Electronic Design
Ford Uses Liquid Heating In Focus Electric To Give Batteries The Edge In Cold Weather

Ford Uses Liquid Heating In Focus Electric To Give Batteries The Edge In Cold Weather

Extreme temperatures can affect battery performance and reduce the range of electronic vehicles. But the Ford Focus Electric, which is the company’s first all-electric passenger car, will use an advanced liquid-heating system that will provide additional power and longer range in severe temperatures (see the figure). This vehicle is a zero-emissions, gasoline-free version of Ford’s Focus model.

To combat extreme weather, Ford’s liquid cooling and heating system will regulate the temperature of its lithium-ion (Li-ion) battery packs. The battery range will not be impacted as much with a liquid-heated system compared to an air system, according to Ford engineers.  The liquid-heated battery operates under a range of ambient temperatures, providing additional power, a longer battery range of about 100 miles, and a preconditioned battery after charging. Both the Chevrolet Volt and Tesla Motors use a similar liquid-heating strategy to regulate battery temperature, but Nissan engineers are using passive air cooling to try to maintain optimum battery temperature, a tactic that critics from other automotive companies are calling “primitive.”

“Batteries are similar to people as they both achieve maximum performance working under moderate, unchanged temperatures,” said Sherif Marakby, Ford director of Electrification Programs and Engineering. “Using a liquid-heated battery system allows Ford to keep the Focus Electric’s battery at a moderate temperature and improve performance whether you are charging or driving in a cold climate.”

Marakby reveals that Ford engineers spent five years working with Li-ion technology and studying the results to try to develop this system. He explains that the team understood the chemistry involved and knew that lower battery performance occurs under extreme temperatures, so they decided the most logical way to ensure the best balance of performance, durability, and life was to actively manage the temperature in the battery pack.

“A liquid-heated battery can accept a charge faster from the regenerative braking that recaptures kinetic energy and sends it back to the battery, essentially providing longer range for the customer in real-world cold weather conditions,” said Marakby. “Additionally, since acceleration in an electric vehicle comes from the power available in the battery, the customer will have more power available if the battery is warmer.”

In extremely cold temperatures, when the vehicle is being charged, the battery will heat through the vehicle control system, utilizing the heating/cooling liquid loop designed specifically to manage the temperature across each cell and the battery pack. The rate of heating will change based on the battery temperature and the rate at which it heats up. The same process will be used to cool the battery in extremely hot situations.

“Even when you’re parking in cold temperatures, as long as the vehicle is plugged in, you will warm up the battery,” explained Marakby. “Basically, customers will have the capability they need right off the bat. They won’t have to wait for the car to warm up.”

On cold days, heated liquid arms the batteries, gradually bringing the system’s temperature to a level that allows it to efficiently accept charge energy and provide enough discharge power to get good vehicle performance. Because of this technology, electric cars will no longer just be an option for people who live in warm cities with consistent temperatures. Anyone, regardless of what climate he or she lives in, will be able to count on their electric vehicle in all weather conditions.

Ford Motors
http://www.ford.com/electric/focuselectric/2012/

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