Hacker News Reader

Okay, cool.

So if I read [1] right, some kind of average price for electricity used in the transport sector in the US as of September 2022 was 12.48 cents/kWh. That would mean that the 500-mile trip costs 500 * 1.5 * 12.48 / 100 = $93.6 in energy.

If that includes hauling tens of thousands of pounds of cargo, that sounds rather a lot like it would make transport powered by electricity commercially sane, right? Nice.

EDIT: I hadn't read the article much; it seems the current power value given is actually 1.7 kWh/mile, so that increased the price to 500 * 1.7 * 12.48 / 100 = $106.08. Not a huge increase, obviously.

Thanks for that math. Seems relatively cheap. How does it compare to gasoline?

(500mi / 6.5mpg) * $5.313 = $408.69

6.5mpg - I just Googled average MPG for a fully loaded Semi, could be wrong.

$5.313 - Most recent highway diesel price (https://www.eia.gov/petroleum/gasdiesel/). I'd expect this is high due to fleet discounts and such.

I feel like that average is really low. Talking with my buddy who is a trucker, he said that 6mpg is on the low end. His truck, which isn't anything special, would usually get 8-9. He said those guys getting 6 or lower are usually owner / operators who have older trucks, either because they like the older trucks or they can't afford to get a new one. Most fleets have much newer trucks, a lot of which can get up to 10mpg or more. That may not seem like a huge improvement, but over thousands of miles it adds up really fast.

Semi-trucks use diesel. Diesel is between $5-$6/gallon:

https://www.eia.gov/petroleum/gasdiesel/

Let's use $5/gallon.

According to random website https://motorask.com/semi-trucks-mileage/

> On average, semi-trucks get around 6.5 miles a gallon

But according to https://www.motorbiscuit.com/how-many-miles-per-gallon-do-se...

> Transporting freight from one location to another isn’t cheap. We all pay so much for shipping because semi-trucks are gas guzzlers. In the early ’70s, it was estimated that the average semi got about 5.6 MPG, but that amount has increased slightly. In 2014, new semi-trucks were required to get 7.2 MPG on average.

Heck, let's use 10 MPG.

500 miles ÷ 10 miles/gallon x $5/gallon = $250.

So even with liberal estimates in diesel's favor, unless my numbers are way off, electric comes out way ahead.

....per trip. What about lifetime?

With a more pessimistic 6.5MPG, using mbell's math, that's 82 cents per mile in fuel. Electric is 19 cents per mile.

An average semi lasts 750,000 miles: https://www.tristatetruck.com/blog/posts/what-is-the-average...

Let's assume for a moment that Tesla has made a motor and batteries that will last that long (far from guaranteed). Heck, let's take some random internet claims at face value and say that the motor will last "millions" of miles and the batteries will last 300,000 miles: https://www.vehiclehistory.com/articles/how-many-miles-will-.... Will these batteries last 300k with a likely use case of being driven to their absolute maximum range every single day?

In that 300,000 miles, the fuel savings of electric will save you 300k * (0.82-0.19) = $189k. Replacing all the battery modules in a Model 3 (82kWh) will cost somewhere in the range of $25k. How much would replacing this giant battery cost?

It's possibly better, but the math isn't particularly clear.

A dead battery isn't dead, it just has a reduced capacity. Usually the battery is considered dead at 80%, so it's a 400 mile truck then. That 400 mile truck is still useful, so it'd probably be cheaper to sell the 400 mile truck and buy a new truck then to replace the battery and sell the old battery.

Another question is: how much of the savings in fuel costs going to go to the operator and how much is going to go to Tesla in purchase price? 5 years ago it was announced at $180K, but it's certainly going to sell for a lot more than that. A Nikola Tre with 360 mile range goes for $270K, so it's quite possible that Tesla will charge $400K for theirs. So you might start off at about $250K in the hole so it'll be hundreds of thousands of miles before the Tesla is cheaper than a diesel.

If the battery lasts 2000 cycles (reasonable for good chemistry… some chemistries can last over 5000 cycles), then that’s 1 million miles. (Tesla’s powertrain is certified for that much, too). At electric 19cents per miles and diesel at 82 cents per mile, that’s $630,000 in savings just for fuel, not to mention Diesel Exhaust Fluid, oil changes, and brakes.

The 500 mile range Tesla Semi cost $180,000 at launch. Let’s say they’re off by nearly a factor of 2, so new Semis will be $315,000. That means you’ll be able to buy 2 500 mile Tesla Semis for just the fuel savings from one.

You're selecting a gas price at all-time highs:

https://agtransport.usda.gov/Fuel/Historical-Diesel-Fuel-Pri...

A fair assessment would be $3/gal (what it was prior to 2021). That changes the price dynamics rather quickly..

Further, you get less bang-for-your buck on electric vehicles in the cold. Everything from the breaks to the power runs less efficiently and you'll lose range / capacity.

I don't see this as a super good deal, though for potentially for short-haul (i.e. a few hundred mile) trucking situation(s).

Just because it's cold outside doesn't mean the truck is cold. Sure it'll be less efficient starting off in the morning, but once it gets going it'll warm up quickly. The truck might be 92% efficient at turning electricity into motion, but 8% of 1.7kWh/mile gives you 130W of heat.

130 watts is nothing in this context?

One issue with most lithium chemistry is that it isn’t rechargeable below freezing - it causes permanent damage to the pack.

Practically speaking, this is solvable using in-pack heaters which divert the charging power to warming up the pack first. This takes time if it’s been allowed to sit. Laws of physics and all.

