DESC:FIELD OF THE INVENTION:
This invention relates to the field of electronics and thermal engineering.

Particularly, this invention relates to cells and battery packs.

Specifically, this invention relates to a battery pack with an in-built refrigerant based thermal management system.

BACKGROUND OF THE INVENTION:
There are different approaches for thermal management of a battery pack based
on power consumption i.e. active thermal management systems and passive thermal management systems.

The active thermal management system consists of power consuming components such as pump, compressor, and / or fans.

The passive thermal management system consists of Phase Change Materials (PCM) or heat sinks to dissipate heat energy from battery into ambient environment and does not involve any power consuming components for heat transfer.

Based on type of coolant used, primary and secondary thermal management systems are main classifications.
In the primary type of thermal management systems, a primary coolant i.e. refrigerant is used directly to extract / add heat into the battery. The refrigerant is directly passed through aluminum cold plates.
In the secondary type of thermal management systems, the refrigerant first cools a secondary coolant like water-ethylene glycol or air and this secondary coolant then circulates inside the cold plates which are in thermal contact with the battery for heat extraction / addition.

The deficiencies, or drawbacks, in the prior art are as follows:
Most of the battery packs are thermally managed using water-ethylene glycol based / secondary cooling technique as mentioned above. These methods need additional heat exchangers for heat transfer between the refrigerant and the water-ethylene glycol coolant. After the water ethylene glycol mixture is cooled / heated, it is further passed into the heat exchanger plates, generally called as cold plates, which are in direct thermal contact with the cell body.
Also, an additional reservoir is required for storing the water-ethylene glycol coolant.
Each of these heat exchangers, used, adds on further inefficiencies in the system as well as causes pressure drop.
Also, the heat transfer rate is severely affected in case of weak thermal contact of the cell body with the cold plate which reduces the overall system efficiency for cooling / heating battery.
Thus, the major drawbacks associated with this technique is additional component requirement (heat exchanger plate), complex design of heat exchangers mainly, the heat exchanger plate and high thermal contact resistances.

The battery pack with passive air-cooling technique has external fins attached. In this case the heat is extracted using ambient air. The active air-cooling technique involves use of fan and heat sink arrangement to increase the heat transfer rate for effective heat dissipation. Also, for vehicle application that has cabin cooling / heating, cabin air is passed over the battery pack for heat extraction / addition. For all these techniques, the working fluid, for heat extraction, is air which is not in direct contact with the cells. Thus, the effective heat transfer rate is very low as compared to the liquid cooling technique. The passive air-cooling technique is, thus, suitable for smaller vehicle applications such as two wheelers where the heat load is substantially low and the available space and volume is very limited as compared to three-wheeler or four-wheeler applications.

Apart from the active and passive air based and liquid based thermal management techniques, there are, known in the art, Phase Change Materials (PCM) wherein the PCM material absorbs heat from the cells and changes its phase. This phase change is mostly from solid to liquid or liquid to gas. The PCM material is effective only within a certain range of temperature zone and is suited for applications wherein the heat load is less. Also, thermal conductivity of the PCM material is low and large amount of PCM material is required for effective heat dissipation leading to increasing in the battery weight and volume.

Therefore, there is a need to alleviate the problems of the prior art.

OBJECTS OF THE INVENTION:
An object of the invention is to provide a novel and inventive air based thermal management system with battery pack internal air as secondary coolant and refrigerant as the primary coolant.

Another object of the invention is to keep a battery operating within the safe temperature zone especially during fast charging and high current discharge conditions.

Yet another object of the invention is to provide a battery pack with better performance during charging and discharging process and to boost overall system efficiency of its thermal management system.

Still another object of the invention is to provide air cooling in terms of light weight and such that no additional heat exchanging parts as well as advantages of liquid cooling in terms of high heat transfer rate.

An additional object of the invention is to ensure temperature non-uniformity across the cells in battery pack is minimum.

SUMMARY OF THE INVENTION:
According to this invention, there is provided a battery pack with an in-built refrigerant based thermal management system.

