Environmental sustainability, more efficient use of energy, and active safety concepts are becoming important requirements for the actual elevation sector. In this context IK4-IKERLAN and ORONA have designed an auxiliary energy storage system (ESS) for a residential elevation application based on lithium-ion cells. Safety and specially lifetime are two of the main concerns surrounding this new technology, which is closely related to the cells operating behavior and temperature asymmetries in the complete ESS. Therefore, the temperature of the cells in battery packs (BPs) needs to be controlled in an efficient way. This paper describes the development of the thermal management system (TMS) designed for this application based on various Computational Fluid Dynamics (CFD) mathematical models. The accuracy of Transient model is validated by using a single module to compare the simulation temperature results with experimental measurements, with a maximum time-averaged temperature prediction error of 1.5 degrees C. The proposed design is validated as it fulfills the requirements for a wide operating window, with a maximum cell temperature of 39 degrees C and a thermal dispersion at system level below 3 degrees C for the worst tested case. A more realistic current profile is checked numerically in the worst ambient and operative conditions for different virtual design variants to propose improvements. (C) 2016 Elsevier Ltd. All rights reserved.