DESC:FIELD OF INVENTION
The present invention generally relates to the field of electric vehicle charging systems, more particularly to a system and method for ultra-fast charging of Li-ion based battery packs. The primary focus of the present invention is to minimize cell degradation that occurs during fast charging, thereby preserving battery lifespan.
BACKGROUND OF THE INVENTION
In contemporary times, the phenomenon of range anxiety represents a significant obstacle in the widespread acceptance of electric vehicles among consumers. Range anxiety refers to the fear or uncertainty among consumers about the limited driving range of electric vehicles and the potential for running out of battery power during the journey. This psychological barrier can significantly impact the decision-making process of individuals considering the adoption of electric vehicles. To address and mitigate range anxiety, one suggested approach is to provide fast and convenient charging options, often referred to as eXtreme Fast Charging (“XFC”). In state-of-the-art technology, fast charging remains a challenge due to the faster degradation of cells, impacting the lifespan of batteries.
In the realm of Li-ion cells, contemporary lithium-ion batteries employ graphite as the anode material. During the charging process of such cells, the simultaneous occurrence of Li plating on the anode and Li intercalation into the anode takes place. While the latter is beneficial for storing energy, the former results in gradual cell degradation over time. Furthermore, achieving a charging time of less than 10 minutes necessitates a 6C charging rate, which can induce Li plating and consequently lead to a substantial reduction in cell’s lifespan alongside raising safety concerns. According to the reported data, the equivalent full cycle life (“EFC”) of a 25Ah automotive Li-ion decreased from 2500 cycles (at 1C charging) to 400 cycles (at 4C charging).
A research paper entitled “Asymmetric Temperature Modulation for Extreme Fast Charging of Lithium-Ion Batteries” by Yang et al, published in Joule Volume 3, Issue 12, December 2019, demonstrated that elevating the charging temperature effectively mitigates Li plating. This increase in temperature improves Li intercalation kinetics, solid-state diffusivity of graphite, and electrolyte conductivity, thereby suppressing the occurrence of Li plating. However, this heightened temperature also accelerates the growth of the solid-electrolyte-interphase (“SEI”), resulting in a loss of Li inventory and a subsequent reduction in cell capacity. Hence, it is crucial to avoid exposing the cells to elevated temperatures during discharge and storage to prevent excessive SEI growth. The Department of Energy, US has recognized both Li plating and the significant requirement of cooling during XFC as critical issues in battery technology.
In light of these findings, the thermal management of the battery packs plays a crucial role in elevating and maintaining cell temperature during XFC. In the XFC process, Joule’s heating results in a substantial generation of heat from the battery pack, leading to a potential risk of thermal runway if not efficiently managed. Thermal runaway poses a significant threat to battery safety, given its potential to cause overheating, fires, and explosions. Therefore, there is a necessity for a battery thermal management system to efficiently maintain the desired temperature throughout the entire charging and discharging cycle.
To address these challenges, the present invention introduces a Li-ion based battery pack that supports ultra-fast charging from 0 to =80% State of Charge (“SOC”) in 10 minutes with minimal cell degradation. The present invention recommends that adopting specific charging practices can contribute to an extended lifespan of the cell. This involves charging the battery at higher temperatures, within prescribed voltage limits and avoiding extremes in SOC. The present invention provides a Li-ion based battery pack with a battery thermal management system incorporating a forced immersion liquid (hereinafter, the terms "liquid" and "coolant" shall be used interchangeably) heating and cooling system through which the desired temperature can be maintained inside the battery pack throughout the effective full cycle. Coolants include, but are not limited to water, mineral oil, fuel, and other dielectric fluids. This collectively serves to minimize the occurrence of Li plating. Therefore, the present invention is designed to promote a more extended and sustainable life for the cell by addressing the challenges associated with lithium plating during the charging process.
