Tesla 2011 Annual Report Download - page 13

Table of Contents
hours using a 240 volt, 40 amp outlet that is widely available in many homes in the United States for electric appliances. A high power
connection capable of 240 volts and 70 amps reduces this charging time to about 4.5 hours. Such a connection can be installed in many homes
with the assistance of a qualified electrician. For additional flexibility, the Tesla Roadster battery pack can also be charged with a 120 volt, 15
amp connection. Using this lower power output, the Tesla Roadster battery pack can be charged to full capacity in about 42 hours. This
flexibility in charging provides customers with additional mobility, while also allowing them to conveniently charge the vehicle overnight at
home.
For the Model S, we plan to offer a high-voltage fast charge option that will enable the vehicle to charge from higher amperage, DC
commercial charging stations that we anticipate may be available in the future.
Motor
Our powertrains currently use custom designed 3-phase induction motors. We believe we have made several important innovations in our
motor design that minimize mass while still providing high power and efficiency. Our motors incorporate a proprietary fabricated copper rotor
design. Our motors also include optimized winding patterns that allow for easy manufacture and fit in as much copper as possible to reduce
resistance and energy losses.
We also use high-quality bearings and precision balancing on the rotor and shaft to enable the spin of the motor up to 13,000 revolutions
per minute, or rpm, in normal operation. Combining this very high rpm rating with an instantaneous stall torque of over 200 foot pounds gives a
broad torque-speed map that allows a single speed gearbox to deliver high vehicle performance.
Gearbox
We have designed a custom, single speed gearbox that is manufactured in-house for the Tesla Roadster. The Roadster gearbox combines
low mass with high efficiency and can match both the speed and torque capabilities of Tesla’s AC induction motors. In comparison to a
gasoline-powered vehicle, the elimination of gear changes contributes to the rapid acceleration characteristics of the Tesla Roadster. We plan to
design and manufacture the gearbox for the upcoming Model S sedan.
Control Software
The performance and safety systems of the Tesla Roadster and its battery required the development of sophisticated control software.
There are numerous processors in the Tesla Roadster to control these functions, and we write custom firmware for many of these processors. The
flow of electricity between the battery pack and the motor must be tightly controlled in order to deliver the performance and behavior expected
in the vehicle. For example, software algorithms enable the vehicle to mimic the “creep” feeling which drivers expect from an internal
combustion engine vehicle without having to apply pressure on the accelerator. Similar algorithms control traction, vehicle stability and the
sustained acceleration and regenerative braking of the vehicle. Drivers use the information systems in the Tesla Roadster to optimize
performance and charging modes and times. Software also is used extensively to monitor the charge state of each of the cells of the battery pack
and to manage all of its safety systems.
We plan to leverage our investment in software for the development of the Model S. In addition to the vehicle control software, we also
intend to develop software for the infotainment system of the Model S.
Vehicle Design and Engineering
In addition to the design, development and production of the powertrain, we have created significant in-
house capabilities in the design and
engineering of electric vehicles and electric vehicle components and
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