Modelling li-ion battery aging for second life business models

Resumen

Electric vehicles are, slowly but steadily, entering into the automotive market. The slow entry is caused, basically, by the high cost of their batteries. Additionally, electric vehicle batteries are considered not useful for traction purposes when they have lost between 20 or 30% of its capacity. At this point, batteries should be recycled by the phew companies capable to do so in Europe, knowing that management of batteries as industrial waste until the recycling factory costs money. In the search of economical incentives and trying to eliminate the recycling costs, the idea of electric vehicle battery reuse for stationary applications appeared, which will take advantage from the benefits of reused batteries selling or by the profit obtained from the 2nd life use. This thesis analyzes the different electric vehicle batteries actually in the market, studying the aspects that should be modified and that have to be taken into account when repurposing them. Moreover, it analyzes the remanufacturing costs taking into account the actual battery checking methods. In order to improve these processes, a novel battery state of health estimation methodology is developed using on-board data. This new methodology observes the voltage recovery evolution when the car stops and relates it to battery aging. This thesis studies the rest of useful life in the different possible applications for second life developing an aging model using Matlab and Simuling tools. This model includes the principal aging factors of a battery and, based on current load requirements and temperature profiles of different stationary applications, it determines their expected lifetime. The presented values can be used, afterwards, for economic evaluation, business model calculations, amortization periods and maintenance schedules. Finally, this thesis finishes with an environmental analysis based on the global warming effect produced by the electric vehicle and the battery reuse during its second life, evaluating their environmental presupposed advantages against internal combustion engine vehicles and the battery reuse in each possible business case. This thesis concludes that electric vehicle battery reuse is surely going to take place sooner or later. The electricity grid is waiting for affordable energy storage systems and battery reuse is foreseen as a good option.