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Comment by amluto | Hacker News Reader

I would love to see Tesla demonstrate that their Superchargers are anywhere near super enough. A couple days ago, I supercharged at the “120 kW” Tesla factory in Fremont. For quite a few minutes, I got 23kW. After a while, it went up to 50kW or so. I checked the other car sharing my charger, and the total was well under 120kW. I suspect the station has an overall power limit. Also, there was a line.

For trucks, you need something like a megawatt to recharge on a lunch break, and a line blows the whole thing up.

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Charge rate is variable based on a huge number of factors, not all of which you can see. It also doesn't charge at the full 120kW the whole time.

Some of the factors that can affect it:

- Whether someone is sharing your charger (iirc every two bays share the same backend infrastructure)

- If you are sharing the charger, then who was plugged in first (the second person to plug in will receive lower priority)

- The State of Charge of the battery pack (the closer to the high/low extremes of charge the slower it will charge)

- Temperature of the battery pack

- Condition of the pack

- Whether there are any restrictions on the pack (some packs if they are supercharged a lot will have caps placed on the charge rate)

I imagine with the 'Megacharger' infrastructure given the sheer amount of power needed, they'll have dedicated infrastructure for the entire bay.

Yup, you're also dealing with companies that may have fixed routes and the capital to develop the infrastructure if it makes financial sense.

Your average consumer isn't going to drop $X0,000 to put in a super/mega-charger but a business might.

Try telling a trucker that their truck didn't finish charging because of complicated reasons.

Electric semis for true long haul will never be viable unless there is a major breakthrough in battery tech. 300 gallons of diesel fuel has so much more energy than even the best batteries could pack into a reasonable size and weight.

Most trucks are driven by a single driver, rather than a team of drivers - this means that they legally must have 30-60 minute breaks every few hours, and can only drive a certain number of hours.

So, lets throw some numbers around:

- Range: 500 miles - Time to recharge 80% (+400 miles) capacity - 30 minutes - Speed Limit (Interstates): 50-75MPH - Maximum Driving Times (USDOT): - 8 hours (followed by a 30min break), - 14 hours (followed by a 10 hour break) - 60/70 hours (in any 7/8 days)

So lets assume 60MPH moving average speed (very high) - gives us over 8.3 hours of driving time.

You add in a 30min break at a megacharger and you've now got yourself another 400 miles of range, which would let you drive for 6.6 hours - at which point you'll be out of hours again.

So you park up and let the truck charge overnight.

I don't see how this is so difficult.

Where are you getting 400 mile range on a semi towing a load coming from 30 minutes of charging?

For the range - you can order either 300 or 500 mile range options.

The range options were said by Tesla to be the range of the truck plus trailer and maximum load, at highway speeds.

The 400 mile mention is the 80% capacity of a 500 mile range pack you'd get by a 30 minute charge. Also information given during the announcement.

[1] https://www.tesla.com/semi

That is for their “megawatt” chargers not the current infrastructure.

And that is a problem just count the average number of semis in a truck stop they’ll all have to share power.

Also many of these truck stops are in the middle of nowhere and while they have electricity they aren’t connected to anything that can provide that much power.

Say you get 100 500kWh semis in a stop that need to be charged 80% that’s 4mW if we’re taking Tesla’s 30min turn around that’s 8mW which is not an unnoticeable portion of what a power plant produces and hour.

> That is for their “megawatt” chargers not the current infrastructure.

I never mentioned 'current' infrastructure, whatever that means. We're clearly talking about Tesla Semi here, that's pretty clearly not going to fit in your ordinary Tesla supercharger stall.

As for the other 'problems' - they are all solvable. I'm sure Fleet operators and major truck stops will all be jointly cooperating to add MW charging infrastructure along the trial routes. It benefits the fleet operator, it benefits the truck stop operator.

Electrical grid operators won't have an issue with it - if you look back at previous postings on HN you'll find several examples where grid operators are struggling to find demand for the grid, given the rise in household efficiency and offshoring of major production infrastructure.

Yes it'll require some work to ensure there's not huge spikes in demand, but that's solvable too. Tesla (and others) are already implementing local battery storage at some of their superchargers. This lets them have a more consistent draw on the grid.

The ends result of this is that you end up having a huge amount of deployed battery storage at truck stops all over, able to take advantage of spikes in energy production, respond to grid shortages, and smartly manage charging of trucks.

Given it's all integrated, there's no reason a major fleet operator wouldn't sign some kind of contract allowing their fleet charging to be slowed or suspended momentarily in return for lower charging costs.

I also suspect that there will be (at least) two categories of charger - the immediate "I'm on a short break" MW charger, where you're expected to move on after getting 80% or more capacity, and then an overnight charging slot where you park up for your 10+ hour break.

Tesla was mentioning 400 miles. I _could have sworn_ they specified those numbers were all with an average load but it seems official numbers are a bit annoying to source. So now I'm curious if that's accurate or not.

That is the number Tesla promised for their megachargars at the presentation of the semi. So they seem to have clear plans to deploy megawatt chargers at their charging stations.

ugh, fixing the formatting, because I keep forgetting this isn't markdown.

- Range: 500 miles

- Time to recharge 80% (+400 miles) capacity - 30 minutes

- Speed Limit (Interstates): 50-75MPH

- Maximum Driving Times (USDOT):

-- 8 hours (followed by a 30min break),

-- 14 hours (followed by a 10 hour break)

-- 60/70 hours (in any 7/8 days)

Major breakthroughs in autonomous driving may change that. If drivers are eliminated, the costs of waiting 30-60 minutes while charging becomes almost 0.

