Alternators are typically the main producers of power in vehicles. They generate alternating current (A/C) and then convert it into Direct Current (D/C), which is what the car’s electrical systems use.
It is the alternator that charges the battery and by extension, powers the dashboard, headlights, radio, and heated seats. Alternators are relatively small and are situated on the front side of the engine.
Since EVs depend on electrical power, many people wonder whether they have alternators. The answer is no – EVs don’t have alternators, and for good reasons. Let’s find out.
What are Alternators and How Do They Work?
In gas-powered vehicles, alternators are connected to the engine by a pulley. When the engine is on, the mechanical power it produces turns a drive belt connected to the pulley.
The pulley is in turn hooked to the alternator’s rotor, which contains magnets or copper oils in its shaft. As these magnets rotate, they are constantly alternating their north and south poles, producing the aptly-named Alternating Current.
The A/C current then moves to the rectifier, where it is converted to Direct Current. This current is primarily channeled to the car’s 12-volt battery, which consequently charges all the electrical equipment in the car.
Why Don’t Electric Cars Have Alternators?
The fact that both EVs and ICE cars have 12-volt batteries means that, ideally, even EVs should have alternators. In reality, however, the two vehicles require different types of power and therefore have different energy sources.
Below are other reasons why alternators can’t work on electric vehicles:
EVs Don’t Need Additional Electricity
To put it simply, the main role of alternators is to generate electrical energy from the engine’s rotational or mechanical energy. Electric cars already have electrical energy stored in their main batteries and do not really need additional power.
Well, manufacturers and even EV owners would not say no to more power, but alternators are highly inefficient. For instance, on average, they lose 50-60% of the energy they receive from the engine.
Nonetheless, electric cars still have the same electrical equipment as ICE cars (headlights, navigation systems, infotainment, etc). All these components require 12 volts or less to work safely.
In contrast, the main (traction) batteries in EVs are usually rated 400 volts or above. Using these to directly power the smaller electrical equipment would be “an overkill” hence the need for the 12-volt batteries.
Since EVs already have energy stored in their batteries, their 12-volt batteries receive their energy straight from the main batteries.
Between the two battery systems lies a converter that converts the DC energy from the main battery into lower voltage power needed by the 12-volt battery. As such, they don’t need the extra power that alternators provide, which comes at huge costs in itself.
Generally, for alternators to ‘generate’ DC power, they have to first convert mechanical power into AC current, and then convert the AC to DC. This is a long, energy-intensive process, and it is much simpler to derive power from an electric charger.
EVs Don’t Have Engines
According to the laws of physics, you can neither create nor destroy energy. You can only convert it into different forms. In essence, alternators don’t ‘create’ AC current – they just convert mechanical energy to AC.
ICE vehicles generate excess mechanical energy from their engines, so it makes sense for some of it to be converted into usable electricity.
On the other hand, the mechanical energy produced by the motors in an EV is what makes the wheels turn. But unlike ICE cars, EVs don’t have plenty of moving parts like pulleys and rotors. As such, they don’t really need their mechanical energy converted to electric power.
If you were to use an alternator on an electric car, you would end up with even less power than you started with in the first place. This is because you would essentially be converting electric energy to electric energy, with some of the energy being lost to inefficiencies.
Alternators Just Don’t Make Sense
Considering the fact that alternators lose a significant amount of energy, EV manufacturers needed to design much simpler and more effective systems. Most EV cars, therefore, use devices called DC-to-DC converters.
As the name suggests, these converters transmit the same type of energy and only modulate the voltages.
DC/DC converters typically sit between the 12-volt battery and the battery pack. They take the 400V (or whatever voltage the battery has), and step it down to the 12 volts needed to charge the smaller battery.
As no electrical system is perfect, DC/DC converters also lose some energy, mostly in form of heat. However, the energy lost is significantly lower than what alternators lose since converters don’t have any moving parts.
Moreover, DC/DC converters are not only more efficient than alternators but are also lighter, more compact, easier to cool, and don’t need any maintenance as they have no moving parts.
Take Away: Are Alternators Old School?
Alternators, although still useful in ICE cars, were designed at a time when propulsion technology was basic and rough-hewn.
In the era of electric propulsion, most of the focus is on efficiency and range, not energy conversion into different forms, which makes alternators less useful.
Hopefully, you now have a better understanding of why electric cars don’t have alternators.
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