VARIOUS PRIOR ARTS HAVE DISCLOSED SIMILAR SYSTEMS AND METHODS
Indian Patent Application IN202321057271 discloses a hybrid system for the thermal management of battery packs with immersion and phase change techniques. In this prior art, oil was used as a medium to transfer the heat from the battery pack to the phase change material (PCM) surrounding the battery enclosure. The stored heat in PCM is then released into the atmosphere through forced and natural air convection. Furthermore, the prior art depends on resistive heaters for heating which are present within the enclosure. The presence of oil, pump, PCM, resistive heaters, etc. in the battery pack increases the overall weight of the system thereby reducing the gravimetric and volumetric energy densities. It is pertinent to note that the present invention provides a Li-ion based battery pack with a thermal management system employing the forced immersion heating/ cooling technique. In this method, the hot/ warm/ cold liquid flows within an enclosure over an array of cells, maintaining the desired temperature during charging. Upon completion of charging, the cold liquid is passed through the enclosure to reduce the temperature of the battery pack to ambient conditions. Once the desired temperature is reached charging is completed, the liquid is drained completely from the pack. In addition, our present invention does not increase the mass of the battery pack, as the fluid flowing through the pack is drained out after the charging process (including cooling of the pack). Furthermore, major components of the battery thermal management system are mounted on the charging station instead of the vehicle, ensuring that there is no drop in the gravimetric and volumetric energy density of the battery pack.
US Patent Application US9527403B2 discloses a method for the thermal conditioning of Electric Vehicles during a charging session. In this prior art, the heating and cooling fluid flows through tubes in contact with the cells to heat/ cool them. This is a non-contact or indirect way of thermal management. It is important to highlight that the present invention provides a Li-ion based battery pack with a thermal management system employing forced immersion liquid heating techniques. In this system, the hot fluid circulates within the modular cell enclosure, making direct contact with the cell. Furthermore, in the aforementioned prior art, the tubes carrying the fluid increase the overall mass of the battery pack hampering the energy density. In contrast, the method proposed by the present invention strategically places major components of the battery thermal management system on the charging station rather than the vehicle. Hence, the elimination of BTMS on the vehicle prevents the increase in the overall mass and therefore, avoids any drop in the energy densities of the battery pack.
US Patent Application US11502341B2 discloses a battery fast charging and cooling system and method of operating. The heating technique mentioned in this prior art is through a heat spreader that will be in contact with the cells with the help of a heat spreader film. The heat transfer path from the source to the cell will be through the heat spreader. Also, the mentioned technique will require modification at the cell level. Furthermore, adding heat spreaders in the cell will increase its mass thereby reducing the gravimetric energy density. It is crucial to emphasize that the heating process proposed by the present invention is based on a forced liquid immersive thermal management system that eliminates thermal resistance between the heat source and the cell. Moreover, the present invention can be implemented on any type of cell irrespective of chemistry and geometry, without requiring modification and with no reduction in the gravimetric energy density.
To solve the aforementioned challenges in the prior art, the present invention introduces a system and method for ultra-fast charging of Li-ion based battery packs, aiming to mitigate the risk of lithium plating and thermal runaway during rapid charging. The battery thermal management system in the present invention focuses on thermal conditioning of the battery pack, ensuring rapid charging with minimal cell degradation. The present invention offers uniform heating and cooling of the battery pack with the help of the external pump that forces hot/ cold liquid to flow over the cells in the battery pack. Notably, in certain prior methods, the hot fluid or cold fluid from the external charging station does not come in direct contact with the cells of the battery pack. This makes the heat transfer from fluid to cell and vice versa less effective. The present invention provides a system that employs a pre-heating mechanism using a forced immersion liquid heating method to elevate the cell temperature to a desired level before charging. The present system utilizes fluid circulation to effectively regulate and maintain the desired temperature for each cell within a battery pack during various stages of the battery’s full cycle. In the present invention, the fluid from the external charging station comes in direct contact with the cells in the battery pack, making the heat transfer effective. The present system also allows any type of heat transfer liquid irrespective of its electrical conductivity (i.e. conductive as well as non-conductive). Moreover, the thermal management technique employed in this present invention offers the advantage of not increasing the mass of the battery pack as the fluid flowing through the pack is drained out after charging. Importantly, the key components of the BTMS are strategically installed in the charging station, while the battery pack is positioned on the vehicle. This setup is designed to avoid any additional weight to the battery thermal management system, thereby safeguarding the gravimetric and volumetric energy densities of the power pack. The present invention also empowers the battery management system to undertake corrective actions, addressing issues arising from lithium plating and preventing detrimental effects on battery performance.

OBJECTS OF THE INVENTION
• It is the main object of the present invention to provide a system and method for ultra-fast charging a Li-ion based battery pack, aiming to mitigate the risk of lithium plating and thermal runaway that occurs during rapid charging.
