EV Energy Storage System (EVESS)

To appreciate the gravity of the research and development involved in this project, this section first presents the overall system diagram in 2, where the proposed EVESS system is shown along with the various component of an EV. This part will be divided into two main modules, the details are given below:

Li-ion Cell Design, Quality and Reliability Testing

Large Lithium-ion (Li) based batteries for the vehicle and grid energy storage are required to unlock the potential of existing Li battery materials and scale-up Li-ion cells to 10-100 Ah sizes without substantially lowering the cell’s energy density remains a key technological challenge. Thermal runaway (TR) in a single Li-ion cell level would cause chain reactions which result in whole battery pack failure, resulting in catastrophic effects in electric vehicles or energy storage devices. So, the battery type selection (cylindrical or pouch) along with cell capacity and quality inconsistencies are the fundamental challenge being faced by local EV manufacturers.

Typically, three types of LIB cell configurations are commonly used for automotive applications: cylindrical, pouch, and prismatic. All utilize stacked sheet-like layers of anodes, separators, and cathodes, saturated with an electrolyte, electrically connected, and sealed in an enclosure.

The cylindrical cells are made by rolling the stacked layers into a jelly roll configuration and then packing it into a solid cylindrical enclosure. One advantage of this configuration is that the round shape distributes internal pressure from side loads relatively evenly about its circumference to tolerate a high level of internal pressure without deformation. However, when assembling many same size cells to create a battery module, packing density suffers by the large fraction of interstices between cylindrical cells.

Pouch cells are made by packing the flat stacked layers into a flexible polymer foil-like enclosure. This can reduce weight, while their flexibility is helpful for assembly and fitting into a finished product. However, the softer construction necessitates a more rigid support structure along with placement away from sharp edges.

Prismatic cells are made by jelly rolling the stacked layers, compressive flattening the jelly roll, and then packing it into a solid enclosure. They can also be made without rolling by stacking numerous sheet-like layers.

The summary of these three types is given in Table 1. Historically, battery cells have used cylindrical designs. This design was used in the mainstream market from alkaline battery cells to Nickel-Metal Hydride (NiMH) battery cells. But, to optimize safety, power, and lifecycle whilst doing so in a costeffective manner it is need of s to assemble cells in an efficient way. As the Chinese made cell's capacity and quality vary with production batch, company, manufacturing date, etc. Furthermore, the feasibility of Li-ion cells for EVs is not tested according to the roads and weather of Pakistan as batteries are sensitive to temperature. In this part, the experimental capacity of the cells will also be tested using a battery cycler prior to their use in the battery pack as the experimental capacity is usually lowered due to the degradation of active materials because of parasitic reactions.

The continuous advances in Li-ion cell technology, for example, advances in electrode material, electrolyte design, and cell design mean that cell characterization tests are necessary to compare the capability and track the evolution of performance over cell life. Such tests should provide useful and comparative data and be repeatable. In addition, it is just as important to understand their limitations. Typically, three parameters: cell capacity, resistance, and open-circuit voltage (OCV) are used to define the electrical performance of Li-ion cells. Cell capacity tests are used to define the maximum capacity in applications under a given load, while OCV tests provide key information on the thermodynamic properties of a cell. Resistance tests, on the other hand, characterize cell dynamics. This will tackle the fundamental problem EVs face which is low mileage and long charging time by proper selection and Li-ion cell design for the parameters such as life span, safety, cost, specific energy & energy performance in Pakistan climate.