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The 250-MPH McLaren Speedtail’s Batteries Are Sealed in a Unique Oil to Keep Them Cool

Complex problems require complex solutions, especially at breakneck speeds.

The McLaren Speedtail is more than an ordinary hybrid. In fact, it’s a parallel hybrid that hides a 1.647-kilowatt-hour capacity, high power-density battery pack and a 300-plus-horsepower electric motor sandwiched between its 4.0-liter V8 and seven-speed dual-clutch automatic. What’s different about this setup is that because this Ultimate Series uses electrification to be faster in a straight line than any other McLaren, its batteries are permanently immersed in an electrically insulative oil to allow the cells to run harder and for longer.

McLaren went for an electric motor derived from Formula E, which generates more than 308 hp of the Speedtail’s total output of 1,055 horsepower. Designed with the help of engineers from sister company McLaren Applied, Woking claims this to be the highest performance installation of an electric motor currently in use on a production road car. The compact unit’s power delivery is 8.3kW/kg, while the battery pack’s power density is four times that of the cells in the 2013 McLaren P1, providing 5.2kW/kg to achieve that 270kW (308-hp) peak figure in rapid fashion.

Dr. Sunoj George, McLaren’s head of electric drive technology, explains how their team achieved the rapid charge and discharge capabilities of the cylindrical cells, which was partly made possible by the oil-based cooling that’s also the first of its kind in a production road car.

Deploying a maximum torque output of 848 foot-pounds, the McLaren Speedtail can reach 186 miles per hour in 13 seconds, continuing on to a top speed of 250 mph.

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