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Keeping just the right temperature

Batteries are a lot like people: they don’t function as efficiently if they’re too cold or too hot.

Batteries are a lot like people: they don’t function as efficiently if they’re too cold or too hot.

With an all-electric vehicle, keeping the battery at its optimum temperature helps to improve charging and increase the vehicle’s range.

For its upcoming Focus Electric, scheduled to launch in Canada next year, Ford uses thermal management technology, a liquid heating and cooling system that works when the car’s lithium-ion battery is plugged in and charging at a wall socket.

“Batteries like to stay around 20 to 30C,” says Sherif Marakby, director of electrification programs and engineering for Ford.

“The performance of a cold battery is worse than a warm one.”

Ford’s system uses a mixture of water and antifreeze that circulates across the cells inside the battery pack.

It’s sealed, so owners don’t have to check it or top it up. It’s also engineered for safety. The water flows through separate channels across the battery surface, and goes nowhere near the terminals or any electrical components.

Depending on the outside temperature, the system uses either a heating element to warm the fluid, or a heat exchanger to cool it, along with a pump to circulate it. Once the vehicle is plugged in to charge it, the system determines if the battery needs to be heated or cooled. If so, it then activates, getting its power strictly from the wall outlet.

“It only happens while it’s charging,” Marakby says.

“We manage that automatically, so the customer doesn’t have to do anything. They just plug in the vehicle. In extreme temperatures, whether it’s too hot or too cold, the chemistry and the battery cells have limitations on how far and how fast they can charge. With this system, it allows the maximum performance from a charge standpoint. You can put more charge into the battery in extremely cold temperatures, and therefore more range.”

Marakby says that liquid cooling is more effective for regulating lithium-ion battery temperatures than an air-cooling system on the larger, more complex battery packs used in electric cars.

The sealed battery retains the temperature for some time, he says, and will stay within its ideal range on the daily drive.

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