Lithium-ion Batteries (LIB) are become more common in our daily usage consumer electronics and in large energy storage devices. Under abuse conditions, LIBs gets overheated and may result in exothermal reactions leading to a thermal runaway with excessive amounts of heat, gas generation. The generated gases within the battery leads to pressure build up until the point at which the battery vent mechanism opens and relieves the flammable gases; subsequent ignition causes battery fire and explosion hazard. The energy release during thermal runaway in a single cell can also initiate thermal runaway in adjacent cells in a pack and damage the entire battery system. Computational Fluid Dynamics (CFD) modelling of the LIB fires will considerably aid in understanding the temperature and heat distribution during thermal runaway and hence can help in design of mitigation measures. There are practical limitations in determining both experiments and theoretically the precise boundary conditions for a very transient LIB fire. Presentation will discuss CFD simulations carried out using an in-house developed solver using open source CFD code OpenFOAM toolbox and approximations adopted in boundary conditions to numerically predict qualitative behaviour of LIB fire.