AC Propulsion tzero. The tZero (a mathematical symbol meaning, 'time from a standing start in sequence') is a hand-built electric sports car designed and built in very limited numbers by the U.S. pioneering company AC Propulsion in the mid 1990's. It was the inspiration and direct predecessor of the Tesla line of electric cars. The only part of the tZero that was not proprietary was the body that was based on the Piontek Sportech sports car, yet many parts of the body and interior were extensively modified. It consists of a Kevlar & Carbon Fiber reinforced body built over a custom hand-built reinforced stainless steel fabricated to package batteries space frame with double wishbone independent suspension and rack and pinion steering. AC Propulsion utilized their AC-150 drivetrain, a single-speed electric system with an overall gear ratio of 9:1.

Experimental mule in early 90's, a complete vehicle the following year and launched in January 1996, only 3 prototypes were built, the last one also being an official VIN production car. Prospect interested buyers included many big celebrities, well known scientists, and silicon valley engineers.  Unfortunately, plans for a viable commercial production were eventually dropped in mid-2003. The name comes from t0, the mathematical symbol for a starting point in time. Due to high production costs, AC Propulsion ceased to produce the tzero. Only three were built, and as of 2024 only 2 survive. The only remaining examples are owned by the company itself and a private owner. The last tZero vehicle built used an advanced/updated ACP Gen 2 system that was capable of V2G (vehicle-to-grid & vehicle-to-vehicle charging system). The tZero vehicles were extensively tested. Even including a cross country USA trip. 

Adjustable Regenerative Braking: Because the car recharges its batteries when the throttle is released slowing sharply as energy is recaptured It can be driven hard using only the accelerator pedal. Also, if the car detects a turn with more than half a g-force (5 m/s²), it eases the rear-wheel regenerative braking to prevent slides.

Original lead–acid battery powered tzero

The original version of the tZero roadster ran on 28 Johnson Controls Optima Yellow Top spiral wound AGM deep cycle lead–acid batteries in series, which produced 150 & 165 kW (220 horsepower) and 177 lbs·ft (240 N·m) of torque at 336 volts and accelerated the  car from a standstill to  in 4.07 seconds. The single gear ratio limited the car's maximum speed to  at 12,000 rpm, although it is said that early prototypes fitted with multiple gear ratios could hit . Even with the single ratio, lead–acid models are capable of completing a quarter mile (400 m) drag race in 13.24 seconds. The expected range per charge of the tzero with the lead–acid batteries is  as a result of consuming only 180 watt hours (DC) per mile (112 Wh/km) on the highway and due to regenerative braking.  The car could be charged from 0 to 95% within an hour. The initial base price of this version was to have been US$90,000. but later exceeded to $150K

Lithium-ion battery conversion

Tom Gage was contacted by Martin Eberhard about the tZero car which Gage had built, and was currently converting to lithium batteries, similar to those that make up the battery packs of laptop computers. Gage stated that Eberhard had multiple "Schemes" and that he had to explain to Eberhard how unfeasible most of his concepts were. The conversion was done over six months from March through September, 2003 and gave the tZero a  range. Lighter than the original version by , the lithium-ion conversion goes from  in 3.6 seconds. The single gear ratio limits the car's maximum speed to just over  at 13,000 rpm with proper gearing, though it has never been tested at greater than the electronic limit of  . The base price of the car was US$220,000. Elon Musk and Martin Eberhard encouraged Tom Gage and Alan Cocconi to move the lithium-ion powered prototype into production. Eberhard then borrowed the converted tZero for three months and used it as a daily driver. The 2003 Li-on tZero version achieved over 320 miles range per charge.

JB Straubel then told Elon Musk about the newly converted, now lithium-ion powered tZero and arranged a test drive. Musk also encouraged AC Propulsion to commercialize the vehicle. Tom Gage, however, again deferred in favor of working on their electrified Scion xB called the eBox. But he put Elon Musk in contact with Martin Eberhard which led to Elon Musk's Series A funding of Tesla Motors in April, 2004 and their hiring JB Straubel.

Long Ranger genset trailer

AC PROPULSION also built a range extender for the tZero.  Known as the Long Ranger this was a portable internal combustion powered generator mounted on a trailer that could be towed behind the car and feed power to the batteries during travel. A tZero with Long Ranger was a series hybrid. The trailer used a  Kawasaki engine with a  fuel tank and achieved  in highway driving over at least . It was rated at  DC output and could maintain . The trailer incorporated a novel "backtracking" feature that automatically steered the trailer wheels allowing even novice drivers to easily back a trailer through complex maneuvers; the company published a video demonstrating the ease with which the trailer could be backed through a set of slalom cones.

Production
, only 2 of the 3 tzero production models remain, since Gruber Motor Company's car was destroyed in a building fire in May 2017. The surviving two models are currently on display at The Petersen Museum.

See also
 La Jamais Contente
 Keio University Eliica
 Lightning GT
 Think Global AS
 Venturi Fétish
 Wrightspeed X1
 Aptera Motors
 Tesla Roadster

References

External links

 Lots of Zoom, With Batteries The New York Times, September 19, 2003

Automotive technologies
Electric sports cars
Electric concept cars
Production electric cars