• It is the primary objective of this invention to provide a system and method for fast charging a Li-ion based battery pack, enabling swift charging from 0% to =80% SOC in less than 10 minutes.
• It is another object of the present invention to provide a battery thermal management system that includes a pre-heating mechanism using a forced immersion liquid heating system to elevate the cell temperature to a desired level before charging.
• It is another object of the present invention to provide a battery thermal management system that effectively regulates and maintains the optimal battery temperature during the charging process.
• It is another object of the present invention to provide a system and method that utilizes fluid circulation from BTMS to the battery pack, effectively controlling its temperature throughout different phases of an effective full cycle.
• It is another object of the present invention to provide a system and method that focuses on the thermal conditioning of the battery pack, ensuring rapid charging with minimal cell degradation.
• It is another object of the present invention to provide a battery thermal management system utilizing PID-controlled liquid immersion heaters to maintain the desired temperature in three liquid reservoirs: hot, warm, and cold.
• It is another object of the present invention to provide a battery thermal management system incorporating a forced immersion liquid cooling system, wherein cold liquid is passed through the Li-ion based battery pack after charging is completed to reduce its temperature to ambient conditions. Once the desired temperature of the pack is reached, the cold liquid is drained completely from the pack.
• It is another object of the present invention to provide a system in which the BTMS is installed in the charging station, while the battery pack is placed on the vehicle to ensure the gravimetric and volumetric energy densities of the power pack remain unaffected.
• It is another object of the present invention to provide the system to enable the battery management system to take corrective actions to resolve the issues raised due to lithium plating and prevent detrimental effects on battery performance.
SUMMARY OF THE INVENTION
The present invention discloses a system and method for ultra-fast charging of a Li-ion based battery pack that can accommodate any commercially available Li-ion cells without requiring cell modification. The present invention provides a battery system where the battery packs are assembled to power electric vehicles. The present system focuses on the thermal conditioning of the battery pack and facilitates rapid charging from 0 to =80% SOC within 10 minutes while ensuring battery longevity. The present invention incorporates a battery thermal management system for the battery pack, ensuring the maintenance of cell temperature throughout various phases of an effective full cycle. This comprehensive cycle includes heating, charging, rest, and cooling.
The present system features a battery enclosure designed to house the battery cells in a confined and modular arrangement. In the heating phase, the hot liquid is precisely pumped into this confined battery enclosure using a forced immersion heating system, ensuring its direct contact with the battery cells. This direct contact is crucial for effectively transferring heat to the cells and elevating their temperature.
After reaching the desired elevated temperature, the charging process is initiated with warm liquid pumped into the battery enclosure instead of hot liquid. This is to ensure that the heat generated during the charging process is removed from the pack while maintaining the desired elevated temperatures during charging. This is critical to avoid thermal runaway of the battery pack. Once charging is completed, the cold liquid is pumped into the cell enclosure using a forced immersion liquid cooling system to cool down the battery pack to ambient conditions. The present system accommodates any type of heat transfer fluid, regardless of its electrical conductivity. The battery enclosure provides a confined pathway for the coolant to extract the generated heat, preventing thermal runaway of the battery pack. Subsequently, the fluid flowing through the pack is drained out after the charging process is completed.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 provides a schematic illustration of the Battery Thermal Management System in accordance with the present invention.
Figure 2 displays a model of the modular enclosure featuring a) A single-cell battery pack and b) A 20-cell battery pack, in accordance with the present invention.
Figure 3 presents a flowchart illustrating the steps involved in the process carried out by the controller unit, in accordance with the present invention.
Figure 4 depicts the schematic layout of the overall system, showcasing the connections between the BTMS, controller unit, charging unit and battery pack in accordance with the present invention.
Figure 5 shows the arrangement of cells with O-rings inside a battery pack in accordance with the present invention.
Figure 6 presents a graph that depicts the state of health (SOH) in relation to the number of cycles in accordance with the present invention.
