What’s Winning the Commercial EV Power Wars? E-Axles or Central Drive Motors?

When you look at even a light-duty electric pickup truck like a Ford F-150 Lightning, you'll find that the civilian side of the automotive world has declared that an electric motor mounted to an axle is the best practice. You'd think that by some measure of trickle down technology or design that the commercial vehicle side would follow the same route. Turns out, that's not the case and that evidence wasn't more clear than it was at the 2023 Advanced Clean Transportation (ACT) Expo in Anaheim, California—just across the street from Disneyland. We spoke with Dana Incorporated, Hexagon Purus, and Motiv Power Systems to find out why most electric commercial vehicles still mount their power sources where, well, an engine might traditionally go, forgoing the packaging efficiency of a motor integrated with the axle.

With electrification and carbon-less fuels becoming a huge push for commercial vehicles in recent times—especially now that states like California will ban the sale of new ICE-powered medium- and heavy-duty vehicles by 2036—the race has begun to figure out the best way to meet this new regulation. While you'd think the big battle would be choosing between all-electric or hydrogen electric, that's not the only one happening. In many ways, the choice on where the electric motor should be placed is equally as hotly contested as what feeds power those batteries. What we find is that commercial vehicle manufacturers are still trying to decide if powering a motor mounted on the chassis—being defined as a "central driver" or "central mount" motor—with legacy components like driveshafts and transmissions connecting it to the axle is the way to build a medium- or heavy-vehicle or if mounting the motor directly to that axle—making it an "e-axle"— is the better way to go. It's not as simple as e-axles are too new and little understood, either. It's also a case of what a vehicle designer is looking to build for.

Motiv-ation To Use Central Driver Motors

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Some builders aren't as keen to trust the total reliability of an e-axle just yet. Motiv Power Systems, a stripped chassis and commercial van builder based in Foster City, California, is one. It has just announced an exclusive contract with Cintas, a business services company out of Mason, Ohio, that's been around since 1968 but has found that using electric commercial vans have great attributes beyond environmental factors such as low maintenance costs and healthier, happier drivers. Drivers who also serve as salespeople at the end of the day.

Motiv has been in business since 2009 and we spoke to CEO, Tim Krauskopf, and CTO and founder, Jim Castelaz, about why Motiv has elected to use legacy components in conjunction with electrification despite building commercial vehicles from the ground up. "Mostly historical reliability," Krauskopf explained to us, "We're using the standard Dana differential and we don't have anything in the axle, brake system, or the diff and driveshaft that is not of decades-old reliability. The motor comes from one of the top five worldwide motor manufacturers. We're just assembling them in an application that's new but we're building on reliability, component by component, that allows us to make sure our uptime is really, really high."

Krauskopf doesn't totally rule out the use of an e-axle, "but I want someone else to kind of be the guinea pig and do it first in the commercial industry." For Motiv's customers, that's also what they are looking for because "What good is the newest when those trucks are down? They're losing revenue."

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Castelaz also brings up cost as a reason why Motiv has gone with central drive motors over e-axles. "We've done a lot of looking at e-axles," he says, "I think, for us, it's really about when does the reliability and cost get to being able to match the central driver. When it does, then we'll transition to that. We just want to make sure that we're always delivering to our fleet customers the most reliable, most cost effective solution we can."

That position makes quite a lot of sense. When you look at the driveline components beyond the transmission on a stripped chassis—or skateboard chassis as Castelaz likes to call Motiv's bodyless offerings—all you see are standardized and bulletproof parts. Nearly every commercial truck utilizes similar looking and robust components. It's not just to deal with the cargo weight but also to ensure that those drivelines last as long as the chassis or longer. Even after being in business for 13 years, Motiv is only now transitioning to a single module to control the entire electrified system—where its inverter, charger and motor controller are all rolled into one—because only now have they found a reliable source for the commercial industry. Something that Tesla has gotten right in the decades it's been around, but Teslas aren't relied upon for revenue like a commercial vehicle is and can experiment a little more freely, despite the detriments that thinking can cause for the real world.

Hexagon Purus Prefers Space

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On the other side of the coin we spoke to is Hexagon Purus and its EVP of Systems, Todd Sloan. Hexagon Purus is a sister company to Hexagon Agility that makes Type Four composite tanks and components for commercial vehicles looking to use gaseous energy production to create power like hydrogen and renewable natural gas (RNG) electric vehicles. Hexagon Purus concentrates on complete vehicle systems and works on batteries, hydrogen storage, and motors for fuel cell and BEVs. They work with major commercial vehicle manufacturers to create the solutions to make these vehicles and are particularly interested in using e-axles. "You go back a couple of years ago," said Sloan, "and the axles were a very new thing. On the first time we were involved with e-axles, it was on the Daimler Innovation Fleet where we supported them on electrifying the M2S and on the Freightliner eCascadia where we did the high voltage battery system." The axle came from Meritor, which joined forces with Cummins earlier this year, and is one of the leading e-axle manufacturers in the commercial vehicle space. "They ended up being very durable," said Sloan, "but at the same time, you had a lot of companies coming out with vehicles that use a central drive motor."

