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How hard would it be to make an electric semi truck

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The other main problem, I see, is that they will have to weigh more for similar range.

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Trucks are not allowed to weigh more than their current 80,000 lb. limit in almost all US states.

Instead, they will have to carry less cargo, requiring more trucks for a given task. I don't think that is practical.

Tesla will have to concentrate on trucks that carry lighter, bulkier cargo to avoid this problem.

GSP
 
Semi Truck, it`s not that hard eg 6 wheel drive each axle driven by it own battery pack, On long drives just the rear 2 axles being used in low power shared mode(less stress on 1 motor), the front axle used to charge each battery as and when it needs charging ?
 
Maybe, the GF cells are so incredibly energy-dense, that a mWh battery is only the size of the engine bay and frame of a conventional long haul tractor.

d7j6f, that's called perpetual motion. Whenever energy changes form, chemical->electrical->kinetic->electrical->chemical, some is lost.
Perpetual motion is physically impossible.
 
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Now if we can apply all these thoughts to a full size RV.....

I like where you're going with this :)

Not Perpetual motion because only 1 motor charging/supplementing 2 motors using, eg your using more than you can generate thus needing to recharge at some point.

The problem with regen is its only about 50% efficient. There is a lot of heat loss there. So essentially you would be driving with the brakes on and losing about 50% of your energy.
 
To remove some of the Regen inefficiency on the front motor fit overdrives backwards eg in Regen mode the shaft input to the regening motor is doubled, thus the motor spins faster generating higher volts/amps.

That doesn't decrease the inefficiency. The inefficiency is created via the moving parts and lost via heat. This would only create a larger braking effect and hence more loss.

Regen is great when you need slight braking, like going down a hill, but it is not effecient. It would be more efficient to just go into neutral than to ever use regen.

On the other hand, your idea could have some practical uses on a semi. When traveling down a steep grade, standard regen would not be enough to slow down the massive momentum of a semi. To have the ability to have a geared regen would act similar to a Jake brake that semi's use now, and could help prevent them from actually having to use the friction brakes.

The idea to have 2 motors supplying power and one providing regen will just not work with today's technology.
 
Not Perpetual motion because only 1 motor charging/supplementing 2 motors using, eg your using more than you can generate thus needing to recharge at some point.

Oh FFS. This just keeps coming up over and over and over and over.

This is not hard.

You're spending 100kW, say, to move the truck at a particular speed.
So you want 100kW from the "regen" motor.

It takes 100kW + the efficiency loss to spin that motor. You have to get that power from the drive motor.

So now it takes 200kW + the efficiency loss to drive the truck forward, but you get 100kW back. Net, you're now spending 100kW + the efficiency loss to maintain your speed.

See the problem?
 
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Natural gas is cleaner burning than Diesel. Production of either fuel is probably not terribly clean.

The big benefit is that natural gas costs about half as much as Diesel. CNG trucks cost tens of thousands more than Diesel trucks however.

GSP
"Terribly Clean"-- Drilling a well for gas (or oil) is equally messy. Both have exploration, leasing, road building activities. Refining raw well head gas into LPG (propane, butane, NGL) is done at very clean Natural Gas Processing Plants. Refining crude into its various petroleum fractions requires a messy pipeline, storage tank field, large refinery with all its distillation towers and furnaces, and then a distribution system of pipes, terminals, delivery trucks and dispensing stations.- one could easily say Diesel is much more messy.

Now a cubic foot of LPG contains much less energy than a cubic foot of diesel - so one needs to burn more to get the same output. If you get 10 mpg on diesel, you would get 5 mpg on LPG. LPG is not usually considered a highway fuel, and diesel is - so the taxes are much different. Cost/mile ... lots of components in that simple number.
Electricity beginning at the meter - compared to LPG or diesel at the meter - using a common denometer of energy (BTU) might cost less, but the big kicker comes in efficiency of use. Used electricity is heat (with 95%+ used for intended purpose); used diesel is smoke soot, CO2, and heat, with perhaps 30% used of intended purpose.
 
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I believe, it will be battery swapping & leasing for long runs.

Could be. Two more things in the favor of semi batter swap:
1. I suspect there's less personal attachment to a specific batter pack, so the 'go back to get your pack on the way home' aspect could be nullified. Leasing is a subset of that option.
2. With the right quantity of packs in the 'system', you can slow down their charge rate to a practical level--to a rate you can feasibly pull at truck stops for a bunch of batteries all charging at once (a single MWh battery might be able to charge at a MW or more)
 
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Could be. Two more things in the favor of semi batter swap:
1. I suspect there's less personal attachment to a specific batter pack, so the 'go back to get your pack on the way home' aspect could be nullified. Leasing is a subset of that option.
2. With the right quantity of packs in the 'system', you can slow down their charge rate to a practical level--to a rate you can feasibly pull at truck stops for a bunch of batteries all charging at once (a single MWh battery might be able to charge at a MW or more)

Battery swapping makes even less sense for large vehicles then it does for passenger vehicles...

Besides, it won't be needed at all as large batteries charge super fast. My feeling is these will be coupled with a new type of Supercharger intended for commercial vehicles - the SuperDupercharger ;)

A 600kW unit should juice the T300 up to 80% in roughly 20 minutes. Introduced in strategic alliance with [gas station company] for deployment along all major transportation routes.
 
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Battery swapping makes even less sense for large vehicles then it does for passenger vehicles...

I think you missed the premise.

The limit on fast charging a fleet of large vehicles could likely be available facility power, not the collective capability of the vehicles/batteries in the fleet.

More succinctly, how many MW are piped into an average truck stop now? What is the [or is there a] ceiling for upgraded electrical capacity?