Caterham has revealed EV Seven – its technology development concept for a future fully electric Seven.
The concept will test the feasibility of a lightweight electric Seven and enable Caterham to move a step closer to bringing a battery electric model to market that is as driver focused as its petrol counterpart.
EV Seven is being engineered in collaboration with Swindon Powertrain Ltd – a leader in the development of advanced and ultra-robust powertrains for both road and motorsport applications. EV Seven is based on the larger Seven chassis and features a bespoke version of Swindon Powertrain’s E Axle, combined with an immersion cooled battery pack.
Immersion battery cooling uses a dielectric fluid, in this case supplied by long-term Caterham technical partner Motul. The fluid is in direct contact with the cells enabling better thermal management during charge and discharge cycles. This cutting-edge technology is at the forefront for battery electric vehicles and, until now, has typically been employed to cool super computers that generate enormous amounts of heat.
Bob Laishley, CEO of Caterham, said: “Any future EV model we produce must be true to the DNA of a Caterham: lightweight, fun-to-drive and driver focused. 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.”
Any electric Seven must be useable on both the road and track. For the latter, this means being capable of a repeatable 20-15-20 drive cycle: the ability to drive on track for 20 minutes and recharge in 15 minutes with enough energy to drive for a further 20 minutes.
“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. 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 race track,” added Laishley.
The weight increase is less than 70kg compared to the current production Seven* it is based upon (meaning a total mass of just under 700kg). Its 51kWh immersion cooled battery is housed in the engine bay and transmission tunnel and is capable of DC rapid charging speeds of up to 152kW. It has a useable capacity of circa 40kWh, safely allowing the battery pack to withstand demanding track use followed by rapid charging without causing premature degradation.
The concept uses a bespoke version of Swindon Powertrain’s E Axle based on the HPDE family. It produces 240bhp at 9,000rpm and instantaneous peak torque of 250Nm. This will deliver a predicted 0-60mph time of approximately 4.0 seconds. The powertrain has been engineered to closely match the performance characteristics of the current production Seven* to ensure EV Seven shares similar driveability to the ICE model.
EV Seven will remain true to the guiding principles of Caterham’s DNA, which is fun, simple and lightweight with an absolute focus on delivering a fantastic driving experience. Chasing performance figures has not been a motivating factor during development, but remaining true to Caterham’s intrinsic values has.
EV Seven will also benefit from a limited slip differential, adjustable Bilstein dampers from the Seven 420 Cup, regenerative braking and quad-piston brake calipers.
“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. 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: lightweight, 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,” added Laishley.
Raphaël Caillé, Managing Director of Swindon Powertrain Ltd, said: “Our history of working with Caterham spans more than three decades – we developed the Vauxhall engine used in the JPE [Jonathan Palmer Evolution] edition Seven in the early 1990s, and we’re thrilled to be able to continue this partnership today through our work on this exciting project.
“The targets we’ve been set for low vehicle weight and battery charging speed are undoubtably ambitious, but the use of cutting-edge immersion cooled battery technology along with our own powertrain components means we’re able to develop an electric Seven that maintains the core values of the original.”
The EV Seven concept will make its public debut at Goodwood Festival of Speed in the UK this July. Caterham is also developing another fully electric sports car concept that it will reveal this year. The design of this project is being led by the brand’s new Chief Designer, Anthony Jannarelly, and further details will be announced in the coming months.
*Article Source http://www.uk.caterhamcars.com/