The invention consists of a battery pack structure which houses cells, electronics, and thermal management components like evaporator, condenser, compressor, capillary etc. The invention comprises a system layout wherein heat exchangers are integrated within the battery to keep the battery operating within safe temperature zone/s especially during fast charging and high current discharge conditions. The system layout incorporates an intercooler arrangement which boosts thermal performance and efficiency of the thermal management system. Functioning of the circuit is controlled by a smart controller unit which takes inputs such as cell temperature, state of charge, battery current, cell, and battery voltages and, accordingly, controls speed of the compressor and fan.

The current invention addresses limitations, mentioned above, by integrating an active air-cooling system within the battery pack structure. This enables a secondary coolant i.e. air inside the battery pack to be in direct contact with cells which enhances heat transfer rate. Cell arrangement and baffles are designed for uniform cooling of cells. Thus, the current invention’s design has advantages of air cooling in terms of light weight and no additional heat exchanging parts as well as advantages of liquid cooling in terms of high heat transfer rate due to direct contact of the secondary coolant i.e. air with the cells.

Major aspects involved in thermal management system of battery packs include ensuring that cell temperature is maintained within 25-30 deg C temperature and temperature non-uniformity across the cells in battery pack is minimum i.e. less than 2 deg C at various operating conditions and ambient temperatures. Furthermore, the power consumption of the thermal management system is parasitic in nature i.e. the power required for the its functioning is taken from the battery pack itself, therefore the thermal management system should be smartly controlled to ensure that temperature objectives are fulfilled and, at the same time, power consumption is kept as minimum as possible. There are different techniques, mentioned above, to meet this objective such as active / passive cooling techniques, air / liquid cooling techniques, Phase Change Materials based cooling techniques etc. The current invention focusses on a novel and inventive air based thermal management system with battery pack internal air as secondary coolant and refrigerant as the primary coolant.

One of the most important aspects is to ensure effective contact between the secondary coolant and the target body i.e. the cells. For prior art liquid cooling systems, this contact is ensured by using heat exchangers and thermal interface materials. These heat exchangers comprise several flow channels in which the secondary coolant flows. These heat exchangers are then maintained in thermal contact with the cells using thermal interface materials like thermal paste, gel, or pads. The current invention needs no such involvement of heat exchangers and thermal interface materials since the secondary coolant is the air inside the battery pack itself. This air is cooled depending on the requirement and is recirculated inside the battery pack. Thus, advantage is achieved in terms of less heat exchanger parts, less system weight, less cost etc. The current invention’s design layout ensures air flows uniformly over all cells and temperature non-uniformity is within 2 deg C. As compared to the existing air based thermal management systems, the working coolant i.e. air is in thermal contact with heat sinks placed in the battery pack. Thus, the heat transfer rate is less in this case as compared to the liquid based thermal management system because of high thermal resistances. The current invention addresses this limitation by direct thermal contact of the secondary coolant i.e. air with the cells thereby achieving high heat transfer rates and at the same time less number of heat exchangers and less design complexity.

According to this invention, there is provided a battery pack with an in-built refrigerant based thermal management system comprising:
- a first zone (Zone A) being a cooling zone configured to host cells and electronics, said cells being grouped together to form modules;
- a second zone (Zone B) being a thermal management section configured to host a thermal management system, said second zone being a condensing section which is open to atmosphere, in that, said second zone consisting, essentially, of at least a Vapor Compressor Refrigeration Cycle (VCRS) cycle-based refrigeration circuit with a controller as configured to dynamically controls functioning of compressor speed; thereby, changing heat extraction capacity of the VCRS cycle as per temperature of cells; and
- said first zone (Zone A) being spaced apart from said second zone (Zone B), thermally and mechanically, by a partition wall.

In at least an embodiment, said second zone (Zone B) consisting, essentially, of a thermal management system which runs on vapor compression cycle/s.

In at least an embodiment, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of thermal cooling components (Zone B) being components selected from a group consisting of evaporator heat exchanger, condenser heat exchanger, compressor, condenser fan, evaporator fan, capillary coil, filter tube, intercooler heat exchanger, air filters, and fans.

