Tesla is aiming to K.O. Freightliner

Another similar clue. Wikipedia says Chevy Volt battery pack weighs 435 lbs. EV range is 35 to 38 miles. If running gasoline only the car would get about 42 mpg. So for that car we have a pretty clear number. 435 lbs of battery does the same amount of work as almost 6 lbs of gasoline....

Diesel? It’s packs about 30% more potential energy than gasoline if I recall...someone else who cares more can research this figure.

But with such numbers, it shouldn’t be too tough to estimate this math out. And I’m admittedly probably not considering something. I’m just an internet jockey, not a rocket surgeon...

 

Yes, you get it... That's exactly the type of data I am looking for. But would expect there to be some kind of industry standard of measure for this. Can't believe all the EV gurus on this forum don't have this data at their finger tips. Seems to me that is critical for everything EV.

I have been an EV fan and user for a long time, incl electric boat motors, bikes and now own an EV car. But fully realize that all my choices were not just based on economics and practicality.

I remember clearly the disappointment of buying an electric boat motor quite a few years back for my little 12" fishing boat. Cost a couple grand and required a very heavy 12V deep cycle battery. But could only troll for about 1 hour, before needing charging again. Replaced it with a small 2.5 hp Suzuki outboard ($500) that would run on many hours at a time on just a pint of gas. And it weighs about a qtr of just the battery, incl the built in gas tank.

 

@craze1cars you gave me an idea and I found some academic mumbo-jumbo with reference to passenger cars, which does the exact type of analysis that @R P is looking for but not with trucks. I guess if I spend some time I can actually understand it (but I am not going to do it). Here are the reference to the two articles and nice graph (there are several more in the article).

The Tesla S has a high curb weight, heavier battery and long range. The Renault has a smaller battery, range comparable to Tesla but a much smaller curb weight. I do not know how to convert this to diesel and to account for actual loads. I am not sure that dynamo-meter with no load will provide much information as there is battery weight, curb weight, towing and carrying weight and range.

If you only want range per kilogram , one can calculate the range per kg of battery for each vehicle and average it. But that will not account for curb weight.

In gas cars, it is just miles per gallon. You don't bother about curb weight.


https://agronomy.emu.ee/wp-content/uploads/2017/04/Vol15SP1_Berjoza.pdf

and
www.tf.llu.lv/conference/proceedings2017/Papers/N316.pdf

 

That comparison of EVs does not help the cause... On the model S, the weight of the battery of the higher range version went up a lot more than the range.

 

That is why you cannot have a simplistic model. There are just too many real life operating variables that cannot be ignored. Why for example did the higher range Tesla go up heavier in battery weight than the range? There must be a reason, I do not know what.

You could may be crunch some numbers and extrapolate. I know I do not have the data to do it.

 

Esimativextrapolation: There's my made up word for the following questionable and partially made up "data":

Avg aerodymanic semi truck can get around 7 mph running OTR. So at 6 lbs per gallon it will take approx 71.5 gallons = 430 lbs of diesel fuel to go 500 miles.

Assuming the car comparison of the Chevy Volt above holds a little bit of water, we need 72.5 times that weight in battery to go the same distance, which means the 500 mile version of the semi truck may need as much as 36,250 lbs of fully charged battery to go the same distance.

Once again, I'm happy to admit there is no doubt in my mind that the above calculations are based on some bad data and inaccurate assumptions. So don't believe it. But it MIGHT be a clue!

And here's a pretty cool article I stumbled on with some more professional-sounding speculation of the likely very heavy curb weight of the Tesla semi trucks, and related limitations it creates (spoiler alert...it weighs less than my "math" above indicates):
https://cleantechnica.com/2019/09/01/how-much-does-the-tesla-semi-weigh/

 

Sounds like an answer seeking a question. Believe what you wish as that is not how real engineers analyze a problem. Ask Mr. Google and pick the answer you choose:


I really have no requirement of for a large truck or even a pickup. I have a Std. Rng. Plus Model 3 and BMW i3-REx. They fully meet my requirements and operational scenario. If you have a question about either of these cars, I'm game but I have no interest in solving a problem that does not match any of my requirements.

Bob Wilson

 

OK, since my Kona comes in both the 39 and 64 kWh (which is what I have), I did a similar range/weight comparison. Turns out the results are opposite of the Tesla S, and what I would have expected.

