Tesla Motors CTO talks future batteries and charging protocols

Image: JB Straubel - Tesla CTO.jpg

Tesla CTO JB Straubel said he's frustrated with aspects of the SAE Combo Connector set. 

Tesla Motors’ energetic Chief Technology Officer JB Straubel literally has had his hands in Tesla’s battery-electric vehicle development since fitting an early AC Propulsion drive into a converted Lotus Elise testbed years ago. As an adjunct to an interview with him in AEI’s 2013 Global Vehicles-North America series (http://www.sae.org/mags/sve/11922/), Straubel elaborates in this Q&A on Tesla’s battery developments, the controversy over global EV charging standards including the SAE “combo connector,” and key learnings from partners Daimler and Toyota.

Is Tesla still wedded to the 18650-form-factor cell? Are you looking beyond it?

For the immediate future we see 18650 as the most compelling. Believe me, we challenge it constantly. It always ends up being very controversial, for reasons I don’t totally understand. Nobody gives a damn about the shape and size of your fuel tank! But for some reason the shape and size of what you put your chemicals in to carry your energy in an EV is super controversial. What people should really debate is what are the nature of the chemicals inside; they’re what determines the cost and performance.

We use a nickel-cobalt-aluminum (LiNiCoAlO2) lithium-ion chemistry for our battery cathode material. We don’t use a titanate, which has about half the energy density but is generally good at high charge rates. Some start-ups are using metal oxides; we fall broadly in that category. At this point we really have heavily customized that cell. We’ve totally custom-engineered that cell working jointly with Panasonic to create. It’s an automotive cell, tested to automotive standards. It doesn’t go into laptops anywhere. What keeps us in that general shape and size is the production and cost efficiency. We’re seeing price points that none of the larger-format cells are able to meet.

The first question we ask when we meet a new cell company is, show us your roadmap and your cost roadmap. Nobody wants to talk about cost—they always leave that to the end of the discussion. That’s silly. For EVs, there are some key safety and performance metrics that are foundational. They have to be there. Beyond that the most important thing is cost efficiency of energy storage. So if anyone has a more cost-efficient cell architecture, we’d be all ears. Right now nobody has proven they have a more cost-effective cell architecture than ours.

Tesla sat on the SAE J1772 charge-connector development committee, then your company introduced its own hardware set, the Tesla Supercharger. Walk me through your decision making for this.

We’ve been working on DC and fast-charge capability for a long time. I feel that’s transformational for EVs. It totally untethers an EV. You can go on trips like a normal car.

There still is no really good standard on this. The SAE committees finalized the new Combo Connector standard, which I’m a little frustrated with because the new combo-standard plug doesn’t have the current-carrying capability of our existing DC plug, in terms of current on the DC pins. I feel that a standard needs to project out at least five, ten years.

What about the communication protocol of the Combo Connector? It’s considered essential for V2G.

That’s fine. We’re definitely commonizing with all of that. The only thing that’s up for debate in all of these standards is the physical geometries of the pins and sockets. Everything else is pretty easy to adapt to. The communication standards are pretty universal. We’re 100% compliant with all the J1772 communication levels, signaling, voltage, everything.

We provide adaptors for all the charging types. The challenge we didn’t want was two plugs. That really left us to differentiate from the physical pin-and-socket combination.

Where do you see global charging standards going?

I’m not an optimist on this. I don’t see it converging. Most of Europe’s totally off in another direction from North America so we’re forced to do something different for our European cars—we’ve got every manner of adaptor, trying to consider 3-phase this and 1-phase that, and what if a car starts in Germany and drives to the U.K.? Japan’s off in a different world with the CHAdeMo standard.

If you were Global EV Charging Czar, how would you solve this problem?

Boy…there isn’t a simple answer for it. I’d try to come up with a solution that doesn’t try to dictate as much of what’s on the car, but dictate a more universal grid-side receptacle and allow flexibility on the car side. Most of the infrastructure has tried to treat EV charging like a gas pump. But so far, on a world-wide scale, that hasn’t worked well. Gas pumps and filling hardware is easy; charging plugs are much more fussy.

China’s putting that "czar" hat on and trying to mandate what everything’s going to be, and it’s still chaos. They still haven’t decided what they want.

What’s your take on inductive charging using a floor mat charger?

It could be very compelling. I’m very optimistic about where that technology will go. Still the cost and efficiency challenges are the ones that stick out the most. There are a lot of start-ups innovating quickly in this space. Inductive could be a great solution for home and maybe business charging. In the near term it will never do supercharging or high power above about 10 kW, but you don’t really need that at home.

How’s it been working with Daimler and Toyota, now Tesla’s long-time partners, in terms of learnings?

It’s been great. They’re very different companies so for me it’s been fascinating to see the different cultures.Toyota's been quite helpful as we ramp up production in terms of operations and supplier quality issues. They’re among the best companies in the world in running a large-scale manufacturing enterprise. They have it down to a science and know what the pitfalls are. They’ve helped us with many different parts of that.

Some of our key learnings from Daimler are in product validation and testing. They bring a lot of rigor and intensity in these areas. They make a really high quality, intensely engineered product. They’re not building at the same volumes and price points as Toyota, so it’s been pretty cool to blend the lessons from those two—while teaching both of them about the electric side.

They’re eager to listen and learn about how we innovate, do software, and solve problems. It’s synergistic. I’d say we’re a little bit ahead of them in how we approach software and electrical engineering.

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