In at least an embodiment, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of an evaporator and condenser heat exchanger, both forming a micro channel heat exchanger such that,
a. in said evaporator, heat exchange takes place between the refrigerant and the air inside the battery pack; and
b. in said condenser, heat exchange takes place between the refrigerant and ambient air.

In at least an embodiment, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of an evaporator and condenser heat exchanger, both forming a micro channel heat exchanger consisting, essentially, of:
- an inlet port for refrigerant;
- multiple tubes through which said refrigerant flows, said tubes being in contact with fins; and
- within each tube being provided are multiple microchannel flow structures of rectangular cross section, said refrigerant flowing through said microchannels and undergoing phase change process.

In at least an embodiment, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of an evaporator and condenser heat exchanger, in that, said condenser is a heat rejection section such that heat absorbed by a refrigerant, from said evaporator, is rejected out to ambient environment through use of a condenser fan and an intercooler.

In at least an embodiment, said second zone (Zone B) comprising a fan configured to suck out air from ambient environment and direct it towards a condenser heat exchanger so that heat rejection from the refrigerant takes place.

In at least an embodiment, said modules being clamped using endplates and a pressure pad being placed in between each cell to absorb stresses resulting from bulging of said cells.

In at least an embodiment, baffles are mounted on a lid of said battery pack, at an angular spacing of 120°, said 120° angular spacing divides total air volume inside said battery pack into three sections, said sections being operative left section, a second section being an operative right section, and a third section being an operative mid-section, on that, said operative left section and said operative right section being symmetric across a centre-line and contains equal number of cells.

In at least an embodiment,
- baffles are mounted on a lid of said battery pack at angular spacing so as to divide total volume of air into three section;
- cold and conditioned air, coming from an evaporator section, of said system’s thermal management system, being first channelized upwards, inside said battery pack, by fans;
- said cold and conditioned air channelized upwards by fans being redirected into the said sections though the baffles, in equal flow rates, because of their equal angular spacing;

In at least an embodiment, said Vapor Compressor Refrigeration Cycle (VCRS) cycle-based refrigeration circuit comprising:
- a compressor wherein the refrigerant is pressurized to a high pressure and high temperature gas which goes into a condenser heat exchanger through an inlet port in a header tube;
- micro channels for flow of said refrigerant such that heat rejection takes place rejected from said refrigerant to ambient air;
- outlet port for allowing said refrigerant to come out before being passed into a capillary tube wherein flashing takes place and a high temperature high pressure refrigerant is converted to low temperature and low-pressure liquid state;
- an evaporator heat exchanger for receiving said refrigerant to be passed through it and back to said compressor; and
- an intercooler system, being an intermediate heat exchanger in which heat exchange takes places between the condensed water and high pressure, high temperature refrigerant line from the condenser, said intercooler system being configured to cool said refrigerant coming out from said condenser heat exchanger, said cooling being done by condensate water obtained in an evaporative section, said evaporator section comprising fans for recirculation of cold air inside said battery pack, with cold air flowing in between said cells and its flow being governed by baffles.

In at least an embodiment, said compressor being located adjacent to a condenser of said condensing section, such that, incoming airflow used to cool said condenser, also cools said compressor, in that, slots being provided in a casing of said condenser section and on an outer casing; thereby, acting as a gateway for ambient airflow into said condenser section for, further, cooling cells.

In at least an embodiment, slots being provided in an outer casing of said evaporator section ; thereby, acting as a gateway for cooled and conditioned airflow from the said evaporator section for into said first zone (Zone A) for further cooling of cells.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:

Figure 1a illustrates a front isometric view of a battery pack layout with Zone A and B;
Figure 1b illustrates a back isometric view of a battery pack layout with Zone A and B;
Figure 2 illustrates a thermal management system layout for the battery pack;
Figure 3 illustrates cell arrangement for the battery pack;
Figure 4 illustrates microchannel heat exchanger for the battery pack;
Figure 5 also illustrates cell arrangement for the battery pack;
Figure 6 represents the flowchart of the controller logic;
Figure 7 illustrates complete flowchart of working of this invention;
Figure 8A illustrates thermal imaging during the experimentation;
Figure 8B illustrates that battery temperature is maintained ~25-30 deg with ~45 deg ambient air and 1C discharge rate;
Figure 9 illustrates test data vide a non-limiting exemplary embodiment, of the working of this current invention, with 0.66 Discharge Test at 45deg C Ambient Temperature; and
Figure 10 illustrates temperature profile versus time at 0.66C discharge rate.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a battery pack with an in-built refrigerant based thermal management system.

