Tesla Roadster #854

Energy Storage System

Tesla described the pack as an Energy Storage System of 6,831 individual lithium-ion cells, “roughly the size of a storage trunk,” and “about 900 pounds.”² Tesla’s service data lists the same cell count and a pack weight of “~900 lb (408 kg).”⁴ The company’s battery paper says the pack was designed around commodity 18650 cells — so named for an 18 mm diameter and 65 mm length — and “stores about 53 kilowatt hours of electric energy.”³ Tesla’s 2011 Form S-1 states that the pack “contains 53 kilowatt-hours of usable energy” and “uses commercially available lithium-ion battery cells.”⁷

Tesla’s official service documentation describes the internal layout as 11 sheets in series, each sheet made of 9 bricks in series, and each brick a group of 69 cells in parallel (11 × 9 × 69 = 6,831).⁶ Official public materials consistently call the chemistry lithium-ion; they do not name a single cell supplier or a more specific cathode chemistry, so those details are omitted here.

Powertrain and gearbox

Tesla’s service data lists the motor as a 3-phase, 4-pole electric motor, rated at 375 V, with a maximum speed of 14,000 rpm.⁴ The company’s 2010 performance specifications describe a “375 volt AC induction air-cooled electric motor with variable frequency drive.” For the Roadster Sport they list “288 peak horsepower (215kW) and 295 lb-ft (400 Nm) of torque,” “0 to 60 mph in 3.7 seconds,” and a top speed of “125 mph (electronically limited).” The same page lists the base Roadster at the same peak horsepower, 273 lb-ft (370 Nm), and 3.9 seconds to 60 mph.¹

Early production used a two-speed transmission. On September 9, 2008, Tesla announced it had “selected BorgWarner Inc. for the production of a single-speed gearbox for the Tesla Roadster.” CTO JB Straubel said that the previous December, “when the two-speed transmission designed by a previous supplier proved not to be durable, we announced we would modify our approach,” and that a more powerful inverter and enhanced motor allowed a single-speed gearbox while still meeting the original performance goals.⁸ That announcement also said the new powertrain “achieves an EPA combined range of 244 miles on a single charge, up from Tesla’s previously announced EPA range of 221 miles.” Tesla’s later 2010 specifications and 2011 S-1 state a range of 245 miles on the EPA combined two-cycle test.¹⁷

Chassis and assembly

In a March 2008 company blog, Tesla wrote that the Roadster is not “an electrified Lotus Elise,” and that “the total number [of shared parts] was under 7% by parts count.” The same post says “body panels (except for the bumpers) are made entirely of carbon fiber to minimize weight.”⁹

Assembly was split. A July 2008 Tesla blog described Lotus assembling the car at Hethel, in the United Kingdom, as a “glider,” with “everything but the battery and powertrain” installed there, then shipped to California. “The Tesla Store about to open in Menlo Park will do the final installation of the battery and powertrain.” The same account states that 6,831 lithium-ion cells were sent from Japan to California, where the battery was built.¹⁰ Tesla’s published curb weight for the Roadster 2 / Roadster Sport is 2,723 lb (1,235 kg), with no occupants or cargo.⁴⁵

Range, firsts, and a long-distance run

Tesla’s October 27, 2009 press release states: “The Tesla Roadster is the first production automobile to use lithium-ion battery cells and the first production EV with a range greater than 200 miles (320 km) per charge.”¹⁴ The same release reports that a Roadster completed 313 miles (501 km) on a single charge in Australia’s Global Green Challenge, a conservation run rather than an EPA test. For the later Roadster 3.0 upgrade package, Tesla estimated “a predicted 40-50% improvement on range” and wrote that, under “a set of speeds and driving conditions,” it could “confidently drive the Roadster 3.0 over 400 miles.” That estimate is not an EPA rating.¹⁶

Versions and the Roadster 3.0 upgrade

Tesla’s service data distinguishes a Roadster 1.5 motor (215 kW, 370 Nm) from a Roadster 2.x motor (215 kW, 400 Nm), both 3-phase, 4-pole units.⁴ The 2008 single-speed BorgWarner powertrain is the official account of the 1.5-era drivetrain change.⁸ Tesla’s 2011 S-1 says the company introduced “the Tesla Roadster 2, and its higher performance option package Roadster Sport,” and that “On July 1, 2010, we introduced the Roadster 2.5, with new styling and an upgraded interior.”⁷ The July 1, 2010 announcement lists a new front fascia and rear diffuser, new seats, power-control hardware for very hot climates, an optional 7-inch touchscreen with back-up camera, and added interior sound reduction.¹³

On December 26, 2014, Tesla announced a prototype “Roadster 3.0 package,” including a pack that “delivers roughly 70kWh in the same package as the original battery,” plus planned aerodynamic and tire changes.¹⁶ In that post Tesla estimated “a predicted 40-50% improvement on range between the original Roadster and Roadster 3.0,” and wrote: “There is a set of speeds and driving conditions where we can confidently drive the Roadster 3.0 over 400 miles.” That is Tesla’s stated estimate for the Roadster 3.0 upgrade package. It is not an EPA rating.¹⁶ In July 2016, Electrek reported that the production retrofit, referred to as R80 for its roughly 80 kWh capacity, had begun to reach owners, and that the retrofitted packs “are rated at about 340 miles of range.”¹⁷ No equivalently solid official source was found for a later “R90” pack, so none is listed here.