This giant battery pack drives a pair of electric motors, which are mounted on the rear subframe, and housed inside water jackets, themselves chilled by coolant piped down from the radiator.
The motors drive a single ratio transmission with an integrated differential. Each motor is rated at 145kW but, more importantly, together they also deliver a whopping 590lb ft of torque from standstill. Although the power from the motors is 48kW down on the equivalent power from the V12, the torque peak is 59lb ft, or 11 percent, up.
The 102EX’s drivetrain offers two strengths of retardation once the driver lifts off the accelerator pedal. ‘Standard’ offers 120Nm of regenerative braking force and ‘Low’ a more neck-testing 210Nm.
What’s it like?
In truth, this electric drivetrain delivers on the Rolls Royce promise more completely than any internal combustion engine could ever manage.
Although the standard-issue V12 engine is a refined as any engine installation on sale today, and does a very impressive job of mustering up the required rising wall of near-silent torque, it’s the way that the torque of the electric motors move the 102EX down the road that is the game-changer.
The surge of forward motion is so uncannily seamless and relentless that your first instinct is that the Phantom’s V12 motor is rendered instantly redundant.
There are two big advantages over internal combustion engines, even one as refined as the Phantom’s V12. Firstly, at speed and under hard acceleration, you can really sense the lack of mechanical reciprocation behind the bulkhead. The second is the unhindered stream of torque, not just because of the characteristics of electric motors, but because of the lack of ratio swapping.
On the winding backroads of West Sussex, the car was quite uncannily relaxing. Ironically, in a car where the owner might spend all of his time in the rear seat, the pleasure is delivered to the driver.
That’s not to say that the Phantom is much of a B-road animal. The steering on this one-off was rather over-light and the position of the front inside wheel wasn’t quite obvious. However, the ride quality over sudden potholes was slightly better in the 102EX than it was in the standard-issue Phantom I tried back-to-back with the electric car.
Perhaps the biggest problem for a future electric Phantom is the fact that the refinement of the cabin results in tyre noise becoming much more obvious to passengers.
Should I buy one?
You can’t. And I’d be surprised if the 102EX progressed much further than a handful being produced for big corporate Phantom customers, such as the Peninsula Hotels Group.
The obvious problem with the 102EX is its mediocre range and even more hopeless recharging time, unless you happen to have access to a industrial-strength electricity supply. Even the current engineering estimates are for a three-year life for the battery pack, given a daily cycling.
Rolls Royce, an understandably cautious company, doesn’t need to spend a year sampling opinion on the idea of a battery-powered Phantom. It needs to start work as soon as possible on a practical solution that sees the wheels of the next-generation Phantom driven by electric motors.
In reality that probably means building a range-extender drivetrain, using an on-board combustion engine (a gas-turbine generator?) to generate electricity.
Rolls Royce 102EX - Phantom Experimental Electric
Top speed: 99.8mph (limited); 0-62mph: 7.8sec; Economy: 120 miles per 20-hour single-phase charge; Co2: zero locally; Kerbweight: 2720kg; Engine: Twin electric motors; Installation: Rear-mounted, RWD; Power: 390bhp combined; Torque: 590lb ft from start; Gearbox: single speed transmission; Battery pack: 71kWh, Lithium-Nickel-Cobalt-Manganese Oxide