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EV EPA Calculated Numbers
- Thread starter Danno
- Start date
OVERKILL
$100 Site Donor 2021
"Real driving", unless you are shredding the tires, again, the difference is irrelevant. I have 475HP in my SRT, the only time I use all of it is if I'm passing somebody or merging with a short on-ramp. It will gladly light up all 4 on anything that isn't dry pavement, especially with the snow tires, and that's nowhere near max power. "Real driving" does not involve tapping into even a small fraction of a 1,000HP electric motor's potential output.
A 1,000HP motor has the POTENTIAL to draw 10x the power of a 100HP motor, for whatever period that is able to be done. Without wheelspin, in daily driving? basically never.
Let's move this back to the right units.
1000HP = 745kW
100HP = 74.5kW
As we've established, electric motors are almost 100% efficient at turning input power (W/kW) into motion (miles, km) over time (kWh).
But it doesn't use meaningfully more power. Electric motors are directly coupled in most applications, you have no transmission or torque converter. This is why EV's are so much more efficient than ICE's in stop and go; in in town driving. You are turning energy into motion, not heat. The exception of course is when you are spinning the tires, but unless you drive like a moron, that isn't happening.
We'll use a 4,400lb EV for this exercise and ignore aero and other factors, since we are talking about around town.
Our 100HP; our 74.5kW EV can get up to 30mph in 6 seconds. So, if we are hooning it (to the floor) everywhere in town with a 30mph speed limit, it takes us 6 seconds to get there. So that's 74.5kW for 6 seconds; 0.0021 of an hour; 0.124kWh.
Our 1,000HP; our 745kW EV can do 0-30 in 1 second. So if we were to somehow hoon it (to the floor) everywhere in town with a 30mph speed limit, it takes us 1 second to get there, so that's 745kW for 1 second; 0.207kWh.
In reality, even if we used 300HP of our 1,000HP EV, which is 0-30mph in around 2.5 seconds; 223.71kW for 2.5 seconds that's 0.155kWh.
Now, do we really think people are driving around doing 2.5 second 0-30 pulls from every intersection? Of course not, so then the gap narrows further.
Furthermore, you are letting off as soon as you get to your target speed and steady state consumption is the same whether there's 74.5kW or 745kW on tap.
So, let's say you stop and go 50x, that's 7.77kWh using 300HP every time, vs 6.2kWh in the 100HP car. I pay $0.14/kWh all-in, so the 300HP car costs me $0.22; costs me 22 cents more on that trip than the 100HP car in this intentionally ridiculous scenario where I'm 0-30'ing everywhere in 2.5 seconds.
It's the steady state rate of consumption, which is tied to the mass of the vehicle, aero...etc that ultimately impacts the real metric, which is miles or km per kWh. This is dictated not by the peak power capability of the electric motor, as I think we've well-established at this point, but rather the average amount of power used to achieve and sustain motivation, which in turn dictates the amount of energy drawn from our battery.
This isn't really a relevant comparison.
The ability for the battery to deliver large amounts of power and energy instantaneously is indeed a byproduct of the size of the battery and its cooling system and cabling (with the exception of the motor cabling) which is all due to the design being focused on being able to charge the battery as fast as possible, which myself and @dogememe already covered earlier.
A petrol car's ability deliver gas to the engine has no bearing on how fast you can fill the tank. But with an EV, the rate at which you can charge the battery (think DC fast charging) requires robust cabling and considerable battery cooling. This is because you aren't moving energy at peak power for a few seconds, but rather moving large amounts of energy over the shortest possible period of time due to the capacity of the pack, which produces incredible amounts of heat. A 350kW fast charger, for example, that's 470HP, but not only for a couple of seconds, for many minutes, if not 10's of minutes.
