The Electric Powered Hot Rod- Amped Up

DC and AC Systems: DC drive systems came out first, because at the time, AC electronic drive technology wasn't available. Both DC and AC systems create maximum torque at zero rpm and beyond, while the internal combustion engine doesn't reach peak torque until well into its upper rpm range. As it takes torque to accelerate a car, an electric motor holds a distinct advantage over an engine when it comes to propulsion. AC drives have distinct advantages over DC: No brushes or commutators are required, there is less maintenance, higher efficiency, higher power-to-weight ratio, and higher reliability. However, AC drives are extremely complex, electronic-intensive, and so far are more expensive than DC drives. So which would be preferred for an electric hot rod? Actually, a DC system would be preferred, as there's no substitute for the raw torque that a series-wound DC motor produces. Also, the DC hardware of today comes in a greater variety with more horsepower for less money than AC.

Batteries: Most electric cars utilize some form of lead-acid battery because they represent what's widely available and affordable. A lead-acid pure battery-powered car will use thick-plated batteries (rather than an automotive starting batteries) so that the batteries can survive repeated deep discharges. Golf cart batteries work very nicely, and come in 6-, 8-, and 12-volt varieties. Every EV is mission-specific, so if you are range-oriented, you'll use 6-volters. If you are more speed and acceleration-oriented, you'll use 12-volters. If you'd like to compromise between the two, you'll use 8-volters. A typical pure battery-powered car conversion will have a battery system of between 96 and 144 volts. If using all 12-volters, you'll lighten the battery load, but have less range. Conversely, if using all 6-volters, the battery weight will be heavier but the range will be extended. A mid-sized automobile or pickup truck conversion with a pack of 24 6-volters will have a top speed up to 90 mph, but a maximum range of only about 70 miles. Many car conversions carry just enough lead-acid battery to run 50 miles max.

There are battery technologies that offer more power and energy than lead-acids. Ni-cads, nickel-metal-hydrides, and lithium-ion technologies fit into this category. Below is a brief comparison as compared to lead-acids of the same size and weight.

As noted, these batteries have their advantages, but the cost can be a project killer. Today, most of the talk is about lithium-based technologies. These batteries are state-of-the-art, and have an added feature in that their specific power (horsepower-to-weight ratio) is ten times higher than lead-acid. So, if you're building an electric hot rod for the -mile, lithium-ion would be the battery of choice.

Electric Hot Rod Expectations: As mentioned previously, every EV is mission-specific. It's up to the builder to define performance expectations in advance before the drive system gets locked into hardware. Definition of performance should include top speed, maximum range, acceleration, and gradeability requirements. Once those plus the weight of the vehicle are known, a set of drive system hardware can be defined. That being said, the table shown is a rough estimate for DC conversion kit cost, battery type and cost, and expected performance that could be placed into an electric street rod of your choice. (Of course, if the vehicle is lighter than average, acceleration will be improved.)

Speed vs. Range: With an EV you can't drive at top speed and expect to achieve maximum range. I've noticed that a "one-third rule" seems to apply. Maximum range occurs when you drive at 1/3 of top speed; conversely, if driving at top speed, only about 1/3 of maximum range will be experienced.