One of the downsides of the lithium-ion battery systems used in electric vehicles is that their performance, reliability, safety and durability can be negatively affected by extreme temperatures. When the all-new Ford Focus Electric debuts later this year in the U.S. it will be powered by a lithium-ion battery – no news there. What is interesting, however, is that the battery system will use cooled and heated liquid to regulate battery temperature, which should extend battery life and maximize driving range.

While air-cooling methods work well for many of today’s smaller car battery systems, Ford said it needed a more aggressive thermal management system for the larger, more complex lithium-ion battery technology that will be powering the company’s all-electric vehicles. Ford chose an active liquid system that heats or chills a coolant before pumping it through the battery cooling system. This loop regulates temperature throughout the system against external conditions.

On hot days, chilled water absorbs heat from the batteries, dispersing it through a radiator before pumping it through the chiller again. On cold days, heated water warms the batteries, gradually bringing the system’s temperature to a level that allows it to provide enough discharge power for expected vehicle performance.

Additionally, the system also plays a major role in charging the vehicle. When the Focus is plugged in to recharge, the vehicle control system will automatically precondition the battery, if needed, to the optimal temperature before accepting charge. If the battery is already at the optimal temperature, the system will automatically accept charge and maintain an optimal temperature.

“All-electric vehicles do not have a conventional engine on board, so it is critical we maximize the performance of the battery under various operating temperatures,” said Sherif Marakby, Ford director, Electrification Program and Engineering. “Active liquid systems are more effective than air systems at regulating lithium-ion battery temperature. As a result, the active liquid system on Focus Electric will play a key role in providing our customers with the best performance possible.”

The Focus Electric, which will be released in the U.S. late this year and in 2012 in Europe, is one of five electrified vehicles Ford will release over the next three years. The Ford Transit Connect Electric small commercial van arrives in late 2010, followed by two next-generation hybrid electric vehicles, as well as a plug-in hybrid electric vehicle in North America in 2012 and Europe in 2013.