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Car Info :
The Saab Sonett III
We worked on the 1972 Saab Sonett III, a two door two seater, sports coupe. It's
composed of a metal frame with a fiberglass body and an approximate curb weight
of 2600 lbs. It measures 12.75 ft in length, 4 ft 11 inches in width, and has an
unloaded height of 3 ft 11 inches.
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The Saab Sonett III
The engine and all associated parts except for the transmission were removed and replaced with an electric motor and controller pair. The fuel tank area was used for power batteries. The car can hold 12 batteries, but currently only holds 7 because of some minor problems with the batteries.
The Saab Sonett's Motor
The Saab has a GE Model 5BT1346B50 series winding motor. It is rated at 20.9 hp and 4700 RPM at 90V. It has a
maximum speed of 6500 RPM. The speed is also increased by using a high voltage power supply for the motor; we are
currently using a 84 V supply (see Batteries below) This is translated into forward (or reverse) motion through the use of the
standard Saab transmission that came with the vehicle.
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Saab Motor
The Saab Sonett's Batteries
The Saab Sonett is currently using 6 AGM (Phoenix) batteries (red black batteries) to power its electric motor, but can hold up to 10 traction batteries, and an auxiliary wet cell battery (white battery) for its electrical system (lights, relay systems, etc.). These 12-volt batteries are connected in series to provide a maximum nominal difference of 72 volts to the motor.
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Saab Batteries
Seven batteries can be stored in the trunk area of the Saab, while the other four (3 AGM (Phoenix) plus the auxiliary battery) can be stored under the hood. The batteries can be disconnected from the motor by using the emergency circuit breaking red dial-switch accessible to the driver.
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Red Dial Switch accessible to driver
For a full charge for 5 to 8 hours, each battery should reach 14.4 V before current is reduced. This number changes a bit depending on whether the battery is an AGM (Phoenix) or flooded-cell (Trojan) with removable caps.
The Saab Sonett's Controller
The controller controls the rotational speed of an electric motor through its
output voltage. The rotation of the motor increases with frequency and duty
cycle of the controller output.
The controller unit is unenclosed, which is not very safe for the components. Most new controller units come in
enclosing boxes. The controller uses a dual power-IGBT system to create the power signal for the motor. The pitch and strength
of the whine it gives off is an indicator of the voltage used as well as the frequency of the power signal and its duty cycle. The
signal is controlled via input from an accelerator pedal, which is used just like a standard pedal. If the pedal is shorted out, the
controller will not provide power to the motor, the same holds true if it goes to an open circuit.
