What are the issues?
Let’s take the Tesla Semi for example, though the other offering available in North America is similar (the Nikola Tre). Let’s imagine a round trip from Boston to Miami and back.
In a diesel truck, you’d fill up your tanks in Boston and head south. You’d probably be getting close to your 11 hour limit around Richmond VA, and get a hotel, or stay in your bunk. In the morning you’d check your tires, maybe fuel up and head out again, this time probably making northern Florida. The following day you’d drive the remaining bit of Florida, do your delivery, and head north. Ideally you’d be able to get roughly back to where you started the day and then have a 2 day trip back, stopping in Northern Virginia or around DC. This would be around 3000 miles, 375 gallons of fuel (at 8mpg, which would be an aerodynamic tractor trailer truck run at the speed limit). It would mean 4 overnight stays, at least 2 fuelling stops. You’d be able to do the transit portion (including driving, fueling, weight stations, tire checks, etc) in about 50 hours, plus any delivery/loading etc. Delivery, loading or other delays could push you into a reset on the road, but for the sake of this discussion we’ll assume no reset necessary. To understand this plan, having a basic understanding of HOS (hours of service) is necessary. https://csa.fmcsa.dot.gov/Documents/HOS_VisorCard.pdf
HYPOTHETICALLY in an electric truck, things would be a bit different. You’d be stopping to charge a lot more often, and spending more time during that charging. Let’s take a look at what that might look like in different scenarios.
Take the Tesla Semi for example.
It’s got a sleeper, 900kwh battery pack and a hypothetical 1.7kwh/mile consumption giving us a hypothetical 500 mile range. Let’s first assume we don’t want to get below 20% or charge above 90%, and that we’ll ACTUALLY be getting 2kwh/mile because everything is harder when running the east coast. So that gives us a max range of 315 between charges. Supposedly the truck is capable of 1MW charging, but that doesn’t currently exist. What we can infer from real-life pictures of the prototypes on the road, and the current supercharger map is that you can plug into multiple V2 superchargers at once. So for this we’ll assume we’re heading to currently existing chargers, dropping trailer, and then hooking up to TWO chargers at once. This would in reality mean hooking up to FOUR chargers at once because superchargers are ganged up in two’s. So if you want the full 250kwh charge speed, you’d need to have the other side of the charger emtpty (charger 1a and 1b share power, so you’d want to hook up to one, and have the other empty to get the maximum). So you’d get to the super charger and need 4 emtpy bays, you’d hook up to 1A (leave 1B emtpy) and 2A (leave 2B emtpy). So that’s what we’ll assume for now, though the likelihood of hitting chargers with 4 empty contiguous spots is tough some times of the day. We’ll want to avoid lunch-time charging. So if Tesla claims the truck will charge the middle 70% in 30 minutes at 1MW, it should be an hour on the doubled up V2 chargers. So that’s 450miles per hour, 225 in a half hour and 112 in a quarter hour. The trick is that in reality, the truck will charge faster at the different SOC, but since we’re planning to keep it between 20% and 90% we’ll use this as an average.
So I’ll do a quick written narrative and then also provide the hypothetical log pages that would go with the trip.
Day 1:
So If we departed terminal in Boston at 6:05am after 5 minute pre-trip, (so a 6am start) with a 90% charge, we’d hit East Rutherford, NJ at 11am with a 230 mile range, We’d take a 30 minute break while charging, but also 15 minutes on-duty at either end of the charge not driving because we’d need to pick & drop the trailer (most likely). We’d depart East Rutherford at noon with 6 hours on duty and 5 hours of driving done.
Then, we’d drive another 5.75 hours/310 miles to Fredricksburg, VA (including some DC traffic, but we’d dodge the worst of it with a 2 hour break from 4pm-6pm, this would also allow us some options if we needed them for split-sleeper time). Hypothetically, we’d be getting there at 7:45pm. Likely we would need 15 minutes on-duty not driving to park the truck for the night and ditch the trailer so off-duty at 8pm. We’d probably only hook up to ONE of the chargers here (to drop the charge time, spread out the charge), since we’d be parked for our 10 hour. At the end of the day, we’d have 10.75 hours drive time (or a little less if traffic was light, but I’m being conservative), 30 minutes on-duty not-driving, and 2.5 hours off-duty. That would put us off-duty right at 14 hours after our start, including planning around some traffic. We’d have 540 miles on, which isn’t TERRIBLE for the Northeast. Mileage may vary on this sort of thing, and usually I make it to Richmond with 10 hours driving, so this is conservative. The 10 hours and Richmond, VA scenario is just as doable with this equipment, assuming good access to the actual chargers and charge-rates are as advertised.
The times I gave for drop & hook are shorter than in reality, but for the sake of playing it safe, we’re saying 15 each time to pick and to drop.
Day 2:
Depart at 6am with a short preptrip and90% charge. We’d drive 5.5 hours to Florence, SC. 15 minute trailer pick/drop and a 30 minute charge and the 15 for hooking again. Depart 12:30, drive 5 hours to St. Johns, FL, get there and do a slower charging routine while sleeping, so go off duty at around 5:45pm including 15 to drop trailer. We’d be stopping early and have 10.5 hours drive time, 45 minutes on-duty not driving, and a 30 minute break in the middle. We’d have done 656 miles. South of DC is a lot faster. Hypothetically, we’d be arriving earlier with more drive-time to spare, but the charging would have taken a little longer, and we’d arrive with a lower SOC on the truck, which wouldn’t matter, as it would be charging overnight on a single 150kwh supercharger. Overnights using the 150kwh units wouldn’t really slow us down since we’d be there for 10 hours.
Day 3:
Depart at 4am with a short pretrip. We’d drive for 5.75 hours getting us there for a morning appointment, around 9:45am. We’d be relatively low on charge having done 350 miles, and likely all at a pretty fast speed. We’d drop trailer at the delivery, bobtail to a charger and go off duty for 2 hours (giving us some flexibility with the sleeper berth provision). We could probably handle this on a doubled up 150kwh charger, or maybe even on a single 250kwh charger. With 2+ hours to play with you’d have some options. At 12;15, you’d go grab the trailer and head north again at 12:45. With 5.25 of drive time left. We’d head north and make it to Palm Coast FL in 4.75 hours at 5:30pm, plus a 15 minute trailer drop would put us off duty at 5:45pm and 10.5 hours of drive time.
Take-aways:
Charging speed is king, more-so than capacity.
The split sleeper berth provision is helpful for slower charging situations. (I’ll map out a day of driving using slower chargers, smaller batteries and the split sleeper).
Slower over-night charging is an option.
Range/Charging speed and a good mid-day charge location is the real key.
The split sleeper provision can make up for a whole different sent of math, one that will accommodate slower charging much more easily. I’ll explore that in a later post using the Nikola Tre as my sample truck.