Tesla S3X power consumption versus high power electric bike (estimates)... WTF

bakaneko

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TLDR, WTF, we need better designed ebikes or more efficient motors. I was just curious as the EV craze is pretty hype at this moment with major automakers adopting into the game. The way the EV YT channels talk and companies talk about performance and how I like to talk about it is a bit different as those channels are consumers and we are actually building the EV.

But, anyways, I found a graph of Tesla power consumption versus speed for its three flag ship cars the S, 3, and X. I then plotted my understanding of the most efficient ebike motors performance up to 100kmh (60mph) and then use the ebike calculator for the rest of the speeds (120,140,160). Note, that the Model 3 weighs on average (range variants) 3800lbs. My ebike weighs 100lbs and that is heavy.

So... At low speeds, we dont even register on the graph (see orange dots) when compared to Tesla. But, as our speed increases, our power consumption rise is not proportional to weight. I know when we ride we are like a giant flag in the wind, but even with that I mean look at this damn graph. At 100 kmh, a 3800lb Tesla is half as efficient as a 100lb~ ebike, LOL. And, its gets worse from there.

What can I say? I mean this just isnt Tesla. The EV (car) is making huge technological and design gains while electric bikes both high and modest power are in the dirt. HUH, am I doing this wrong? Am I missing something?
 

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Hi,
aerodynamics of bicycle or motorcycle is awfull. you can make the same observation if you compare a 300lb motorcycle to a 3000lb car, both will draw similar power at highway speed.

But I think something is wrong on the curves.
For example for the Tesla model 3 at 40km/h, the energy consumption/km is 5000W/40km/h = 125wh/km
at 80km/h it's 8000W/ 80km/h = 100wh/km
It's not possible, energy consumption per km should be significantly higher at double speed, not lower ...
 
found it on interweebs. i was just curious about how EVs do batteries and how they can advertise the range and mileage. i mean if this is right it means their aero must be damn good or something is happening in their motors that is not happening in ours.
 
Yep nothing new here. My 500lb motorcycle gets worse mileage on the highway than my Camry.

Making a bike aerodynamic is generally not practical, but if you look at velomobiles, despite far greater weight they always outperform unfaired bikes at speed. Nothing with a person sticking out on top of it is gonna be aerodynamic.

Keep in mind those are cruising consumption numbers. In stop and go traffic, the car still weighs 3500 lbs or whatever, and the bike will kick it's ass in terms of the amount of energy consumed during acceleration.

Keep in mind weight doesn't matter once it's moving, only when you're accelerating or decelerating it. Conservation of energy and such.
 
Yup, aerodynamics is a force NOT to be underestimated. With good rolling resistance tires (forget moto tires!) RR can be significantly reduced, too.

I am designing a e-velomobile with CdA of about 0.07 - so 2kwh battery should last me about 500 km with average speed of about 50kmh, and that is a relatively conservative estimate.
 
One look at the speeds often achieved on velocycles and recumbents with windshields when compared with most upright bikes tells me aero must play a huge role, especially as the speeds increase. I'd bet if you put a conventional ebike on a pair of rollers with no resistance your power consumption would go down dramatically, not that I've tried it.

I do know that the faster you go the harder it becomes to push through the air, so every bit helps. Once you really get up there in speed (think salt flats) it can take dramatic power increases to go even 1mph faster when aero is your limiting factor.
 
HK12K said:
I'd bet if you put a conventional ebike on a pair of rollers with no resistance your power consumption would go down dramatically, not that I've tried it.

At low speeds it would be pretty significant but once you get above 20-25 mph or so rolling resistance becomes a less significant part of overall drag, as it increases in a linear fashion as opposed to wind resistance which increases as a square of speed.

So at 30 mph you have 1.5 times the rolling resistance as at 20mph, but you have about double the wind resistance. At 40 mph you have 2x rolling resistance and 4x wind resistance, and so on.
 
All I know is that 5kW of power in a Chevy Volt will get you to 17 mph while on either of my ebikes that same 5kW gets me to 50mph. The gauge on my P100D shows a usage gauge that is not digital like the Volt, so I cant see anything below the lowest 20Kw increment to compare. I do know that when running a mid to high 10 second 1/4 mile I usually hit between 550-565kW of battery output.
 

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Cd means nothing without surface area to multiply it by. Bike surface area is smaller, but Cd is worse.

Generally near highway speeds, for an emoto vs ev car, you can convert the range 2:1 with the same battery size in favour of emoto.
 
If you are consistently riding at 30-MPH or more, there is a significant efficiency gain to building a semi-recumbent with a front fairing and tail-sock.

A low-recumbent is simply not safe on the same roads as cars, even with a visibility flag. You could also go for a full-bodied velomobile, that has openings on the bottom to allow your feet down at stops.