Figure 1a illustrates a front isometric view of a battery pack layout with Zone A and B.
Figure 1b illustrates a back isometric view of a battery pack layout with Zone A and B.

The battery pack, of this invention, consists an in-built refrigerant-based thermal management unit.

In at least an embodiment of this invention, the battery pack is divided into two major zones: Zone A and Zone B.
In at least an embodiment of Zone A, it comprises cells, electronics, busbars, wire harness. The Zone A is a cooling zone wherein the cells and electronics are located.
In at least an embodiment of Zone B, it comprises of the thermal management system components such as evaporator heat exchanger, condenser heat exchanger, compressor, and fans. The Zone B is a condensing section which is open to atmosphere. Inside Zone B, a fan sucks air from ambient environment and directs it towards the condenser heat exchanger so that heat rejection from the refrigerant takes place.
In the battery pack, of this invention, a Vapor Compressor Refrigeration Cycle (VCRS) cycle-based refrigeration circuit is made.

In at least an embodiment, Zone A and Zone B is thermally and mechanically isolated by a partition wall 1. The Vapor Compressor Refrigeration Cycle (VCRS) cycle-based refrigeration circuit starts from a compressor 9 wherein a refrigerant goes into the condenser heat exchanger 8 through an inlet port 24 in a header tube 22. The refrigerant flows through micro channels 21 and heat rejection takes place rejected from the refrigerant to the ambient air. The refrigerant, subsequently, comes out of the outlet port 25 and is passed into a capillary tube 11 wherein flashing takes place and a high temperature high pressure refrigerant is converted to low temperature and low-pressure liquid state. Subsequently, it is passed into an evaporator heat exchanger 12 and then back into to the compressor 9, the cycle then repeats itself. An intercooler system 11 is designed which cools the refrigerant coming out from the condenser heat exchanger 8. This cooling is done by the condensate water obtained in the evaporative section. The evaporator section comprises fans 15, 16, and 17 for recirculation of cold air inside the battery pack. The cold air flows in between the cells and its flow is governed by the baffles 18, 19, and 20.

Figure 1c illustrates a detailed view of the thermal management system.
Figure 2 illustrates a thermal management system layout for the battery pack.

Zone B consists of a thermal management system which runs on vapor compression cycle/s. The components, of the thermal management system, are compressor, condenser fan, condenser, evaporator fan, evaporator, capillary coil, filter tube, intercooler, air filter, and controller. The evaporator and condenser heat exchanger are micro channel heat exchanger. In evaporator, the heat exchange takes place between the refrigerant and the air inside the battery pack. Whereas the on condenser the heat exchange takes place between the refrigerant and ambient air. The intercooler system is an intermediate heat exchanger in which heat exchange takes places between the condensed water and high pressure, high temperature refrigerant line from the condenser. Whereas as Zone A consists cells grouped together in form of modules and mounting channels for fixing the battery modules into the battery casing.

The primary coolant used in this system is, preferably, refrigerant R134a. The condensing section, as shown in Fig 1C, is a heat rejection section. Heat absorbed by the refrigerant, from the evaporator section, is rejected out to ambient environment through the use of a condenser fan and an intercooler.
The compressor also generates heat during its operation. The placement of the compressor is kept in such a way that airflow, through the condenser, also cools the compressor. Slots observed in the casing of the condenser section, on the outer casing, serves as a gateway for ambient airflow into the condenser section. The slot size, placement, and its total quantity is kept in such a way that the pressure loss is minimum. Similarly, the evaporator section is shown in Fig 1C.
The evaporator section mainly houses the evaporator and its fan. Slots observed in the outer casing of the evaporator section are serves as gateways for the air inside the battery pack. The air inside the battery pack is sucked in at the evaporator section and heat is extracted out of it resulting in the decrease of its temperature. Then this cold air is channeled onto each of the cells to effectively cool the cells.

