What is an electric vehicle and how does it work? These two questions are the starting point for many people when it comes to electric vehicles.
The Basics
What is an electric vehicle?
Commonly, when people are new to electric vehicles and hear a car is power by electricity, their first surprised response is “‘No gas?”. Yes, that’s right, no gas. A pure electric vehicle (EV) is a vehicle powered 100% by electricity. Electric vehicles work by turning a motor with electricity from one or more storage sources. A good example of a production electric vehicle is the Tesla Roadster.
What is a hybrid electric vehicle?
A hybrid electric vehicle is a vehicle that uses two or more fuel sources to power it. The most common type of hybrid available today is the gas-electric hybrid. A gas-electric hybrid uses both an electric motor and a gas engine to power the vehicle. Popular hybrid electric vehicles available today include the Toyota Prius and Honda Insight.
Types of electric vehicles?
Just like there are many types of cars and trucks, there are different types of EVs. Almost all EVs use batteries to store electricity until it is ready to use, however the original source of that electricity classifies vehicle into a few difference categories. The two main classes of EVs are plug-in electric vehicles and solar electric vehicles. Solar EVs generate electricity from photovoltaic cells using sunlight, while plug-in electric vehicles fill batteries using an external energy source such as the Power Grid (or more commonly referred to as a standard electrical outlet). Today the most common type of electric vehicle is the plug-in battery electric vehicle.
Electric Vehicles and Batteries
As I said before, almost all EVs use chemical batteries to store electricity just like a fuel tank in a gas car. There are numerous types of batteries in production today, each with their own set of attributes. Electric vehicles require large amounts of power rather quickly from batteries, thus only batteries that are designed for large power supply can be used in electric vehicles. Here I will talk about the different types of vehicle batteries and the pros and cons for each.
Lead Acid
Lead-acid (PbA) batteries are batteries that use the chemical reaction between lead (Pb) and sulphuric acid to generate electricity. There are two subtypes of lead-acid batteries, flooded lead-acid and valve-regulated lead-acid (VRLA). Lead-acid based batteries are the oldest and most common battery in existence, dating back to the 1800s. PbA batteries designed for “deep cycle” applications can deliver the power required to power an EV and people have been building electric vehicles with these for decades. A few of the reasons they have been used in EV in the past is that flooded PbAs are relatively inexpensive, are commonly available, and they are easy to use without any monitoring. A set of flooded PbAs powerful enough to move a vehicle could cost under $1,000, be purchased off the shelf locally in town, and be used immediately in a vehicle without any monitoring. The ease of use of PbAs make them ideal for use in budget constrained, entry level, or hobby EV projects. Some of the down sides to PbA batteries is their energy density, weight and life. The amount of energy a PbA battery can store given its size (commonly referred to as ‘energy density’) is rather low; about 30-40 Wh/kg. This means that to improve range or performance a vehicle must add more weight. Eventually the energy to weight ratio becomes unmanageable for a generally acceptable passenger vehicle. Very early electric vehicles used flooded lead-acid batteries including one of the first commercially available EVs in the 1970s, the Comuta-car and CitiCar.
Nickel-Cadmium and Nickel-metal Hydride
Nickel-Cadmium (NiCad) batteries use a nickel oxide and cadmium chemical reaction to generate electricity. NiCad based batteries were created at the very end of the 1800s and came to prominence through the 20th century as the most popular rechargeable battery. NiCad batteries have a number of positive attributes that make them attractive for use in electric vehicles. They are capable of high discharge rates, NiCads have a higher energy density than lead-acid (about 40–60 Wh/kg), and they have a longer functional life. These advantages lead to a rise in popularity of NiCads for EV applications for a number of years, especially in the early 2000’s when the price for large power NiCad packs decreased enough to become attractive. In the later 2000’s the popularity of NiCad declined due to a number of disadvantages including safety concerns over toxic Cadmium, and energy density compared to newer chemistries.
Nickel-metal Hydride (NiMH) batteries were developed in the 1980s and are viewed as having a less environmental impact than NiCad based cells. NiMH popularity has increased over NiCad due in part to those environmental concerns, a higher energy density (30–80 Wh/kg), and a decrease in cost per KHr as compared to popular NiCad cells. NiMH batteries were successfully used in the GM EV-1 in the mid 90s and in hybrid electric battery packs from Toyota, Honda and Ford in the 2000’s.
Lithium Based Batteries
Technical Links
The Smart Drive has an electric vehicle project! Check out all the electric vehicle project posts at http://thesmartdrive.com/category/project/electric-car/ or visit the electric vehicle project page at http://thesmartdrive.com/electric-car/
Electric Auto Association: http://www.eaaev.org/
Electric Vehicle Conversion page: http://www.evhelp.com/
Electro Automotive Conversion Kits: http://electroauto.com/
Chevy Volt production vehicle: http://www.chevrolet.com/electriccar/
Tesla Motors production vehicles: http://www.teslamotors.com/
1990 Mazda Miata conversion: http://ourworld.compuserve.co…ries/electric.htm
1991 VW Cabriolet conversion: http://thesmartdrive.com/teamev/
2002 Mazda Protege-5: http://www.evalbum.com/2419
Barack Obama’s sustainable energy commitment: http://www.whitehouse.gov/blog/09/03/19/Electric/