When the 2112 Ford Focus Electric debuts in late 2011, it and the Chevrolet Volt will have a common feature in addition to their LG Chem lithium polymer cells. Ford confirms that the Focus EV will employ a liquid-cooled battery pack with automatic thermal management, just like the Chevy.
Ford opted for active thermal management solution in order to help maximize the Focus EV's battery performance and lifespan. By protecting the battery from overheating, the system can help prevent the development of cracks in the electrodes. Those imperfections eventually reduce the pack's ability to hold a charge. Conversely, warming the cells when cold will improve the battery pack's winter performance. When the car is plugged in, the thermal management system will use grid power to precondition the battery before charging actually starts.
So far, Nissan and Mitsubishi are the only major EV manufacturers that are sticking with passive air cooling for plug-in vehicles. Nissan has committed to an eight-year warranty, but it remains unclear how well the battery will hold up over regular use in differing climates.
FORD USES INNOVATIVE LIQUID-COOLED BATTERY SYSTEM TO HELP FOCUS ELECTRIC OWNERS MAXIMIZE RANGE
- The all-new Ford Focus Electric, which debuts in late 2011 in the U.S. and 2012 in Europe, will be powered by a lithium-ion battery system that utilizes cooled and heated liquid to regulate battery temperature, extend battery life and maximize driving range
- The innovative thermal management technology helps the Focus Electric operate efficiently in a range of ambient temperatures
- Focus Electric is one of five new electrified vehicles Ford will deliver over the next three years in North America and Europe. The Focus Electric will be built at Ford's retooled Michigan Assembly Plant
Thermal management of lithium-ion battery systems is critical to the success of all-electric vehicles because extreme temperatures can affect performance, reliability, safety and durability. Ford has chosen an advanced active liquid-cooling and heating system to regulate the temperature of its lithium-ion battery packs, which are designed to operate under a range of ambient conditions.
"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 active liquid cooling and heating system also enables the Focus Electric to automatically precondition the battery pack temperature during daily recharging. When the vehicle is plugged in to the power grid, the vehicle system will be able to warm up the battery on cold days and cool it down on hot days.
The Focus Electric will be built at Ford's retooled Michigan Assembly Plant and will be available in late 2011. The vehicle will have an expected range of up to 100 miles and use no gasoline at all.
Battery thermal management in action
While air-cooling methods work well for many of today's smaller car battery systems, the larger, more complex lithium-ion battery technology powering Ford's all-electric vehicles calls for an aggressive thermal management system.
An active liquid system 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 efficiently accept charge energy and provide enough discharge power for expected vehicle performance.
"Extreme temperatures impact a battery's life and performance, making it crucial to have an effective cooling and heating system to regulate temperature for these demanding applications," said Anand Sankaran, Ford executive technical leader, Energy Storage and HV Systems.
The liquid cooling system also plays a role in charging the vehicle. When the all-electric 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.
"We are working closely with our technology partners to accelerate the development of our lithium-ion battery systems to help our future EV customers get the most out of their vehicles," Marakby said. "Our goal is to build an electric vehicle that delivers on the quality and performance customers have come to expect from Ford."
Focus Electric is one of five electrified vehicles Ford will release over the next three years. In addition to the Focus Electric, 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.
Electrified vehicles are one part of Ford's broader strategy to offer a wide range of environmentally friendly, advanced technology solutions to improve fuel economy and lower CO2 emissions affordably for customers around the world.