The Electric Powered Hot Rod- Amped Up

Motor Options: Electric motors are rated differently than internal combustion engines. ICEs are rated in peak hp, the peak is fairly narrow, and located well into the higher rpm range. An electric motor is rated in both continuous and peak hp. An electric motor's hp peak has a broad distribution, kind of like a bell-shaped curve. Because of the difference in rating systems and different distribution of hp, an ICE can be replaced by an electric motor with a continuous rating of only 1/3 or ; a 30 hp (continuous) electric motor can do the same work as a 100 hp ICE.

With AC drive systems, the most powerful EV motor around can be found in the Tesla electric. It can put out around 250 hp peak, and about 100 hp continuous. Tesla hardware is not commercially available, but an AC-150 system made by AC Propulsion in San Dimas, California, is rated at 220 hp peak/85 hp continuous. Of course, the motor alone is meaningless without the power inverter to drive it. System cost is about $28,000, and that does not include batteries.

With DC drive systems, motors are available from 5 to 400 hp peak. If one motor can't put out the desired amount of power, then try two or more. Many DC motors are double-shafted. The shaft of one can be coupled in tandem with another, or they can be coupled together with a common belt arrangement. Series-wound DC motors are preferred for drag racing. The raw torque-per-amp that they generate is amazing. For example, with my 2-motor, 2x400 hp electric roadster project, each motor puts out up to 775 lb-ft of torque for 1,550 lb-ft total. With a DC motor, horsepower and torque numbers are not commensurate. Most ICEs with 400 hp will produce about 400 lb-ft of torque, plus or minus, yet a 400 hp DC motor can put out close to two times the torque-to-hp ratio. You might say they are more like a diesel engine in nature. A 400 hp diesel can put out close to 800 lb-ft of torque. However, a DC motor will not "run out of torque" at low speed like a diesel engine. Depending on how they're loaded, DC motors can produce their high torque to 4,000 rpm and beyond before it begins to roll off.

Transmission vs. No Transmission: Since electric motors produce maximum torque at very low rpm, it's natural to think that they can be used without a transmission. This is not necessarily true. The heavier a vehicle is, the more torque it takes to accelerate it. If a vehicle is very heavy, the torque required for acceleration may be more than an electric motor can produce, depending on the gear ratio between the motor and the wheels. (Anyone who tries to drive a gas-engine car from a standing start in second or third gear can relate to "torque required vs. torque produced.") In a nutshell, heavy vehicles should consider using a transmission with their electric motor, and lighter vehicles may be able to get away without one. When using a fixed ratio between motor and wheel (no transmission), the ratio should be carefully chosen to provide a compromise between top speed and acceptable acceleration. If you gear it too low, you'll have good acceleration, but you won't hit the top speed you want. If you gear it too high, you'll be able to hit desired top speed, but the acceleration rate to get there may be unacceptable. Slow acceleration under high torque demand throws away a lot of energy in the form of heat.