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.

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.

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.

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.