Provided below is the list of components of the present invention along with its reference numerals:
PART DESCRIPTION REFERENCE NUMERAL
Battery Pack 100
Battery Thermal Management System (BTMS) 102
Hot Liquid Reservoir 104
Warm Liquid Reservoir 106
Cold Liquid Reservoir 108
Thermocouple 110
Immersion Heater 112
2/2 DC Solenoid Valves 114
Y- Joint 116
Pump 118
Liquid Inlet 120
Liquid Outlet 122
Modular Enclosure 124
Top Cover 126
Bottom Cover 128
Li-ion Cell 130
Radiator 132
O-Rings 134
Controller Unit 136
Charging Unit 138
Input Protection Circuit 140
Output Protection Circuit 142
AC to DC Rectifier 144
Charging Gun 146
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of examples in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concept of the term appropriately to describe its own invention in the best way. The present invention should be construed as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, it should be understood that equivalents and modifications are possible.
DETAILED DESCRIPTION OF THE INVENTION WITH RESPECT TO THE DRAWINGS
The present invention as embodied by "System and method for ultra-fast charging of Li-ion based battery pack" succinctly fulfills the above-mentioned need(s) in the art. The present invention has objective(s) arising as a result of the above-mentioned need(s), said objective(s) being enumerated below. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/ or any functional equivalent(s) even though, such structural alternative(s) and/ or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation(s)/ modification(s) applied to the structural alternative(s)/ functional alternative(s) within its scope and purview. The present invention may be embodied in other specific form(s) without departing from the spirit or essential attributes thereof.
Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
The present invention provides a system and method for ultra-fast charging of Li-ion-based battery packs, addressing concerns related to lithium plating and thermal runaway that occurs during rapid charging. It features a Li-ion-based battery pack that can seamlessly accommodate any commercially available Li-ion cells without necessitating any cell modification. The present system focuses on the thermal conditioning of the battery pack and facilitates rapid charging from 0 to =80% SOC within 10 minutes while ensuring battery longevity. The present invention incorporates a battery thermal management system for the battery pack, ensuring the maintenance of cell temperature throughout various phases of an effective full cycle.
In the preferred embodiment of the present invention, as shown in Figure.1 the system consists of various building blocks such as a Battery Pack (100), a Battery Thermal Management System (102), a Controller Unit (136), and a Charging Unit (138).
In the preferred embodiment of the present invention, wherein the present invention provides a confined and modular cell enclosure (124), as shown in Figure 2, constructed from any material that can provide the required strength at high temperatures and is also inert to the working fluid. The present arrangement of the enclosure can accommodate any commercially available Li-ion cells (130). The cell (130) is positioned between the top and bottom covers (126, 128) and sealed with O-rings (134) at the terminals as shown in Figure 5. This arrangement facilitates a swift process for replacing cells in case of damage. A temperature sensor (thermocouple) (110) is fixed to the negative terminal of the cell to monitor the temperature of the battery pack (100) during the heating, charging, and cooling .
Figure 2 displays a model of the modular enclosure featuring: a) a single-cell battery pack and b) a 20-cell battery pack. The proposed design is modular in nature and can be assembled in any form factor to achieve the desired capacity.
In the preferred embodiment of the present invention, wherein the present invention employs the BTMS (102) to maintain the cell at the desired temperature during the various phases of an effective full cycle. It comprises PID-controlled liquid immersion heaters (112), working liquid reservoirs i.e. hot, warm, and cold (104, 106 & 108),
a thermocouple (110), a DC Pump (118), a DC Solenoid valve (114) and a radiator (132). The PID-controlled liquid heaters (112) are strategically placed in three liquid reservoirs (104, 106 & 108) and are responsible for maintaining the desired temperatures in the liquid reservoirs. A thermocouple (110) is used to measure the temperature of the liquid in reservoirs. The DC pump (118) facilitates the transfer of hot or cold liquid from the reservoir into the battery pack (100), while the DC Solenoid valve (114) guides the liquid flow from the reservoir to the battery pack (100), based on the instructions of the controller unit. The radiator (132) is used to remove excess heat from the battery pack (100) to maintain safe operating temperatures.
In the preferred embodiment of the present invention, wherein the controller unit (136) is designed to cut off the cell from the charging unit (138) and pump the cold fluid into the cell enclosure if the cell temperature exceeds a certain threshold. Similarly, when the charging current or voltage surpasses the predefined threshold values, the cell will be electrically isolated from the charging unit (138). This ensures the safety of the cells, preventing them from the thermal runaway.
The controller unit modulates the charging process of the Li-ion-based battery pack (100) in accordance with the pre-defined charging instructions as illustrated in the flowchart in figure 3 as mentioned below:
(i) When the charging gun (146) is connected to the battery pack (100), the controller unit (136) activates the battery thermal management system (102), circulating hot liquid (T1) to the battery pack (100).
