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by HardEric 1932 days ago
actually adding 15,000 lb of battery to the truck reduces its efficiency significantly. Imagine loosing 15k of payload when you only had 60k to begin with, your new payload of 45k means you have to drive the route 4 times compared to 3 times for a diesel truck with our device.

Hopefully that makes sense.
1 comments
virtualdom 1932 days ago
A 600 mile battery - say 1-1.2MWh - should only weigh around 10-12K lbs (at 260-300 wh/kg). And you can throw out the 5K lb carbon capture device, and 5K lbs of engine, transmission, exhaust, cooling and fuel system. Add back 500 lbs of electric motors. The payload difference is actually not that significant, certainly not 33% more payload for the diesel+CCS. Such a big battery would be expensive though. I expect most EV semis will have 300 - 500 miles of range. This system sounds good for decarbonizing the diesels that are already on the road though!
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HardEric 1931 days ago
you can throw away the 5k of engine and drivetrain components, and then throw in 6k in electric motors, transaxles/transmissions and added copper wiring

From the vehicles I have actually built and weighed there is a much larger increase in weight than you are predicting.

Tesla model 3 curb weight 3897 lb and 200 mile highway range. https://www.caranddriver.com/tesla/model-3

Toyota camry curb weight 3340 and 616 mile highway range. https://www.caranddriver.com/toyota/camry/specs

You can see that 1/3 the range for the same weight, and this only gets worse as the vehicle gets heavier. For class 8 trucks wind drag is a very small percentage of the losses, rolling resistance from weight is the largest loses. So I don't think linear distance scaling you assume adds up.

Its going to be an interesting transition and we know that electric trucks will be great for some use cases but its going to take a mix of solutions, especially in countries where their grid infrastructure is no where near as robust as ours.

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virtualdom 1930 days ago
You've compared the range of a Model 3 driven at 75MPH to a Camry driven at 48MPH, for one thing. But I don't know why you would bring passenger cars into the discussion, since you can't scale performance linearly from cars to class 8 trucks. You've already made that mistake by scaling cabin heating requirements linearly with battery capacity, for example.

> For class 8 trucks wind drag is a very small percentage of the losses, rolling resistance from weight is the largest loses.

According to this source[1], for class 8 trucks at max gross weight on level road, aero and rolling resistance losses are the same around 50MPH, and aero dominates after that. Is that source wrong, or out of date? Source says "aerodynamic drag and tire rolling resistance are major contributors to energy loss" - neither is a "very small percentage".

From everything I've read publicly, EV semis won't have transmissions or transaxles, just motors on the drive shafts (4x120lbs). Not sure where you get 6k lbs, even including the "added copper wiring".

I can totally see a 1-2 ton payload advantage for diesel+CCS over EV semis when the required range is 500+ miles, just not a 15k lbs advantage. Ultimately the market will decide what tech to use for different routes though, and I agree that a variety of solutions will be utilized.

[1] https://www.nap.edu/read/13288/chapter/7#79

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