350kW Supercharger "Children's Toy" Not for Cars, but the Semi

[timpierc]

So given Elon's announcement yesterday that the semi will indeed be long haul, I have a theory to put out there.

I don't believe the next versions (350kW or above) of the supercharger will be meant for the cars (S,X, 3) but instead for the semis. Given the peak performance levels of the S and X, the maximum amount their motors can handle discharging at once is around 400kw. So that's more or less the limit of the wiring internal to the car to receive a charging current from a supercharger. To install a separate series of wires to allow just for faster charging that the motors can't handle is in my opinion a waste of weight, and expense.

If you have the semis though with a BAB (big ass battery) then this supercharger amount makes perfect sense. The only time truckers are making money, is when they're driving. So the supercharger will have to be massive to be able to get the battery back up to "full" so it can get back on the road. This also helps the concept, because now you don't have Model S, X, & 3's taking up room on a supercharger that would prevent truckers from making money.

So given Musk so far has never explicitly said that the next version of the superchargers will be for the cars, I'm throwing it out there they'll be for the Semi.

 

[TonyWilliams]

The same Supercharger cabinets that are currently on a 500KVA to 1000KVA transformer can just as easily be all wired together to pump that into a truck.

I predict that the truck will be 750kW minimum, probably 1MW. There are some buses around the world over 1MW.

What will be most interesting to me is the method used to plug the truck in. I seriously doubt humans will be doing it.

 

[wdolson]

The Model S/X battery can only discharge at 400 KW for a fairly short period and then the car will go into thermal protection. The current superchargers can charge at 145KW, which I suspect is what the 100KWh pack can come close to. The smaller packs are more limited than that.

Looking at the hints out there, I agree with you that I think the 350+KW chargers will be for semis only. It may be possible to plug a car into one, but it will be limited to what the car can handle.

I also wonder if Tesla is working on a solid state battery for the truck. The current best li-ion chemistries right now just don't appear to lend themselves to long haul trucks. I could be wrong and Tesla might be looking at li-ion cells in the truck, but with the larger energy demand of a big rig, I would think a semi would need a massive battery pack that would be staggeringly expensive to have any decent range.

Solid state batteries were in the news a few months ago. Several labs have prototypes and one was demonstrated in the PBS Nova program on next gen batteries. But it's a rule of thumb that it takes 10+ years to get new battery tech from the lab and into production. Where the announced batteries are now, that would be sometime in the mid-2020s, though the Tesla semi might be coming out around 2020. If Tesla has been secretly working on a solid state battery and they are actually ahead of the competition, then they might be looking to entering production with the solid state battery around the same time frame the truck is supposed to be hitting the market.

A solid state battery semi makes sense. It can charge faster and has higher energy density than a li-ion pack.

A solid state pack in the Model S/X would be amazing too. The top of the line car would have a 200 KWh battery in the same space. It would also be lighter so the range of the car would be a bit better. The Model S 200D would get close to 700 miles range. That might eliminate the need to supercharge at all, you'd just look for a hotel with a destination charger.

 

[transpondster]

Solid state batteries were in the news a few months ago. Several labs have prototypes and one was demonstrated in the PBS Nova program on next gen batteries. But it's a rule of thumb that it takes 10+ years to get new battery tech from the lab and into production. Where the announced batteries are now, that would be sometime in the mid-2020s, though the Tesla semi might be coming out around 2020. If Tesla has been secretly working on a solid state battery and they are actually ahead of the competition, then they might be looking to entering production with the solid state battery around the same time frame the truck is supposed to be hitting the market.

A solid state battery semi makes sense. It can charge faster and has higher energy density than a li-ion pack.

A solid state pack in the Model S/X would be amazing too. The top of the line car would have a 200 KWh battery in the same space. It would also be lighter so the range of the car would be a bit better. The Model S 200D would get close to 700 miles range. That might eliminate the need to supercharge at all, you'd just look for a hotel with a destination charger.

solid state battery on PBS have about order of magnitude higher resistance, no way it can charge/discharge faster without running into thermal problems.

 

[wdolson]

solid state battery on PBS have about order of magnitude higher resistance, no way it can charge/discharge faster without running into thermal problems.

The Zimmerman battery (on Nova) is just one example. John Goodenough is confident his team is on the path of a solid state battery that would charge and discharge fast enough for use in electric cars.

Tesla is famously tight lipped about its R&D. We don't know for sure what they are working on. They have hired some battery experts who might just be working on better li-ion technologies (moving things ahead an increment or two) or they might have a team working on the next big thing. We won't know for sure until they tell us.

I have been thinking since Elon's announcement that long haul semis just aren't really feasible with existing li-ion technology. But the last few days I have been looking at it from a different perspective in light of all the research coming to light of solid state lithium technologies. There are a lot of hype in the battery world that turns out to be nothing in the end, but some heavy hitters like John Goodenough (who was one of the pioneers of li-ion technology) are saying they are close to breakthroughs in solid state batteries.

What if Tesla is actually ahead of everyone and the world doesn't know it yet? They wouldn't have to be ahead by much, just enough to have the solid state battery ready for the semi's introduction to the market.

 

[J1mbo]

If the truck had 3 independently-cooled 100kWh packs then a 350kW charger would make sense.

 

[timpierc]

Nothing indicates Tesla has solid state batteries in the works. As Straubel has said on multiple occasions Li-Ion is the best in town when it comes to power density, manufacturability, and costs. A lot of people forget those last two when it comes to batteries.

There are batteries that are better than what Tesla has, the problem is they cost a fortune to make, and probably can't be done outside a laboratory at this time. Musk has said there's an open invitation to his office if you can bring him a battery that's better than what they currently have given the three criteria above.

