In today's world, electric vehicle (EV) production is increasing due to updated regulations, the fight against the climate crisis and governments' pressure on automotive manufacturers. In this context, it is not sustainable to consider currently produced cars with internal combustion engines as unusable in the future. The body design of a traditional internal combustion car differs from today's EVs. For this reason, when starting the electrical retrofitting of an existing design, the first step should be started with the flexible battery pack design for available spaces. This thesis introduces flexible-modular battery pack design and assembly of equipment such as traction assembly including gearbox, powerbox and 1.8kW charger in available spaces for the first generation Fiat Panda in Solidworks 2023 environment.