From SanFranciscoEVA

WhyElectricCars.pdf

What IS an EV anyway?

An Electric Vehicle (commonly called an "EV") is a vehicle which is powered by electricity. Pretty simple, eh? EVs can take almost any form: cars, SUVs, submarines, trains, scooters, airplanes, cruise ships, and ebikes ...not to mention drag racers, forklifts, cargo trikes, hot rods, road-runners, torpedoes, sports cars, station wagons, blimps, motorcycles, wheelchairs, spacecraft.... well, you get the idea.

An EV is any form of transportation that has:

• its wheels (or propeller, etc) turned by one or more electric motors
• a source of electricity (usually carried onboard the vehicle)
• a way to control the amount of electricity which goes to the motor(s)
• a way to recharge the source of electricity (often carried onboard the vehicle)

Motors

EVs can use either DC (Direct Current) or AC (Alternating Current) motors. A motor is a device which uses energy in order to perform work. In general, the more energy a motor is given, the more work it will do, up to the point where the motor burns itself out. Electric motors come in many sizes - the motors used in average EV conversions (ie: a gas car which has been converted to electricity) are the rough shape of a paint can and are about 9"-11" in diameter.

Electricity

EVs are powered by electrical energy. Electricity can be generated and stored by many diverse methods. Most EV drivers rely on large-scale (municipal or private) power plants to generate the electricity they use, and simply "plug-in" as needed. An electric charge has Voltage (which indicates how "fast" the charge is), and Amperage (which indicates how "heavy" the charge is). The electric current in common household and business wall sockets "runs" at 110v (providing ca. 10-30amps, or more), and many homes and businesses also have 220v (which includes more amps; socket is often in the garage, for the washer/drier, etc) and (more rarely, with even greater amps available) some have 440v connections. For safety purposes, the law stipulates that each voltage level has it's own unique socket geometry. [NOTE: the idea of electricity having "speed" and "weight" is just an analogy, used to illustrate the nature of electrical energy. Think about rocks: a light rock moving at a high enough speed will carry as much energy as a heavy rock moving at low speed. It's the same with electricity: an electrical charge with 1 Amp at 100 Volts has the same amount of energy as a charge with 100 Amps at 1 Volt. 1 Amp at 1 Volt equals 1 Watt, by the way.]

Batteries: Electrical charge is usually stored in a Battery. A battery will supply a certain number of Amps ("units of weight"), at ("the speed of") a certain Voltage, for a certain amount of time. The capacity of an EV's battery pack will be balanced against the Amperage and Voltage requirements of its motor(s) during the course of operation (ie: the distance/time the EV will be driven between charges). That is to say, the greater the range an EV needs, the larger the capacity it's battery pack needs to have.

Actually, the amount of total energy which can be discharged from a battery pack depends on how the battery pack is being discharged. Each different kind of battery chemistry (eg: PbA, NiMH, NiZn, LiP, NiCad, etc) has a different "sweet spot" (ie: optimal ratio between the number of amps drawn and the voltage at which they are being drawn), at which the greatest amount of power can be discharged from the pack at any given time.

Batteries are getting better every day. There are many different types of batteries available today, and many more new types on the way.

One of the most promising battery types available today is Lithium Polymer (LiP, already used in most modern cell phones and electric radio control model airplanes), in terms of it's power-to-weight ratio, which can give an EV car or truck a range of 200-300 miles between charges - at least as far as many cars today can go on a single tank of gas. LiP is currently expensive, but the price will drop as production volume increases, and it may well be the "breakthrough" batteries which finally puts an EV in every garage.

Another good battery chemistry is Nickel Zinc (NiZn), which might not have an energy density as good as LiP, but it's still better than PbA (eg: a standard 12v lead-acid car battery) and the materials it's made of are plentiful, inexpensive, and not toxic like lead is.

Considering the huge number of different advanced battery technologies currently being researched, developed, and prototyped, plus all of the near-future advances already being proposed utilizing nano-scale engineering techniques, battery technology is, today, just at the beginning of a major leap forward. In any case, right now - today - even a hobby-built EV conversion using an inexpensive lead-acid battery pack will do, on a single charge, 80-90% of everyday driving in the USA, and cars that are built as EVs from the ground up have even better performance.

Controllers

The speed of an EV is determined by how fast the motor is turning. Generally, the higher the Voltage supplied to the motor, the faster the motor turns (until the motor burns out). The Amperage a motor draws depends on how much work is required in order to maintain the speed of rotation as determined by the Voltage.

A Controller is an electronic device which regulates how much electrical charge is being moved from the battery pack to the EV's motor(s). (A general rule is: the more power the controller can deliver, the heavier it will be - this is because big heavy chunks of metal are often used to control large electrical charges.)

