Title
Hybrid Battery thermal management system with liquid channel and nano doped Phase change material for effective cooling.
Field of Invention
The present invention uses hybrid battery thermal management in which the battery module was inserted in a paraffin wax enhanced with AI2O3 nanoparticle pack and a coolant was circulated through a copper coil around the battery. From this, we can prevent the rises of temperature in the battery module and enhance the performance of the battery. Background of Invention
At present world, increase of carbon emission by Internal Combustion (IC) engines and sudden rises of the petrol and diesel rates become the crucial problem. So, the whole world turns toward electric vehicle usage which is zero carbon emission. In the present budget 2022, Indian government stated the battery swapping policy which will help to improve the electric vehicle usage among the people. Compare to four-wheeler and three-wheeler vehicles, two-wheeler vehicle usage is more in India. The fuel to electric vehicle is Li-ion battery which power the motor. The major drawback in Li-ion battery is increase of temperature beyond the critical level of 20°C-40°C during higher charge or discharger rate. Moreover, the temperature should be within the operating level to enhance the efficiency and lifetime of the Li-ion battery. To manage the temperature within operating level, battery thermal management should be implemented to the electric vehicle. The two main classification of battery thermal management are passive and active thermal management. Mostly, Phase change material is used in passive thermal management system. The major advantage of passive method is no external energy source added to the system for cooling or heating the battery. For active method, the cooling of battery is perform using water circulation, air flow inside the battery pack etc. Active method shows faster cooling rate than the passive method; This experiment integrates the advantage of both active and passive method, to build a hybrid battery thermal management system. The main aim of this experiment is to maintain the temperature of the battery in an operating limit within 20°C to 40°C. By using a hybrid battery thermal management system, the temperature of the lithium-ion battery 18650 model is to be maintained in an operating range to ensure the safety and the life of the battery in electric vehicles. To enhance the property of paraffin in the passive method, AI2O3 nanoparticles can be added with paraffin in three different ratios of 5%, 10%, and 15% and for the active method, the water was

circulated in a counter flow direction through the copper coil. In this study, several investigational analyses were carried out such as free convection, PCM (only paraffin), PCM (paraffin) with AI2O3 (5%, 10%, and 15%), and hybrid (both active and passive). Each investigation was carried out under different C rates (0.5 C, 1 C, 2C, 3C). Then the comparison is made for the results derived from this investigation.
SUMMARY OF THE INVENTION
By using hybrid battery thermal management, we can utilize the advantage of both active and passive methods. In this present investigation on hybrid battery thermal management, the copper coil was inserted into the passive pack paraffin enhanced with 10% AI2O3 and the water has been supplied through the copper coil. In this experimental study at different C rates in different conditions, the hybrid battery thermal management containing both active and passive methods show good performance in thermal management when compared to the other thermal management methods..It can minimize the temperature of the battery system in a superior manner to other battery thermal management. To maintain the temperature of the battery in an operating range. This hybrid battery thermal management will be a suitable choice to avoid the failure of the battery system in Electric vehicles.
DETAIL DESCRIPTION OF FIGURES AND TABLES
The figures and tables are used to understand further knowledge about the invention. The
details of the figures and tables are described below,
Table 1: Specifications of Li ion battery
Figure 1: Battery Connection and charging device setup.
Figure 2: Circuit diagram of charging setup
Figure 3: Discharge lamp and pattern
Figure 4.1: 3D wire model of hybrid battery thermal management system
Figure 4.2: 3D model of hybrid battery thermal management system
Figure 4.3: Die for hybrid battery thermal management system
Figure 5: Paraffin wax and Samples SI, S2 and S3 for Test Condition
Figure 6: FT-IR graph of Paraffin wax and Samples SI, S2 and S3
Table 2: Properties of AI2O3 Nano-particles
Table 3: Properties of paraffin wax
Figure 7: Preparation of Hybrid BTMS setup
Figure 8: Pump and liquid cooling system

