric / IC Engine Vehicles (Cranes, Earthmovers, Construction equipment, Forklifts, etc.), Battery Packs used in Hybrid Electric Vehicles (Micro, Full, Plug-in (PHEV)), Batteries used in Hydrogen Fuel Cell Electric Vehicles (FCEV), Batteries used in Energy Storage System (ESS) for Renewable Energy storage, Batteries used in Energy Storage System (ESS) for Power-backup in Domestic and Industrial Applications, Batteries used in portable Energy Storage Systems (ESS) for Applications like Service-vans, Ambulances, Mobile (Portable) Charging Stations etc.

[0043] The present invention discloses a hybrid system for thermal management of battery packs (1) with immersion and phase change techniques comprising at least one battery enclosure (2), at least one battery cell (4) configured to be at least partially immersed within a dielectric fluid (28) in the battery enclosure (2), at least one fluid circulation system (FCS) (6) configured to circulate the dielectric fluid (28) inside the battery enclosure (2) to facilitate uniform cooling of each of the battery cells (4), at least one heat sink (38) integrated with at least one phase change material (PCM) (30) configured be mounted on or be an integral-part of the battery enclosure (2), at least one immersed heating system (IHS) configured for heating the dielectric fluid (28), at least one external air flow system (EAFS) configured to be mounted at proximity of the external side of the battery enclosure (2) for cooling the heat sink (38) externally, plurality of temperature sensors to sense the temperature of battery cell (4), dielectric fluid (28), PCM (30), ambient air and a processor (18) configured to operate the FCS (6), IHS and EAFS based on the inputs received from the temperature sensors.

[0044] The present invention also discloses the FCS (6) is configured with a fluid circulation device (26), at least partially submerged in the dielectric fluid (28) for suction of fluid (28) through at least one flow channel and an outflow of said dielectric fluid (28) from said fluid circulation device (26) is configured through at least one outflow-channel (34), over the inner surface of the PCM heat sinks (30). The heat sink (38) is configured with an internal surface (12), an external surface (14) and PCM (30) sealed / enclosed between the said surfaces (12, 14). The internal surface (12) is configured to receive heat from the dielectric fluid (28) to transfer heat to the PCM (30). The PCM (30) is configured to absorb heat from the internal surface (12) and transfer heat to the external surface (14) for effective cooling of dielectric fluid (28). The PCM (30) is configured to change state from solid to liquid at a predefined temperature by receiving heat from the dielectric fluid (28) and change state from liquid to solid by releasing heat to the surrounding. The internal surface (12) of heat sink (38) is configured with a thermally conductive material constituted in the form of fins, pin-fins, dimples, extrusions, etc. for uniform conductive heat transfer and temperature distribution inside the PCM (30) for maximum heat storage capabilities. The external surface (14) of heat sink (38) is configured with a thermally conductive material constituted in the form of rectangular fins, parabolic fins, pin-fins, dimples, skived fins, tube-fins, louver fins, extrusions, etc. for convective and radiative heat transfer to the surrounding air. The internal surface (12) and external surface (14) are integrated with the PCM (30) or modularly attached by means of either of, or a combination of fasteners, rivets, structural / thermal adhesives, etc. The processor (18) constitute of microcontroller or microprocessor. The processor (18) is configured to turn ON the EAFS based on temperature of PCM Heat Sink (38) exceeding above a predetermined threshold value or based on the ambient temperature dropping below a predetermined threshold value to convert the state of PCM (30) from liquid to solid. The IHS is configured with at least one heating element (16) immersed in the dielectric fluid (28) to heat the dielectric fluid (28) in cold weather conditions. The processor (18) is configured to turn ON the IHS based on the temperature of battery cells (4) dropping below a predetermined threshold value. The processor (18) is configured to turn ON the FCS (6) based on the temperature of at least one battery cell (4) exceeding above a predetermined threshold value or based on the difference between the maximum and minimum temperature of different battery cells (4) exceeding above a predetermined threshold value. The battery pack (1) is configured with a drain port (22) mounted at the bottom of the battery enclosure (2) for removal of the dielectric fluid (28) and an inlet port (20) mounted on a battery enclosure lid (10) for refilling of new dielectric fluid (28). The battery pack (1) is configuredwith at least one pressure relief vent (24) mounted on top of the battery enclosure lid (10) to release all the gases generated inside the battery pack during thermal runaway events. The fluid circulation device (26) constitute of pumps, fans etc. The heating element (16) constitute of resistance wire-types, ceramic and semiconductor types, thick films (NTC / PTC) or polymer PTC types heaters. The PCM (30) is configured from any one of paraffin waxes, non-paraffin organics, hydrated salts or metallic. The dielectric fluid (28) is configured from one of the synthetic dielectric esters, Naphthenic based and Paraffinic based oils or Silicone Oils. The EAFS constitute of fans, blowers, air-pumps, etc. The FCS (6) and IHS are configured to be operated by the battery pack (1) or external power supply. The flow channel constitutes of spaces between battery-cells and enclosure, ducts, tubes, etc. and said outflow channel constitutes of orifices, nozzles, etc

[0045] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include the following:

[0046] Some embodiments of the present subject matter provide a system for thermal management of battery packs.

[0047] Some embodiments of the present subject matter provide a system for thermal management of battery packs by immersion cooling and phase change cooling.

[0048] Some embodiments of the present subject matter provide a system for thermal management of battery packs having an immersed heating system for heating the battery cells.

[0049] Some embodiments of the present subject matter provide a system for thermal management of battery packs having an external air flow system for cooling of battery pack.