(ii) The controller unit (136) monitors the temperature at the battery’s negative terminal to check if it has reached a threshold (T2), which is the minimum temperature required for efficient charging. If the battery’s negative terminal temperature has not yet reached T2, the controller unit (136) continues circulating hot liquid (T1) until the battery cells reach the required temperature (T2).
(iii) Once the battery pack (100) reaches the desired elevated temperature (T2), the charging process is initiated. Simultaneously, the controller unit switches valves to start pumping warm liquid (T3) to maintain optimal charging temperature and prevent overheating.
(iv) During charging, the controller unit (136) monitors the battery’s status to determine if cut-off criteria have been met. If these criteria are met, the controller unit (136) stops charging to prevent overcharging. It also switches the valves to circulate cold liquid (T4) to cool the battery pack (100) to ambient temperature. If the cut-off criteria have not been met, the system continues charging.
(v) After charging, the controller unit (136) checks if the negative terminal temperature of the battery pack (100) has cooled to ambient temperature. If the temperature has not yet reached ambient temperature, the controller unit (136) continues to pump cold liquid (T4) to the battery pack (100) until the desired temperature is achieved. Once the temperature reaches ambient, the controller drains the coolant from the battery pack.
(vi) The charging gun can then be disconnected from the vehicle.

Where,
• T1 is the temperature of the hot liquid used to warm the battery pack (100).
• T2 is the threshold temperature required to initiate charging.
• T3 is the temperature of the warm liquid used to maintain the optimal battery temperature during charging.
• T4 is the temperature of the cold liquid used after charging to cool the battery pack (100) down to an ambient temperature.
Therefore, T1>T2>T3>T4 represents the progressive temperature flow in the battery thermal management system during the charging process.
In the preferred embodiment of the present invention, wherein the charging unit (138), consists of an input protection circuit (140) and output protection circuit (142), AC to DC rectifier (144). The rectifier (144) and controller unit (136) together allow the cell to be charged at desired C ratings. The input protection circuit (140) safeguards the charging unit from potential power surges, voltage fluctuations, or other electrical anomalies that could damage the charger or the battery. The output protection circuit (142) prevents the battery from overcharging, over-voltage, or excessive current. The AC to DC rectifier (144) converts the alternating current (AC) from the power source into direct current (DC), which is the type of current required for charging the battery.
Figure 4 depicts the schematic layout of the overall system, showcasing the connections between the BTMS (102), controller unit (136), charging unit (138), and battery pack (100). As shown in Figure 4, the key components of the BTMS (102), along with the controller unit (136) and the charging unit (138) are strategically installed in the charging station, while the battery pack (100) is positioned on the vehicle, and the charging gun (146) serves as the handheld part of the charger, that connects the charger to the vehicle’s charging port. This setup is designed to avoid any additional weight to the battery thermal management system, thereby safeguarding the gravimetric and volumetric energy densities of the power pack. Moreover, the thermal management technique employed in this present invention offers the advantage of not increasing the mass of the battery pack as the fluid flowing through the pack is drained out after charging
In the preferred embodiment of the present invention, wherein the method for ultra-fast charging of Li-ion-based battery packs (100) comprises the following steps:
(i) Employing the Battery Thermal Management System (BTMS) (102) to maintain optimal cell temperatures during the effective full cycle, encompassing various phases such as heating, charging, and cooling;
(ii) PID-controlled liquid immersion heaters (112) in three reservoirs – hot, warm, and cold, maintain the three reservoirs at three different temperatures;
(iii) In the heating phase, the hot liquid is precisely pumped into the confined battery enclosure (124) using a forced immersion heating system, ensuring direct contact with the battery cells (130), which transfers heat to the cells (130) and elevating their temperature;
(iv) After reaching the desired elevated temperature of the battery pack, the charging process is initiated with warm liquid pumped to the battery pack (100) instead of hot liquid to take away the heat from the cells while maintaining the elevated temperatures;
(v) After the battery pack (100) is charged, the cold liquid is pumped into the cell enclosure (124) using a forced immersion liquid cooling system to cool the battery pack (100) to ambient temperatures;
(vi) Subsequently, the fluid flowing through the pack is drained out after charging;

EXAMPLE
The present invention provides (i) a Battery Pack (100), (ii) a Battery Thermal Management System (102), (iii) a Controller Unit (136), (iv) a Charging Unit (138), (v) the Battery Enclosure (124) which houses a plurality of Li-ion cells (130). BTMS (102) to maintain the cell at the desired temperature during the various phases of an effective full cycle. It comprises PID-controlled liquid immersion heaters (112), working liquid reservoirs i.e. hot, warm, and cold (104, 106 & 108), a thermocouple (110), a DC Pump (118), and a DC Solenoid valve (114). A thermocouple (110) is used to measure the temperature of the liquid in reservoirs. The DC pump (118) facilitates the transfer of hot or cold liquid from the reservoir into the cell enclosure (124) and vice versa, while the DC Solenoid valve (114) guides the liquid flow from the reservoir to the cell enclosure (124) and vice versa, based on the instructions from the controller unit. The method of charging the Li-ion cell at elevated temperatures comprises of:
• The PID-controlled liquid immersion heaters (112) are provided in three reservoirs – hot, warm, and cold (104, 106 & 108), which maintain the three reservoirs at three different temperatures.