Table 4: C rate and their explanation
Figure 9: Investigation on Natural convection at 0.5C
Figure 10: Investigation on Passive BTMS PARAFFIN WAX + AI2O3 PACK AT 0.5C
Figure 11: Investigation on Hybrid BTMS pack at 3C
Table 5: Maximum temperature value for various investigation
DETAIL DESCRIPTION OF THE INVENTION
In this invention setup, the battery module consists of fifteen cylindrical Li ion cells. The specifications of Li ion cells are listed in Table 1. In this module all the Li ion cells are placed vertically and connected in 3 series and 5 parallel (3s 5p) configuration in order to sum up the voltage of each cell. The charging of Li ion battery consists of 12V transformer and a bridge rectifier circuit as shown in figure 1. The charging setup circuit has a transformer to step down the 230V AC voltage into a 12V AC voltage which is then converted into a unidirectional pulsating DC voltage by the four diodes shown in figure 2.
The 12V DC, 50-Watt discharging lamp are used to discharge the Li ion battery. The discharging lamp used for the invention is shown in figure 3. In this invention, the discharging process is carried out at various rates are listed in Table 4. The discharging condition at various C rates are 0.5 C - Single 12 V DC 50-Watt lamp connected as a discharging load to the batteries, 1 C- Two 12 V DC 50-Watt lamps connected as a discharging load to the batteries, 2 C- Four 12 V DC 50-Watt lamps connected as a discharging load to the batteries. 3 C- Six 12 V DC 50-Watt lamps connected as a discharging load to the batteries.
The Li-ion cells are inserted in the Paraffin wax which is used as Phase change material (PCM). Phase change material helps in storing and releasing the large amount of heat during solidifying and melting at a fixed point. During the period of melting, heat is absorbed and stored as latent heat by PCM up to the maximum without any increase in temperature.
Paraffin has low thermal conductivity and also low specific heat capacity. To enhance this property of paraffin, Nano particles like AI2O3 and CuO are used as an additive with paraffin to improve the thermal performance of the system. AI2O3 Nano particles have high thermal conductivity and high melting point. But also, there was a limitation in adding Nano particles to the paraffin. High concentration of the addition of Nano particles results in the agglomeration, that reduce the thermal performance of the system. For that the concentration of Nano particles should be in an optimum range. The addition of AI2O3 in to the paraffin wax

results in high melting point. The properties of the AI2O3 Nano particles were shown in table 3.
The paraffin wax setup is made by melting the paraffin wax pellet with AI2O3 Nano particles with and then it is poured in a Die box which made for the invention. Die for hybrid battery thermal management system is shown in figure 4.1, 4.2 and 4.3. Then the setup is allowed to solidify and then it is removed from the die. Preparation process of paraffin wax setup is shown in the figure 2.5. Various properties of Paraffin wax are listed in the Table 2.
The temperature of Li-ion cells is measured at their positive and negative terminals by temperature sensors. The sensor used in the invention is LM35 temperature sensor module which is connected to Arduino mega 2560.
In this invention, the coolant like air, water and ethylene glycol (C2H6O2) etc. can be circulated through a coil or pipes system. The main purpose of circulating a coolant is to increase the heat absorption rate from the battery pack. So, that we can achieve faster cooling rate and maintain the battery pack within the safety limit. The cheap and easily available coolant was air and water. Comparing each water is better coolant than air because it has high thermal conductivity of 0.58 W/mK. In our experiment, we circulate water through a copper coil of diameter 5mm in counter flow direction with flow rate of 400 L/h from the pump placed inside the tank.
The 3D wire model of hybrid thermal management system is shown in figure 4.1. In this 3D model, the PCM in hexagonal prism and enough spaces are made between the Li-ion cells. To find out the chemical composition present in the material we underwent FT-IR test. The test was done for paraffin wax, AI2O3 nanoparticle and paraffin enhanced with AI2O3 nanoparticle with different percentage (5%, 10%, and 15%) as presented in figure 5. The peak value obtained from the test helps to identify the functional group in the material. The combined graph obtained in the FT-IR test for paraffin wax, AI2O3 nanoparticle and paraffin wax enhanced with AI2O3 nanoparticle at different percentage was shown in the figure 6.
Investigation is initiated under a constant charging condition of 1.5C rate to find operating limit of Li-ion battery for all the test cases. Next, Investigation is made for various category with various discharge rate. First, the investigation on three Li-ion cells with natural convection with different C rates (0.5C, 1C, 2C, 3C) is made as shown in figure 7. In this investigation, thermal management system is not applied, process is carried out only by natural convection under various discharge rate the investigation is carried out. Second, Investigation

on passive thermal management system is made under various discharge rate(0.5C,lC,2C,3C) is shown in figure 8.In this investigation the AI2O3 nano particles percentage is also varied like 5%,10%,15% .The maximum temperature and the cooling time required is obtained and it is noted. Last, Investigation on hybrid thermal management system is carried out under various discharge rate (0.5C, 1C, 2C, 3C) with suitable AI2O3 percentage. Similarly, as per the last investigation the maximum temperature and cooling time required is noted. The result shows that under natural convection for 3C discharge rate the temperature rises to 51.16°C, but when the hybrid technique was implemented the temperature decrease to 40.81°C for same discharge rate. The test condition results are presented in Table 4 and Figure 12 as a comparision plot on Temperature Vs C rating for the test Conditions. From the obtained result, it shows that the benefit of AI2O3 nanoparticles enhanced in paraffin wax in hybrid battery thermal management in the electric vehicles maintain the temperature of the battery pack within the safety limit. On comparing, the results of the all investigation made the hybrid thermal management system that have paraffin enhanced with 10% AI2O3, the maximum temperature becomes more significantly smaller than other cases, which indicates the superiority of hybrid thermal management system of batteries.
ADVANTAGES OF PRESENT INVENTION
• To regulate temperature of the cells of the Li ion battery in Electric Vehicles.
• To increase the life span of the Li ion battery.
• To reduce the maximum operating temperature of battery.
• To improve the efficiency of the battery.
• To reduce the time of cooling after discharging for Li ion batteries