Daimler trucks and the need for ground up EV design

Daimler continue to make announcements detailing their electric truck plans, which at first glance look like a great step in the right direction by an incumbent automaker that is seemingly waking up to the threat of the shift to electrification. However, despite a seemingly warm reception to the press releases from many in the industry, I think it is disappointing to see that Daimler seem to be persisting with their plans to electrify existing trucks rather than design them from the ground up.

‘Introducing our innovation fleet’

For the sake of their own future prosperity, I think Daimler need to have a look at their interpretation of the word innovation, as they risk having their own Kodak moment in their commercial vehicle division with this approach. They are the world’s leading commercial vehicle maker by quite a margin. For now.

The extent to which Daimler has a duty to commit their resources more effectively is not dissimilar to VW's duty to redirect investment to put the wrongs of their dieselgate scandal right. The company has the history, the engineering pedigree and the obligation to do much better (let's not go in to recent news about cheat devices in Mercedes cars!) Commercial vehicles are a considerable contributor to CO2 and air quality issues so the opportunity to have an impact is huge.

There is nothing wrong with Mercedes Benz engineers - they are clearly a talented bunch, as they have produced some fine vehicles over the years. That said, what they know is internal combustion, and they are clearly hampered by having to take their orders from a board of directors that seems to be grappling with the reality of the need to scrap a lot of their legacy thinking in favour of remaining competitive in a rapidly evolving industry.

The fundamental truth of the matter is that retrofitting a vehicle that was originally designed for internal combustion to be electric is never going to work. It really doesn’t matter how talented your engineers are - given this as a project brief they will apply their talents to come up with something half-decent, but still far from fit for purpose, and with it too expensive and otherwise compromised to have any chance of competing with purpose built options.

Ryan Popple, CEO of Proterra, a US based electric bus company is better placed to make the argument than I ever could be. Embedded in this article from Electrek is an interview in which Popple explains how his company has the competitive edge over some manufacturers that are attempting to retrofit diesel buses. If you have the time, it’s worth a listen to the whole interview - there is a great deal of very interesting insight from Mr. Popple here, including his reasoning that even for commercial and transit applications, battery electric will win out over hydrogen, but that is a topic for another day. I subscribe to the podcast it comes from (The Energy Gang) and would highly recommend it. It covers a range of topics from electric transport through renewable energy, energy storage etc. Here are a few of the key quotes (from around the 22 minute mark):

‘Some of the things that Proterra got right… number 1 - don’t do a converted electric vehicle. So if you are an OEM and you are trying to take an existing ICE vehicle and you are trying to turn it in to an electric vehicle that’s the wrong answer. That’s like trying to convert a dinosaur into a mammal. Way too many of the subsystems are different. The product is not going to survive the surgery. Don’t Frankenstein an existing product and expect that it’s going to be a good EV. You’re going to end up with a product that’s too heavy, doesn’t have good driving performance and is too expensive, so you won’t be able to offer a compelling price to market’.

‘You have to start from scratch’.

‘You cannot delete the combustion part, drag and drop the electric part and think that’s going to go well… it works but it’s not a product’.

Interestingly, he says that the place where he learned this key lesson was Tesla - Popple was an executive there before joining Proterra as CEO in May 2014 via a role in venture capital with Kleiner Perkins.

So let's dive in to some of the detail here. Daimler’s press release for the eActros discusses some of the specifications and this gives good insight in to the extent to which they are compromising by trying to retrofit an ICE design to be electric. Here is the key paragraph, with my comments in [bold]:

‘The basis for the eActros is provided by the frame of the Actros [that’s not a good start]. Otherwise, however, the vehicle architecture has been configured specifically for an electric drive system, with a high proportion of specific components [high proportion should really read ‘almost all’]. The drive axle, for example, is based on the ZF AVE 130 that has already proved its worth as a low-floor portal axle in hybrid and fuel-cell buses from Mercedes-Benz and is now being fundamentally revised for the eActros [sounds like the definition of bodge]. The axle housing has been completely redesigned and is mounted in a significantly higher position [compromise which is likely to impact driving performance/practicality], thereby increasing the ground clearance to more than 200 mm. The drive system comprises two electric motors located close to the rear-axle wheel hubs. These three-phase asynchronous motors are liquid-cooled [more than they need to be because they are hauling unnecessary additional weight and in turn contributing even more weight from the cooling system] and operate with a nominal voltage of 400 volts. They generate an output of 125 kW each, with maximum torque of 485 Nm each. The gearing ratios convert this into 11 000 Nm each, resulting in driving performance on a par with that of a diesel truck’ [‘on a par’ is a terrible missed opportunity].

This can be illustrated with a look at a comparison between some figures that Daimler have released and the claims made about Tesla’s upcoming semi truck - claims that customers in the Tesla semi test program have confirmed as accurate:

Daimler’s press release states that the 25 ton variant of their eActros will have a 240kwh battery and a 200km (125 miles) range - that’s 1920wh/m. Tesla have stated ‘less than 2000wh/mile for their 80,000 lb (36 ton) version. Do the (admittedly oversimplified) maths to make them comparable weight, and the Daimler effort gives away at least 730wh/mile - that’s a huge difference. This detail alone makes for a very uncompetitive offering as it will always be more expensive to run a less efficient truck.

The single most sensitive component in any fleet operator’s considerations is running cost - there is no hope of Daimler competing with purpose built options where the efficiency is this much worse.