Both the Amperage and the Voltage being fed to an EV's motor can be separately controlled, and a good controller will limit or boost each as needed in order to control the EV's acceleration and speed. Like batteries, different motor types have different power profiles - ranges of amp/volt ratios at which the motor will most optimally perform. The better a controller is, the more accurately it will deliver the most optimal amp/volt ratio from the battery pack to the motor at any given time.

While many good EV controllers take advantage of onboard programmable computers and data storage, a controller can be as simple as an on/off switch. In fact, one popular method of controlling DC motors is little more than an on/off switch that turns on and off thousands of times per second (PWM - Pulse Width Modulation), with the frequency of the switching and interval between the switching determining how fast, and with how much power, the motor will turn. The controller itself is controlled by the driver (that's you), using the accelerator (eg: the "gas" pedal). Some controllers can also take the electric charge (or "current") generated by the motor when it is "free wheeling" (an electric motor becomes a generator when an external force turns the motor, such as when an EV is rolling down a hill, for example), and send it back to the battery pack (or to some other energy storage device, such as a pack of super-capacitors or a flywheel). This is called "regenerative braking", and it can significantly extend an EV's range, especially when driving in stop-and-go traffic.

Recharging

Because EV's use electricity, there is almost no limit to the ways that power can be generated for use in an EV. Electricity can be generated using energy from such diverse sources as steam, falling water, heat, combustion, wind, ocean tides, sunlight, physical motion, or chemical reactions.

Whatever source of electricity is used, an electronic device (called a "charger") is required to regulate the flow of electric charge from the source into the EV's storage device (eg: battery pack). As with controllers, a charger can be as simple as a direct connection between the source and the battery pack, but a good charger will alter the Amperage and Voltage of the current during the charging cycle to best suit the type of battery being used. Typically, most batteries can be charged up to about 80% full just about as fast as electricity can be pumped into it, and then require a lower, more carefully regulated, amount of current to "fill up" the remaining 20%. Because each battery chemistry is different, good chargers are adjustable or even programmable, and EV hobbyists continue to experiment and gather data to find the best charging profiles for different types of batteries.

Electric vehicles include more than just autos

For an introduction to electric bicycles, scooters, and motorcycles, see this article and sidebar in The New York Times (requires registration):

• http://tinyurl.com/6h5ab
• http://tinyurl.com/4l6jv

What's an EV Good For?

• Clean - EVs are a clean, efficient, and nearly silent method of transportation that are inexpensive to operate, smog-free, and have very flexible design limits. Other than the batteries (which need to be replaced occasionally, though some types of batteries last much longer than others) the major parts of an EV (motor, controller, charger) will typically work reliably for a very long time with little, or no, maintenance.

• Power - While it is possible to have EVs that are very efficient and use very little power, it is also possible to have EVs that are extremely powerful and are at least as quick as the most expensive high performance sports cars on the road.

• Speed - Unlike internal combustion engines (gas, diesel, etc), electric motors have a nearly instantateous reaction time, giving EVs a thrilling level of driving performance that gas engines simply can't match. 0-60mph acceleration in the 4-5 second range is easily accessible, and there's plenty of room for improvement on that by good mechanics! EVs have begun to make their mark in the racing world over the past few years, and are an exciting option for racing enthusiasts.

• Performance - Since the heaviest part of an EV (its batteries) can be placed anywhere, EVs are easily built with optimally-located centers of gravity, again giving them driving performance characteristics which gasoline-powered cars cannot match.

• Flexibility - Electricity can be easily generated in a wide variety of ways, so EVs do not rely upon the fragile global infrastructure of oil fields, tanker ships, pipelines, refineries, interstate trucking, and networks of service stations in order to operate. For example, many people already power their EVs (as well as their homes) solely with electricity generated by solar panels on their rooftops! And farms with enough wind can pay for themselves by selling electricity generated with mega-watt sized (readily financible, quickly installed, and easily maintained) wind turbines, using less than an acre of land each (much of which can still be cultivated or used for grazing once the wind turbine has been installed)!

Why Are People Who Drive EVs Always Grinning?

It's that EV Grin. Everyone gets it the first time they take a ride in a real EV.

Perhaps it's the quiet hum of the motors as the EV leaps forward. Or the eye-opening surprise at the unexpected G-forces. Yeah, that's all part of it.

It's easy to grin, too, when your cost-per-mile for electricity is a LOT lower than the cost-per-mile for gasoline (not even counting the cost of routine tune-ups, oil changes, spark plugs, filters, gaskets, etc, that EVs do not require).

Because there are so many ways to generate electricity, and because electricity is so universally available, EVs offer drivers transportation independence. And every home can easily generate all the electricity it needs (including the power needed for an EV, or two) using solar panels on the roof and small kilowatt-sized wind turbines on the flagpole or chimney, providing true energy independence. But even using "grid" power (from the local power utility) it is still cheaper and cleaner to drive electric than to drive a gas-burning vehicle.