Contents
In this post, all the information you need to know about electric cars will be listed so that it helps you in making the right decision and manage your expectations.
What is an electric car and what are the electric car types?
By definition, an Electric car is a vehicle that is propelled by one or more electric motors. There are at least 4 different types of electric cars. Let’s have a look at what they are:
Pure EV
(Electric Vehicle)
- No IC engine
- Only electric drive
- Battery pack size is large (20-80 kWh)
- Example: Nissan Leaf, Tesla Model S
Pure EV occupy 61% of the EV market
HEV
(Hybrid Electric Vehicle)
- Has IC engine and electric motor
- The batteries get charged by the engine
- Battery pack size is medium (6-12 kWh)
- Example: Honda Civic Hybrid
PHEV
(Plug-in Hybrid Vehicle)
- Has IC engine and electric motor
- The batteries can be charged from an external source (plug)
- Battery pack size is medium (6-12 kWh)
- Example: BMW i-8
MHEV
(Mild Hybrid Vehicle)
- IC engine and electric motor
- Turns off the engine and switches to motor when coasting, braking and restarting quickly
- Cannot be solely driven on electric motor
- Example: Chevrolet Silverado Hybrid
There is one more option that can be placed in the subcategory of the pure EV. This is called the Range Extended vehicle (REEV). The range extended vehicle has an internal combustion engine but one that is not connected to the drive-train. The IC engine is only there as an electric generator that runs on petrol. Its function is to charge the batteries when the charge drops below a certain level or generate electricity to power the motor.
All you need to know about Electric/Hybrid cars
History of Electric Vehicles
Contrary to the popular belief, Electric cars have existed even before the internal combustion engine cars came along. A very historic and well-known electric car is that of Thomas Parker, made in 1884.However, the battery technology at the time could not match the richness of energy that fossil fuels (petrol and diesel) provided. Electric cars got reduced in their role as milk floats, space vehicles (lunar rover), bumper cars and then golf buggies. In the 1990s, pressure from environmentalist pushed the automotive industry towards production of low emission and efficient vehicles. The idea of noiseless and emission less electric cars was put on the table. At that time automobile manufactures in the US approached the idea with scepticism. On the other hand, Japanese manufacturer Toyota successfully rolled out the world’s first massed produced hybrid car in Prius.It should be noted that GM in the US also brought forward the “EV1” in the late 90s. The car was received warmly. However, GM itself pulled the plug on the program which sparked an angry response from customers and resulted in a loss of reputation. A documentary, “Who Killed the electric car” on this controversy was produced by Sony pictures. It covered the reasons behind the move. Students are advised to watch the documentary in their spare time.
It was almost a decade later after the Tesla Roadster was introduced that the idea of an all-electric car became a reality. The Roadster was aided by a step change in battery technology i.e. the arrival of Lithium Ion batteries. Several manufacturers started following suit.
Thomas Parker Electric Car 1884
Even in the late 2000’s, more than 80% of the electric cars on the road were DIY projects i.e. people converting their existing petrol or diesel car into an electric drive. The engine would be replaced by a motor and the fuel tank and trunk space would be utilized to fill batteries.
The rise in the demand for low priced electric car on the back of Kyoto protocol gave opportunity to several small manufacturers to enter the EV market. This included manufacturers from India and China.
Today nearly all mainstream car manufacturers are designing Electric cars. It has been suggested that a tipping point is near (around 2020) when electric car production would become cheaper than conventional cars.
Useful link: Who killed the electric car
What are the main benefit of using electric cars?
Electric cars are extremely efficient. Compared to the conventional IC engine cars, where less than 15% of the energy in the fuel translates into physical movement, in electric cars up to 90 percent of the energy in the batteries can be converted into movement.This means electric cars can be 6 times efficient and in most cases, are also 3-4 times cheaper to run. Just to put this into perspective, A petrol car normally has an economy of 14 cents per mile. Electric cars have an economy of only 3 -4 cents per mile.Electric cars are also environmentally friendly. If powered by renewable energy, they have zero running emissions. Scientist have suggested that even if EVs are powered by electricity from a coal fired power plant, they can still be better in environmental terms because of their high efficiency.
