That was a great video from BestInTESLA, great channel.
This goes to the topic of where Tesla may choose to deploy their battery
capacity which is no longer their "limiting factor"...
In addition to the CyberTruck, or an inexpensive car, there is the Semi,
and their accompanying Mega Pack which will allow a route location to
use "Dump Charging" in order to skirt grid peak demand and instead even
earn money by leveraging stationary storage along with renewables to do
grid energy arbitrage with the likes of their AutoBidder (Their VPP
(Virtual Power Plant) AI Software already in production.
Turns out that the Semi and Co-Located Grid Storage with renewables
might have the larger societal impact than a cheaper BEV for the masses.
Related to lowering the cost for a sedan, do keep in mind that all
Teslas for the past decade have included their full ADAS (FSD) suite.
There was another video today (https://youtu.be/Vx-BpSCypjU probably)
pointing out that Tesla has lost Billions worth of hardware by
installing this hardware suite in every single car. Why would they do
this? Because it accelerates their ability to both solve FSD and then
to sell FSD which is a value multiplier for all of those 2+million
vehicles already deployed.
----
A similar protip, Paying for YouTube Premium is well worth it
IMHO because it eliminates all advertising and allows for 2x playback.
Another good video: https://youtu.be/DtGQ6KC3t1c
: How the Tesla Semi “Broke the Laws of Physics”
: Channel: The Limiting Factor
:* An EXCELLENT Channel all should watch all Videos.
50,411 views Jan 23, 2023
When Tesla unveiled their Semi 5 years ago, auto industry was skeptical
to say the least. As Daimler put it, Tesla must be defying the laws of
physics.
In this video we'll look at how the Tesla Semi "Broke the Laws of Physics"
Timeline
00:00 Intro
01:09 Drag Coefficient
02:05 Powertrain
03:31 Tesla’s 20% Advantage
04:36 The Plaid Motor
06:56 The Limiting Factor for Regen
10:53 1000 Volt Triangle
11:49 Summary
Read before commenting on regen and 17% cost advantage:
1) At 12:35 I say that the Semi recaptures 90%. Obviously this is one
way efficiency. The round trip efficiency would be 81% because it has
to go from battery to wheel and then wheel to battery. More on this in
the next video.
2) A lot of people are thinking the 17% cost estimate is mine. It's
from Tesla - directly from their unveiling event. Cleanerwatt did an
update of this on his channel, go check it out.
https://www.youtube.com/watch?v=WIzcaBSFud8&t=951s
Transcript
0:05 Welcome back everyone!
0:06 I’m Jordan Giesige and this is The Limiting Factor.
0:09 When Tesla unveiled the Semi 5 years ago, the auto industry was
skeptical to say the
0:14 least.
0:15 As Daimler put it, Tesla must be defying the laws of physics.
0:18 With the Tesla semi now on the road reaching 500 miles of range,
clearly no new physics
0:24 are required.
0:25 However, this begs the question.
0:26 “Why did so many people assume that the Tesla Semi was just smoke
and mirrors?”
0:31 In short, it was a failure of imagination.
0:33 There were of course the obvious opportunities to improve
efficiency, like the aerodynamics
0:38 of the Semi or ensuring that energy is used efficiently throughout
the powertrain.
0:43 But, there are also some non-obvious opportunities, like synergies
between triple plaid motor
0:48 powertrain and the 900kWh battery pack that Tesla didn’t talk about
in the Semi Delivery
0:54 Event.
0:55 Before we begin, a special thanks to my Patreon supporters and
YouTube members.
1:00 This is the support that gives me the freedom to avoid chasing the
algorithm and sponsors.
1:05 As always, the links for support are in the description.
1:09 To kick things off, let’s start with the obvious reasons why the
Tesla Semi was able
1:13 to achieve 500 miles of range, then we’ll get into the not so obvious.
1:17 Most people know that the Tesla Semi has a drag coefficient that’s
almost half that
1:22 of a diesel Semi and even better than a Bugatti supercar.
1:25 A drag coefficient is simply a measure of how efficiently an object
moves through the
1:30 air.
1:31 Lower resistance means greater efficiency and therefore range.
1:34 However, it doesn’t take into account the amount of air that the
object displaces.
1:39 Greater surface also increases total drag.
1:42 Therefore, although it’s cool that the Semi has a slicker
aerodynamic shape than the Bugatti,
1:47 it’s not the best comparison because the Bugatti is so much smaller.
