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Why don’t electric vehicles have alternators?
Why aren’t electric vehicles fitted with an alternator that can charge the battery while one drives; similar to how a gas engines recharge their batteries? With all the advancement in technology it would seem that they have figured it out and won’t implement it to force people to pay for electricity or my own lack of knowledge on the subject.
Well, people have the perpetual energy is impossible part down, but I’d also note that they basically do have alternators. That’s what regenerative braking functional is. You slow the car and convert kinetic energy back into electrical potential energy - with significant inefficiency, of course, but it can significantly increase the range of EVs in start and stop traffic and is part of what gives hybrids their fantastic city mpg.
What you're describing is perpetual energy and that does not exist due to friction. Driving an alternator puts more drain on the motor and uses more electricity than it generates.
I'd like to add that alternators as we know them from cars are utterly inefficient. I don't have numbers at hand, but I believe the efficiency is 60-70%.
Ex-physicist here. Electricity is weird. If you think about it, it's hard to "store" electricity - batteries and capacitors are actually chemical energy stores. Electricity is more about transferring energy from one form to another.
That helps explain why motors are different from engines.
Engines turn chemical energy (petrol) into kinetic and heat energy directly (the combustion process), but with a motor you use electricity as a go-between for the battery.
This makes motors and alternators the same thing, just working in opposite directions (chemical-electrical-kinetic or kinetic-electrical-chemical). Actually there's nothing stopping you running a motor in reverse to behave as an alternator, which is how regenerative braking works!
So yes, electric cars do have alternators, it's the same as the motor :D
Edit: In answer to your question about paying for electricity, the fundamental problem is that all of these conversion steps are lossy. When you use a battery, the process of turning chemical energy into electrical makes the battery heat up, which you can't get back. The motor is lossy, so friction causes the motor to whine and heat up, so that is also lost. A moving car is lossy, because of wind resistance and friction from the road. And regenerative braking is lossy for all the same reasons.
You are completely correct that, in an ideal world, we'd never have to pay for electricity again. It's not a conspiracy to make people pay, it's there's a fundamental loss to everything we do.
It's fine for a gas engine to recharge the battery because all that battery really does is power the electronics and the starter motor. Plus the engine doesn't use the battery as a power source, it's an engine.
You can't have a motor charge the battery that's powering it because there's losses at every step, the motor is not 100% efficient, the alternator is not 100%, charging a battery probably isn't 100% efficient and there's no room temperature super conductors in sight.
An alternator on a gas car is like a gas generator: you burn gas to crank the generator, which makes electricity. An alternator on an electric vehicle would be like draining a battery to crank a generator to make electricity: you can’t get more power out than what you put in, so it’s easier to just get electricity straight out of the battery.
Hope that made sense!
A motor and a generator are kinda inverse things. If you use a generator on am elecgroc car you'd use up all the kinetic energy that the motor was producing to begin with.
Everyone has already pointed out the interplay between motors/generators and the laws of thermodynamics.
I want to also point out that hybrids work more in line with OP's suggestion. They have both an ICE and battery paired to motors. The battery is charged with a combination of regenerative breaking, internal combustion with an alternator, and plug-in for PHEVs.
More creatively, there is the Ariel Hipercar which uses a jet turbine to extend its battery range: https://insideevs.com/news/607736/ariel-hipercar-1180-horsepower-electric-jet-engine/
So you want to more strain on the electric motor to make less electricity than what goes in?
All of these top-level replies are reminding me of that scene in the Barbie movie where they distract the Kens by tempting them to mansplain things to them.
I'm not criticizing anyone. I just found it amusing.
Maybe not criticizing, but it does sound a lot like judging.
I don’t think there is much mansplaining going on, or even at all. OP’s question is naive to a point where it is really hard to answer this question without becoming condescending. So this is what you end up with: nice people trying to explain a very basic principle without sounding like a dick. Or maybe there still is some depth to the question I haven’t been able to see, in which case… I’m not sure.
Which comments here do you find condescending and why?
I don't. I'm not saying anyone is mansplaining. I'm just saying it reminds me of that scene.
There's an old saying that the best way to increase engagement is to be wrong on the internet. That's not exactly what happened, but it's close. I think everyone here's just trying to be helpful. OP did ask a question, and he got the answer.
I didn't mean to offend anyone. I'll delete my comment if anyone asks me to. I just thought it was funny and wanted to share it.
(paging @caliper; sorry, I must have missed your reply somehow.)
Sorry, I wasn't taking offense, you're fine (I've not seen the film).
I don't think OP is wrong, and I said as much in my reply. Their idea is pretty right actually, it's just a bit incomplete.