The size of the battery has nothing to do with the power output of a electrical motor, provided that the battery is of the proper voltage, correct? a volt is a volt. more volts = more power, in Dc correct? you put 11v through a 9v motor=burnt motor.....that is not what I am talking about.
power is volts
range is amps
correct?
at 20% the 1000hp motor will put out 200hp? yes or no?
what really moves the vehicle is torque, and with electrical motors, torque is flat, correct?
is your stance that the system requirements for 1000hp is the same as 200hp?, cabling cooling tires, brakes etc? That is what I am thinking you are saying.
My whole point is that they do not need to be 1000 hp, and a 200hp would be sufficient for normal use, and would be cheaper to build, cheaper to maintain and by those things, more "efficient" to the end consumer. yes or no?
Sure, but if you were to hook up a scanner, you would see above 80% load a whole lot more than what you display.
what about it?
OVERKILL
$100 Site Donor 2021
You missed the point I was making. We don't size batteries at 2kWh, because a 2kWh battery wouldn't be sufficient for reasonable range. We size batteries at north of 60kWh, and to charge that capacity, in a reasonable amount of time, requires a high rate of charge, and a high rate of charge produces a large amount of heat, and requires large interconnects. So we need cabling, and cooling capacity, sufficient to handle all of that over the duration required to charge the battery to capacity.
So, as a byproduct of large batteries designed to be able to sustain a high rate of CHARGE, they are able to deliver a high rate of DISCHARGE. This enables the use of high powered motors basically incidentally.
Follow?
Of course, wasn't that clear from the 0-30 stuff I was showing you?
Technically, power moves the vehicle. You can deliver torque and zero movement. Movement means work is being performed, and the rate at which work is being performed is power. Electric motors can deliver full torque at 0RPM (no work), and yes, the amount of torque they can apply is constant.
I'm saying most of that has no impact on the efficiency except the tires. And, per my Tesla examples, there's not much of a weight difference either.
Do you think there's a big manufacturing cost difference between the standard range RWD Model Y (342HP) and the AWD Model Y Performance (527HP)? They use the same casting, same body, same interior bits...etc. That's the point @Torrid was making. Even the 1,000HP Plaid, Tesla is almost certainly making a much higher margin on that compared to the regular S and S Performance. It has some upgrades, but those upgrades are not huge in scope.
The Model 3 and Model Y are popular because:
A) Tesla
B) They are the size and body styles people want
A modern Ford Festiva (which it sounds like you are envisioning) wth a 100HP electric motor and 50kWh battery might eventually become cheaper to produce (right now, Tesla has a considerable advantage in that space) but given how much of the cost of the vehicle is the battery and then engineering in modern crash worthiness and modern safety features, it wouldn't be as cheap as you might expect. And it wouldn't sell in numbers that would make it viable.
So, working within the bounds of what people will actually buy in volumes to sustain production and profitability, while 1,000HP may be on the absurd end of the scale (hence the Plaid), 5 or 600 HP is easy to offer at a premium and with little to no additional cost to the manufacturer, depending on their platform design. And, unlike with petrol-fuelled vehicles, there isn't an operating cost penalty; there isn't an efficiency penalty in opting for that premium for the buyer.
Don't need to hook up a scanner, I can see that info on the SRT data logging screens. I will check the next time I'm out.
80% load isn't 380HP though, because peak torque doesn't occur until a specific RPM, same with peak power. This is fundamentally quite different from how output is commanded from an electric motor.
I am no expert, but my understanding is it is the amount of energy you can feed the motor; battery discharge rate. This is largely dependent on temperature.
Perhaps others can chime in.
The internal resistance of a battery rises with colder temperatures. This increase in resistance hinders current flow.
Yes, my understanding is the battery can transfer more energy when hot enough, which is why the battery preheats when navigating to a Supercharger.
OVERKILL
$100 Site Donor 2021
Yep, there's a range of "optimum" temperature for batteries. My buddy's LFP home batteries for his off-grid setup won't charge below like 5C or something, so he has to heat the room they are in.
