Electric Performance cars

Off Topic
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Ohboy, I’m no good in electronics like batteries, that’s not the kind of engineering I do, but I do have some (3rd bach and masters) classes in electric motors and their drive systems as an electromechical engineering student, so I can try explain why that “1300 hp” figure is quite likely horseshit, especially coming from a Chinese company (great people, but their working standards aren’t quite up to snuff).

Well, Tesla for example uses induction electric engines, and they’re getting increasingly popular. Explaining all the ways these can be driven and how they work would require a lot of lectures. Let me attempt to summarize:

They don’t have a powered rotor like DC motors do, or synchronous AC motors do. Instead the rotor is shortcircuited, but the magnetic field of the stator creates currents in the rotor if it turns relative to eachother. Now how would the magnetic field turn? By the powers of Alternating Current ofcourse. with 3 phases you can perfectly make a rotating magnetic field. The bigger the speed difference, the more current through the rotor, and the more the rotor creates its own magnetic field, thus the more torque the motor generates.

This is the huge advantage of AC induction engines: only 1 moving part, and only 2 parts that wear: the bearings. They last as long their bearings do, unless if you melt the damn thing down due to overheating.

And that’s where the party trick of the Nio and the Ludicrous mode of Tesla comes in: The more current, the stronger the magnetic field, but also more heat. You can “overclock” electric engines to above what they can cool for a short moment, until the engine temperature gets too high, close to melting its own damn coils. So: the shorter the time span you need the power, the more you can overclock the thing. Brief dyno run? Lol 1300 hp, yo. 10 second drag run? Sure let’s overclock that beast for that ridiculous 0-60 and let the car cool down the next 15 minutes until the next run. 24 hours Le Mans race? Yeah no, I didn’t think so.

If you want to overclock your electric car in the future you’d do it exactly like you do now with the CPUs you do now: Up the cooling, ramp up the numbers and pray to god it doesn’t break.

image.jpg554×666 142 KB

(graph probably is from a 4 pole AC induction motor, not sure source)

A standard “2 pole” AC motor can go up to 3000 rpm with 50 Hz AC electricity, with which 3000 rpm would be the “speed” of the stator’s magnetic field. Now with modern electronics though, something called “frequency inverters” exist, which can alter the frequency of the electricity supplied by converting it from AC to DC, to then to AC again. You can perfectly program these pieces of kit to work with any engine within their power rating, make them produce max torque at any rpm (until overheating, either due to lack of cooling if the fan is attached to the motor’s axle, or due to too high power (P=Trpm/602*pi)). Although above a certain rpm it’s wiser to get a gearbox (somewhere 8000-30000 rpm, idk, I’m no expert).

TL;DR: Electric engines can be overclocked for a short time span, and their drives behave like VVT/VVL but better.

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22

MPGe is mathematically IDENTICAL to taking the EPA rated range and dividing it by the battery’s capacity, only instead of using ‘the equivalent amount of energy as 1 gallon of gasoline’, you’re using the full capacity of the battery pack.

Also, electricity in my part of the US is between $0.05-$0.07 per kWh. The ‘gallon of gasoline’ equivalent of energy would cost $2.38, within the margin of error for regular unleaded; but because an EV is more than twice as efficient as even a hybrid, energy costs are less than half.

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OK im going to go off of my experience with r.c. racing for this but it should apply for regular cars too. Any battery has its peak voltage at its full capacity, as soon as you use some of the capacity you lose some of the voltage and voltage, for an electric motor, is power. I know somebody that actually runs a company that cells batteries for our cars (2 cell lithium polymer) and they have tried adjusting the fomulation purely to reduce the dropoff in voltage as they get used so for this graph
https://img.rcgroups.com/http://www.rcuniverse.com/magazine/reviews/1183/AMPD14_DischargeCurve.jpg?h=48MwHmPihmngOXLS6R1vWw
They want to shift the curve up as capacity decrease as we are limited to 8.44 volts (they can be charged higher but they get unstable at that point so the rules limit us to 8.44). Also before our race we get 1-2 minutes of practice to make sure our car is handling well and, especially for spec classes, you want to do as few laps as possible to get to the point where you are happy with the car as it will slow you down over the course of the 4 minute race if you spend all 2 minutes practicing.

EDIT: As you can see with the graph the voltage drops off very quickly as the battery nears “empty” and you can definitely feel that when driving as a few laps before the battery hits the cutoff (its unsafe to discharge them below 3 volts/cell so power cut off when you get close) it will be noticably slower then at the start.

