A common question amongst car enthusiasts, particularly those who are interested in building their own cars, is Why don’t electric cars have alternators?
The prevailing logic when this discussion comes up is that electric cars having alternators means they will be able to charge themselves as you drive it.
Whilst this might make sense at first glance, we need to address a number of reasons why electric cars don’t have alternators. Before we do this, it’s worth discussing what an alternator is, as this will enable us to answer the question posed in this article.
What Is An Alternator?
Put very simply, an alternator is a type of small generator that generates AC (Alternating Current). They’re used in modern automobiles as a way of charging the vehicle’s battery and electrical systems while the engine is running.
As cars became more complicated, they required more electrical power. Before the 1960s, vehicles used a DC dynamo generator with commutators.
These were unable to meet the demands of the modern automobile, as greater power was needed to run things like electric wipers, larger headlamps, and other accessories.
How Does An Alternator Work?
When the vehicle is in operation, a belt located on the vehicle’s engine is used to spin a pulley connected to the rotor of an alternator. Within the drive shaft, there are either magnets or coils of copper wire with a small DC current flowing through them.
This flow of electric current creates a magnetic field. As this shaft rotates thanks to the pulley, the magnetic field induces current which flows through a matching set of coils.
The magnetic field within the rotor alternates polarity, which means that the flow of electricity “flip-flops” hundreds of times a second and reverses direction. This is what is known as AC (Alternating Current).
By using diodes, the AC is converted to DC (Direct Current). With the use of a voltage control circuit, the output voltage is regulated and charges the vehicle’s 12V battery.
Where Does The Current Come From?
As mentioned above, there is a small DC current flowing through the magnets or copper wire in the drive shaft. Where does this current come from?
To answer this question, we need to talk about the Laws of Thermodynamics. Galileo, Bernoulli, and Newton studied the natural laws of motion and the natural world and developed what has become known as the Laws of Thermodynamics.
They noticed that there are certain rules in play that are always being followed by things in motion.
Within the Laws of Thermodynamics, there is what is known as the Law of Conservation of Energy. The central idea of the Law of Conversation of Energy is that “energy can not be created or destroyed, it can only be transformed from one form to another.”
As for an alternator, the fossil fuel engine attached by a belt or pulley gives mechanical energy to the alternator, which is then converted into electrical energy. In this process, electricity isn’t created, it was another form of energy which is converted.
It’s worth mentioning that the mechanical energy of the vehicle’s engine isn’t perfectly converted into electrical energy. In the process, some energy is converted to kinetic energy, which translates to vibration, heat, and noise.
Despite energy efficiency not being 100%, it is enough to keep the vehicle’s battery charged and powering the electrical systems.
Another noteworthy point is that combustion engines run on chemical energy (gasoline/diesel) which is ignited and changes to thermal energy which moves the piston, which in turn drives the crankshaft. Only when the crankshaft is turning does the alternator receive any energy.
Why Don’t Electric Cars Have Alternators?
With the above in mind, it may seem obvious to note that an electric vehicle doesn’t have a combustion engine. The combustion engine is the driving force that generates the electric current via the alternator, without this in an electric vehicle an alternator is at best not worth it.
The energy that powers the alternator and generates electricity is the mechanical energy created by the engine’s combustion of fossil fuels. It is being converted into electrical energy.
It is more than possible to install an alternator into an electric vehicle. In this instance, we’d be using the battery of the electric vehicle to spin the motor, which could spin the alternator and generate electricity.
However, all we’d really be doing is using electricity to generate electricity. Taking into account that the conversion rate when this is happening isn’t 100%, we would end up making a smaller amount of electricity than we started with.
The bottom line is that installing an alternator in an electric vehicle, under the idea that it will be able to power itself, simply isn’t efficient. As mentioned above, an electric vehicle using an alternator would run the battery flat much quicker than without an alternator.
An alternator in a standard combustion engine vehicle is absolutely essential in order for the vehicle to function properly.
Whilst the combustion engine gives the vehicle the kinetic energy to move (via a series of other energy transformations), the alternator gives power to the electrical accessories.
It is worth noting that there is a cost involved in this transference of energy to the alternator. The cost is that this process demands fuel, even more so than just running the engine on its own.
The relationship between the engine and the alternator is almost symbiotic. Meaning that one cannot work without the other. If a vehicle’s battery is flat, the vehicle will not start. This is due to the fact that when the ignition is turned on, it is the battery of the vehicle which starts the engine.
As electric vehicles have been designed from the ground up to eliminate the need for a combustion engine, adding an alternator would simply be pointless.