ABSTRACT Harsh thermal conditions in the engine compartment pose challenges for many OEMs for granting long lifetime of batteries. With the raising spread of new battery technologies for several types of applications, many efforts are needed to grant stable heat distribution across cells. The paper investigates the modelling of heat distribution inside a common SLI-type battery using two different approaches (lumped-masse and solid conduction) and then analyzes the effects of a cost-effective, passive thermal insulator on such distribution. Designing a model that can handle in a simple and effective way different boundary conditions is key to be able to analyze in a quick way the impact of several possible battery-pack designs both for current and future on-vehicle applications.