Especially if the truck can hand off its payload to a fully charged & waiting replacement cab.

If you have access to a fleet or don't need the same truck back, it becomes more of a baton relay than a marathon.

With the kind of infrastructure required for that, I can't help but think it would just be a lousy version of an electric railway. At least for long hauls with high throughput.

How would it be lousy? The cars can now go anywhere and dynamically route instead of being stuck on rails and the infrastructure costs are orders of magnitude less.

That's like saying that circuit switched networks are better than packet switched.

They would be if packets had enormous per-packet overhead.

At some point you start wondering about improving intermodal transportation. Using rail for longer distances with trucks handling the last 50-100 miles.

Isn't it the other way around? With drivers, you can fit the charging inside the already mandated breaks, while without driver, you have to introduce longer breaks to get enough charge.

Idle time of EV-rig per day (30min charge every 4 hours): ~11% Idle time of Non-EV-rig per day (5min refueling every 4 hours): ~2%

Sure, for short distance trips where loading/unloading takes as long as charging the EV-rig, it doesn't make a difference, but for longer hauls, the charging pauses of EV-rigs will severely cut into utilization of the fleet.

Semi's actually get ~6.5 MPG so they only need around 5x the batteries to get the same distance as normal electric cars. The huge tanks are over 24 hours driving time and are most there so you can pick the states to refuel in.

Battery volume and weight density is not that bad when you consider the weight savings without an IC engine, transmission etc. Gasoline gallon equivalent tables ignore the vastly lower efficiency of IC engines. Costs are mostly non issue as trucks would charge daily making them break even before cars.

The actual problem is manufacturing capacity which has been ramping up but has a long way to go.

Yes but long haul trucking involves distances much farther then the range of any normal electric car.

Good point about substituting the weight of the engine for batteries. Still I think you're going to be way short in total energy density.

And it's not like you can just pack the trailer with batteries either, you still need to allow for the weight of the cargo and there is a gross weight limit on 18-wheelers.

They don't exceed highway speed so swapping batteries every X miles will be worth it if they reduce total costs by doing so.

As to weight the engine weighs ~3000 lb and 300 gallons of gas weigh ~1,900 gallons. Transmission is another 700lb, include tank weight and verious odds and ends and you can get ~5 hours at highway speed. Assuming a battery swap takes 10 minutes. That's easily worth saving 50+k per year in operating expenses.

2200lb for gas, 3000lb for the engine, 700lb for the transmission. Say 7k lb total. Compare this now to the electric one. The battery alone would weight 33k pounds. Engine and transmission would add another 2k. 5 times more than ICE. The battery would also cost $200k.

they are already driving them, they seem to have about the range. you can read about this in tesla newsgroup sites, like tmc.

Are you suggesting that Tesla hasn't done the math or are just flat out lying?

He used the weasel words "true long haul". Tesla was clear about what the truck can do; you're replying to someone who wants to argue with unclear statements. Not a good plan.

Would a hybrid system using an electric generator to recharge the batteries be more efficient given the advantages of electric vehicles, such as regenerative braking?

I would think if a series hybrid were more efficient than a conventional mechanical drive and transmission, it would already have been adopted. Trucking companies will spend money even for small gains in fuel efficiency because they drive so many miles.

I also think that regen braking in semis would be trickier because a lot of the braking happens on the trailer wheels so you would need to fit all the trailers with regenerative braking equipment.

Long haul trucks fairly hit the breaks as that ends up costing a lot of money. However, a truck specifically for mountainous areas may benifit from a hybrid transmission.

1. tesla superchargers share a the 'bank of chargers' at 2 spots. look for 2a, 2b, those two spots are shared. pick one that doesn't have a paired spot in use 2. they charger at a higher rate when your car has a lower charge. 3. they cool the battery when charging to prevent harm, if its really hot this can lower charge ability. there's a similar thing with cold temps

They are reliable and predictable with those factors.

There is already extensive discussion of how to charge higher power systems like trucks, tesla has a plan, google for details. the easiest thing is just several superchargers together. by the way, a supercharger spot is just a bank of regular chargers working together, feeding dc directly to your car's battery. its not magic, it's all pretty easy to understand once you get some basic info.

I believe the superchargers use on-site batteries to buffer demand to the grid. Perhaps the local battery was depleted, so they backed off charge rates to avoid hitting the grid too hard.

Some do, some don’t. Usually only where Tesla is charged demand charges for peaks by the utility.

As far as I know, none do. The big one in Gilroy has a big battery pack that seems to sell storage and VARs to the grid.

In CA, basically every commercial rate structure includes peak demand charges.

The Fremont factory supercharger has always been the worst one in the network. Be social with some owners, you'll be surprised what you might find out.

Solar. Freakin. Roadways.

Have you seen the roads through most of the country? We can't keep tar and stone in decent condition, no way we'd keep those solar panels running.

Of course, it was a reference to a viral video a few years back with the same title. A joke, if you will.

Would have been a hit on Reddit.

These are like two different problems, though probably compounding. Allowing vehicle charging while moving is an interesting problem, regardless of where the power comes from (well, it’s way easier if it’s attsched to the truck).

I don't think the solar road is meant to charge the cars while driving, it's just a place to install solar panels.

Same thing is it not? Wireless charging would be nice, or the trollybus tech.

Not necessarily. Driving over a solar panel doesn't charge your electric car.

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