Lithium-ion cells for electronics and automotive applications have an excellent safety record. However, safety-related events can sometimes occur during routine testing of prototype designs, especially in the case of designs using new electrode materials, new separators and/or new electrolytes. High precision measurements of coulombic efficiency have recently been shown to have great value in predictions of the impact of electrolyte additives on cell lifetime. In order to apply those methods to prototype automotive cells, special compact temperature-controlled boxes were required that could maintain the temperature to +/- 0.05 degrees C precision and ensure the safety of the laboratory. These versatile temperature-controlled boxes were designed to accommodate cells as small as coin cells and as large as 40 Ah automotive pouch cells. The ability of the design to prevent cell-to-cell fire propagation and to channel smoke and flame away from the rest of the laboratory was experimentally verified. It is hoped that the information presented here will be of value to those designing precision testing facilities for large Li-ion cells. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.047302jes] All rights reserved.