CATERHAM REVEALS ELECTRIC SEVEN CONCEPT

Caterham is the latest automotive brand to join the electric revolution, unveiling their ‘EV Seven’ concept. This will be used to test the feasibility of a production version of the iconic Seven using battery electric power to ensure it meets key targets of light weight and track-focussed performance that are a hallmark of all Caterham models.

“Any future EV model we produce must be true to the DNA of a Caterham: lightweight, fun-to-drive and driver focused,” said Bob Laishley, CEO of Caterham. “The main objective for this project is to develop a vehicle with a weight delta of no more than the equivalent of having a passenger on board. We’re never going to launch a one tonne Seven – we’d rather not do it.”

Given they have no experience in EVs themselves, Caterham turned to specialist UK firm, Swindon Powertrain Ltd., to develop the EV Seven drivetrain. To meet Caterham’s requirements, which included a fast recharge ability to suit the high-performance driving – ie. track days – that many Seven drivers engage in, Swindon modified their existing E Axle power unit and paired that with an immersion cooled battery pack.

The E Axle electric motor sits in the boot area, driving the rear wheels via a single-speed transmission, while a 51kWh battery occupies the transmission tunnel and some of the engine bay in the traditional Seven shape. This placement also helps even out the front/rear weight distribution.

Immersion cooling for the concept’s battery has previously been applied to super computers and uses dielectric fluid that enables better thermal management during repeated charge and discharge cycles.

In Caterham’s case, a ‘20-15-20’ cycle from the electric powertrain will theoretically allow 20 minutes of flat-out driving on a track before fast recharge in 15 minutes (using a 152kW DC fast charger), then a further 20 minutes on track. To ensure battery longevity, only 40kWh of the total 51kWh is usable. Of course, this doesn’t address the lack of DC charging infrastructure, 152kW or otherwise, at racetracks.

“Building a Seven that’s capable of a Sunday morning drive is achievable with current battery technology, but the challenge is for track use where the energy consumption is greatly increased,” Laishley explained. “At the moment, immersion battery cooling is one of the best solutions in terms of coping with the rapid charge and discharge cycles that would be experienced on a racetrack.”

Closely matching the existing Seven in terms of performance has been a key driver of the EV Seven project, too, so outputs of 179kW (240hp) and 250Nm are comparable to the 2.0-litre, four-cylinder Caterham Seven 485 (174kW and 206Nm), as is the estimated 0-100km/h acceleration of 4.0 seconds (3.4 seconds from the 485) and top speed of 209km/h (225km/h). While the battery increases the EV Seven’s weight to approximately 700kg, Caterham says this is comparable to a conventional Seven 485 carrying a passenger.

Other listed features on the EV Seven concept include a limited slip diff, adjustable Bilstein suspension and 13-inch wheels, while the ventilated disc brakes with four-piston calipers benefit from regenerative braking made possible by the EV powertrain.

Caterham are at pains to point out that the EV Seven concept is not the forerunner to a production model in the near future.

“We do not have plans to put EV Seven into production at this stage - it’s a test bed to see how well an EV powertrain works for our customers’ specific use cases,” Laishley added.

“We’re doing this project with our eyes wide open, so that we can learn how to deliver the specific Caterham vehicle attributes necessary for a Seven: light weight, simple and fun to drive. We’re going to bring this to market at the right time, when the future generation of battery technology allows it, and that’s why now is the time for us to trial the concept.”