TESLA ENGINEER-BOOSTS EVv>RANGETÖVIEW HEIGHT

JB Straubel is this year's Engineer of the Year^ for his dogged determination to boost theA range of battery-powered electric vehicles

STORY.CHARLES J. MURRAY,

SENIOR TECHNICAL EDITOR, ELECTRONICS

hen Charol Straubel's 14-year-old son was rebuilding an old electricgolf cart in 1989,slie found herself driving the boy from town to town in Wisconsin, sometimes as far asSO miles, in search of batteries, tires and electric motors.

" I tewa-s passionate about it." Straubel recalls. "He wroteto liiefnanuiacturers for informaiion. He worked on it everyday, all day long, all evening long, until he got it to run."

What Straubtl didn't know back then WAS that her .son, "JB"Straubel, would still be on a motor-and-hattery mission 20years later. J B Straubel, now the chicFtechnical officer ofTeslaMotors I nc, is the 2009 Design News Engineer ot the Year,largely because he's as obsessed with electric vehicles today ashe was when he and his mother were crisscrossing Wisconsinin search ofgolicart parts in 1989.

The difference, though, is that the 2009 version of JBStraubel is now applying that same lire and passion to a mis-sion that's meaningful not just to him, but also to the globalauto industry and to the nation, as well.

"It really feels like we're trying to change the world," says JBStraubcl (JB stands for Jeffrey Brian; he prel̂ ers not to punctu-ate it) of hi.s company's task. "There's a real David and Goliathfeel to it."

I f the task of changing the world is daunt-¡ng; however, that hasn't stopped Straubel andhis fellow engineers at Tesla. Before rolling out the prototypeIesla Roadster in 2006, the company's engineering staff settheir sites on an incredibly ambitious 250-mile, battery-onlyrange (or the vehicle, and then came within a hair of meeting it.I he Roadster's final, EPA-verified, 244-mile range was approxi-mately three times that ot the now infamous General MotorsE V1, which hi t the streets a decade earlier.

That stunning achievement not only turned heads amongsLich competitors as General Motors, it.set the stage for theemergence of electric vehicles in a way that hadn't been ex-pected yet by the automotive community. At the time, mostengineers wondered aloud about the range and costs of elec-tric vehicles (EVs). especially since no production cars had yetreached 150 miles, let alone 244.

"It would have been substantially easier to make a car thatwas quick, handled well, and did everything else the Roadsterdoes, but had 150 mJlesof range, ' Straubel says now. "Butholding the bar at the 200-mile level was something that wascritical to changing perceptions about EVs. From the earliestdays, it was something we set out to do."

A Bigger Visioni-or Straubel, however, taking aim at daunting EV goals nowlooks morclike a matter of destiny ttian determination. Sincefinding the rusty, 30-year-old golf cart in an Egg Harbor,Wl, junkyard 20 years ago, Straubel appears to have been ona trajectory that would inevitably land him in the world ofvehicle engineering. While still in junior high school, he builta working hover craft for a science fair. Another time, he com-mandeered his family leaf blower to construct a blow furnace.

COVER STORY

which he used to melt aluminum, although it was never clearwhy a pre-high-school-age boy needed molten aluminum.

"JB was born to be an engineer," Carol Straubel says. "He wasalways passionate about anything that had wheels and requiredengineering."

Not surprisingly, Straubel's college days also neatly posi-tioned him for the world of alternate propulsion. At Stan-ford University's School of Engineering, he created his ownacademic major in energy systems engineering and earned amaster's degree in it.

"It was a great fit For me because it let me follow my pas-sion," Straubel says now. "It's kind ofeerie to see how my ca-reer lias followed what I wanted to do at the time."

Straubel joined lesla at theground-lloor level in 2004 afterstints at Rosen Motors, which built hybrid power trains forcars, and after attempting ro start his own company aimedat creating electric airplanes. Before arriving atTcsla. he also

worked with Stanford colleagues on a solarvehicle racing team and kept in touch withfriends at AC Propulsion, which built an elec-

tric spons car capable of going from 0 10 60 mph in under fourseconds. No matter what Straubel did, electric ptopulsion wasalways at the core.

"1 was talking to anyone and everyone to promote theidea that EVs had turned a corner," Straubel recalls. "Itold them that with new battery technology they could gomuch, much farther than anyone thought was possible. 1wanted to demonstrate my ideas in a working vehicle andbreak a few perceptions."

