As part of General Motors (GM) ongoing effort in engineering the next generation energy storage systems for future electric vehicles, this paper presents many of the key system and vehicle level issues that GM has found to be relevant or unique to the use of Li-ion batteries in vehicle applications. The issues presented include battery life, thermal management, crash worthiness and electronic monitoring systems. A focused effort on understanding each of these issues is underway at GM, but additionally, work is being done to optimize how these issues interact with each other at the vehicle level. This optimization is a key element to ensuring the vehicle ultimately meets customer expectations. Copyright (C) 2009 John Wiley & Sons, Ltd.