Some scientists criticise electric cars and suggest that they only shift the emission to the point of electricity generation. A term called “The Long Tailpipe” is used in reference to this thesis. Nonetheless electric vehicles have literally helped to clear the air in many congested city centres.
One must remember that in an electric car the engine does not need to run when the vehicle is stationary. Furthermore, electric cars have the capability of recouping the kinetic energy. In a normal car, a huge amount of energy is lost as heat on the brakes. In an electric car, much of this energy can be recycled to recharge the batteries. Electric vehicles can also charge the batteries when going down a slope in a hilly area.
For Island communities, electric vehicles are ideal. They can be charged from a local renewable resource. This frees the island communities from reliance on diesel imports.
An Electric car has far lesser moving components. A motor is a very simple device compared to an IC engine. Therefore, the reliability of electric cars is very high because there are lesser components at risk of wear and tear and hence breaking down.
Fast Facts
“As of November 2012, a Nissan Leaf driving 500 miles (800 km) per week is estimated to cost US $600 per year in charging costs in Illinois, U.S., as compared to US $2,300 per year in fuel costs for an average new car using regular gasoline”
A study made in the UK in 2008, concluded that electric vehicles had the potential to cut down carbon dioxide and greenhouse gas emissions by at least 40%, even taking into account the emissions due to current electricity generation in the UK and emissions relating to the production and disposal of electric vehicles.
Engineering and Technical Details
The range of electric car is heavily tied to the battery energy density. Lithium Ion technology has allowed electric cars to have range greater than 200 miles thus shattering the range anxiety that had kept the technology down. Most electric cars have also a low coefficient of drag, which makes them go the extra miles. The Tesla model S for example has a coefficient of drag of 0.24.
Initially it was thought that to cut the development cost, existing chassis of conventional cars should be used for developing EVs. The cavity for petrol tank and car boot space was to provide space for batteries. However, having a bespoke platform has really helped in lifting the electric car and in fact has given it superiority over conventional cars. The batteries pack in modern electric car is not a separable attachment. It is an integral structural member of the car and adds to the stiffness of the frame. This approach has also freed up space and has allowed more batteries to be accommodated. The Tesla model S for example has a variant that has a battery pack of around 100 kWh capacity.
It should be noted that the batteries cannot charge when the cell temperature goes beyond the range of 0 to 45 ºC. So, when the battery is too cold or too hot, charging the battery leads to excessive heat generation that has the potential to permanently damage the cells. Therefore, an active cooling system is always beneficial and allows the car battery to cope with high ambient temperatures.
Now we will cover three key components of Electric cars. Namely, the electric motor, the battery pack and the motor controller.
Electric Motors
The first EVs to appear on the scene had a DC motor. With a DC motor, the advantage was that no conversion was required from the battery current which was also DC. Therefore, the DC motor eliminated the need of an inverter. The other advantage of a DC drive is the extreme amount of torque that the motor furnishes when driving off. In a drag race, it is impossible to beat a car with DC motor. The disadvantage of a DC drive is that at high RPM, the torque drops. So, electric cars that had a DC motor struggled when climbing uphill even at moderate speeds. Earlier models of G-Wiz had a DC drive.
Incorporating AC motor is more complex in terms of circuitry; however, it has huge benefits. While torque may be not as high as a DC motor of a similar size, but an AC motor retains its torque levels even at high RPM. All modern EVs have AC motors. There can be cars with one, two or even four electric motors.
The Battery Pack
The battery pack is the most critical component and the most expensive component of an EV.
