Electric Cars Tech

If you are in the market for an EV or just looking for a dangerous amount of knowledge, the next few paragraphs will get you up to speed. If you want to dive deeper, the links that follow the article will have you engineering your own electric vehicle conversion in no time.

Basics
All-electric cars, a.k.a. electric vehicles (EV) or battery electric vehicles (BEV), are propelled purely by means of an electric motor powered by an on-board battery (to be precise, the battery powers a controller which in turn powers the motor). The battery can be recharged using a standard electrical outlet or at a charging station.

Motor Types
AC Motors
Virtually all of the EV's and hybrids on the market use AC motors. Alternating-Current motors are better for continuous power (hills). Starting power is slower, but the motor can run at high RPMs without overheating. Because they can run at high RPMs they do not require a transmission. They can also move a heavier vehicle.

AC motors are best suited to the regenerative braking systems featured in both EVs and hybrids. Regenerative braking, which returns braking power to the battery, combined with superior efficiency make for better fuel economy. Generally speaking, AC motors run more smoothly and can be precisely controlled. For these reasons, production model electric cars and hybrids use AC motors.

AC motors have significant disadvantages, particularly for the DIY hobbyist. They are more expensive than DC Motors and so are the battery packs. They are also more complicated to control. Because battery output is DC, they require a converter which takes up a lot of space.

DC Motors
Though the debate rages on, about the pros and cons of AC vs DC, DC Motors are the favorite choice of DIYers who convert their gas-powered cars to electric. DC motors are more affordable and easier to control. They also have greater initial torque and higher peak power, so they are popular with racers.

A major disadvantage of DC motors is a tendency to overheat. They also become very large and heavy according to their power output.

AC conversion kits are now available and will become more popular for conversions. However, there are a wide variety of DC motor designs which may improve for EV application.

Battery types
Batteries are the greatest obstacle to the proliferation of EVs. Electric cars require a lot of batteries which must be installed in an array and housed in a battery pack. These batteries are heavy (the Tesla Roadster's battery pack weighs 1,000 lbs) and take up a lot of cubic centimeters. Then there is the simple fact that batteries run out of power and must be recharged.

"But regular cars have to be refueled," you might say. True, but if we're going to replace gas stations with charging stations we're going to have a parking problem because batteries take a long time to recharge.

Three types of batteries are found in electric cars:
Lead-acid batteries
Oldest type of rechargeable battery. Cheap to produce and compatible with existing electronics. Messy, toxic and prone to explosion.
Lithium ion batteries [Li-ion]
High energy-to-mass ratio (which means less weight per unit of stored energy). They retain their stored energy when not in use but lose capacity with age. Considered to have the most potential for mass-market EVs but the most advanced models are too expensive. NiMH batteries are toxic and require special handling to recycle.
Nickel metal hydride [NiMH]
Good energy-to-mass ratio (a.k.a. energy density). Non-toxic which makes for easy recycling. The major disadvantage to nickel metal hydride batteries is that they don't hold a charge very well when they aren't being used.
The problems with battery technology explain why there is so much excitement around fuel cells. Compared to batteries, fuel cells will be smaller, much lighter and instantly rechargeable