The Speedtail has highest specific battery power of any production road car.

McLaren has lifted the lid on its new Speedtail hyper GT car after it achieved a top speed of 250 mph in high speed validation tests in the US.

The three-seater combines a supremely aerodynamic profile with low vehicle weight, and a race-bred hybrid electric drive system that incorporates pioneering battery technology to set a new benchmark for hybridised hypercars.

That hybrid drivetrain includes McLaren's trademark 4.0-litre V8, but with new lightweight air-intake system, improved cylinder head cooling and a revised piston design to deliver 747 bhp alone.

McLaren reveals Speedtail electric secrets

On the elctric side, engineers from McLaren Applied, the McLaren Group division that focuses on virtual product development, telemetry, electrification and control, helped integrate motorsport-developed inverter and DC/DC converter technology to further enhance the car's performance.

A high power cylindrical cell, arranged in a unique array, delivers the best power-to-weight ratio of any high voltage battery available today, and has four times the power denisty of McLaren's only other hybrid hypercar effort, the P1

McLaren reveals Speedtail electric secrets

The battery design enables the Speedtail to deploy its energy in a smart way, because the cells are thermally controlled by a dielectrical cooling system and permanently immersed in a lightweight, electrically insulative oil which quickly transfers heat away from the cells – a first for a production road car.

Formula E-derived technology gives the Speedtail the highest performance installation ‒ including cooling and integration ‒ of any electric motor currently in use on a production road car. The electrification ups the overall figure to 1055 bhp thanks to a setup that's twice as efficient of any other road car, with a power delivery figure of 8.3kW/kg.

Gallery: McLaren reveals Speedtail electric secrets