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Comment by SigmundA | Hacker News Reader

Very interested to see details. I have a hard time believing it will be purely battery based and able to do "long haul".

Typical semis carry 300 gallons of diesel and have a 2000 mile range. You would probably need to a 4 to 5 megawatt-hour battery to equal that. At today's price your looking at a million+ dollar battery that weighs 50,000 lbs and would take 40 hours to recharge on a super charger. Just makes no sense.

Lets say by "long haul" they mean 500 miles, still at least a megawatt hour battery that cost 300k, weighs 10k and takes 10 hours to charge. What trucker would buy that?

Perhaps it will be targeted at urban delivery with a even smaller battery.

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Well, a class 8 trucks has a gross weight of over 33,000 pounds. Let's pretend that Musk gets that 1MWh by slapping some Powerwall 2 units on a truck frame.

The Powerwall 2 has a capacity of 200 kWh, costs $5,500 and weighs ~3,500 pounds. So we're looking at 17,500 pounds and $27,500 for that 1 MWh of batteries.

That's about half the minimum gross weight of the truck at a fairly reasonable price compared to the vehicle cost as a whole.

I'm sure there would some significant weight savings using a electric drive versus the large diesel engine + drivetrain. How much savings? I have no idea, but it should significantly cut into the battery weight penalty.

Edit: Looks like a typical heavy duty engine (Cummings ISX15) is only about 3,000 pounds, dry weight. The Model S electric motors are only 70 pounds, so let's say at least one Powerwall is "free" weight-wise.

Also, the ISX15 looks to be >$20,000 for rebuilt engine, so the battery costs look approximately comparable to a traditional engine price.

Powerwall 2 is only 14kwh at 270lbs for $5500, or about $400 per kwh. You must mean the power pack 2 which cost 80k.

Musk wants $100/kwh cost from the Gigafactory, but market is currently above $300.

Semi tractors only weigh 15-20k lbs your talking a battery that weighs as much as the tractor. 300 gallons of diesel is 2000 lbs and the engine and transmission is about 3000 lbs. it would be at least 10k heavier which reduce carrying capacity since gross is capped at 88,000 lbs total not to mention space.

Now throw in the autonomous factor. Subtract driver labor costs and throw in near 24/7 operation (vs. human drivers which are required to stop for rest breaks).

Semi doesn't have be electric to be autonomous, Frieghtliner is already showing diesel autonomous prototypes.

True, and to those add the cost of externalities like mining on natural ecosystems and pollution on climate warming and our health.

Are recharge breaks less time than human breaks?

I suspect battery swaps are on the agenda.

You are correct re the Powerwall and Powerpack confusion. I had gotten the information off of the Wikipedia article and accidentally combined information from the two tables.

That definitely changes the cost/weight/power equations.

Didn't Tesla have this thing where they changed the battery from a model S in like 2 minutes? Scale that to a semi and the 40 hour charge time is a moot point.

How would you even inventory such batteries? Yikes.

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