Browsing by Author "Mollik, Md. Sazib"

Developing rapid charging protocols for lithium-iron-phosphate (LiFePo4) battery is a key issue for a wider deployment of electric vehicles. A combined experimental and analytical study has been performed to investigate the rapid charging and heat generation characteristics of lithium-iron power battery in the present work. The effect of the internal temperature of the battery has been investigated during the medium, fast, and rapid charge process. The main drawback of LiFePo4 battery is overcharge, overcurrent, extreme condition the separator will melt causing internal short-circuit, the battery will take longer time for charging, and high temperature which affects longevity, efficiency, and battery life cycle. Experimentally investigate the LiFePo4 battery charging characteristics and temperature rise behavior are carried out based on 1C, 2C, and 2.5C charging rate. Moreover, the constant current-constant voltage (CC-CV) charging method has been applied for medium, fast, and rapid charging and analyzing the battery internal temperature using N-type thermistor. Battery charging and thermal management system have been developed based on battery charging performances and levels of raised temperature. Refrigerant-134a cooling system is capable to maintain battery temperature within 20oC~40oC range. Battery charging voltage, current, SOC and battery rasing temperature has been monitor during the charge of LiFePo4 battery. On the other hand, MATLAB/Simulink based custom-designed tool was developed. A dynamic model of lithium-iron-phosphate battery is proposed in this research by considering the significant temperature and capacity fading effects. Results have shown that the LiFePo4 battery can be used for rapid charging up to 85% by maintaining the condition for lifespan of the battery and to shorten the charging time. The simulation results showed that the battery charging model can truly reflect the dynamic output characteristic of lithium-iron batteries. The simulation and experimental results show that the battery can be charged around 1 hour and 55 minutes for medium charging (SOC 100%), 56 minutes for fast charging (SOC 100%) and nearly 31 minutes for rapid charging (SOC 85%). In the experiment, LiFePo4 battery was tested with different charging rates (1C, 2C, and 2.5C). The prototype charger can control battery charging systems for different charging rates such as medium, fast and rapid charging and also able to monitor raised temperature of the battery. Additionally, high charging current has been used for rapid charging where the SOC is 85% due to battery performance. The developed model of a battery charging system shows good performances with several control methods. The LiFePo4 battery operating temperature range is 20oC~40oC where this range has been exceeded for fast, and rapid charging and the experimental battery temperature becomes nearly 47oC. This is why the thermal management system has been developed for fast and rapid charging to control battery temperature. The Variable Frequency Driver (VFD) can control compressor motor frequency where the frequency range is 25Hz-60Hz. Battery average charging temperature has been kept below 25oC, which helps battery performance and lifetime. The evaporator average surface temperature is 14oC which helps for better performance while rapid charging. Experimental results have shown good agreement with simulation results where the maximum variation has been found around 7% only.

Due to enhanced mechanical strength, superior flame-resistance, decreased gas permeability, montmorillonite nano-clay has been introduced to the jute-polyester resin composite materials for structural application. Long fiber Bangla special tossa jute is being used as reinforcement materials along with 0%, 1%, 3% and 5% addition of nano-clay within the matrix-fiber mixture. These hand lay-up processed 32 cm×32 cm×3 mm plates are used to make samples for tensile test (115 mm × 19.42 mm× 3 mm) and flexural test (125 mm x12.7 mm x3 mm) and impact test (55 mm x10 mm x 10 mm) as per ASTM standards. Yield strengths, percentage of elongation, modulus of elasticity and fracture strength have been calculated from the tensile test for 0%, 1%, 3% and 5% nano-clay filled composites respectively under two different strain rates (0.5 mm/min and 0.8 mm/min). Stress- strain superimposed curves shows clearly that 1% nano-clay filled composite possesses superior mechanical properties in terms of yield strength (3.6 MPa, 0.5 mm/min) and fracture strength (22.39 MPa, 0.5 mm/min) due to optimum density and homogeneous mixture of the added clay. It is interesting to note that 0%, 3% and 5% filled nano-clay filled composites show not much difference in terms of yield strength even-though breaking strength for 3% nano-clay filled composite shows higher value. Effect of temperature and high humidity were evaluated for this nano-clay filled composite through the hydrothermal test for 15 days in the environmental chamber. Environmental degradation was not remarkable due to the exposure of the temperature 80oC and 95% RH for this time period. Thermal behaviours of this jute composite were studied via dynamic mechanical analysis, thermogravimetric analysis and differential scanning calorimetry. The doped hand lay-up processed plates are used to make samples for dynamic mechanical analysis (50 mm × 12.7 mm × 3 mm) and thermogravimetry (6.75mg to 6.85mg) testing as per ASTM standards. Temperature induced weight loss due to Thermal decomposition were measured and char residue were calculated up to 1000ºC where 5% added nano clay samples showed better thermal stability. Viscoelastic properties through storage modulous and loss modulus showed better stability with 1% nanoclay added composite in dynamic mechanical analysis. Moisture and temperature did not affect the tested samples significantly in diminutive exposure for 1% nano clay added samples even though there is a loss of storage modulus of 12 to 30% for 3% and 5% nanoclay added samples, respectively. Further, fractographic evolution for the raw jute is performed by Scanning electron microscopy and field emission scanning electron microscope which shows the continuous unbroken jute fiber cellulose and tress of nano clay. Fractured jute fiber void and nano particles were identified in the fractrographic analysis. It is evident from this investigation composite up to 1wt% both for mechanical and thermal performance. No advantage is observed in terms of mechanical and thermal properties beyond this optimum limit of 1wt%.