Also, to expand on dragawns point a bit, electric motors usually perform better when they are cold as it creates a stronger magnetic force which increases their torque. It used to be that before our races a couple of the racers who were striving for every single advantage possible would take a can of air and turn it upside to spray the motor and “freeze” them so they would have that little bit more power. For batteries they generally prefer to be warm as the higher temperature reduces the internal resistance of the battery so it can give off its power at a higher rate however at too high a temperature it becomes unsafe.

Overall, im really not sure why whenever you see an electric car they’re designed to have no grills because it looks aerodynamic and efficient but they could possibly be made more efficient if they had a cooling system to keep the motors and batteries in their ideal operating temperatures.

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As @Strop hinted at… the price per kWh is a bare-faced lie. Yes, the electricity itself costs basically nothing, but the delivery and supply charges make up for 2/3rds of my bill. That will not change when charging a car.

Let me give an example…

Last month I paid $76.34 for electricity.
I used 263kWh of it at 7.8707 cents / kWh. That’s $20.70 for the supply.
The delivery charge is 11.3346 cents / Kwh. That’s $29.81 for the delivery.
Then there’s the “basic service charge” of $16.43, and then taxes, and more and more bullshit until I get to my $76.34.

So realistically speaking… I pay $0.29 per kWh… not $0.08… and I’m quite sure that most people, at least in the US are in the same situation. Go read your bills.

In other words… when the battery runs out, I don’t have a car for the next 8 to 12 hours instead of sinking 15 minutes to drive to a gas station and fill-up… which in my case is more like 3 minutes because there’s a gas-station litterally 15 meters/yards from my home. :wink:

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This is fortunately now a gross exaggeration.

It’s more like anywhere between 40 minutes and 2-3 hours :stuck_out_tongue:

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Uh… according to what I just Googled… a full charge for the Tesla S takes from 8 to 9.5 hours using a 240v outlet. With a standard outlet, you get just 5 miles of range per hour.

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oh yeah, sorry, forgot I was referring to the Tesla Supercharging stations which can crank up the power a fair bit more than your 240v outlet. Not particularly relevant to me, seeing as there’s no way I can afford a Model S, X, P85D, P95D etc. and even the Model 3 is a bit superfluous for the price range we’ll be getting it in Australia.

(But hey! Charging at your Tesla supercharging station means you get to skip the energy bill entirely!)

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“Tesla currently has 2,636 Superchargers at 373 locations across the United States, Canada, and Mexico”

Yeah… you’ll have to move where you live to be within your Tesla’s range to even find one. So unless you happen to live next to one; this shouldn’t even be a consideration.

Realistically speaking; the 240v charger is your only option if you can install one, and if a Tesla’s maximum range is enough for your daily tasks, because you won’t have enough time to charge it the same day. I assume that range will significantly decrease throughout the car’s life time as well.

If you don’t have a 240v charger… then just no.

Then comes my question… why would you ever want an electric car if they have such end-user difficulties and cost so much more; both in buy-in, and in “fuel” costs? This is something I’l never understand, so I guess I’m just asking a rhetorical question.

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As someone who beleives the Auto industry should have been moving beyond electric cars since long ago, I’m not going to argue for something I don’t believe in, but I guess the idea (or Elon’s grand plan) is to roll out superchargers to the point they’re as common as fuel pumps. Of course, for that to actually make practical sense, one would need to be able to charge the vehicle in under 3 minutes, and that doesn’t seem at all possible in the near future, AFAIK.

However, if you bothered to switch perspective, things could look differently and it could simply be a matter of whether you’re willing to change (I know you’re not so whatever… and I don’t quite believe in this particular change myself so also whatever, but I’ll play Devil’s advocate). Chances are most of us here have a smart phone. We complain about the shitty battery life of 1-2 days and less if you’re browsing or streaming Spotify etc. (oh for the days of the brick Nokias which would go an entire week if you spent all day yakking on it or not). The charging on those phones is coming down to say an hour, which is apparently fantastic considering it used to be many more times than that. Also, in this day and age we’re mostly fucking glued to the damn things all the time to the point we carry our chargers with us and forever lament this gross inconvenience but without it, omg, FOMO.

