Tesla Roadster Gets 400-Mile Range Upgrade
By Bradley Iger
December 29, 2014
On Christmas day, Tesla CEO Elon Musk took to Twitter to announce a little gift to fans of the company’s Lotus-based all-electric sports car: a substantial boost in the Roadster’s driving range. Taking lessons learned while fine-tuning the Model S sedan, Tesla has now applied that development experience to the diminutive two seater, which Musk asserts will now “enable non-stop travel from LA to SF”.
Where the previous iterations of the Roadster used a 53kWh battery pack, the Roadster 3.0 will now sport a battery pack offering 70 kWh while remaining in an identically sized package. The development and evolution of battery cell design continues to move along at a rapid pace, and the hardware has evolved substantially since the original Roadster’s debut in 2008, making the retrofit of the newest cell technology an obvious focal point when Tesla sought to update the Roadster.
The Roadster 3.0 will also benefit from less aerodynamic drag by way of a revised body kit, which brings the vehicle’s drag coefficient down from 0.36 Cd to 0.31, a 15 percent improvement. Also helping to bolster the Roadster’s efficiency is new set of tires, along with improvements in wheel bearing design and brake drag, all of which are said to help improve rolling resistance.
Tesla says this retrofittable kit is still in the prototype phase, so details on how the aerodynamic bits will affect the Roadster’s appearance, whether the Roadster will now be compatible with Tesla’s Supercharger network, and pricing for the upgrade all remain a mystery at this point. We do know that these upgrades will not be applicable to the Model S “in the near term”, though Tesla has a solid track record of continuing to offer upgrades to older models as new technology becomes available. Check out the press release from Tesla for additional details.
The Roadster 3.0 package applies what we've learned in Model S to Roadster. No new Model S battery pack or major range upgrade is expected in the near term.
Battery technology has continued a steady improvement in recent years, as has our experience in optimizing total vehicle efficiency through Model S development. We have long been excited to apply our learning back to our first vehicle, and are thrilled to do just that with the prototype Roadster 3.0 package. It consists of three main improvement areas.
The original Roadster battery was the very first lithium ion battery put into production in any vehicle. It was state of the art in 2008, but cell technology has improved substantially since then. We have identified a new cell that has 31% more energy than the original Roadster cell. Using this new cell we have created a battery pack that delivers roughly 70kWh in the same package as the original battery.
The original Roadster had a drag coefficient (Cd) of 0.36. Using modern computational methods we expect to make a 15% improvement, dropping the total Cd down to 0.31 with a retrofit aero kit.
3. Rolling Resistance
The original Roadster tires have a rolling resistance coefficient (Crr) of 11.0 kg/ton. New tires that we will use on the Roadster 3.0 have a Crr of roughly 8.9 kg/ton, about a 20% improvement. We are also making improvements in the wheel bearings and residual brake drag that further reduce overall rolling resistance of the car.
Combining all of these improvements we can achieve a predicted 40-50% improvement on range between the original Roadster and Roadster 3.0. There is a set of speeds and driving conditions where we can confidently drive the Roadster 3.0 over 400 miles. We will be demonstrating this in the real world during a non-stop drive from San Francisco to Los Angeles in the early weeks of 2015.
We are confident that this will not be the last update the Roadster will receive in the many years to come.