The state of the battery is mainly defined by two parameters: state of charge (SOC) and, state of health (SOH). Both parameters influence performance in the battery and are dependant on each other (Jossen et al., 1999).
Cells: The actual batteries. These can be any type, such as lithium-ion, nickel-metal hydride, or lead-acid. Battery Management System (BMS): This is the brain of the battery pack. It monitors the state of the batteries to optimize performance and ensure safety. Connectors: To link the batteries together.
The battery pack embraces different systems of interrelated subsystems necessary to meet technical and life requirements according to the applications (Warner, 2015). The expand of the technology depends on the cost, safety, cycle life, energy density and power density.
Connectors: To link the batteries together. They maintain the electrical flow and balance the load across all cells. Housing/Casing: This protects the internal components from physical damage and environmental factors. Battery packs work by connecting multiple individual cells in series or parallel to increase voltage or capacity.
For this reason, the safety of the battery pack is also related to the performance of the mechanical parts. By reducing the weight, the efficiency of the battery can be improved in terms of life cycle and range, at the same time, the battery has to preserve high strength and resistance to vibrations (Shui et al., 2018).
Uneven temperature distribution leads to different charge and discharge behaviours causing electrical unbalance in the modules which reduces the performance of the battery pack. When a battery pack is integrated with the vehicle, it becomes a more complex system confronting many safety problems (Garg et al., 2016).