Comment by aresant | Hacker News Reader

Comment by aresant | Hacker News Reader

What could validate this article's hypothesis is if Tesla manages to roll out a Class 8 Truck that meets the industry's needs.

Musk tweeted earlier this year "Tesla Semi truck unveil set for September. Team has done an amazing job. Seriously next level."

I am involved in a logistics startup that leverages Class 8 trucks and the specs are brutal.

Our trucks need a 500+ mile range and have to haul 40,000 - 50,000 pounds, and do it 5 - 6 days a week reliably.

It's hard to conceive how an electric drive train & battery array could manage to deliver on those basic specs.

But since 2000 heavy trucks have accounted for 40% of the TOTAL growth in oil demand, and similar gains are projected over the next few decades.(2)

And capital on the fleet side is very organized and effecient.

EG if lifetime operating costs of electric are significantly lower w/a longer useful equipment lifetime adoption will be rapid.

(1) https://twitter.com/elonmusk/status/852580027178696704

(2) http://www.iea.org/newsroom/news/2017/july/iea-study-unveils...

Trucking is one area where the per-mile costs are really important, unlike most passenger cars. The cost of electricity is generally much much less than the cost of fuel, so there's definitely the potential for a compelling offer for hauling, even if its only a subset of all uses of semi trucks.

Electric drive trains are excellent at heavy loads; many huge haul trucks, trains, etc. use diesel electric where the diesel is just a fuel source to generate electricity for the real workhorse, the electric motor.

So it's really just the battery that's the hard part here.

Most EVs get ~3.3 mi/kWh. If the increased air resistance means only a third of that efficiency, a 450 kWh battery would be sufficient for 500 mile range. That's about 3 tons of weight, which is a lot, and take up about 2 feet of space behind the cab, perhaps. But since a diesel engine itself is going to weigh about 1 ton more than the electric motors and inverters, it's not a completely outrageous amount of overage.

Of course, the battery alone for this would be about $100,000k, as much typical tractor cabs these days. So clearly there would be some sort of swap program, and battery usage would be charged.

This all becomes a ton easier if designed for just, say, 250 miles before swapping batteries. But napkin math suggests that 500 miles isn't completely implausible, if you can get over the up front capital costs, and the slightly lower hauling capacity.

Also don't forget the battery charging time. If your battery takes two days to charge, it will be show stopper to even start with.

Well I did say: "So clearly there would be some sort of swap program"

Though my intent was mostly so that the capital cost could be amortized over many uses by independent truckers, rather than them having to take out an upfront loan for the massive cost of the battery. But it also makes the timeliness of charging a non-issue.

Swapping is an option if the batteries aren't owned by the drivers/truck owners. Otherwise its a huge issue.

I don't want to buy a new truck and have my new battery swapped for a 5 years old battery, then have a break down somewhere and pay for it.

> Most EVs get ~3.3 mi/kWh

Not if they're hauling around 40,000 - 50,000 lbs of freight.

And in the next sentence I completely spitball that it may be a third of that.

That's based on the drag, which is most of the energy spent on hauling.

Though another benefit of electric is that the kinetic energy of accelerating 50,000 lbs to 55mph can be regenerated, instead of lost entirely. And it's not an insignificant amount of potential energy, at really close to 2kWh.

> Most EVs get ~3.3 mi/kWh.

Not even close. BMW runs electric trucks between production facilities and our 169kWh trucks (Terberg YT202-EV) which haul up to 34,000kg get at most 100km out of that, often less. So you're looking at about 0.6km/kWh or 0.37mi/kWh. It will be more with less stopping (although there isn't a lot of stopping on our routes) but nowhere near your estimate.

I appreciate your data! However I wasn't trying to say that trucks will get 3.3 mi/kWh, this was apparently quite confusingly phrased, as I meant passenger vehicles.

My spitball of 1.1 mi/kWh was clearly way too high still.

> But since 2000 heavy trucks have accounted for 40% of the TOTAL growth in oil demand

I kept trying to parse this (and then got shocked and was like "no, that can't be true...") before going on and realizing I was reading a garden path sentence.

https://en.wikipedia.org/wiki/Garden_path_sentence

Thank you I hadn't read the description of that before.

