Electric Trucks are Ready for the Road

2022 September 19 Twitter See all posts


New designs that can utilize cheaper battery chemistries will alleviate scaling problems.

Electric Trucks Need a Battery Breakthrough?

Bill Gates opined in 2020:

Even with big breakthroughs in battery technology, electric vehicles will probably never be a practical solution for things like 18-wheelers, cargo ships, and passenger jets. Electricity works when you need to cover short distances, but we need a different solution for heavy, long-haul vehicles.

Gates was far from alone in having these views. How has that prediction turned out?

Next Generation Electric Trucks

In the meantime, more truck makers have announced new long-range designs. They will have to use the most energy-dense battery chemistries, right?

Daimler eActros Long Haul

Mercedes/Daimler plans to start manufacturing this truck in 2024, and it uses lithium iron phosphate (LFP) batteries.

LFP batteries are taking the world by storm. They have lower energy density than lithium nickel and cobalt-based chemistries that power high-performance electric cars like Tesla's top-tier models.

Analysts relegated them to golf carts, e-rickshaws, and short-range vehicles. Battery pack manufacturers have turned this view upside down by improving packaging efficiency and reducing pack weight per kilowatt-hour. Even companies like Tesla expect LFP to make up three-quarters of their volume. The energy density is good enough, while LFP is cheaper and doesn't use minerals like cobalt and nickel that are likely to see bottlenecks.

Daimler pushes the envelope further by putting LFP batteries in a long-range truck.

A Day in The Life

Will the eActros be practical as a Class-8 truck? We can model a trucker's day to see. Regulations mean a driver can only drive eleven hours per day and can't work more than 14 hours, including breaks, traffic, etc. An electric truck meets the requirement if it can fit driving and charging into 14 hours.

Stats:

For simplicity, we will assume the truck always starts at 80% charge and stops to recharge at 20%. It can drive 2.85 hours at 65 miles per hour. Then we need to add ten minutes to each charging stop to get on/off the road. So the truck has to spend 40 minutes idle every 2.85 hours.

The eActros can fully utilize our driver's hours like a diesel truck. Some caveats are that a lead foot driver going over 65 miles per hour would get worse mileage per charge. That could be partially offset by starting with a ~95% charge, and overnight charging means the truck only needs three charging stops instead of 3.85.

How Did They Do It?

Manufacturers use clever engineering on top of improving battery packs.

Drag and tire friction dominate energy expenditure. Engineering effort to improve drag is worth so much more with electric vehicles. And modeling software has gotten good.

The 20%-80% charge time is relatively speedy. LFP batteries have a longer life than nickel formulations, so you can abuse them a little more by charging faster. Running batteries lower than 20% can shorten life, and charging slows significantly over 80% charge. Chargers run at constant voltage, so the pack voltage converges on the charging voltage as the batteries fill, reducing the driving force. It ends up being advantageous to operate in this 20-80 range rather than running the pack dry and charging to near full.

Challenges

To charge at that speed means using over 1 megawatt of power! Truck stops will need extensive electrical infrastructure. Typical electrical vehicle charging is cheap for trickle charging but costs many times more for fast charging because power is expensive. Trucks won't see the fuel savings if they have to pay more for speedy charging.

Most solutions require storage, carefully planned charging, onsite generation, or all three. A low-utilization truck stop would benefit from storage that allows it to trickle charge batteries (or possibly fly wheels!) that can fill the occasional truck at full power. The same truck stop might also benefit from building a solar farm to reduce its electricity cost. A busy truck stop can schedule trucks ahead of time to maintain high usage rates and defray mostly fixed power charges.

Trucking's Electric Future

Trucks have a short replacement cycle because they can drive over 200,000 miles a year. The trucking fleet could electrify at a rapid rate later in this decade. The ability to use LFP batteries removes many possible scaling bottlenecks. Refined lithium may be in short supply today, but the cure for high prices is high prices.