Ni-MH battery ageing: from comprehensive study to electrochemical modelling for state-of charge and state-of-health estimation

Battery ageing is a key issue and experimental studies and modeling developments are critically needed to assess the underlying mechanisms that govern these complex and interrelated ageing processes. Indeed, molecular level processes then govern the long term operation of battery systems, their performance limitations and failure. This paper presents an advanced 0D-electrochemical and thermal model of a nickel-metal hydride (Ni-MH) cell recently calibrated to describe a 6,5 Ah, 168 cells, 202V nominal Ni-MH commercial battery pack and discusses its potential benefits to better understand battery performance and ageing. Comparison is made between a new pack and a three years/70 000 km old pack through high pulse power characterization test and modeling. On the basis of the electrochemical lumped parameter model under development, new energy management strategies could be proposed to ensure a precise state-of-charge (SoC) and state-of-health (SoH) on-board estimation to improve life duration of batteries. It is worth noting that the Ni-MH battery model is detailed as a case study in this paper, but this modelling approach can be applied to any Li-ion technologies.