 

[timpierc]

Battery design for the Semi.

I've been seeing a lot of people saying that if you disconnect the cab from the trailer, it'd be like a sports car. My prediction is when you buy a Tesla Semi you're buying the cab and trailer. The trailer will have the majority of the battery pack. It's the only way it makes sense to pull off long haul. I'm guessing the battery pack is integrated into the floor of the trailer, probably for most of the length of the trailer. This also gives Tesla the advantage to maximize the performance of the entire system aerodynamically. You won't be able to bring in your own trailer. It's a system

The cab houses the drivetrain, and a small battery pack to allow for disconnecting from the trailer, but this battery pack would give only a small range. I'm guessing less than 15 miles.

 

[ItsNotAboutTheMoney]

Let me repeat: the "children's toys" comment was Elon Musk's response to a twitter question about 350kW charging. That question came shortly after the announcement of summer installation of a 350kW CCS charger, which would be capable of charging one car at 350kW or up to 4 cars sharing the load.

Typical Supercharger installations are 4 cabinet sites, which makes those sites more powerful overall than the announced CCS site. Tesla now regularly installs larger sites and it expects to be building sites with close to 2MW total power.

Also note that there are no production CCS cars that charge at 350kW, so for now it'll simply be a 4-car CCS charger at the rates that the cars can take.

I view Elon Musk's response as his typical sniping and not any kind of indication that Tesla cars will be able to charge at 350kW.

Having said that, given that Tesla is working on a semi, it makes sense that they are already working on charging at greater than 350kW. But for a semi, which would have a very large pack, that's nothing special. The real challenge is charging at high C rates. Tesla's recent patent for under-car charging looks like an attempt better to manage the heating challenges of high power.

 

[pilotSteve]

So given Elon's announcement yesterday that the semi will indeed be long haul, I have a theory to put out there.

I don't believe the next versions (350kW or above) of the supercharger will be meant for the cars (S,X, 3) but instead for the semis. Given the peak performance levels of the S and X, the maximum amount their motors can handle discharging at once is around 400kw. So that's more or less the limit of the wiring internal to the car to receive a charging current from a supercharger. To install a separate series of wires to allow just for faster charging that the motors can't handle is in my opinion a waste of weight, and expense.

If you have the semis though with a BAB (big ass battery) then this supercharger amount makes perfect sense. The only time truckers are making money, is when they're driving. So the supercharger will have to be massive to be able to get the battery back up to "full" so it can get back on the road. This also helps the concept, because now you don't have Model S, X, & 3's taking up room on a supercharger that would prevent truckers from making money.

So given Musk so far has never explicitly said that the next version of the superchargers will be for the cars, I'm throwing it out there they'll be for the Semi.

... and located along interstate trucking routes.

 

[wdolson]

Battery design for the Semi.

I've been seeing a lot of people saying that if you disconnect the cab from the trailer, it'd be like a sports car. My prediction is when you buy a Tesla Semi you're buying the cab and trailer. The trailer will have the majority of the battery pack. It's the only way it makes sense to pull off long haul. I'm guessing the battery pack is integrated into the floor of the trailer, probably for most of the length of the trailer. This also gives Tesla the advantage to maximize the performance of the entire system aerodynamically. You won't be able to bring in your own trailer. It's a system

The cab houses the drivetrain, and a small battery pack to allow for disconnecting from the trailer, but this battery pack would give only a small range. I'm guessing less than 15 miles.

If you eliminate the large diesel engine in a semi tractor and put the motors on the axles, that frees up a tremendous amount of space for something else. Trailers might have batteries, but the tractor is likely going to have a significant battery pack on its own.

 

[Brovane]

If you eliminate the large diesel engine in a semi tractor and put the motors on the axles, that frees up a tremendous amount of space for something else. Trailers might have batteries, but the tractor is likely going to have a significant battery pack on its own.

I concur, if you drop to much weight off the tractor you will start to have traction issues. Between the engine/transmission and fuel, you are dropping over 4000lbs of Mass off the tractor.

 

[timpierc]

I concur, if you drop to much weight off the tractor you will start to have traction issues. Between the engine/transmission and fuel, you are dropping over 4000lbs of Mass off the tractor.

So Elon compensates with a hot tub for the driver to add weight for traction. Instead of sitting down in seats, the driver luxuriously lounges in a hot tub while watching the road, and the autopilot does it's thing.

(Just like the Captain of the Golgafrinchian Ark B in Restaurant at the End of the Universe )

 

[nativewolf]

I concur, if you drop to much weight off the tractor you will start to have traction issues. Between the engine/transmission and fuel, you are dropping over 4000lbs of Mass off the tractor.

I wondered how much a drivetrain would weigh, I own a medium duty truck but I'm guessing it is about 1/2 the cost of my vehicle (1990 vintage) or about 6000 lbs. Granted there were lots of improvements after 1990 but.... is a semi only 4k lbs for the drivetrain? The trucks come in at about 17k lbs or so. Don't forget you'd be losing differentials, etc too.

 

[GlmnAlyAirCar]

I wondered how much a drivetrain would weigh, I own a medium duty truck but I'm guessing it is about 1/2 the cost of my vehicle (1990 vintage) or about 6000 lbs. Granted there were lots of improvements after 1990 but.... is a semi only 4k lbs for the drivetrain? The trucks come in at about 17k lbs or so. Don't forget you'd be losing differentials, etc too.

You're right - that's a lot of weight that would come off that could be replaced by batteries in the tractor. I envision a three-motor system, one for each axle. I have trouble believing batteries would be incorporated in the trailer. That would be a severe limit of this vehicle - not being able to connect to the 99.9999% of the trailers out there.