Browsing by Author "Rahman, Md Mizanur"

The use of clean and green energy is becoming more and more important in today's world. Electric vehicles (EVs) / hybrid electric vehicles (HEVs) are currently best choice for the environment as public or private transportation. Battery-packs have been employed as an energy source to provide the power to run the traction motor in electric vehicles (EVs) / hybrid electric vehicles (HEVs). Battery needs to be delivered the peak power to meet demand of the vehicle within short time. The cells of battery packs suffer from the state-of charge (SOC) and state-of-discharge (SOD) which could incur unbalancing problem due to natural phenomena such as ambient temperature, chemical degradation and internal impedance. Many conventional balancing techniques have been developed for balancing the battery cells, both in charging and discharging period with emphasizing simple control, efficient, low cost and easy to implement. This study presents an advanced battery charge balancing (BCB) system to perform the balancing of battery cells in four modes, namely: (a) charging, (b) discharging, (c) both in charging and discharging and (d) inoperative. The resonant LC network is connected with each of the cases by using switching components. In general, the inrush high spike current occurs in switching devices due to the inductor components, which could damage the switching components and increase the total system power loss. In our developed BCB, flyback snubber circuit consisting of diode and capacitor has been introduced with the inductor component in parallel. The charge balancing time has been reduced significantly by using two parallel LC series networks instead of the single LC series network. In simulation, the cell voltages were balanced in 5sec that has reduced the balancing time by 37% without considering battery internal resistance. In experimentally, battery cells voltage variations were recorded 11.27% and 9.1% in 2 minutes and 10 minutes respectively.

The lithium-ion battery pack is a very important part of an electric vehicle (EV) and is an expensive component. If there is no proper battery management system (BMS) for the lithium-ion battery pack, the overall performance could be affected in several ways, including the lifecycle, charging-discharging behaviour, safety and ambient temperature. Because a battery pack is exposed to different conditions, such as ambient temperature, aging and manufacturing variation, over state of charge (SOC) and under depth of discharge (DOD), the charge of the series connected cells becomes unbalanced. During the rapid charge balancing (transferring) process, the internal temperature of the cells may exceed its allowable limit (46°C) which results in unstable balancing behaviour. Besides this, communication makes the BMS convenient and even smarter by connecting all the sensors, including the sensors for voltage, current, SOC and temperature, of the battery pack. However, a large number of wire terminations in the BMS, including among the sensors, are liable to safety failure and are not fully reliable. To help address these issues, this research focuses on developing a BMS that includes a charge balancing system and wireless communication system for three series connected battery cells. Several local control units and one central controller are used to achieve this. The charge balancing system uses a DC to DC converter and a controlled algorithm, which considers internal ambient temperature, to overcome the challenges associated with the charge balancing process. With this approach, the increasing internal temperatures in the battery cells are maintained within the range of 27°C to 35°C. Real time information is monitored and used to control the functionality of the battery pack using wireless communication. The wireless communication system, using the ZigBee communication protocol and point-to-point topology, has reduced wiring problems, as well as size and cost, compared to the conventional communication system. The simulation results of this system have been verified by the experimental results. The wireless communication and control management system developed in this research can be applied to large battery packs to improve their overall performance.