1:51 The better comparison is the diesel truck, which has a much higher
drag coefficient and
1:56 has a similar surface area to the Tesla Semi.
1:58 We’ll take a look at how the Tesla Semi compares to other electric
Semis later in
2:03 the video.
2:04 Next, the powertrain.
2:06 A typical electric vehicle has a roughly 86% battery to wheel
efficiency.
2:11 Roughly 5% of the energy is lost in the battery itself due to
electrical and chemical inefficiencies,
2:16 5% is lost to converting DC power from the battery to AC power for
the motors, and 5%
2:23 of the energy is lost to inefficiencies in the motor.
2:26 This means 14% of the energy is lost to heat rather than generating
forward motion.
2:31 But, that’s a typical electric vehicle.
2:34 For a Tesla and other well engineered electric vehicles, 3% is lost
in the battery itself,
2:39 1% converting DC to AC power, and 3% is lost to inefficiencies in
the motor.
2:45 This means, at most, a Tesla has a total efficiency of 93% from
battery cell to wheel.
2:52 However, bear in mind that the 93% figure is a peak efficiency figure.
2:56 The average efficiency probably is around 90%.
2:59 Overall, Tesla’s powertrain efficiency advantage of 4% over a
typical electric vehicle doesn’t
3:06 seem like much, but as we’ll see, it adds up.
3:09 As a side note, if you’re curious where I got the efficiency
numbers from, it was
3:13 from a 2021 Car and Driver Magazine article on the Tesla Plaid
Model S. Bear in mind,
3:18 the car and driver article was poorly written from a technical
perspective so I had to interpret
3:23 it as best I could.
3:24 Regardless, you’ll find the 93% and 90% figures I arrived at
roughly align with the
3:30 article.
3:31 Moving along, the aerodynamic and powertrain efficiencies compound
on each other along
3:36 with other innovations like Tesla’s Octovalve and heat pump system
to provide about 20%
3:42 greater efficiency than a typical electric vehicle.
3:44 There are outliers, such as the Lucid air that aren’t shown on this
chart, but in
3:48 most cases, Tesla is usually best in class.
3:52 But, is same true for the Tesla semi versus other electric Semis?
3:57 Yes.
3:58 This summary table from EV Universe shows that the Tesla Semi is
nearly twice as efficient
4:03 as the worst performing Semi, the BYD 8TT.
4:07 And it’s about 18% better than the next best performer, the Volvo
VNR electric.
4:13 Considering the Tesla Semi has a battery pack that’s about 62%
larger and heavier than
4:18 the Volvo, how is it that the Tesla Semi is still significantly
more efficient?
4:23 I think there’s more that’s going on here beyond just aerodynamics
and better electronics.
4:28 My view is the Tesla Semi actually gets some surprising leverage
from its larger battery
4:33 pack and triple motor set up.
4:35 First, it’s worth noting that, at the unveiling of the Semi, Tesla
said the vehicle would
4:40 use four motors.
4:41 However, in the production version of the Semi, it only uses three.
4:46 This means tesla was able to remove weight from the vehicle which
will increase range
4:50 and efficiency.
4:51 How was Tesla able to remove one of the motors in the production
version?
4:55 This is where Tesla’s plaid motor comes in.
4:58 The plaid motor was unveiled by Tesla in 2021 along with the newest
version of Tesla’s
5:03 Model S Sedan.
5:04 Rather than using a steel jacket to hold the rotor of the electric
motor together, the
5:08 plaid motor uses carbon fiber.
5:10 This allows the Plaid motor to reach higher RPM before the rotor at
the centre of the
5:15 motor flies apart, which means higher power density.
5:19 Additionally, the thin carbon fiber wrap on the rotor of the plaid
motor should reduce
5:24 parasitic magnetic fields high RPM as compared to an electric motor
with a steel sleeve,
5:30 which may also help improve power output.
5:33 There’s a lot more to the plaid motor than that, and I eventually
plan on doing a deep
5:37 dive video on it.
5:38 What all this means is that the plaid motor delivers about 35%
higher power at high RPM,
5:44 and maintains that power to 20,000 RPM at high efficiency.
5:48 This both allowed Tesla to remove a motor and gear the motor for
high RPM heavy load
5:53 use cases like the Semi.