A full-bodied velo may be problematic in cross-winds, so having an open passenger compartment in the center would be the most radical I would build.
 
st35326 said:
All I know is that 5kW of power in a Chevy Volt will get you to 17 mph while on either of my ebikes that same 5kW gets me to 50mph. The gauge on my P100D shows a usage gauge that is not digital like the Volt, so I cant see anything below the lowest 20Kw increment to compare. I do know that when running a mid to high 10 second 1/4 mile I usually hit between 550-565kW of battery output.

hmm, so do you think that model is wrong. of course, that model is a model. but then the ebike calculator for the 120+ kmh is also a model...
 
bakaneko said:
st35326 said:
All I know is that 5kW of power in a Chevy Volt will get you to 17 mph while on either of my ebikes that same 5kW gets me to 50mph. The gauge on my P100D shows a usage gauge that is not digital like the Volt, so I cant see anything below the lowest 20Kw increment to compare. I do know that when running a mid to high 10 second 1/4 mile I usually hit between 550-565kW of battery output.

hmm, so do you think that model is wrong. of course, that model is a model. but then the ebike calculator for the 120+ kmh is also a model...

It is all consistent with your initial graph. 17 mph is 27.4 km/h. So his Chevy Volt just isn't as efficient at 5kW of power as the Tesla - give or take accuracy of the graph and measurements.

Also, I don't see your graph as painting a bleak picture at all. As st35326 pointed out, e-bikes go lots faster at low power inputs and lower speeds. The percentage gap in power consumption is huge at these lower speeds. And all of this reflects real world experience that teaches us that our power consumption increases pretty rapidly after speeds of about 25 mph (40 km/h). Hence the general recommendation to keep speeds at 20 mph or below if you want to get long range on your ebike batteries.

Bikes and e-bikes are excellent for travelling at relatively low speeds using low power input levels. They are not designed for high speeds. There are better designs for that.
 
wturber said:
Bikes and e-bikes are excellent for travelling at relatively low speeds using low power input levels. They are not designed for high speeds. There are better designs for that.

yeh, i mean okay. its just my vision of green mobility isnt right based on these numbers. my assumption was even an electric car was much more inefficient at commuting speeds 40-60mph versus a high power ebike/emoto. i assume two wheelers not only had fun but also save the environment due to much better fuel economy or efficiency. from that graph this is not the case. ideally, one would have an emoto for commuting and then an ICE/EV for groceries or long trips and then really be green.

as a goal, i wanted to build a 125cc equivalent emoto with high efficiency and a 30-40kwH battery. but to really do something special i need to beat Tesla by atleast a factor of 3 in efficiency. looks like that might be extremely difficult. note, i do not like the current emoto designs out there; too much like a gas motorcycle and not efficient or battery centric designs.

NOTE: To build a 30-40kwH battery centric, aero emoto would require atleast 20-30K to develop and well out of my scope atm. I wish I could do it and make it futuristic looking...
 
bakaneko said:
my assumption was even an electric car was much more inefficient at commuting speeds 40-60mph versus a high power ebike/emoto. i assume two wheelers not only had fun but also save the environment due to much better fuel economy or efficiency.
They can. But only if you make them as (or more) aerodynamic than the more efficient vehicles.

You can start by looking at Vetter designs.
 
Bikes are much more efficient than cars in primary acceleration, when aero drag has little effect. The faster they are going, the more cars are taking advantage. Of course, a bike that is fully faired will be better. When 2 vehicles are equal in aero drag, their weight is making the efficiency difference.
 
I think you're all forgetting cars use AC motor and not DC, where the AC motor gets better efficiency at high speed because they hold the torque more linearly
 
TY for insightful replies. Looks like we need to get more aero and more efficient motors at high speeds and bigger batteries. Obviously, this is in the emoto and high power ebike realm and not the legal ebike.
 
brone said:
I think you're all forgetting cars use AC motor and not DC, where the AC motor gets better efficiency at high speed because they hold the torque more linearly
Most modern ebike motors run on 3 phase ac as well. The controller is a dc to ac converter.
 
Craig Vetter was a pioneer, and if you check out his research, I believe he convered this pretty thoroughly.

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People vastly overestimate the effect of a vehicle's weight on efficiency. It's ALL about aerodynamics and motor efficiency. Bicycles have trash aerodynamics.

Also Tesla Model 3s have some kind of super ultra high-efficiency Switched Reluctance Motors. SRMs are also used extensively in robots, printers, etc.

Here's a good article explaining *why* it's so efficient: https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/
 
MAXIMUM_AMPS said:
People vastly overestimate the effect of a vehicle's weight on efficiency. It's ALL about aerodynamics and motor efficiency. Bicycles have trash aerodynamics.

Also Tesla Model 3s have some kind of super ultra high-efficiency Switched Reluctance Motors. SRMs are also used extensively in robots, printers, etc.

Here's a good article explaining *why* it's so efficient: https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/

YES BUT THE RESULTS ARE SHOCKING!!! :lol:
 
bakaneko said:
TY for insightful replies. Looks like we need to get more aero and more efficient motors at high speeds and bigger batteries.

Given that the more efficient PMDC motors are above 90% already, how much more do you think is reasonably available there? It's a dead end.

Noisy, energy hogging and murderous high speeds are what we have to develop away from. That's the low hanging fruit of increased efficiency, and it pays all kinds of other dividends at the same time.

I suggest 20 mph inside city limits, 55 mph on intercity highways. We can set our own sane limits, or circumstances will set them for us (but we won't like the other implications).
 
bakaneko said:
YES BUT THE RESULTS ARE SHOCKING!!! :lol:


6% gain in efficiency over the Model S is pretty good, all things considered. Granted the Model S was already 83% efficient, but still.
 
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