In the past, electric cars have used lead acid and Nickel Metal Hydride batteries. Modern EV’s utilise Li-ion batteries that have much higher energy density than lead acid. The battery pack is not just a bunch of batteries lumped together but a much-engineered apparatus. Lithium Ion batteries are often easily penetrable and therefore the pack must be designed such that there is no ingress.
The pack should also provide safe venting of gases in case of thermal runaway and the pack should have a capable thermal management system that can both cool and heat the batteries when needed. There are several battery chemistries within Lithium ion umbrella.
Likewise, there are several configurations of the batteries (pouch, cylindrical prismatic). A battery pack can be extremely varied. In some cases, it may have several dozen large cells or several thousand small cells. The cooling system of a battery pack can be active or passive. Within active systems there are liquid cool and air cooled options. High performance EVs always use a liquid cooling system because of its effectiveness.
The battery is controlled by a Battery Management System or BMS. The BMS is an electronic system that makes decisions regarding battery charging/discharging based on battery temperatures and state of charge. It protects the battery from overcharging or undercharging. It also helps in stabilising the battery temperature by regulating the coolant flow. It can also disconnect and isolate the battery pack altogether for safety reasons.
The Motor Controller
The motor controller is essentially the brains of the whole EV. It is a three-way interface between human input, the motor, and the battery pack. The motor controller takes the input from the driver (gas pedal) and converts it into signals for the BMS. It also controls the electric motor. It supplies more current to the motor when more torque is required and increases the voltage across the motor when high rpm is required. Likewise, it turns on/off the regenerative system when needed.
Charging of the Battery
One can install home charging points. In many countries, the energy supplier will provide you with home charging points at a small price. The maximum power for home based charger is limited. For instance, in the UK, chargers cannot exceed more than 13 kW. The higher the power rating of a charger, the quicker the batteries will charge. Commercial Charging points are also available in many town centres, shopping areas, office car parks and services. Commercial charging points can be up to 50 kW or even more. Tesla for instance has superchargers that have a power rating of 120 kW.
It should be noted that charging is an asymptotic process. In other words, the from 10%-t 80% charge, it takes 50% of the time while topping up the remaining 20% i.e. bringing the charge from 80% to 100% may also require the same amount of time.
What are the disadvantages of an electric car?
Electric cars perform their best in moderate climates. It is therefore no surprise that they sell the most in places with mild weather like San Francisco. In extreme climates there are two draw backs.
Firstly, energy that goes into cabin climate control reduces the overall range. For example, people living in hot places like Arizona have reported a loss in range.
The second disadvantage is that compared to conventional cars, electric car infrastructure is not as developed. Charging points are few and far between. Although they are growing at a much faster rate, nonetheless it will take time before they become comparable to conventional car services. Similarly, mechanics that deal with electric cars are very few. If the car breakdown, it must be taken to the dealership and not a private garage.
Future of Electric car
It should be noted Lithium Sulphur batteries are being tested at present. They have far more superior energy density compared to lithium Ion. Lithium Sulphur batteries can also be produced at a much cheaper cost. Therefore, this technology will give a shot in the arm to the EV industry. Kyoto protocol has also helped electric cars industry to evolve. In the future, there will be more driver-less electric pods on the roads. The number of charging points is increasing every single day. The battery price has already dropped to $150 per kWh. It has been reported that once the price drops to $100 per kilowatt-hour, it will prove to be the tipping point i.e. the point where electric car demand will surpass conventional car demand. Battery prices are coming down about 8% per annum with mass production, and are expected to drop further
Fast Facts
“Battery Price of US$125 per kilowatt hour by 2022 is estimated”
“Several national and local governments have established tax credits, subsidies, and other incentives to reduce the net purchase price of electric cars and other plug-ins”
Conclusion
- Electric cars are more expensive to purchase
- But they are cheaper to run electric car are economical
- Electric cars are easier to maintain (less moving parts)
- Electric cars are fast.
- With 500 miles per week commute, electric cars can save more than $1500 per year
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