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Comment by 0wis | Hacker News Reader

Is it really a problem ? I mean, apart from the quantity of lithium needed to create this « enormous » battery, is weight a real limitation factor ? We currently have no info on the full truck weight but I am sure Tesla found ways to optimise weight everywhere else. Mechanical components for a 1000000 miles rated vehicle are heavy and without a gearbox and a crankshaft, I assume the rest of the truck is lighter than its gas counterparts. I am no expert so maybe we are dealing with other orders of magnitude. Anyway, would this impact the maximum cargo weight ?

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> ... but I am sure Tesla found ways to optimise weight everywhere else.

This is kind of a "the entire industry is dumb" assumption.

I mean, sometimes industries are dumb, and there are certainly people driving oversized vehicles on the road right now, but if you can find places to optimize vehicle weight outside of the engine/transmission/fuel you're replacing with batteries/motors, that applies to regular old semi-trucks; if you can make a semi-truck weigh 5000 lbs less without compromising on its design parameters, you can make every other semi-truck on the road more fuel efficient and save like 6% of your fuel costs, while also allowing you to haul bigger loads than competitors' trucks.

Everyone making semi-trucks is interested in that, not just Tesla.

Everybody else is using a chassis designed for ICE, so something that handle a vibrating 5000 lb engine, a vibrating 1000lb transmission and can hang 2000lb in fuel. They then need to add reinforcement to hang a 10,000 lb battery.

I'm fairly confident some of the rest of the industry could get a comparable weight if they started from scratch and they optimized for EV only. But that's two assumptions that don't currently hold.

Though I only gave it a quick search and it seems annoying difficult to find straightforward spec sheets for semi tractors like you can for any piece of CAT equipment, [0]"As we highlighted above, there are several ways to measure a semi-truck’s weight, and the maximum legal weight for a fully-loaded semi in the United States is 80,000 pounds. The lowest unladen weight is roughly 25,000 pounds, but will typically be closer to 35,000."

So, 10,000+ pounds for the power pack alone is a sizable chunk of the maximum allowable weight, and could potentially eat into the allowance for cargo, more so for restricted routes like older inner city bridges with tight weight limits and the like.

[0]https://www.jdpower.com/cars/shopping-guides/how-much-does-a...

Tesla does get a small buffer for the battery size, due to EV trucks being allowed 82k instead of 80k lbs max.[0] Doesn't save the entire extra budget though.

[0]: https://afdc.energy.gov/laws/11682

> NGVs and PEVs may exceed the federal maximum gross vehicle weight limit for comparable conventional fuel vehicles by up to 2,000 pounds (lbs.). The NGV or PEV must not exceed a maximum gross vehicle weight of 82,000 lbs. (Reference Public Law 116-6 and 23 U.S. Code 127(s))

I’m curious how often fully loaded semis hit 80000 lbs. a quick google seems to show me maximum capacity instead of average/median weights…

Not at all uncommon, though my experience is with equipment rather than general containerized or palletized cargo.

e.g. a CAT D8T bulldozer weighs in at over 80,000lbs all on its own and they are often trucked around as a complete unit, so you're looking at 20-35,000 more for the trailer and tractor to haul it. Heavier pieces of equipment like D9's (108,000#) or D10's (145,000#) are generally 2-3 loads of chassis/tracks/blade&attachments.

Just an aside, a D9 is a real hellbeast. I got to drive one on some forestry work and there's not much out there that makes it stop moving. Gives me a stiff willy just thinking about it.

Both the CAT D9 and the Tesla Model 3 Performance advertise 450 HP.

Agricultural products, heavy equipment hauls, bulk materials, etc. regularly hit 80k pounds and above. Truckers picking routes to bypass scales is a meme for a reason.

Drivers being ticketed for overloaded trucks was a constant complaint in my childhood home back in IL, where the head of the household owned a concrete construction company.

Apparently the highway patrol would camp out in the industrial/shipping areas and watch for compressed suspensions/bulging tire sidewalls on big trucks as a monthly fundraising exercise.

Obviously there's a business incentive to move as much as you possibly can at once...

>watch for compressed suspensions/bulging tire sidewalls on big trucks as a monthly fundraising exercise.

I am unhappy with this description. An overloaded truck is a safety issue, and also a long term road-wear issue.

> I am unhappy with this description. An overloaded truck is a safety issue, and also a long term road-wear issue.

Sure, except this fundraising didn't stop the activity. It just took a cut from the profits, and the vehicles drove off AIUI. This was Illinois in the late 80s-early 90s I'm talking about...

It's not about safety. The 80k limit comes from limiting wear and tear on roads. Pretty much every semi truck is built to tolerate 120-150k without caring though wear and tear on the trucks really starts to increase a lot beyond that.

Some states have higher weight limits when the ground is frozen.

Any time you see a trailer that carries some sort of bulk good it is safe to assume that that trailer is right at the max weight.

EV trucks are allowed to have a maximum weight of 82,000 pounds instead of 80,000 for ICE trucks.

The Youtube channel Engineering Explained went over the Tesla Semi, and the weight of the EV cab should be pretty similar to an ICE cab. Also EV trucks are allowed another 2k pounds.

https://youtu.be/Uv44W7xa4IU

"Also EV trucks are allowed another 2k pounds" - Ah that explains the 82,000lbs mentioned in the Tesla demo. Max weight for conventional trucks is 80K.

There were about 10-12 concrete barriers as load in the demo each weighing 39,000lbs. So the weight being carried is around 40ishK lbs. So rough approximation - half the weight of the truck is load and half is the truck itself.

Speaking as a former shipping and receiving guy, well, yes. It suggests some 11,000 pounds less capacity on a standard semi, which are highly regulated as far as maximum weight/mass goes.

A semi weighs between 10,000 and 25,000 lb. A semi's ICE engine weighs around 3,000lb.

I don't work in the industry. I just observe three things:

1) the weight variance of a semi encompasses the amount imputed to the battery

2) 3,000lb of weight can be saved by not having a diesel engine plus another 2,000lb not having fuel. (Both of which will be in the total gross weight of the semi) some of which will of course be replaced by electric motors.

3) it's a speculative weight. It might also not weigh that much. Might is doing a lot of heavy lifting.

A fourth point: trucks routinely travel partly empty because of weight distribution issues. Not every TEU is full.

Logistics is fascinating. TCO is the closest most computer scientists get to "how can owning a Mac be cheaper than owning a Windows PC" but logistics does this almost every sum. Weight and carry capacity may not be the sole deciding factor here when a semi is worth $500k and has a 2nd hand value and is a finance decision with tail costs and operation costs.

You can make some of that back by the removal of the engine and fuel (though you still need something akin to a motor and perhaps a transmission). Likely parts of the truck will have to be converted to aluminum - perhaps the trailer itself.

A full semi can have 300 gallons of diesel which itself is about 2000 pounds, so we're down to a 9,000 pound difference.

And some percentage are short haul, which are often not even near to fully loaded. Could be as high as 40-50%.

Except the vehicle has made weight reductions elsewhere, including engine, transmission, emissions control, fuel tank, etc. A typical useful payload is around 44,000pounds still keeping under the 80,000pound limit, and the Tesla Semi was able to do that (electric trucks are allowed ~2000pounds extra).

2,000 extra pounds for electric vehicles.

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