North American fleet owners like their vehicle specs. They demand choices from their OEM partners for components ranging from frame rail thickness to wheel seals. We have choices in engine displacement, torque and horsepower ratings, even fuel tank capacity.
Will fleets have similar spec’ing choices for electric-vehicle batteries?
In these early days, OEMs are making most of the spec’ing decisions for battery-electric trucks, but fleets will eventually be offered choices.
“OEMs and fleets are still on the upside of the EV learning curve,” said Rick Mihelic, director of emerging technologies at the North American Council for Freight Efficiency and formerly a vehicle performance engineer at Peterbilt. “The OEMs don’t have all the answers yet. It will take a few years to flesh out all the options, but I expect fleets will eventually have options when it comes to batteries.”
Different battery types and chemistries eventually will prove better suited to certain applications than others. Lithium-titanium-oxide (LTO) batteries, for example, can be charged quickly and respond well to regenerative charging, but they have low energy density (they are heavier). Nickel-manganese-cobalt (NMC) batteries, on the other hand, are lighter and have high storage capacity. They are well-suited for long-range applications, but they are relatively new to the market and still in development.
The different chemistries come with trade-offs in weight, capacity, performance, fast charging capability, packaging, and recyclability. Certain battery types require different battery management and/or thermal management systems, which may add cost and certain packaging requirements to the truck.
“Depending on what you’re going to do with the battery, you might choose a different chemistry for different applications, even within the same fleet,” said John Warner, chief customer officer for American Battery Solutions, speaking at a Study Group session at the American Trucking Associations’ Technology & Maintenance Council 2022 annual meeting in Orlando, Florida.
Spec’ing options are necessarily limited at the moment, but eventually you may be able to consider trade-offs in the battery spec, such as the ability to fast charge to take advantage of regenerative charging and opportunity charging, or a heavier battery where weight isn’t a huge concern.
Battery size and weight are serious concerns, so optimizing the battery for the application is critical. Warner compared a package delivery vehicle with a refuse truck and a Class 8 long haul truck. He noted the package delivery vehicle would consume about 1.3 kilowatt-hours per mile. For a range of 150 miles, it would need a battery of about 115 kWh. A refuse truck, obviously heavier, would get about 0.6 miles per kWh. Its battery would need to be about 166 kWh to complete a day’s work.
“As the vehicle weight increases, energy demand increases,” Warner said. “You also have to build in some contingency for hot or cold weather, and some reserve. But if you can rely on regen charging, as in a high stop-start application like refuse or package delivery, choosing a battery chemistry optimized for regen charging may let you get away with a smaller, lighter battery overall.”
When you start considering the various chemistries on the market, the pros and cons of each soon become apparent. In the short term, selection will be limited to what the OEMs are comfortable with, but fleets will need to get up to speed on the offerings and their potential benefits.
“Fleets will need to understand the parameters associated with high-voltage batteries and how they will fit into the operation,” said Raul Battista, manager of alternative power systems at Penske Truck Leasing, co-presenting on the same Study Group session.
For example, is the battery’s life cycle based on time, hours, miles, or energy throughput? Does DC fast charging have adverse effects on your warranty? These factors and others should be considered when deciding the application of your vehicle and its battery needs.
Packaging is another interesting part of the equation. The actual battery cells used in commercial EV batteries look much like a typical AA-size flashlight battery. Hundreds or thousands of them are wired together and packaged into modules of standard capacities. How many modules you get depends on the capacity you’re looking for and the available space on the chassis, and how much energy you can pack into a module depends on the cell form factor.
Common forms include cylindrical, prismatic and pouch, and each as its own pros and cons. Cylindrical cells are considered very safe and among the least expensive to manufacture, but they have the lowest packing efficiency and thus a relatively lower energy density than other forms.
Pouch cells are lighter and have greater packaging efficiency. They lend themselves well to thermal management due to their high surface area and thin enclosures — but they are easily pierced.
Prismatic cells offer great packaging efficiency and are equal to or better than most other cell forms in safety, thermal management and energy density.
“There’s really no one-size-fits-all solution,” Warner said. “From a battery maker standpoint, it depends on what you’re going to do with the battery.”
The type of enclosure is important, Warner stressed. “What type of enclosure is it? What environment is going into? How can we crash-proof it? Will its position on the vehicle protect it or expose it?”