This is hardly an argument for saying this is the way things ought to be if the electric car industry supersedes the ICE one, but unfortunately, given where we’re headed, that’s a possible endgame. What lifestyle changes are we actually prepared to make and what changes will be needed for this to be a viable thing? At least you can just plug in your car to the outlet overnight when most of us are sleeping, perhaps this is considered a fair tradeoff for not driving to the gas station on a daily basis.

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i think lectricity should keep its magic, lying nose outta the affairs of internal combustion engines! ( I’m just kidding, AC/DC (?) cars are awesome, because they’re quiet. would never own one, $$$.) :slight_smile:

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yeah, wonder what these guys would drive, for real

Maybe wunna deez:

http://www.aussievault.com.au/media/vaults/121/entries/images/1895/8187/image-966-644.jpg

ok I’m done derailing, carry on

p.s. I’m Aussie, I had to do it

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32

Forgive me if I missed the point, but I don’t agree with the metaphor of this being the invention of the smartphone, it’s more Apple vs Android. Cars have been around for over a century now, and the difference between ICE and electric cars are more like what features would be on phones. Electric cars got neat features like torque vectoring and the “overclocking” I discussed, but at the moment we’re faced with the slow recharge trade-off.

Battery tech is evolving quickly at the moment, 10% capacity gain on average yearly I believe, we’ll have to see if that technology hits a wall like CPUs and SSDs did though. Also the big advantage of petrol with refueling is that it’s chemical energy is in liquid form. Electricity is in electrons form, essentially a solid, that instead from flowing straight in has to jump from atom to atom. This generates more heat and requires a lot more “pressure” to get as many as possible electrons stuffed inside the car as fast as possible. A quite physical limitation unless you can isolate electrons in some sort of liquid. Ofcourse over the years more powerful supercharging stations may appear, but they’ll probably never be pouring-in-a-liquid fast and reliable. But how fast refueling is fast enough? For daily driving you can plug in when back home, and for long journeys you need to stop for food and rest. Maybe at some point it will be “fast enough”.

My main problem with electric cars at the moment is the electricity net itself: If in Belgium everyone suddenly switched to an electric car we’d as a nation suddenly burn up coal and gas instead of petrol and diesel. When nuclear fusion becomes a thing: sure, but right now we’re struggling to create “green” electricity as is. Electric cars may be 3-4x as efficient, but their batteries eventually become a fuel/maintenance cost aswell as they degrade too much.

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Yeah the apple vs android analogy was slightly different focus to what I was getting at (since between ICE and electric cars, while there were old electric prototypes petrol won out for nearly a century), but my point wasn’t awfully strong or specific and what you say later about specific technological limitations of electrical energy is very helpful. It still answers my question in that for a cultural shift to accept electric cars as mainstream and even to entertain the possibility they’ll become our predominant form of auto transport would require seismic shifts in technology and energy infrastructure to surmount major inconveniences and difficulties. I’m sure Elon Musk has a plan for that, but who else will get on board?

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Electric cars have potential (heh), even in the performance department! rcracer11m has made some good points on how they make power, but there’s quite a bit to that!

Power here doesn’t come from just Voltage, but is a product of Voltage and Current.
To increase power, one needs to supply either a higher voltage, or allow for a higher current flow.
Incidentally, a higher voltage forces a higher current to flow, even if the entire system’s Resistance stays the same.
Now, Resistance is an interesting thing here. The electricity has to flow from the battery through the power converter/regulator electronics, through the motor itself, then back. All of these components provide certain Resistances which add up since these components are basically in series.
The total Resistance of the system determines the Current that will flow when the Voltage is given, as the Current equals Voltage divided by Resistance. The lower the Resistance, the more Current will flow, even if the Voltage stays the same.

One can make a performance electric car, with a beefy motor that is very capable of converting huge amounts of electric power into brutal wheel torque and bundle it together with electronics that can feed that lightning-eating beast. The component that is now resisting to provide current for the power is the battery pack! The cells have an internal resistance, and this provides a limit of how much power you can draw from them. The voltage they provide drops as the load on them increases (on top of a partial discharge causing the voltage to drop, too). The internal resistance also influences the power input with which you can recharge safely, without overheating.
Figure why most high output EV’s usually come along with more batteries (or even buffer capacitors?) to compensate, by spreading the requested load over the larger pack.

