I have a discussion with my coworker and we came up to with the question where is the surplus power from a dynamo machine in a car going if the battery is full and the rest is not used up by the car?
It is wasted with a big resistor or is the dynamo machine uncoupling or someting else?
It provides power for the other electrical functions in the car.
Yes, but what if more is produced than consumed, where goes the surplus?
From what I understand, there is no surpus, the alternator varies the amount of electricity produced based on the demand (up to its maximum rated current). It varies it by varying the speed of the alternator relative to the speed of the engine.
If there was any excess they would most likely just dump it as heat.
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This is a good point. As for example when I was watching a video on Youtube, of what happens when you hit the brakes.
This is that energy is always transformed, it never gets decreased or lost. This is a law in thermodynamics.
As for example reduction in kinetic motion (speed) is the noticeable effect. But looking at the entire big picture, what happens actually is that kinetic motion is converted to heat through multiple factors (air resistance + wheel hinges + brake clamps + tire friction).
In terms of what happens to the electricity in the battery, you can use the above concepts + some others. As for example electicity used to power the circuit board itself and also electicity that naturally leaks to the environment.
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If the power generating system produces more power than is consumed, the power is wasted.
This is why electrical utilities construct things like âpumped-storage facilities,â which basically act like gigantic storage batteries. They pump water up a hill into reservoirs when they have surplus power, so they can run the water back down the hill to generate power in periods of peak demand. (The pumps serve double-duty as generators, and they can reverse their roles at a momentâs notice.)
In a âcar dynamoâ situation, there is likely to be some kind of mechanical transmission system which reacts to the fact that increased electrical demand will produce a greater mechanical strain on the dynamo. This can be used to automatically route more mechanical force from the engine. Because otherwise, the excess power is going to have to go somewhere as (unwanted) heat.
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Letâs hope that they would not attach crypto miners to our future carsâŚ
Coming soon, car companies advertising how the new in-car crypto-miners can help you make the payments for the high-priced EV you were forced to buy (because ICE vehicles were banned).
Donât laugh, because mining services are already being built into certain antivirus products and cars today are essentially computers on wheels. The only barrier is how it can be marketed.
i also think that there never really is a surplus. you can easily observe this with bicycle dynamos, that are only hard to turn if there is a consumer.
i also found this (first google result):
A spinning generator is generating voltage, but with no load there is no current and since power is voltage times current, no power.
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That cant be true, if you put power in, does not matter which kind, it must go somewhere. If the magnets in a dyname induce a magnetic field there must be electical power generated, no matter if there is a consumer.
itâs true though. you can ask any physicist for a more detailed explanation.
any physicists here? 
I found this link
https://electronics.stackexchange.com/questions/244132/what-happens-to-a-generator-when-we-rotate-it-in-open-circuitno-load
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The âelectric carâ idea will fall flat on its face come winter or desert summer, because there is no excess heat generated by an electric motor that can be used to heat or cool the car. So, that power has to be withdrawn from the battery, which will drastically curtail its range.
The simple fact of the matter is that people like Elon Musk have figured out how to use present government interest (and money âŚ) to make themselves extremely rich developing a technology that ultimately wonât work. Your âoh so greenâ electric car, which you cannot drive for long distances, is in most parts of the USA powered by coal. But the âshowers of blessingsâ are coming from above, and landing in a few very rich menâs pockets as usual.
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Just to be the devilâs advocate here, but -why- do you think it is all still powered by coal?
Or the US not sticking to the Paris Agreement? Or the fact that the US is super slow in transitioning to other sources of power other than fossil? Or it took ages to get rid of lead enriched gasoline, despite massive amounts of medical studies saying it caused lots of deceases?
A lot of the first cars ever built were electric, but battery tech in those days was abysmal compared to a modern battery cell.
Donât go âhigh and mightyâ with this, as all car manufacturers go electric even faster than 5 years ago.
And in true American fashion, they even resurrected the âmighty Hummerâ as a electric version⌠
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To note, the big problem with EVâs right now is their weight, their range, their recharge time, the long-term safety of storing them in a garage, and the longevity of the batteries. There is a step being taken to solve all five of these problems in the form of solid-state batteries.
Outside of that, the biggest problem is national governments that believe that anything can be done in any time frame if you simply believe with all your heart. Even Elon Musk admits that transitioning the entire fleet of vehicles in the next decade or so is not feasible. The technology I mentioned for starters will take a while to roll out on a large scale.
On top of that, the only realistic way to ânet zeroâ is the mass-scale construction of reactors, something the government made very expensive on purpose by drowning the technology in a mountain of red tape (sorry, windmills and solar panels wonât cut it unless everyone is forced to cut their standard of living to a bare-bones existence). Are you prepared to go back to 1990âs style low-resolution image rendering because the only machines available are ultra-low power eco-boxes?
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If I look over here, most people who wouldnât really qualify for EVâs at the moment, are people that drive a lot for their work. And long charging becomes an issue.
Range anxiety for most people is between the ears, as their daily travel to and from the office often sits well below the 100km mark. Which means most EVâs will get you by for most of the week, or all week with a in-between charge at home or the office.
The other big problem, besides the points Ace_Dragon mentions, is the electrical grid. There is no way the current grid (everywhere) is capable of supporting a move to EVâs. There will have to be significant investments in upgrading the grid, so we can support all that extra load. Besides making houses less dependent on gas.
But I think we moved away far from the original question here 
At this moment, the majority of the electrical power grid within the United States is still powered by the most-abundant (and, cheapest) fossil fuel available there: coal.
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wrong. itâs only 20% coal. renewables already overtook coal.
still 60% fossil but itâs cleaner to burn that in big power plants than in car engines.
According to that report, coal by itself produces 1.7% more energy than all renewables⌠renewables have definitely not overtaken coal, yet
In a modern power plant, coal can be burned very cleanly. The biggest environmental problem with it is the ash that is left over.
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