• In the heating phase, the hot liquid is precisely pumped into the confined battery enclosure (124) using a forced immersion heating system, ensuring direct contact with the battery cells (130), which transfers heat to the cells (130) and elevates their temperature.
• After reaching the desired elevated temperature of the battery pack, the charging process is initiated with warm liquid pumped into the battery enclosure (124) instead of hot liquid to take away the heat from the cells while maintaining the elevated temperatures.
• After the battery pack (100) is charged, the cold liquid is pumped into the cell enclosure (124) using a forced immersion liquid cooling system to cool the battery pack (100) to ambient temperatures.
• Subsequently, the fluid flowing through the pack (100) is drained out after charging.
• The controller unit (136) is designed to cut off the cell from the charging unit (138) and pump the cold fluid into the cell enclosure (124) if the cell temperature exceeds a certain threshold to prevent thermal runaway.
• When the charging current or voltage surpasses the predefined threshold values, the cell will be electrically isolated from the charging unit.
Thus, the present invention provides a system and method for charging the Li-ion cell at elevated temperatures to suppress Li plating on the anode, thereby mitigating cell degradation. This process also enhances chemical kinetics, contributing to fast charging. It is crucial to avoid higher charging voltages to prevent electrical abuse. Furthermore, fast charging a cell to 100% SOC may have an adverse effect on the overall life expectancy of the cell. Balancing the need for rapid charging with the long-term health of the cell is a key consideration in the design and implementation of this present charging system.
EXPERIMENTAL RESULTS
Figure 6 illustrates a graph representing the state of health (SOH) plotted against the number of cycles, showing the impact of repeated charging and discharging on the overall health of the battery pack. As the number of cycles increases, the graph illustrates how SOH typically trends, offering insights into battery longevity and efficiency over time.
When the proposed BTMS is ON (represented by circles and a dotted line), the battery maintains a high SOH for a significantly greater number of cycles. Even after 2000 cycles, the battery’s SOH remains above 80%. When the proposed BTMS is OFF (represented by triangles and a steep dashed line), the battery’s SOH drops sharply within a few cycles, quickly decreasing to about 40% SO. This rapid decline indicates accelerated degradation without an effective thermal management system.
Thus, the present invention demonstrates rapid charging (0-80% SOC) of a Li-ion cell in 10 minutes with minimal degradation. It shows that charging the LFP cell at elevated temperatures suppresses Li plating on the anode, thereby mitigating cell degradation. It also enhances chemical kinetics and contributes towards fast charging. However, higher charging voltages should be carefully avoided to prevent electrical abuse. Also, fast charging a cell to 100% SOC has a negative impact on cell life.
ADVANTAGES OF THE PRESENT INVENTION
• Rapid charging with minimal cell degradation: The present system addresses the risk associated with lithium plating and thermal runaway during fast charging.
• Extended Battery Lifespan: The BTMS focuses on the thermal conditioning of the battery pack, which is crucial for extending the overall lifespan by mitigating Li-plating and the performance of the batteries.
• Uniform Heating and Cooling: The present system ensures uniform heating and cooling of the battery pack, promoting consistent and efficient temperature management across the pack.
