Thermal Analysis of a battery in an electronic device for an outdoor application

Abstract

For the effective working of an electronic product, operating temperature of the components on PCB should be below the safe limits. Along with the components, other aspects like the housing material, battery, mountings, connectors etc. should also be analyzed critically from thermal point of view. For safe operation and to avoid any explosion of the battery, temperature in and around battery should be below the limiting temperature. The equipment in consideration is made up of polyester plastic and mounted in an open field, exposed to solar radiations and ambient air. Housing consists of a PCB along with heat dissipating components over it. Components are modelled as lumped models with accurate size, as mentioned in the datasheet. Heat is transferred from the components to the board through conduction. This heat is spread from the board to internal air through convection and radiation. Solar flux transfers the heat to the housing through radiations, which in turn transfers heat to internal air through convection and radiation. At thermal steady state, in-flow and out-flow of heat between internal air and ambient air is balanced. In this paper, surface temperature and ambient temperature around the battery is analyzed at different air flows and different orientations to comment on the appropriate position for placing the product. This will also help in evaluating pertinent time for replacement of battery and the maintenance cost of the product. Steady state thermal simulation is carried out in FloTHERM™. The situation duplicated is maximum temperature in the geographical region with maximum solar flux and various air flows that the product may experience in its life time. The simulation model consists of the entire product and air domain. All three modes of heat transfer (i.e. conduction, convection and radiation) are considered.