Computational Method to Determine the on Board Available Electrical Capacity/energy of Lead - Acid Starting Batteries, of Automotive Vehicles

A suitable sizing of electrical energy amount necessary to be stored on board is one of the most important conditions to assure the optimal operational environment of modern automotive vehicles. The paper presents a short synthesis of an original method to determine the available energy (capacity) or state of charge (SOC) of the on board leadacid starting battery of land automotive vehicles, developed by SC INAR SA Brasov, as partner in the project ”Energy Optimized Electrical Systems for Land Transport, Using Batteries and Supercapacitors. TRANS SUPERCAP” in partnership with „Transilvania University of Brasov”, as project leader. The mathematical model is a result of processing data picked up in the starting cycle of IC engines. The algorithm and software developed in the study could be a real help for design engineers , service technicians, as well as for vehicle drivers, to estimate the on board electrical energy reserve in the engine starting cycle, at different states of charge (SOC) of the battery in use. The paper revealed the main data necesary to be processed, to indicate the present state of charge (SOC) of a given battery: ambient temperature , battery terminal voltage, and discharging battery current.The study concluded with a valuable method to indicate the available electrical energy ( the on board energy reserve), to maintain the battery state of charge „ready to start”. The momentary battery specific data are continually measured,analysed and compared with the external caracteristics(curves) of a given type, and size of starting battery in use in the starting cycle of IC engines. The computing model is approaching the battery ́s energy(capacity) availability with starting power requirements of automotive vehicle engine,.and could be displayed on the dash board numerically[%] as a ratio between the present capacity and the rated capacity of the battery at rated temperature [+23 +/5 ̊C].