What do I have to expect if I choose an electric car?

Photo by Splinter

We have finally reached the third type of  “alternative” power source, currently offered by OEMs on the market.

After the well known sources, that is LPG and CNG, I examined the various type of “hybrid power source“, in three specific posts whose links you will find at the end of this article.

In this new post I tried to outline the characteristic elements of power supply in the automotive sector focusing on what are the strengths and which the aspects that limit its diffusion.

This is a purely technical article so I won’t focus on all the environmental and commercial aspects.

For those who want to deepen some elements that I mentioned in the post, we can, in the comments, start a more specific and fruitful discussion.

Power supply

For an electrically powered vehicle, I mean a vehicle (two or more wheels) with an electric engine that uses as primary energy source the chemical energy stored in one or more rechargeable batteries, and made switched by them, to the engine, as electricity.

Today the market offers a huge number of electric means of transport such as the skateboards, bicycles, micro cars, motorcycles, cars, large trucks, buses and even prototypes of air vehicles.

Some of these means help concretely, for example, people with mobility problems, or for short trips in delimited spaces.

Another part of these electrified products, in my opinion, have fun functions or only image purposes.

The electric cars are now marketed by almost all car manufacturers and also by companies started up only for this purpose.

While heavy vehicles, Truck and Bus, except for some Chinese buses, arenÕt commercialized yet although we have been talking about it for a few years.

Main components of electric traction

Vehicles with exclusive power supply don’t have, of course, all the heat structure (engine), the tank and the exhaust system.

On the other hand they must have:

• Electric motor with gearbox or adaptor;
• Inverter;
• Traction batteries;
• Battery charger;
• Power and signal wiring;
• Electric motor cooling system and inverter.

Let’s briefly see the main features of these components:

• Electric motor: there are now many types of it, low and high voltage, low and high speeds, asynchronous and synchronous, integrating the gearbox (drive wheel), etc.;
• Inverter: component that manages the electric motor by the accelerator and brake pedal signals; transforms the direct energy of batteries into three-phase alternating one, into traction and vice versa during the energy recovery;
• Traction batteries: they depend on both the characteristics of the electric engine (voltage and electricity) and the autonomy of the car and are controlled both in charge and discharge by an electronic component called BMS(Battery Management System), which controls charge voltage, temperature of every single cell of which the package is composed;
• Charger: device that, connected to the power outlet, switches the alternating electricity in continuous one according to the characteristics required by the traction batteries;
• Power and signal cabling: specific for traction power supply and component management;
• Electric motor cooling and inverter system: installation, whose maximum coolant temperature must be around 70 ¡ C, which cool the electric motor and inverter.

Then there are some common components in the car with a thermal engine that will have to be electrified.

It is about:

• A / C compressor;
• heater;
• power-assisted depressor;
• power steering pump, if hydraulic, because on thermal cars they are normally controlled by the thermal engine.

Operating modes

The Italian market, has currently in the list of products BMW, CITROEN, HYNDAI, KIA, MERCEDES, MITSUBISHI, PEUGEOT, RENAULT, SMART, TESLA and VOLKSWAGEN; with prices ranging from about 24,000 euros of a SMART FORTWO ED to about 157,000 euros for a TESLA XP100D.

For all these models, the solutions are 3 and depend mainly on the type of electric engine used:

1. 1. Electric motor (s) coupled to a single-gear reduction gearbox acting on the front or rear wheels or both.
      It is the most common, simple and cheapest solution. The electric motor must allow the thrust uphill, at least up to a full load gradient of 25% and a speed suitable for highway driving;
   2. Electric motor that transmits the movement to a differential through a traditional or mechanical continuous or automatic or robotic mechanical gearbox.
      This solution is adopted on very high performance cars or when the maximum number of revolutions of the electric motor is low (- 5.000rpm).
      This solution is much more complicated and expensive than the one described in point A, especially if the gearbox is not continuous for managing the gear shift;
      
      

      Diagram of the electrical connections (12Volt and signal on CAN network) among the several control units for the management of electric traction.

   3. Motors installed between brake disc and wheel rim only on two wheels or on all four (wheel drive).
      This solution is hardly used on cars due to the fact that it is necessary to design specific wheel sides, high unsprung masses, and a very sophisticated torque control on electric motors according to the adhesions of the 4 tires in contact points with the road.

ADVANTAGES

1. Noiselessness
2. Easy to drive
3. Possibility of exceptional performance

DISADVANTAGES

1. High cost
2. High weight
3. Charging time of batteries in high traction
4. Reduced autonomy, less 60% on the motorway if compared to the city
   
5. Reduction of the autonomy of approx. 20/30% for temperatures below – 20°C
6. Reduction of the autonomy of approx. 20% for air conditioner use

*****

My personal opinion is that probably the future of cars will ALSO be electric as long as renewable energy sources will be developed and today’s problems will be improved.
Today, despite the advertising, there are still many controversial points: the economy and the ecological nature of the materials used (environmental impact) and the real advantages in using the vehicle.

*****

1. What do I have to expect if I choose a CNG car?
2. What do I have to expect if I choose a LPG car?
   
3. What do I have to expect if I choose a hybrid car? (Parallel hybrid)
4. What do I have to expect if I choose a hybrid car? (Hybrid series)
5. What do I have to expect if I choose a hybrid car? (Parallel/series)
6. What do I have to expect if I choose an electric car?
7. What do I have to expect if I choose a hydrogen-powered car?

Translated by Federica Izzo