Modeling and evaluation of nickel manganese cobalt based Li-ion storage for stationary applications

Lithium-ion (Li-ion) based batteries are commonly used in many applications such as electric vehicles, utility-scale storage, and consumer electronics. To maximize power utilization and optimize runtime voltage-current (V-I) characteristics, it is imperative to predict these batteries' behavior for varying load profiles accurately. In this work, we first perform electrical modeling of two commonly used Li-ion cell chemistries, i.e., Nickel Manganese Cobalt (NMC) and Lithium Iron Phosphate (LiFePO4), using the modified Shepherd equation. Secondly, we evaluate the operation of NMC based Li-ion chemistry's operation for a stationary uninterruptible power supply (UPS) application commonly used in developing countries to cater to utility grid intermittency. The evaluation of cells is done through the 2RC model to ascertain the V-I behavior of these cells in a much more frequent charge-discharge regime in UPSs compared to standard EV applications. A UPS system's real charge/discharge pattern is taken with an average daily outage of up to 6 hrs. Finally, a comparison between the life and cost of Li-ion intervention is made and compared to a conventionally used lead-acid battery, which dominates over 90% of stationery UPS markets in developing countries.