The cycle begins with liquid low pressure and low temperature at the inlet of the evaporator. This liquid refrigerant absorbs latent heat by extracting this heat from the air inside the battery pack and transforms into gaseous state. This low pressure – low temperature gaseous refrigerant then goes into the compressor wherein it gets compressed into high temperature and high-pressure gas which in turn is passed into a condenser heat exchanger. In the condenser, heat is rejected from the refrigerant into the ambient. This latent heat rejection results into liquid refrigerant at high pressure and temperature at the outlet of the condenser. The refrigerant is further subcooled using an intercooler arrangement wherein the condensate water from the evaporator section exchanges heat with the high pressure and high temperature refrigerant. In this process the condensate water evaporates and there is a slight decrease in the temperature of the liquid refrigerant which is termed as subcooling. The subcooled refrigerant then enters into the capillary. wherein which is very small diameter tube. In the capillary there is a sudden pressure drop and a portion of refrigerant evaporates known as flashing of gas. The energy required for flashing is supplied by the refrigerant itself therefore it rapidly reduces the temperature of the refrigerant. Once the refrigerant is at the outlet of the capillary tube it is majorly in liquid state with very low temperature and pressure along with some portion in the gaseous state. This refrigerant is charged into the evaporator section again and the cycle repeats.
The controller as shown in Fig 1C is placed on the lid of the outer casing. It dynamically controls functioning of the compressor speed; thereby, changing volume flow rates of the refrigerant as per the temperature of the cells. The variable speed operation by the controller also results into optimised power consumption of the system thereby making the thermal management system very efficient from energy consumption point of view.

In at least an embodiment, of the invention, the evaporative cooling-based intercooler 11 is discussed further. The temperature of the evaporator heat exchanger is less than dew point temperature of ambient air. This results into condensation of water vapour inside the evaporator section. The invention consists of a design layout wherein all the condensate water is directly subjected to thermal contact with the refrigerant line emerging from the condenser heat exchanger as shown in Fig 2. Based on the principle of evaporative cooling, the condensate water evaporates by taking heat from the hot refrigerant line. Thus, it achieves two-fold benefits:
1) Condensed water from the evaporator section is removed;
2) Heat rejection from the refrigerant in the condenser section is increased.
The latter increases the Coefficient of Performance (COP) of the system.
Benefits obtained include:
- Removal of water condensation inside battery pack by evaporation process;
- Increase in system efficiency due to subcooling of refrigerant inside condenser section.

Figure 3 illustrates cell arrangement for the battery pack.
Figure 5 also illustrates cell arrangement for the battery pack.

The cold air from the evaporator is circulated uniformly to all cells by the fans and baffles. Heat extracted from the cells by the cold air is transferred to the refrigerant in the evaporator section.

As shown in Figure 2. The Zone A is the section which is allotted for the placement of the cells. The Zone A is compatible with cells of all form factors, dimensions, geometrical sizes and shapes and chemistry. As shown in Fig 3, we can see the prismatic cells mounted in the Zone A.

As shown in Figure 5, the arrangement of cells is done in a systematic manner to arrest the bulging of the cells and vibrations thereby making the battery pack sturdy to sustain harsh on road conditions. The cells are first categorized and grouped together in the form of module/s. Each of these modules are properly clamped using endplates and a special purpose foam, named as pressure pad, is placed in between each cell to which absorbs stresses resulting from the bulging of the cells. These modules are bolted on the pack casing using nut and bolt arrangement. The baffles are the guideways for the flow of air. The cold air from the evaporator section is directed by the baffles uniformly throughout the battery pack.

