Reliability Analysis of Different Cell Configurations of Lithium ion battery Pack

Abstract

To infer and predict the reliability of the remaining
useful life of a lithium-ion (Li-ion) battery is very significant in the
sectors associated with power source proficiency. As an energy
source of electric vehicles (EV), Li-ion battery is getting attention
due to its lighter weight and capability of storing higher energy.
Problems with the reliability arises while li-ion batteries of higher
voltages are required. As in this case several li-ion cells are
connected in series and failure of one cell may cause the failure of
the whole battery pack. In this paper, Firstly, the capacity
degradation of li-ion cells after each cycle is observed and secondly
with the help of MATLAB 2016 a mathematical model is
developed using Weibull Probability Distribution and Exponential
Distribution to find the reliability of different types of cell
configurations of a non-redundant li-ion battery pack. The
mathematical model shows that the parallel-series configuration
of cells is more reliable than the series configuration of cells. The
mathematical model also shows that if the discharge rate (C-rate)
remains constant; there could be an optimum number for
increasing the cells in the parallel module of a parallel-series
configuration of cells of a non-redundant li-ion battery pack; after
which only increasing the number of cells in parallel module
doesn’t increase the reliability of the whole battery pack
significantly.