5:55 For the Plaid Model S, those 20,000 RPM are geared to propel a 2
tonne sedan from 0-60
6:01 in two seconds, on a vehicle with a top speed of over 200 mph.
6:06 For the Semi, Tesla used the same 20,000 RPM motors and geared them
to propel a 40 ton
6:12 vehicle from 0-60 in 20 seconds on a vehicle that probably has a
top speed of around 85
6:19 mph.
6:20 Interestingly, Tesla could’ve gotten away with two motors or even 1
motor in the Tesla
6:25 Semi and it still would’ve been able to accelerate at the same
speed as a Diesel Semi
6:29 from 0-60.
6:31 In fact, the Volvo VNR I mentioned earlier has two electric motors
that put out 400 kilowatts
6:37 of power, which is about half the power of the Tesla Semi.
6:41 Furthermore, the Volvo needs a two speed transmission.
6:44 The Tesla Semi doesn’t need a transmission with more than one gear
because their motors
6:49 are so powerful and have such a high RPM limit.
6:52 They can just use one gear and rev it up to 85 mph.
6:56 This begs the question: Why did Tesla put three motors on the Tesla
Semi if they weren’t
7:01 necessary to keep up with the power of a Diesel Semi.
7:04 Once again, it comes back to efficiency.
7:06 First, the use of three motors allows Tesla to optimise one of the
motors for cruising
7:10 speed.
7:11 This allows the other two motors which are geared for acceleration
to disengage at cruise
7:16 speed.
7:17 We saw something similar with the old Tesla Model S P85D.
7:20 By adding an electric motor they were able to improve the range of
the dual motor Model
7:24 S by more than 11% over the single motor version by optimising one
motor for acceleration and
7:30 one motor for highway cruising.
7:32 Second, three electric motors allows the Tesla Semi to recapture
more energy through regenerative
7:38 braking than a typical Tesla vehicle, and it may not be for the
reasons you think.
7:42 Let’s look at a Tesla Model 3 to get a better understanding of
what’s going on here.
7:46 An all-wheel drive Tesla Model 3 is able to regenerate around 70
kilowatts with two electric
7:52 motors.
7:53 Obviously, a Tesla Semi that weighs 20 times as much will need to
recapture at least an
7:58 order of magnitude more power.
8:00 So what’s the limiting factor here and how can we break it?
8:03 For the Model 3, the roughly 70 kW regen limit is software limited.
8:08 But why the software limit?
8:09 It’s most likely to maximise battery life.
8:12 Yes, performance Model 3s with roughly the same motors and battery
pack can regen up
8:17 to 100kW with track mode, but that vehicle has higher profit margin
and Tesla can afford
8:23 the extra potential warranty claims from intermittent track abuse.
8:27 Some might argue also that the regen limit of 70-100 kW can’t be
due to battery limitations
8:33 because a Model 3 can accept up to 250 kW of power on a Tesla
Supercharger.
8:39 The catch is that it can only accept a 250 kilowatts when the
battery is both at a low
8:43 state of charge and when the battery pack’s gone through a
preconditioning cycle to increase
8:48 the charge uptake.
8:50 Even then, it takes a minute or two for the battery to spool up
from 100 kW to 250 kilowatts
8:55 of power.
8:56 That’s not a luxury the vehicle has under spontaneous braking loads.
9:00 So if I’m correct and the battery is the limiting factor for
regenerative breaking,
9:05 then a larger battery pack with a larger energy reservoir should
allow for more energy to
9:10 be recaptured during each breaking event.
9:13 The Semi battery pack has roughly 900 kWh of useable energy storage.
9:18 This is over 11 times the energy stored in a 78.5 kWh Model 3 battery.
9:25 That means rather that than accepting 70 kW of regen power like the
Model 3 battery pack,
9:30 the Semi battery pack should be able to comfortably accept 770
kilowatts of regen power.
9:36 However, can the triple motor set up of the Plaid power train
regenerate that much power?
9:42 It appears so, the Plaid powertrain in the Model S can pump out
over a thousand horsepower.
9:47 If those motors are used to generate power rather than use it, and
1020 horsepower is
9:52 760 kilowatts of power, then everything falls neatly into
alignment. 760 kilowatts of regen
9:59 power paired with a battery pack that can comfortably accept 770
kilowatts of power.
10:05 That is, my view is that the primary purpose of the triple motors
of the Semi doesn’t
10:10 appear to be acceleration and powering up hills with ease, but
rather so that the Semi
10:15 doesn’t need to use its brakes.