He also pointed out that these central drivers are cheaper and work with legacy components but said that the e-axle is "a more efficient way to drive your wheels. We went with 'let's do the more difficult thing that's potentially more efficient. '" Sloan then went on to explain how the e-axle would eventually become cheaper, "In the long run it's going to be cheaper because there's fewer components. The beauty of getting rid of the driveshafts is now you have all that free frame rail space." He then showed off how freeing up the central frame rails not only give you more room for batteries, but now, with no battery packs hanging on the sides of the frame rails, you can add things that are important to the commercial vehicle industry. For example, you now have more room to add hydraulically operated brushes to the sides of an electrified street sweeper. If you have a drink delivery van, the side doors can now extend all the way down to the ground to make stacking crates on your hand truck easier. Boom trucks can have their outriggers mounted to the sides of the chassis. And so on.

However, one use case that caught our attention was a concept Class 8 semi from Hino Motors, the commercial vehicle manufacturer under the Toyota organization. It was done in partnership with Hexagon Purus to develop an electrified version of the XL 4x2 tractor cab chassis. The interesting part is just how short this Class 8 is while retaining a large 528-kWh battery pack—why? It uses an e-axle, rather than a central driver. In this configuration, this truck would get around 250 miles of range, more than enough for those last-mile fleets that can't or don't want to use a straight truck.

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"Anything that needs a trailer instead of a straight truck, like a drink distributor or grocery delivery or anything that needs a trailer but can't get into some tight corners, this concept is going to be a perfect application," said Sloan. Instead of using a Meritor e-axle, this Hino is using an Allison Transmission (yes, that Allison Transmission, Chevrolet Duramax fans) eGen Power 100D e-axle. It's a dual-motor e-axle with a two-speed gearbox with a maximum torque output of 34,665.42 lb-ft (most likely with gearing multiplication influence for this number and playing the same numbers game GMC did with the Hummer EV) and delivering a peak of 871.66 hp at 650 volts, but is capable of taking up to 900 volts.

"But again," continued Sloan, "you can see that by not having a central drive motor, we can actually shorten this wheelbase even more to make a stubby truck with a tight turnaround and turning radius for customers who need it like those in the city. If you have a central drive motor that is as powerful as this is, it's going to be quite big on its own and then you still need a driveshaft." Even if you mount it so that the central driver is rear mounted, you can't take advantage of it being a shorter wheelbase because now you have something sticking out the back." Of course, if you needed more range you could still use this axle and hydrogen fuel cells to go over 1,000 miles but at that point, you'll want a longer wheelbase so you can hotel in a sleeper cab truck instead of a day cab like this one.

Dana Does Both

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Speaking of recognizable manufacturers in the commercial space, one brand that is taking advantage of both designs is Dana Incorporated. Yes, the same Dana that supplies your Jeep Wrangler and Gladiator with that coveted Dana 44 axle. The Ohio-based brand also builds many components for the commercial vehicle industry, from filters to axles, and its expertise fits right into this discussion. We spoke with Jeremy Frenznick, Senior Director of Commercial Vehicle Engineering at Dana, and Jason Sidders, Senior Manager of Advanced Powertrain Applications Engineering at Dana, to see what this legendary brand was catering towards. Spoiler warning, turns out it's both central driver and e-axle.

"We have solutions that are not only an integrated e-axle stand point," said Frenznick, "but also on a central mount—whether it's a direct drive or geared central mount, but our customers are in various stages of evolution or what they're willing to do to architect new designs." There are also the customers who aren't building whole new trucks but are, instead, refitting existing trucks to meet these new standards. "A central mount is great for retrofit, where you have an existing footprint between the frame rails and you need to do something quick," added Frenznick, "and we've architected both central mount and e-axle so that we're able to provide those solutions depending on what the customers are looking for."

Even for Dana, the e-axle isn't a wholly new design as the axle and even the housing itself are built off of existing commercial truck parts. Only the addition of the motor is new. "You look at the architecture and it has a lot of the same bits and pieces," said Sidders, "the same building blocks that we have been doing for a really long time. It's just that the bits and pieces are kind of put in a different orientation." He pointed out the eS9000r and, save for the electric motor and its components, "It's still an S130 differential inside an S130 housing with matching bearings." The design guidelines and validation are also done to their electric drives just as they have been doing for their axles, electric motors, and inverters since the company was founded nearly 100 years ago.

"It's kind of more like the commercial market is a little bit more comfortable with one versus the other right now, in some cases," Frenznick added, "But in other cases they are 100 percent all for integrated e-axles. There's no threshold or appetite for not being successful and having concessions on durability or robustness and we have to take that same firm mindset about how we're going to design, how we're going to validate, and make sure that there's no shortcuts taken."

There Isn't A Right Answer, Right Now

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It's interesting to look at the commercial vehicle space and compare itto the enthusiast space where owners are converting their own vehicles to electrified power. Just like the enthusiasts, there just isn't a single right answer. Vehicles either purpose-built or retrofitted with electric power in either industry are still a Wild West of sorts. From the looks of it, we're going to continue to see both central driver and e-axle motors in the commercial space for a while. At least until the e-axle becomes cheaper, because with companies like Meritor, Allison Transmission, and Dana Incorporated building them, the reliability is already there. Once that cost comes down for manufacturers, expect more of them to switch to e-axles just like the "civilian" manufacturers have done for several years now. Until then, it's going to be fun to watch and see the innovations that develop for both types of electrified solutions.