Cold and conditioned air, coming from the evaporator section, is first channelized upwards, inside the battery pack, by fans 15, 16, and 17. The baffles (18, 19, 20) are mounted on a lid of the battery pack, at an angular spacing of 120°, as shown in Figure 5. The 120° angular spacing divides total air volume inside the battery pack into three sections. The cold and conditioned air channelized upwards by fans is redirected into the three sections though the baffles (18, 19, 20), in equal flow rates, because of their equal angular spacing. Each of these three sections, shown in Figure 3, is namely divided into a first section being an operative left section, a second section being an operative right section, and a third section being an operative mid-section. The operative left section and the operative right section are symmetric across a centre-line and contains equal number of cells. The baffles (18, 19, 20) channelize air flow equally into the operative left section and the operative right section for uniform cooling of all cells.

Figure 4 illustrates microchannel heat exchanger for the battery pack.

The details of the microchannel heat exchangers are shown in Fig4. The inlet port of the refrigerant is 24. There are multiple tubes 22 through which the refrigerant flows, these tubes are in contact with the fins 27. Within each tube there are multiple microchannel flow structures 21 of rectangular cross section as shown. The refrigerant flows through these microchannel and undergoes the phase change process. The flow of refrigerant inside microchannel heat exchanger is shown by the arrows.

In at least an embodiment, of the invention, the micro channel heat exchanger 8 is discussed further. The heat exchanger 8 of microchannel 21 cross section is implemented. The design parameters of the heat exchangers that are optimized are the channel cross section, number of channels in a tube, number of tubes, header and baffle placement as shown in Figure 4.
Benefits obtained include:
- Compact Sizing and Lightweight;
- Reduced pressure drop;
- High heat transfer rate

In at least an embodiment, of the invention, a BTMS Controller for variable speed compressor is discussed further. The BTMS controller functions based on the temperature of the cells, battery current, battery state of health, battery state of charge, battery and cell voltage. All these battery parameters are inputs to the controller which the controller analyses and controls the compressor speed accordingly.

When the heat load is high, the compressor speed is changed by the controller. For high heat loads, the compressor functions at high speed and vice versa. Since the compressor is the most power consuming component, the controller algorithm ensures that its functioning is such that the average power consumption of compressor is reduced. The controller algorithm also predicts hazard events like thermal runaway/fire and generates alerts and action items such as turning off the main power line to avoid propagation of fire.

Figure 6 illustrates a schematic block diagram of battery pack components according to this invention.
Figure 7 illustrates a flowchart depicting controller logic for the system of this invention.
The controller algorithm is based on a set of technical parameters that is provided real time by the Battery Management System (BMS) Figure 5. These technical parameters which are provided as an input to the controller algorithm are as follows:
1) Cell voltages
2) Battery pack voltage
3) Battery pack current
4) Battery State of Charge (SOC)
5) Battery State of Health (SOH)
6) Cell temperature values.

The parameters mentioned above are logged by BMS and are transmitted to the Battery Thermal Management Controller via CAN (Controller Area Network) Line. The Battery Thermal Management Controller process these inputs from the BMS and generates output signals which controls the speed of the compressor. There is a two-way communication between the Battery Thermal Management Controller (BTMC) and Battery Management System (BMS) as signified by the bi directional arrow which enables the BTMC Controller to either turn off/on the BMS based on the controller logic.

Besides the parameters mentioned above other thermal specific parameters that the BTMC monitors are:
1) Evaporator temperature
2) Compressor temperature
Based on the input parameters mentioned above the microcontroller governs the speed of the compressor. As shown in the Figure 6, the first step is the voltage checking process and post successful completion the evaporator fan is immediately turned ON. Based on the cell temperatures, voltages, battery current and State of Charge (SOC) governs the speed of the compressor. The compressor is made to operate at a default speed for a set time value and then it adjusts the speed as per the dynamic operating conditions of the cells. The compressor functioning is stopped in case the evaporator temperature reaches below the lower cut-off limit of the evaporator. This is done to prevent frosting and icing at the evaporator section. Also, once all the cell temperatures are within the desired temperature limit, the compressor is turned OFF. Based on the cell temperature values and the battery State of Health (SOH), temperature gradient is calculated and 1D thermal circuit model is computed to predict the instances of thermal runaway incident. Each of the parameters mentioned above is allocated a weightage factor which is used to calculate the probability of thermal runaway event. Once high probability of thermal runaway is observed, then the BMS is immediately notified and the power circuit is cut off.
Figure 6 represents the flowchart of the controller logic. The terminologies are explained below:
• Lower cut-off limit of evaporator: The temperature cut-off limit of the evaporator below which the compressor is turned OFF.
• Upper cutoff limit of compressor: The temperature cut off limit of compressor above which the compressor is turned OFF
• Lower cutoff limit of cell: The temperature cutoff limit of cell below which the compressor is turned OFF

The current invention is applicable for all types of cell geometries like cylindrical, pouch and prismatic.