The 64kWh version has a range of 546 kms (NEDC) while the 39 KWh has 345 kms. That's 58% increase in range. The 64 weighs 1685 kgs, while the 39 weighs 1535 kgs, which is only a 10% increase, and I assume is all in the extra battery weight.
https://evcompare.io/cars/compare/?comparing-cars=hyundai_kona_electric_long-range_2018-vs-hyundai_kona_electric_standard-range_2018-vs-kia_niro_ev_2018-vs-kia_niro_ev_long-range_2018-vs-kia_soul_ev_2014-vs-kia_soul_ev_2018

So, compared to the Tesla it seems the Hyundai battery technology is a lot more efficient than the Tesla's. Or is it something else.

I know rolling resistance is a big factor, but generally speaking per weight, larger vehicles are more efficient. That's why we haul stuff around in large semis and trains.

However, and this could be a major obstacle, too. Very, very large batteries might indeed be less efficient, because they consist of many, many small batteries (eg 18650's) which all have to linked together in parallel and series to provide the appropriate voltage and amps. That could mean a lot of extra BMS (and TMS) to keep them all working properly. Not too mention the greatly increased rate of failure (when even just 1 cell fails) and risk of fire. Maybe Musk is waiting for new battery technology to become usable to overcome this obstacle.

 

Yeah, lots of variables and assumptions. That's why I was looking to start with a simplistic ratio comparing ICE and EVs without any other variables. Depending on what that is, very large EVs might be a non starter given current battery technology.

 

Bob, if you have nothing intelligent to add to this discussion, why are you responding?? We are talking about EV semis, not Model 3s or i3s. I believe there is another forum below for those.

 

Ask Mr. Google.

Bob Wilson

 

Hey, where did you find this picture of me?

 

Hey, I think this may be the first time you've addressed me directly, 101101.

There are reasons why diesel is currently the energy source of choice for long-distance trucking, and battery packs aren't. That will of course change, and hopefully soon as battery tech continues to improve; but nobody has yet proven the economic case for using large trucks for hauling freight. If they had, then such companies as Smith Electric Trucks wouldn't have failed.

That is a tragedy, because Smith had opened up a branch here in Kansas City, where I live, before they went out of business.


I hope that the Tesla Semi Truck will prove to be a resounding success in the market, but I don't think that's at all guaranteed. In fact, I'd say it's likely that Tesla doesn't think it can compete using current battery tech, and that's why Tesla hasn't moved forward with putting it into production. Likely Tesla is waiting on a new type of battery they plan to put into production, or have some battery maker put into production for them. I've seen others express that opinion, and my guess is they're right. I think we'll know more after Tesla's upcoming "Battery Tech and Powertrain Investor's Day" presentation, hopefully coming in first quarter 2020.

As far as the other points you made, 101101... I'm going to stand on what I've already said on this subject.

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Small cars such as the Kona are generally more energy-efficient than larger ones such as the Model S, particularly when the smaller car is specifically geared to prioritize energy efficiency over performance, as (for example) the Ioniq and the Kona are. Smaller frontal area means less energy needed to fight wind resistance. For a typical car, at 55 MPH half of the energy goes just to fighting wind resistance. And since that goes up as the square of the speed, it's a lot worse at freeway speeds.

Trains aren't more energy-efficient because they're larger. They're more energy-efficient because (a) rolling on rails on hard, inflexible metal wheels produces a lot less rolling resistance than rolling on flexible tires, and (b) pulling a long train of cars behind an engine is a much more energy-efficient method of hauling freight than carrying smaller loads in individual trucks.

The economic case for tractor-trailer trucks doesn't have much to do with energy efficiency. At only 6-7 MPG, the energy efficiency is lousy. The economic case has more to do with logistics and scheduling. Rather little freight was carried cross-country in tractor-trailer rigs until "just in time" delivery became the industry norm. Before that, long distance freight hauling was mostly by water transport or rail.

* * * * *

Part of the reason for that change was the way the U.S. tax code for industry was change, so they started getting charged for inventory. Before that, it didn't matter that much if it took weeks for a shipment to arrive. There was an initial cost for "filling up the pipeline", but after shipments started arriving, that was irrelevant for most wholesalers.

But when the U.S. started taxing inventory, all the inventory in the supply chain started getting taxed. That meant manufacturers had much more incentive to schedule shipments to arrive within the shortest possible time, so they would pay the least amount of tax on it. Thus "just in time" shipping became the norm.