10:17 This means the Semi can harvest every bit of kinetic energy while
going down hills and
10:22 braking, turning it into chemical energy for the battery rather
than thermal energy like
10:26 would if the brakes were used.
10:28 And, that means the 500 mile range version of the Semi may gain
some efficiency advantages
10:34 over other Semis on the market that have smaller battery packs.
10:37 This is because the larger battery pack and triple motors might
allow it to soak up every
10:42 drop of energy on steep downhill runs that might overwhelm a
smaller battery pack.
10:47 As usual, this educated speculation on my part, so let me know
what you think in the
10:52 comments below.
10:53 Lastly, the Tesla Semi is getting an upgrade from Tesla’s typical
3-500 volt architecture
10:59 to a 1000 volt architecture.
11:01 Does this offer any efficiency benefits?
11:03 Yes, but the extent depends on how Tesla leveraged the extra voltage.
11:08 Increasing the voltage of an electrical architecture can actually
be leveraged in several ways.
11:13 It can be used to reduce wire thickness to reduce costs, increase
power output, or improve
11:19 efficiency by reducing heat generation.
11:21 A good way to think of it is the triangle on screen.
11:24 By increasing the voltage, you can focus on one corner of the
triangle or pick a combination
11:29 of benefits.
11:30 Optimising for one corner of the triangle naturally moves you
further from the other
11:34 corners.
11:35 Trade -off decisions are required.
11:37 That is, we know Tesla will derive benefits from the 1000 volt
architecture, but the extent
11:42 of those benefits and where they were applied is something we
won’t know until there’s
11:47 a teardown of the Tesla Semi.
11:49 In summary, why did Daimler say that the Tesla Semi was breaking
the laws of physics and
11:54 why did Bill Gates say that that the Tesla Semi would probably
never work?
11:58 It’s because they reasoned by analogy.
12:00 They looked at current Semis on the market and seemed to assume
that an electric Semi
12:05 would be the same thing as a diesel Semi, except carrying 5 tonnes
of extra battery
12:09 weight.
12:10 That is, they failed to look at electric Semis with an open mind
and to design from a blank
12:15 sheet of paper and didn’t ask the right questions.
12:18 For example: What if we make the brakes redundant by pairing
12:21 the large battery pack with extra motors to capture every bit of
kinetic energy rather
12:26 than wasting that energy as brake heat?
12:29 That means any energy spent on an uphill or accelerating could be
recaptured on the downhill
12:34 or decelerating.
12:36 In the case of a Tesla, that would be about 90% of the energy
recaptured.
12:40 Next, what if we optimised one of the three motors for cruising
speed and disengaged the
12:46 other two motors to maximise energy efficiency at highway speeds?
12:50 Finally, why don’t we reshape the Semi so that it’s smooth and
bullet-like, rather
12:55 than just taking a typical Semi tractor and sticking some
batteries in it?
12:59 I do think that the Tesla Semi may have lost some cargo capacity
compared to a Diesel semi,
13:05 but nowhere near enough to make the Semi commercially unviable.
13:08 According to battery design.net, the Tesla Semi probably weighs
about 2.4 tonnes more
13:14 than a typical Semi.
13:15 However, electric Semis are also allowed leeway of an extra tonne.
13:20 So, overall, the Semi loses at most about 1.4 tonnes of cargo
capacity, which is about
13:26 a 7% cargo penalty.
13:28 With that said we also have to take into account that Semis often
aren’t carrying their maximum
13:34 rated cargo weight anyways and the fact the Tesla Semi will be
about 17% cheaper to operate.
13:40 So, even with a cargo handicap, not only is the Tesla Semi
possible, it’s a much more
13:45 profitable option for routes that are within it’s 500 mile range.
13:50 Before I close things out, I want to say a big thinks to Here We
Go Again on Twitter!
13:54 The discussions we had after the Semi event massively upgraded my
understanding of superchargers,
14:00 electric motors, and inverters.
14:01 That saved me days or weeks of research and a lot of potential errors.
14:05 If you enjoyed this video, please consider supporting me on
Patreon with the link at
14:10 the end of the video or as a YouTube member.
14:12 You can find the details in the description, and I look forward to
hearing from you.
14:15 A special thanks to my YouTube members, and all the other patrons
listed in the credits.
14:19 I appreciate all of your support, and thanks for tuning in.
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