Introduction to Electric Vehicles

As the name implies, electric vehicles are powered by an electric motor rather than a gasoline engine. Certainly, more silent than conventional gasoline powered vehicles, the primary reason why there is such interest in further developing this technology is its potential to positively impact the environment.

Electric vs. Gasoline-Powered Vehicles

There are obviously significant differences between electric and gasoline powered vehicles:

• An electric motor replaces the gasoline engine.
• The electric motor gets its power from a controller which is, in turn, powered by rechargeable batteries. The controller can best be viewed as the conduit between the accelerator pedal and the amount of power delivered to the vehicle and the batteries provide the power.
• A gasoline engine gets its power from fuel via a conglomeration of lines, pipes, hoses and a manifold where as an electric car’s “power train” is primarily wires.

Perhaps a way to better understand the difference is to explore the process it takes to convert a gasoline-powered vehicle to one powered by electricity:

• Remove the gasoline engine, muffler, catalytic converter, tail pipe and gas tank.
• Remove the clutch assembly but leave the manual transmission in place, locked in second gear.
• Bolt a new AC electric motor to the transmission.
• Add an electric controller to control the AC motor.
• Install a battery tray with enough 12-volt lead-acid batteries to create 300 volts DC in the front of the car.
• Install additional electric motors to provide power to the water pump, power steering pump and air conditioner.
• Add a vacuum pump for the power brakes
• Replace the shifter for a manual transmission with a switch to control forward and reverse.
• Add an electric water heater to provide heat and a charger to recharge the batteries. Typically, these cars can be charged from a normal 120-volt or 240-volt outlet or from a magna-charge inductive charging paddle.
• Replace the gas gauge with a volt meter.

With these and perhaps other less significant changes made, the actual starting and operation of the vehicle is not appreciably different. Simply put the key in the ignition and turn it to the “on” position. Shift into “drive,” and push the accelerator pedal and go. There are some differences, though in terms of operating performance (subject to continuing improvement in technology):

• The range is considerably shorter (typically around 50 miles), which depending on the driving routine of the individual, may or may not be a significant limitation.
• The time to go from 0 to 60 miles per hour can be as high as 15 seconds.
• Recharging the car after a 50 mile trip consumes about 12 kWh of electricity or less than $1.00, or $.02 per mile (less than a quarter the cost of gasoline).
• The batteries, typically lasing 20,000 miles, are heavy (approximately 1,100 pounds), with replacement costs in the range of $2,000 (or $0.10 per mile). This is obviously the weak link in the equation, leading to a drive to develop fuel cells.

Electric Vehicle Motors

Electric vehicles use either AC or DC motors. Typically:

• DC motors, simpler and less expensive, operate between 96 and 192 volts providing between 20,000 and 30,000 watts of power. These motors can be overdriven up to a factor of 10-to-1 for short periods of time, which is great for short bursts of acceleration. If using this feature, the operator must be careful to monitor the heat of the motor, as DC motors can self-destruct.
• AC motors are 3-phased, operating at 240 volts AC with a 300 volt battery pack. Not only are these types of installations easier to match in terms of size, shape or power rating, they also have a “regeneration” feature where, during braking, the motor transforms into a generator and repowers the batteries.

Batteries – the Weak Link with Electric Vehicles

There are a number of issues with current lead-acid battery technologies:

• The batteries are heavy, typically more than 1,000 pounds, and bulky. It is not unusual for a vehicle to require 50 lead-acid batteries or over 14,000 cubic inches of space.
• Their capacity is limited. A lead-acid battery pack holds between 12 and 15 kWh of electricity for a range of 50 miles.
• Recharging times range between 4 and 10 hours.
• The battery life is 3 to 4 years, usually enough for 200 full charge / discharge cycles and their replacement is cost is quire high at $2,000 per battery pack. NiMH batteries can serve as an alternative to the lead-acid batteries, more than doubling the range of the vehicles and extending battery life to 10 years. However, the cost of NiMH battery pack is as high as $30,000. This pricing issue will likely abate over the next few years as technology advances.

Factoring these challenges into a comparative analysis of batteries vs. gasoline yields the following:

• 2 gallons of gasoline (or 15 pounds) costs less than $7.00 and takes 30 seconds to pour into the gas tank.
• The equivalent comparison for lead-acid batteries is 1,000 pounds of lead-acid batteries at a cost of $2,000 taking 4 hours to recharge.

This comparison leads inevitably to a need for better technology to make electric vehicles more commercially viable: smaller, lighter and instantly rechargeable fuel cells. Though technically feasible, there is still a significant amount of research and development to perform before this alternative to batteries becomes operational.

1. energyauthority says:

   May 20, 2010 at 2:10 pm

   Please feel free to use the quotes…thanks