This is an example of why we can't have a well-informed opinion on this particular subject with just a simplified case study. There are a lot of factors involved when we start looking at the economic case for different shipping methods.

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Tesla has mostly already solved that problem. In fact, they solved that before the Gen I Roadster was put into production. Every cell in a Tesla battery pack is attached with a fusible link, which (at least in theory) will melt away and remove a faulty cell from functioning in the pack. In other words, Tesla has designed their packs to allow a few cells to fail without significantly affecting the overall operation and performance of the pack.

Other than some severe accidents where the battery pack was penetrated and physical damage done to cells, very few Tesla cars have had a battery fire due to runaway cell overheating. That is doubly remarkable considering Tesla uses higher energy density cells than are found in other auto makers' BEVs.

In summary: The very small risk of cell failure and much smaller risk of fire is almost certainly not why Tesla has delayed putting the Semi Truck into production. In fact, we need look no farther than the ongoing shortage of cell supply to explain that. I've suggested a more complex reason in a post upstream, but really Occam's Razor shaves in the directly of it simply being a matter of cell supply. Of course, there may be more than one reason for the delay, but Occam's Razor points to a limited cell supply being the primary reason. Note that Tesla isn't putting the Model Y into production until after the Shanghai Gigafactory starts producing Model 3's using cells from other sources.

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Anyone who really wants to dive into the numbers for comparing the Tesla Semi Truck's weight, power consumption, etc. to a diesel semi tractor's specs should look at the 4-part series that George Bower and Keith Ritter did for InsideEVs news.

One might take issue with some of the assumptions they have chosen, but they have certainly taken a very comprehensive look at the factors involved. Certainly it's a much more thorough analysis than my own "Napkin Math 1.0" estimate, as one InsideEVs writer called it back in the day.

https://insideevs.com/news/336239/exploring-the-hows-and-cans-of-the-tesla-semi-part-1/

https://insideevs.com/news/336242/tesla-semi-truck-battery-probably-lighter-than-you-think-part-2/

https://insideevs.com/news/336273/the-tesla-semi-weighs-in-part-3/

https://insideevs.com/news/336275/the-tesla-semi-costs-part-4/

In particular, on the issue of weight: Keith and George estimated 7,945 lbs. saved in a BEV semi tractor by removing various unneeded parts of a diesel semi (engine, transmission, fuel tanks, exhaust, etc.), and estimated the weight of BEV powertrain including a 900 kWh battery pack (presumably for the 500 mile version of the Tesla Semi Truck) at 12,765 lbs.

So, if I have this right, their estimation is that a Long Range Tesla Semi Truck would weigh 4820 lbs. more than its diesel semi tractor equivalent. That's only 6% of the gross weight of a fully loaded 80,000 lb. semi tractor-trailer rig. I submit that for a lot of fleet operators -- not all of them by any means, but for a lot of them -- that's going to be an insignificant difference.

 

Just to be clear, my question has nothing to do with the weight of the battery as a percentage of the vehicle gross load weight on a semi or train. It is about the weight of the batteries vs weight of fuel to achieve range. So far no one has been able to answer that although lots of off tangent speculation about the what the battery will be in the new Tesla semi, if it ever does make it to final production. Once we know that starting point, I have a lot more questions, but too many hypothetical possibilities to explore without that concrete starting point.

And PP, your comments about the Kona and Ioniq comparison are way off base. Totally different vehicles and EV drive train generation. The Kona is more similar to the new Niro and Soul. These are definitely not very drag efficient vehicles either compared to the Ioniq and Teslas. You should do a little more basic research before commenting about the Hyundai/Kia EVs.

There is a question though, why the Kona seems to be much more efficient with a larger battery than the Model S with the larger battery despite the larger frontal area of the Kona vs the sleek aerodynamic shape of the Teslas. Could it be that Hyundai's battery technology and implementation is superior to Tesla's?

This battery size question does not always makes sense with actual results, which makes speculation on future vehicle battery size efficiencies even more of a pure guessing game. But have to admit reading some of the posts here are good entertainment, esp 101's. Haven't yet figured out what planet he is on.

 

But singling out the weight of the battery vs. the weight of fuel is a pointless comparison. The electric motor is very much lighter than the diesel engine, and the BEV doesn't need a heavy transmission, or an exhaust system, or several other things that George and Kieth list in their analysis. The proper comparison would be between the weights of the entire ICEV powertrain vs. the entire EV powertrain, exactly as George and Keith have done.

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