Tesla Semi charging question

[wayner]

There have been some recent stories about Tesla announcing 1MW wireless induction charging for semis.

How would this work at an Interstate truck stop - like a Flying J. How many trucks would they need to be able to charge simultaneously, and do these locations have large enough transmission lines to handle the power requirements. I can imagine that being an issue at some rural locations.

 

[AMPd]

No one knows

 

[ThomasD]

There have been some recent stories about Tesla announcing 1MW wireless induction charging for semis.

How would this work at an Interstate truck stop - like a Flying J. How many trucks would they need to be able to charge simultaneously, and do these locations have large enough transmission lines to handle the power requirements. I can imagine that being an issue at some rural locations.

I recently towed a trailer from Florida to Ohio and the most trucks I saw refueling at once was 7. So I'm going to say at least charging for a minimum of 5 trucks at once

 

[wayner]

Bringing this back to life. How much power would a semi need while charging? Is about 2MW the right number? This estimate comes from assuming that a semi will need about 10X the power of a passenger vehicle and SCs provide about 200kW to Supercharge a typical Tesla car.

So to charge five trucks would require 10MW of power. I have to think that 10MW is a lot of power - how would you get that much power to truck stops? Wouldn't you need to run some high capacity transmission lines from sub-stations?

 

[roblab]

I think this would depend on whether you were going for long distance or local trucking. A long haul trucker will want to charge quickly so he can get back on the road again (Maybe with TACC or NoAP). I've seen semis charging here in Napa at the south location, using two charge cables at once (standard car charging stations), and although a semi is large, its power needs aren't all THAT hard to supply. I've heard they'd need two or three batteries, but then again I've heard that one or two motors would do it. Diesel engines are really poor when it comes to acceleration, and they need 5-10 gears to do it, while one electric motor has the power for startup and for cruising down the road, even up a grade. The main difference is the distance. Once a truck is moving, its power needs drop considerably, and aerodynamics are the main factor. The long haul trucker would need more battery, but there's plenty of room for those (two or three?) to supply the motor or motors. The batteries shouldn't be a whole lot heavier than the big diesel engines plus their 300+ gallons of fuel. There's no reason to believe that a charger couldn't be placed at the loading dock to charge while loading the trailer, either.

And, yes, I used to drive Freighliners and K-whoppers back and forth across Missouri. Among other things.

 

[wayner]

300 gallons of fuel is about 15-20X what a car has, correct? So wouldn't we expect to need a similar ratio of battery capacity on a Semi? So to charge the semi battery in the same time that it takes to charge a car at a Supercharger would take 15-20X power? Maybe a little less given what you talk about with more efficiency in an electric motor. But that will still get you to around 10X the power, which is a lot.

 

[MP3Mike]

300 gallons of fuel is about 15-20X what a car has, correct? So wouldn't we expect to need a similar ratio of battery capacity on a Semi?

No. A Semi gets ~6.5 MPG, so 300 gallons gets it almost 2,000 miles. An electric Semi is not going to have that kind of range. Tesla is saying ~500 miles of range for the longer range one. And less than 2 kWh/mile. So a 1 MW charger should be able to charge it mostly full in about an hour.

But more to the point is in an electric Semi I suspect that they will assume that you will plug in and charge during every required rest break and probably every stop to load/unload. So with a 1 MW charger and starting with a full battery they would drive for ~8 hours, stop and charge for their require 30 minute rest break, and then drive for another ~4 hours, which essentially gets them past their allowable hours to drive for the day, so they could stop and plug in to a slower charge to charge to full overnight while they sleep. They would only need a ~150 kW charger to charge to full from empty in ~8 hours. (Unless they are team driving. And electric Semis don't need to replace all Semis right away.)

Of course most Semis aren't long haul driving > 700 miles per day. And that isn't the target market for the Tesla Semi. Initial use of the Tesla Semi will likely be local routs under 500 miles per day. So they will just charge overnight between shifts.

To go back to your calculation, by range, a long range Tesla Semi will only carry about 75 gallons worth of electricity. (But only ~13 gallons worth of diesel by energy.)

Notes:

• All calculations based on 2kWh/mile, which the Tesla Semi is supposed to do better than. (We just don't know how much better.)
• The 2kWh/mile is based on a full load, ~80k pounds, which most loads are volume limited not weight limited.
• Semi drivers don't always fill their tanks full, as it reduces their mileage and hauling capacity.

 

[wayner]

Thanks Mike - that makes a lot of sense. I believe here in Canada a local grocery chain has signed up with Tesla to test the semi. That makes sense as the semi would be used to go from the warehouse to the local stores and won't be driving that far in any given day.

 

[drdumont]

A totally superfluous question, but has anyone noted if the Semi will use a new humongo single piece connector, or several possibly easier to handle connectors, or multiple versions of the standard Tesla power connector?
I read somewhere that someone had seen a Semi charging from two standard Supercharger connectors, but of course, I am sure the design is still in progress.

 

[ThomasD]

Will the batteries have higher degradation than the cars due to more frequent and higher charging rates? Tesla states 1 million mile warranty. Over how many years and what percentage of degradation?

 

[Olle]

A totally superfluous question, but has anyone noted if the Semi will use a new humongo single piece connector, or several possibly easier to handle connectors, or multiple versions of the standard Tesla power connector?
I read somewhere that someone had seen a Semi charging from two standard Supercharger connectors, but of course, I am sure the design is still in progress.

A very good question. Many have been wondering about this. From the pictures of the existing Semi charger it looks like there is one cable per stall. It won't be humongo however, a 2 MW water cooled charging cable can come in somewhere in the order 10 kg/m, easily manageable for a person.