Extended range of electric vehicles is seen as a mean to accelerate the market penetration of electric vehicles. However, putting more and more battery cells in a pack may lead to an unsuitable usage regarding battery lifetime. In this paper, we assess the impact of oversizing batteries in their lifetime and their total cost of ownership. Simulation results reveal a reduction in battery lifetime of larger batteries when charge is not adapted, dramatically increasing the total cost of ownership. On the contrary, optimisation of the charging strategy preserves the battery's performances for a longer time and lead to important cost savings.