• Compatibility with various heat transfer liquids: The present system allows the use of any type of heat transfer liquid, irrespective of its electrical conductivity.
• Separation of BTMS components from battery pack: The present system is designed in such a way that the major components of the BTMS (including pump, reservoir, radiator & coolant) are positioned in the charging station, preserving gravimetric and volumetric energy densities of the battery pack in addition to avoiding any system level complications within the pack.
• Scalability and adaptability: The present system is designed to accommodate any commercially available Li-ion cells without any modifications, providing scalability and adaptability to various battery pack configurations. This makes it suitable for a wide range of applications and vehicle types.
Although the proposed concept has been described as a way of example with reference to various models, it is not limited to the disclosed embodiment and that alternative designs could be constructed without deviating from the scope of invention as defined above.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the scope of the invention may be made by a person skilled in the art. ,CLAIMS:We Claim,
1. A System for ultra-fast charging of Li-ion based battery pack, comprising of:
(i) a Battery pack (100) with an enclosure (124) which comprises of plurality of Li-ion cells (130);
(ii) a Battery Thermal Management System (BTMS) (102) which maintains the desired temperature of the cells (130);
(iii) a Controller Unit (136) which is coupled to the BTMS (102), wherein the controller unit modulates the charging process of the battery pack (100) in accordance with the pre-defined charging instructions;
(iv) a Charging Unit (138) which is coupled to the controller unit (136) and is provided with an input and output protection circuit (140 & 142), AC to DC rectifier (144);
wherein the Battery Thermal Management System (BTMS) (102) maintains optimal cell temperatures during the effective full cycle, encompassing various phases such as heating, charging, and cooling.
2. The system as claimed in claim 1, wherein the BTMS (102) comprises of:
(i) PID-controlled liquid immersion heaters (112);
(ii) working liquid reservoirs i.e. hot, warm, and cold (104, 106 & 108);
(iii) a thermocouple (110), wherein the thermocouple (110) is used to measure the temperature of the liquid in reservoirs;
(iv) a DC Pump (118), which facilitates the transfer of hot or cold liquid from the reservoir into the cell enclosure (124) and vice versa;
(v) a DC Solenoid valve (114), which guides the liquid flow from the reservoir to the cell enclosure (124) and vice versa, based on the instructions from the controller unit;
(vi) a radiator (132), which is used to remove excess heat from the battery pack (100) to maintain safe operating temperatures;
3. The system as claimed in claim 2, wherein the PID-controlled liquid heaters (112) are strategically placed in three liquid reservoirs (104, 106 & 108), for maintaining the desired temperatures in the liquid reservoirs.

4. The system as claimed in claim 1, wherein the controller unit (136) and charging unit (138) allow the battery pack (100) to be charged at desired C ratings.

5. A method of working of the system as claimed in Claim 1, wherein the controller unit (136) modulates the charging process of the Li-ion-based battery pack (100), comprising the steps of:
(i) The PID-controlled liquid immersion heaters (112) are provided in three reservoirs – hot, warm, and cold, which maintain the three reservoirs at three different temperatures;
(ii) In the heating phase, the hot liquid is precisely pumped into the confined battery enclosure (124) using a forced immersion heating system, ensuring direct contact with the battery cells (130), which transfers heat to the cells (130) and elevating their temperature;
(iii) After reaching the desired elevated temperature of the battery pack (100), the charging process is initiated with warm liquid pumped into the battery enclosure (124) instead of hot liquid;
(iv) After the battery pack (100) is charged, the cold liquid is pumped into the cell enclosure (124) using a forced immersion liquid cooling system to cool the battery pack to ambient temperatures;
(v) Subsequently, the fluid flowing through the pack (100) is drained out after charging;
Wherein the heat generated during the charging process is removed from the pack while maintaining the desired temperatures during charging and thus preventing thermal runaway.

6. The method as claimed in claim 4, wherein the controller unit (136) is designed to cut off the cell from the charging unit and pump the cold fluid into the cell enclosure if the cell temperature exceeds a certain threshold to prevent thermal runaway.

7. The method as claimed in claim 4, wherein when the charging current or voltage surpasses the predefined threshold values, the cell will be electrically isolated from the charging unit.

8. The method as claimed in claim 4, wherein the method accommodates any type of heat transfer fluid, with any kind of electrical conductivity.