An internal combustion engine car can be converted into a fully electric one using a retrofit kit. This thesis study intends to advance the development of a unique algorithm for a vehicle control unit that is a component of a retrofit kit for vintage automobiles. The development of the battery management system's (BMS) features is specifically discussed. The algorithm is tested in accordance with the model-based design methodology while being developed in the LabVIEW environment. In the first section, the requirement analysis of the BMS algorithm is carried out and its first implementation is proposed. The functionality that have been developed include organizing battery management through a state machine, managing contactors, dealing with faults, controlling charging, taking care of overcharge and over discharge for the protections of cells and handling a current limiter for safety.