Charging these batteries is also going to take time, a lot of it, and significant charging infrastructure.

Short haul might go through a tank a day, but long haul often uses two drivers working in shifts and can cover 1000+ miles a day easily. It takes 30 minutes or less to refill a diesel long haul truck.

Unless they can get charging times down to an hour or less (which if it is a 875kwh pack like some folks think, that means literally megawatt sustained charging rates), it would require a major change in how long haul truckers work to have a chance.

Current superchargers max out at 250kw, which at max rates would take 3-4 hours to recharge, and they require a decent amount of expensive infrastructure to be able to support that.

If it is much cheaper, that could happen though!

In the video of the delivery event they announced new Megawatt chargers.

Not only did Tesla announce Megawatt chargers they claim will do 70% charging in 30 minutes, but this isn't a sleeper cab, so you're not going to have two drivers doing shifts anyway. And there's no need to worry about the pack freezing during use. The pack can be thermally insulated and the temperature is typically controlled via a coolant loop, possibly using a heat pump to maintain temperature. They're also typically automatically pre-heated before leaving.

If you plug in to charge immediately after driving, the temperature issue isn't a problem as both charging and discharging the battery produce some heat.

(Additionally, the "can't charge below freezing" is a chemistry-dependent thing... it's really only essential for certain chemistries like lithium-iron-phosphate, not the type they're using on the long range Tesla Semi... although acceptable charge rate does reduce at lower temperatures due to lower charge-carrier mobility IIRC.)

Stopping for 30 minutes to add another ~350 miles to the range will mean that a driver won't be limited by the truck in how long they can drive in a day. Additionally, charging is way safer than pumping diesel fuel, so drivers don't need to tend to their truck during charging (unlike fueling), freeing them up to rest or clean up or eat.

Tesla has done an excellent job installing Supercharging infrastructure in the last 10 years in the US (better than everyone else combined, although it's getting better), so installing Megacharging infrastructure seems like something they'll be easily capable of.

Thanks for correcting me! That does indeed seem like they have a very solid product now.

Even at $3/gallon it’s still $150, so that’s 50% more than the electric cost.

I also realize there may be other trade offs and costs involved. The energy cost was asked about so that’s what I answered.

FWIW: I own a 2017 Volt and love it. 50 miles all electric then another 350 or so ICE miles. Those 50 miles cover ~ 90% of its lifetime miles. Electric here is 0.11/kWh. I really wanted the flexibility of electric and gasoline having had reliability issues with both energy sources here in NC.

You appear to be shadow-banned because of your second ever comment, which, while wildly offensive, does not appear to be a statement that you believe but instead an explanation of what Meloni believes.

> If that includes hauling tens of thousands of pounds of cargo...

That is the question. I am very curious if that includes cargo and if so how much weight. I suspect it doesn't include cargo. If it doesn't include cargo, diesel trucks will be far cheaper

If you're looking at historic fuel prices ($3/gal diesel [1]) and what modern trucks are getting (7-10mpg [2]) with loads. You're talking ~$150-$215 for a diesel truck. Plus you have fuel everywhere (less infrastructure costs), quicker refuels, easier repairs, etc.

The cold and time will also siphon off the efficiency of the battery powered trucks. Colder climates will see a 5-10% drop in efficiency in winter, and that'll grow over time. Making it less cost effective in northern climates.

The only way this truck makes any sense would be short-haul (single day round-trip deliveries) and government subsidies IMO. Plenty of market, but not quite where it needs to be.

[1] https://agtransport.usda.gov/Fuel/Historical-Diesel-Fuel-Pri...

[2] https://lonestarclassictruckclub.org/average-fuel-mileage-fo...

Had you bothered to watch the presentation from last night, or done any cursory research this morning in place of inserting your "suspect it doesn't include cargo", you might know that this includes 82,000lbs of cargo.

Tesla also released a video[1] showing a time-lapse of a fully loaded truck going from Fremont to San Diego fully loaded with no charge stop. (The trip does include a 30 minute bio break as required by law.)

[1] https://youtu.be/GtgaYEh-qSk

You're talking about battery cells, but you need to look at the battery _pack_ energy density. The model 3 battery pack, which uses the same cells as semi, is about 170Wh/kg. The numbers in TFA are very reasonable estimates.

I already addressed that by including mass overhead for the overall battery. And sure, it’s always possible to assume more conservative numbers for a whole battery and assume Tesla DIDN’T do any engineering work to reduce overall battery mass, but that’s not something you should put in a headline.

(Tesla has typically done better than their peers in overall battery specific energy as well as energy per mile.)

You're using a 16-17% figure for packaging overhead? That's low. Even with relatively expensive construction techniques (for example if you're doing EVTOL) you see 20-25% packaging overhead.

I agree, but a long haul, full payload electric Semi is a very challenging project comparable to an electric aircraft since you’re limited to near the same maximum total weight. I’m merely pointing out that such a battery pack is one possible solution, one that cannot be ruled out based on public information.

The in-use 2170 batteries are apparently 250Wh/kg. With that figure and a more realistic packaging overhead of 30% I'm seeing something like 190Wh/kg, which is more in line with your observation.

From the numbers I can find, the Model S 85kWh has 7104 18650 cells - if we use 49g for mass of cell, that's 767lb of cell vs the pack weight of 1200lb~, or a very rough packaging overhead of ~36%

This is a naïve analysis but it helps assuage my ego, as I've worked on designs for 26650 based packs where we would have been quite happy to hit 30% overhead :) That being said, I realize people can, and do in fact make more mass efficient packs.

Wow, selenianboondocks. That's a blast from the past.