Figure 8A illustrates thermal imaging during the experimentation.
The following observations can be made:
- Average Temperature of battery pack: 30.5@0.5C charging rate
- Inlet Coolant air temperature: 23-25 deg C

The test data for multiple such tests are plotted in the further figures.

Figure 8B illustrates that battery temperature is maintained ~25-30 deg with ~45 deg ambient air and 1C discharge rate.

Figure 9 illustrates test data vide a non-limiting exemplary embodiment, of the working of this current invention, with 0.66 Discharge Test at 45deg C Ambient Temperature.

Figure 10 illustrates temperature profile versus time at 0.66C discharge rate.

Observation: Cell Average temperature is maintained between 28-30deg C with ambient air temperature as high as 45-50deg C at 0.6C rate.
Conclusion: The battery pack with inbuilt refrigerant based thermal management system is able to perform at the desired objectives.

TECHNICAL ADVANTAGES:
1) Reduced power consumption by compressor;
2) Battery health and performance is improved because the invention ensures that battery is operated within the ideal temperature range;
3) Predictive and preventive thermal runaway algorithms enhances vehicle and battery safety;
4) Removal of condensed water through inter cooler heat exchanger;
5) Microchannel heat exchangers for superior heat transfer, compact size and light weight;
6) Smart Controller which ensures minimum power consumption for the functioning of the unit.

The TECHNICAL ADVANCEMENT, of this invention, lies in providing an air based thermal management system with battery pack’s internal air as secondary coolant and refrigerant as the primary coolant. This battery pack is configured to integrate the active air-refrigerant based thermal management system within the battery pack structure. It ensures effective contact between the secondary coolant and the target body i.e. the cells. The current invention provides a layout which ensures that the air inside the battery pack acts as secondary coolant and is in thermal contact with cells placed in the battery pack.

The TECHNICAL ADVANCEMENT, of this invention, also lies in provided a design which has advantages of air cooling in terms of light weight and no additional heat exchanging parts as well as advantages of liquid cooling in terms of high heat transfer rate due to direct contact of the secondary coolant i.e. air with the cells. Furthermore, the current invention’s design layout ensures air flows uniformly over all cells and temperature non-uniformity is within 2 deg C.

While this detailed description has disclosed certain specific embodiments for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

,CLAIMS:WE CLAIM,

1. A battery pack with an in-built refrigerant based thermal management system comprising:
- a first zone (Zone A) being a cooling zone configured to host cells and electronics, said cells being grouped together to form modules;
- a second zone (Zone B) being a thermal management section configured to host a thermal management system, said second zone being a condensing section which is open to atmosphere, in that, said second zone consisting, essentially, of at least a Vapor Compressor Refrigeration Cycle (VCRS) cycle-based refrigeration circuit with a controller as configured to dynamically controls functioning of compressor speed; thereby, changing heat extraction capacity of the VCRS cycle as per temperature of cells; and
- said first zone (Zone A) being spaced apart from said second zone (Zone B), thermally and mechanically, by a partition wall (1).

2. The system as claimed in claim 1 wherein, said second zone (Zone B) consisting, essentially, of a thermal management system which runs on vapor compression cycle/s.

3. The system as claimed in claim 1 wherein, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of thermal cooling components (Zone B) being components selected from a group consisting of evaporator heat exchanger, condenser heat exchanger, compressor, condenser fan, evaporator fan, capillary coil, filter tube, intercooler heat exchanger, air filters, and fans.

4. The system as claimed in claim 1 wherein, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of an evaporator and condenser heat exchanger, both forming a micro channel heat exchanger such that,
a. in said evaporator, heat exchange takes place between the refrigerant and the air inside the battery pack; and
b. in said condenser, heat exchange takes place between the refrigerant and ambient air.