[0050] Although implementations for a hybrid system for thermal management of battery packs with immersion and phase change techniques have been described in language specific to structural features and / or system, it is to be understood that the appended claims are not necessarily limited to the specific features or described. Rather, the specific features are disclosed as examples of implementations.

[0051] Figures 1-13 are now described using the reference numbers stated in the below table.

Claims

CLAIMS:

1. A hybrid system for thermal management of battery packs (1) with immersion and phase change techniques comprising: at least one battery enclosure (2); at least one battery cell (4) configured to be at least partially immersed within a dielectric fluid (28) in the battery enclosure (2); at least one fluid circulation system (FCS) (6) configured to circulate the dielectric fluid (28) inside the battery enclosure (2) to facilitate uniform cooling of each of the battery cells (4); at least one heat sink (38) integrated with at least one phase change material (PCM) (30) configured be mounted on or be an integral-part of the battery enclosure (2); at least one immersed heating system (IHS) configured for heating the dielectric fluid (28); at least one external air flow system (EAFS) configured to be mounted at proximity of the external side of the battery enclosure (2) for cooling the heat sink (38) externally; plurality of temperature sensors to sense the temperature of battery cell (4), dielectric fluid (28), PCM (30) and ambient air; and a processor (18) configured to operate the FCS (6), IHS and EAFS based on the inputs received from the temperature sensors.

2. The system as claimed in claim 1, wherein said FCS (6) is configured with a fluid circulation device (26), at least partially submerged in the dielectric fluid (28) for suction of fluid (28) through at least one flow channel and an outflow of said dielectric fluid (28) from said fluid circulation device (26) is configured through at least one outflow-channel (34), over the inner surface of the PCM heat sinks (30).

3. The system as claimed in claim 1, wherein said heat sink (38) is configured with an internal surface (12), an external surface (14) and PCM (30) sealed / enclosed between the said surfaces (12, 14).

4. The system as claimed in claim 1, wherein said internal surface (12) is configured to receive heat from the dielectric fluid (28) to transfer heat to the PCM (30).

5. The system as claimed in claim 1, wherein said PCM (30) is configured to absorb heat from the internal surface (12) and transfer heat to the external surface (14) for effective cooling of dielectric fluid (28).

6. The system as claimed in claim 1, wherein said PCM (30) is configured to change state from solid to liquid at a predefined temperature by receiving heat from the dielectric fluid (28) and change state from liquid to solid by releasing heat to the surrounding.

7. The system as claimed in claim 1, wherein said internal surface (12) of heat sink (38) is configured with a thermally conductive material constituted in the form of fins, pin-fins, dimples, extrusions, etc. for uniform conductive heat transfer and temperature distribution inside the PCM (30) for maximum heat storage capabilities.

8. The system as claimed in claim 1, wherein said external surface (14) of heat sink (38) is configured with a thermally conductive material constituted in the form of rectangular fins, parabolic fins, pin-fins, dimples, skived fins, tube-fins, louver fins, extrusions, etc. for convective and radiative heat transfer to the surrounding air.

9. The system as claimed in claim 1, wherein said internal surface (12) and external surface (14) are integrated with the PCM (30) or modularly attached by means of either of, or a combination of fasteners, rivets, structural / thermal adhesives, etc.

10. The system as claimed in claim 1, wherein said processor (18) constitute of microcontroller or microprocessor.

11. The system as claimed in claim 1, wherein said processor (18) is configured to turn ON the EAFS based on temperature of PCM Heat Sink (38) exceeding above a predetermined threshold value or based on the ambient temperature dropping below a predetermined threshold value to convert the state of PCM (30) from liquid to solid.

12. The system as claimed in claim 1, wherein said IHS is configured with at least one heating element (16) immersed in the dielectric fluid (28) to heat the dielectric fluid (28) in cold weather conditions.

13. The system as claimed in claim 1, wherein said processor (18) is configured to turn ON the IHS based on the temperature of battery cells (4) dropping below a predetermined threshold value.

14. The system as claimed in claim 1, wherein said processor (18) is configured to turn ON the FCS (6) based on the temperature of at least one battery cell (4) exceeding above a predetermined threshold value or based on the difference between the maximum and minimum temperature of different battery cells (4) exceeding above a predetermined threshold value.

15. The system as claimed in claim 1, wherein said battery pack (1) is configured with a drain port (22) mounted at the bottom of the battery enclosure (2) for removal of the dielectric fluid (28) and an inlet port (20) mounted on a battery enclosure lid (10) for refilling of new dielectric fluid (28).

16. The system as claimed in claim 1, wherein said battery pack (1) is configured with at least one pressure relief vent (24) mounted on top of the battery enclosure lid (10) to release all the gases generated inside the battery pack during thermal runaway events.

17. The system as claimed in claim 1, wherein said fluid circulation device (26) constitute of pumps, fans etc.

18. The system as claimed in claim 1, wherein said heating element (16) constitute of resistance wire-types, ceramic and semiconductor types, thick films (NTC / PTC) or polymer PTC types heaters.

19. The system as claimed in claim 1, wherein said PCM (30) is configured from any one of paraffin waxes, non-paraffin organics, hydrated salts or metafiles.

20. The system as claimed in claim 1, wherein said dielectric fluid (28) is configured from one of the synthetic dielectric esters, Naphthenic based and Paraffinic based oils or Silicone Oils.

21. The system as claimed in claim 1, wherein said EAFS constitute of fans, blowers, air- pumps, etc.

22. The system as claimed in claim 1, wherein said FCS (6) and IHS are configured to be operated by the battery pack (1) or external power supply.

23. The system as claimed in claim 1, wherein said flow channel constitutes of spaces between battery-cells and enclosure, ducts, tubes, etc. and said outflow channel constitutes of orifices, nozzles, etc.

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