After looking up the definition of garden path sentence... I'm not sure this fits the bill.

It doesn't look like a misleading statement to me. Unless you mean it's missing a comma after '2000'?

It's hard for me to tell what the most likely interpretation is, but yes, a comma could certainly disambiguate it. As it was written, I was expecting it to go "But since 2000 heavy trucks have accounted for 40% of the TOTAL growth in oil demand, and since [foo] is also true, we expect that [blah]..." but then my mental model just crashed.

I think it does.

"Since 2000 heavy trucks have" tells me "2000 heavy trucks" did something and I'm going to read what that something caused.

It's only when I get to "and similar gains are projected over the next few decades." that it's clear the author meant "Since the year 2000, heavy trucks have".

It's a garden path sentence because the initial interpretation while you're reading it is incorrect and you only realise this when you get to the end and reprocess the start.

If the author put a comma there, it would be clear on first read: "Since 2000, heavy trucks have".

I get what you mean now. I think I mentally auto-corrected the sentence on the first pass and never really considered the literal meaning.

Charging I think is generally misunderstood. More room to work with (like in a truck) means you can either add more cells or have more space between cells, meaning you can pump more energy in (and out) within the thermal constraints. I suspect the Tesla semi will charge very fast for this kind of reason - much faster than Tesla's cars (not more slowly as people seem to expect).

If the semi is also made with "commodity" components like seems to be the idea (for instance using Model 3 motors[1]), then the cost of ownership equation becomes very appealing. This kind of modularity is yet another inherent advantage over ICE technology.

Also in this case I imagine multiple motors are more efficient than a single large motor for long-distance travel because of better thermal control for the motors themselves.

[1] https://electrek.co/2017/05/03/tesla-semi-model-3-electric-m...

I am imagining a battery pack that can be moved into place on pallet jack. Also, bigger more voluminous batteries can suck down more power, limited by thermal load, not current.

Exactly. If you can throw 2 battery packs into the semi, it can be charged twice as fast as a Tesla car without doing anything else. The actual equation (miles/minute) has a few variables (mileage of semi, weight, charge curves), but the conclusion seems to be that it would charge really fast. I don't think they're going to bother with swapping.

There's Nikola One and Toyota's Project Portal though both use hydrogen rather than batteries. And as you say, Tesla is working on one.

Electric motors should be fine for torque, and great for efficiency (with regenerative braking). Range is obviously the main issue.

But is range really such a problem? Imagine you can just swap the battery pack at recharge stations. That would be a pain for cars (different batteries, batteries built into the chassis, consumers being worried about the new battery being OK, consumers not knowing how to swap them, consumers not planning routes properly), but for trucks you can standardize.

100 battery swap stations across the US could cover a lot of high volume truck routes. Tesla cars are low volume, and the battery can't be swapped (because they're built into the bottom of the chassis), and Tesla can still afford those power charging stations. Trucks seem a little more "blocky" than cars though, so perhaps a swappable battery is possible?

It doesn't need to cover every edge case, in the first rollout, just enough to steal business away on high volume routes.

Tesla batteries can be swaped. They have a video showing it, and a single station doing it, but there is no need for it atm. Ive been driving my Model S for 2+ years now, and the charging options are plenty. Link to video of battery swap https://youtu.be/HlaQuKk9bFg

Wow, I didn't know that. And that's a lot faster than I would have guessed.

From Tesla: "a Supercharger provides up to 170 miles of range in as little as 30 minutes".

Yes, there is certainly a need for swapping batteries if you drive 500 miles a day, and are being paid to deliver on a tight schedule - you don't want to spend an extra hour and a half charging. But if you're spending 6 minutes swapping those batteries out (2 minutes per change), it's a lot more viable (especially if an EV can go up hills faster).

People don't drive a Tesla 500 miles a day, and even if they do they don't mind a few 30 minute breaks. Trucks are a bit different.

I think we will see some smart solutions in the future, and next generation charging hinted by Tesla and promised by the likes of Porsche for the Porsche Mission E, would reduce charging times by half. https://newsroom.porsche.com/en/technology/porsche-engineeri...

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