5. The system as claimed in claim 1 wherein, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of an evaporator and condenser heat exchanger, both forming a micro channel heat exchanger consisting, essentially, of:
- an inlet port (24) for refrigerant;
- multiple tubes (22) through which said refrigerant flows, said tubes (22) being in contact with fins (27); and
- within each tube being provided are multiple microchannel flow structures (21) of rectangular cross section, said refrigerant flowing through said microchannels and undergoing phase change process.

6. The system as claimed in claim 1 wherein, said second zone (Zone B) consisting, essentially, of a thermal management system consisting, essentially, of an evaporator and condenser heat exchanger, in that, said condenser is a heat rejection section such that heat absorbed by a refrigerant, from said evaporator, is rejected out to ambient environment through use of a condenser fan and an intercooler.

7. The system as claimed in claim 1 wherein, said second zone (Zone B) comprising a fan configured to suck out air from ambient environment and direct it towards a condenser heat exchanger so that heat rejection from the refrigerant takes place.

8. The system as claimed in claim 1 wherein, said modules being clamped using endplates and a pressure pad being placed in between each cell to absorb stresses resulting from bulging of said cells.

9. The system as claimed in claim 1 wherein, baffles (18, 19, 20) are mounted on a lid of said battery pack, at an angular spacing of 120°, said 120° angular spacing divides total air volume inside said battery pack into three sections, said sections being operative left section, a second section being an operative right section, and a third section being an operative mid-section, on that, said operative left section and said operative right section being symmetric across a centre-line and contains equal number of cells.

10. The system as claimed in claim 1 wherein,
- baffles (18, 19, 20) are mounted on a lid of said battery pack at angular spacing so as to divide total volume of air into three section;
- cold and conditioned air, coming from an evaporator section, of said system’s thermal management system, being first channelized upwards, inside said battery pack, by fans (15, 16, and 17);
- said cold and conditioned air channelized upwards by fans (15, 16, and 17) being redirected into the said sections though the baffles (18, 19, 20), in equal flow rates, because of their equal angular spacing;

11. The system as claimed in claim 1 wherein, said Vapor Compressor Refrigeration Cycle (VCRS) cycle-based refrigeration circuit comprising:
- a compressor (9) wherein the refrigerant is pressurized to a high pressure and high temperature gas which goes into a condenser heat exchanger (8) through an inlet port (24) in a header tube (22);
- micro channels (21) for flow of said refrigerant such that heat rejection takes place rejected from said refrigerant to ambient air;
- outlet port (25) for allowing said refrigerant to come out before being passed into a capillary tube (11) wherein flashing takes place and a high temperature high pressure refrigerant is converted to low temperature and low-pressure liquid state;
- an evaporator heat exchanger (12) for receiving said refrigerant to be passed through it and back to said compressor (9); and
- an intercooler system (11), being an intermediate heat exchanger in which heat exchange takes places between the condensed water and high pressure, high temperature refrigerant line from the condenser, said intercooler system (11) being configured to cool said refrigerant coming out from said condenser heat exchanger (8), said cooling being done by condensate water obtained in an evaporative section, said evaporator section comprising fans (15, 16, and 17) for recirculation of cold air inside said battery pack, with cold air flowing in between said cells and its flow being governed by baffles (18, 19, and 20).

12. The system as claimed in claim 1 wherein, said compressor being located adjacent to a condenser of said condensing section, such that, incoming airflow used to cool said condenser, also cools said compressor, in that, slots (6) being provided in a casing of said condenser section and on an outer casing; thereby, acting as a gateway for ambient airflow into said condenser section for, further, cooling cells.

13. The system as claimed in claim 1 wherein, slots (3) being provided in an outer casing of said evaporator section ; thereby, acting as a gateway for cooled and conditioned airflow from the said evaporator section for into said first zone (Zone A) for further cooling of cells.

Dated this 27th day of February, 2023

CHIRAG TANNA
of INK IDÉE
APPLICANT’S PATENT AGENT
REGN. NO. IN/PA - 1785