High School Senior builds “700 HP” electric Honda S2000

Honda S2000 with electric motors installedYogi Berra once said: “In theory there is no difference between theory and practice. In practice there is.” Juan Ehringer, a high school senior, is undertaking the ambitious project of converting his Honda S2000 to 100% electric power, and is putting both theory and practice to the test.

Purchased for $6000 in running condition with a few cosmetic issues, Juan tore out the factory 240 HP F20C engine, transmission, interior and gas tank. In its place are two 9” NetGain Motors TransWarp 9 motors .

Why the “700 HP” in the title? Well the TransWarp 9 is only rated at 34 HP, though this is for ‘continuous’ use. With two motors this would imply a total output of 68 HP. In a drag racing application the voltage and current passed to the motor could be much higher than designed but there are still limits.

In theory the lithium-ion battery pack is capable of capable of outputting 343 Volts at over 2400 amps, which equates to 823 kilowatts or some 1100 HP. This power needs to be passed through a controller (to vary the voltage/current to the motors), and it has a limit of 2000 amps, reducing theoretical output to 343 kW or 920 HP. Juan then assumes an 85% drivetrain efficiency and calculates a power output of 782 HP.

As JayLS pointed out the efficiency of the motors dictates that some 52 kW of energy will be dissipated at 700 HP. What is 52 kW, or 70 HP, of energy? An average internal combustion engine is about 30% efficient. The energy that doesn’t make it to the flywheel is converted to heat, through the cooling system and exhaust. So 70 HP of heat is approximately the amount of energy that a 30 HP internal combustion engine ‘rejects’ through exhaust gas heat and the cooling system at full output. It’s also the amount of heat put off by about thirty-five 1500 Watt toasters, and all of this heat is concentrated in the electric motors.

In addition batteries heat up when discharged and user JayLS also voices concerns that battery temperatures would be critical and their life live would be severely compromised. Electric-powered vehicles, like their internal combustion counterparts, also have to worry about proper cooling.

John Wayland of Portland, Oregon races a 1972 Datsun 1200, dubbed the White Zombie, with similar specifications. His electric vehicle, utilizing lead-acid batteries, runs twin Impulse 9 motors rated at 30 HP in continuous use. With a weight of only 2348 lbs he has run the ¼ mile at 10.400s @ 117.21 mph. A video of his car at the drag strip can be seen here:

We estimate Juan’s car will have a curb weight of about 3000 lb (almost 30% more than John’s Datsun) and with motors rated for 10% more power he could expect slightly slower, though still very quick, quarter mile times.

As the factory brakes rely on a vacuum source for braking assist he installed a pump and reservoir to maintain the factory braking components.

The stock S2000 is definitely not up to the task of the torque to be produced by the electric motors so Juan chose a Ford 8.8” and custom axles. Again the stock braking components and sensors are retained to help simplify the conversion.

We wish Juan the best of luck and his project car will teach him more theory and real-world engineering than any class he will take in high school!

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Source: http://hackaday.com/2012/09/16/700-hp-electric-honda-s2000-built-by-high-school-senior/ and http://www.s2ki.com/s2000/topic/975497-wait-that-isnt-an-f20c/