These will be spec’ing concerns for fleets sensitive to wheelbase length, tare weight, and the configuration of the truck. Vocational vehicles may be particularly challenging, considering the weight and frame-space requirements of the onboard implements.
Part of the challenge presently is the number of systems and standards out there. The battery makers can design systems to suit any application, not just for trucks. At some point, though, the need to manage manufacturing costs will force certain packaging configurations. Those require standards. There is no shortage of standards out there. Warner listed five off the top of his head. And Europe and China have different standards than we do here in North America.
Battery weight is an additional and very problematic consideration. Speaking at a separate Technical Session at the TMC meeting, Bill Bliem, senior vice president of fleet services at NFI, shared some actual vehicle and battery weights from his own fleet of pre-production BEV tractors.
“Fifty miles of range is going to require about 100 kW/h of energy, which right now weighs 1,375 pounds,” he said. “I'll let you digest that for a second, and you can do the math for longer ranges.”
Other weights and ranges he cited in his presentation included:
For the complete tractor, Bleim said a typical diesel day-cab in his fleet weighs about 15,600 pounds, but an electric day-cab with a couple of hundred miles of range weighs about 22,000 pounds. As for the trucks he has ordered with a 350-mile range, he said they will tip the scales at 29,000 pounds without a driver and without a trailer.
Battery fires, though relatively rare today because of the scarcity of electric vehicles on the road, are a significant concern for vehicle owners as well as emergency responders. A lithium-ion battery can burst into flames hours or even days after the damage occurs, Battista pointed out.
“They can be exceptionally difficult to extinguish, and with the massive amounts of energy in commercial battery systems, they can flare up again and again,” he said. “They emit combustible and harmful gases, and there’s a risk of environmental contamination due to the contaminate run-off water from firefighting efforts.”
Even a single cell failure within a battery pack can lead to a vehicle level event. Batteries are subject to crash testing, as are diesel, natural gas, and hydrogen storage tanks. But crash testing standards for BEVs are still a work on progress.
“I’m working on a lot of standards committees right now, because they haven't been written yet,” Warner said.
Battery safety at the standards level won’t be a fleet concern, beyond knowing the battery is certified. However, fleets will have to be up to speed on firefighting procedures for potential in-shop or post-crash fires and when dealing with first responders and the community at large.
The next great hope in batteries is solid state. They are a work in progress that everyone hopes will succeed. Current lithium-ion batteries contain a liquid electrolyte; solid-state batteries use a solid electrolyte. This makes solid-state batteries lighter, with greater energy density and thus more range per pound. They also recharge faster. Solid-state batteries are common in small devices such as computers and cell phone, but it’s proving difficult to scale the batteries up to the size and capacity needed for cars, much less commercial vehicles.
The prospect of have a better battery just beyond the horizon gives electric truck buyers jitters. Nobody wants to invest heavily in what could prove to be a marooned technology. Fortunately, according to Warner, solid-state batteries are still a few years out from commercial deployment.
“I think you’ll see some automakers playing with some kind of low-volume production probably in 2025 to 2026, but it will be more like 2030 by the time it expands out into the rest of the industry,” he said.
He noted that it will come in in phases, starting with a hybrid of sorts with a metal anode and maybe a gel or a semi-liquid electrolyte.
Fleets will eventually be confronted with what to do with worn-out or expired batteries that have diminished capacity to hold a charge. While batteries are presently an enormous part of the total cost of an electric vehicle, prices are coming down, so chances are the replacement batteries you will be looking at will be lighter, more powerful, and less expensive. But you probably won’t get a good trade-in deal on the existing batteries because they may be obsolete by trade-in time.
Experts are saying there will be a market for those batteries as stationary energy storage, and they can be downsized to operate in smaller devices. It’s still too far off to see clearly what uses your present batteries will come to, but fleets will eventually have to make cradle-to-grave decisions about their battery specifications.
There’s no time like the present to start getting up to speed on EV batteries.
There are a variety of battery chemistries currently in service. They are all under the lithium-ion umbrella and they are good at different things, but there’s no silver bullet. Some have been around a while and are undergoing continuous improvement. Some are new and on the cutting edge. Others are hybrids of two or more different chemistries or structures. You’ll be seeing more of these acronyms going forward.
Written by Jim Park