And this is just one reason why I call out Lithium-ion cells for EV’s for being very much a fad, especially for performance EV’s and Hybrid vehicles! Sure, they currently are the go-to cells for capacity to weight (what gives you range), but due to higher internal resistance are very much inferior to Nickel-Zinc and to some extent even Nickel-Metal Hydride in terms of power to weight potential (what gives you go).

It’s also not just power to weight for which I began to adore the potential of Nickel-Zinc, but also because the materials you make these out of are simply more common than stupid Lithium! So, cheaper and on top of that likely better recyclable, too! Ohh, and of course can be charged relatively quick! And did I mention that it is possibly safer due to it NOT containing stupid reactive Lithium? One thing that could be an issue with them are the recharging cycles, but that’s barely worse with them.

Ohh well, Lithium-ion became the meta, possibly due to range-anxiety becoming a meme, since they are slightly better for that, and maybe momentarily more development and production going in towards Lithium-cells.

Also, I feel like there are either EV’s just made by manufacturers to give off a “LOOK WE DO GREEN” Image, or they put serious development into it to make it… more expensive. “Ohh, you want an electric hatchback with adequate performance? We’ve made it with a carbon fibre chassis!”. I’m looking at you, BMW. Heck, it seems like most EV’s that have ‘adequate performance’, which in my view means 200km/125 miles range on a charge and a top speed of at least 160kmh/100mph, is usually coming at a premium, with countless features standard.
An abused niche market. Might unfortunately stay that way unless charging infrastructure is commonly available! At least on highway rest stops and parking lots and garages that are nearby where one lives!
I know the argument also floats around that using an EV basically just offsets the emissions to a fossil fuel power plant again. That’s regionally true, but again, regionally. It’d only be around 50% true for me, the rest is renewable.

But there is potential. I’d like an EV that is not just a premium/luxury snobmobile, but still is capable.


I enjoy the sound of that one! As much as I enjoy the sound of an Inline 5! Or a Diesel I4.

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wrt. the Nio EP9 again, I’m still trying to figure out the validity of their various claims, not least the one where they say 200% downforce of an F1 car and the ability to pull 2.35 lateral g…

coz if it’s true that would be super cool but if it’s fudging the numbers like how peak power outputs in EVs comes with massive caveats, then I’d be rather less impressed.

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@Strop One way they could fudge the power number is by taking instantaneous power draw at 0 RPM when the motor is basically 0% efficient and draws the most current, there will still be voltage at the battery pack terminals. I have seen way too much specsmanship in the past to believe much of any tech claims even after they hit the market until it is proven reliably.

@4LGE I bought a battery powered lawn mower to replace the dead gas one I had, for the convenience and ease of use. The only problem is all of them were painted green with eco adverts all over them. Tempted to paint it a normal red and black to get rid of the snob factor on it.

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I think the main resistance (hah, electricity puns) against electric performance cars comes from their lack of interaction. The good ol’ stick is gone, and a lot if not everything is by wire, some interaction got lost. I think a lot of manual drivers on the forum just like myself get a good satisfying feeling trying to get the most out of the engine by being in the right gear on the right time at that situation, whether it’s to maximize fuel economy, speed, or a balance between.

Now, with strong independent electric cars who don’t need no human fiddling with the drivetrain, how would we replace that?

Perhaps with a split brake pedal for manual torque vectoring? This way the human can control himself how severe the effect occurs, and on which side, which can quite possibly make the EV ridiculously nimble and add another aspect to driver skill.

Instead of a gear lever, an overdrive control that enables a manual setting of how much current (above nominal) the engine, until it comes close to overheating, in which the control is automatically disabled and the engine has to run below nominal current for awhile to cool down. Consider it a sort of nitrous that blows the welds on your intake manifolds temporarily.

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That and there are still a few things that have to come to pass before electric cars can truly be mainstream. One of which (and I have no clue why this isn’t required yet) is a universal charging port shape. Just as how any car can fill up at any gas station, we need it to be so any electric car can charge up at any charging station. It seems stupid that there isn’t such a thing yet.

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39

One of the reasons we don’t have a standard plug format is we don’t have a suitable one that can deliver enough power safely, reliably, and efficiently yet. To charge 100kWh in say 15 minutes off of a 440v plug will draw nearly 1000 amps not including any losses

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So it’s just as @KA24DE pointed out earlier. We simply don’t have the infrastructure to support EVs over great distances without some serious planning. Which is why (at least for now) onboard generators in the form of small engines (Hammerhead Eagle i Thrust FTW) makes more sense.

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