Through his aerospace connections, Straubel eventuallymet I'ayPal entrepreneur Elon Musk and described his ideas.Musk subsequently invested in Tesla Motors (which was look-ing for an initial round of funding) and brought the29-year-oidStrauhel on board a.s chief technology officer.

"Elon had a much bigger vision for (the company),"Straubel says. "It aligned so well with what I was already doingthat it was impossible not to get excited."

Reality StrikesFor Tesla Motors; however, the transition from a loose groupof Silicon Valley rebels to automobile manufacturer was notan easy one. Suddenly, the company's engineers had to worryabout issues such as manufacturabllit^\ reliability, safety andcost. The idea of building a high-end, high-performance,electrically powered two-scat vehicle now looked more daunt-ing, especially since the new engineering team had almost noexperience in the auto industry.

From the beginning, however, Straubel had no intentionof backing off his primar)'goal, which was to build a car withenough range to change those public perceptions.

DESIGN NEWS SEPTEMBER 2009 Iwww.designnewï.com] 45

"We wanted a 250-mile range," Straubelrecalls. "Thar was rhe number we were gun-ning for from Day One."

Led by Smiubel, rhe engineering teambegan by picking a small form-facror lithium-ion battery cell iike those used in consumerelectronics, hi all/Iesla engineers employedmore than 6,800 of rhe cells, which measure18 mm in diameter by 6>mm long (slightlylarger than a AA battery), in a pack thatweighs about 450 kg (990 lb). By combiningthousands of small cells, rather a few hugeones, the engineering team was able to maxi-mize heat removal because the smaller cellsoffered vasdy more surface area, they say. In awhite paperon the subject, Tesla's engineer-ing team explains that the surface area of the 6,800 batteries is27 square meters ̂ —-about seven times more than if they hadused 20 large batteries. Thar means they have about seven timesmore area for heat transfer ar rhe surface of the cells.

Moreover, Straubel and otherTesIa engineers teamed up tocreate a patented cooling system rhat mitigares the possibilityof thermal runaway— a phenomenon that has been known tohappen, however rarely, in laptops and other consumer elec-tronic products that use lithium-ion. Tesla's cooling systemuses a manifold and cooling rubes ro run a 50/50 mix of warerand glycol through the pack., drawing hear away from the bat-teries. As a result, the possibilit)' of a cell sparking and setting aneighborafire is dramatically diminished.

"As the energydensity of these cells increases, the numberof packaging and cooling problems increases," Straubel says."You're trying ro package a lot more energy into a much tighr-er space and suddenly cool ing becomes a big issue."

Pulling the Right LeversDespite the engineers' best efîorrs on the battery, however.Sträube! and his ream quickly found that they were still fallingfar short ofcheir 250-mile goat. Even with a barteiy pack en-ergy density approaching 200 W-hr/kg, Straubel says, rhe ve-

Team EffortTesia CTO JB Straubel attributes theRoadster's success to a small-team,interdisciplinary approach marked byselflessness. Engineering team mem-bers, he says, had to be able to moveeasily from cooling to crashworthinessand from manufacturability to reliabil-ity. "It's been a stellar team," he says."That's what makes it so much fun."

Key contributors to the Roadster'stechnical success include:

— Jim Dunlay, manager of powerelectronics and battery systems— Dorian West, manager ofRoadster battery development

— Drew Baglino, motor controlsoftware

— Scott Kohn, battery pack design

— Wes Hermann, battery pack design

COVER STORY

hide inirially achieved a range of abour 170 mÍÍe.s. Worse,there was no obvious culprir to blame for the shortfall.

" It's one of rhose classic problems where rhere's not asingle major solution," he says. "It really takes a broad sys-rems-levei viewpoint to understand all the little 'levers' youhave, and to understand that you can pull 10 or 15 smalllevers to get a good outcome in the end."

Indeed,Tesla's team pulled a riiultittideof those"levers" to reach theitgoal. Primary among rhose wasimproving the vehicle's aerodynamics, decreasing itsrolling resistance, changing the brake calipers, adjustingtire pressure and switching from a two-speed toa single-speed gearbox.

For Straubel, the stickiest of those problems was thegearbox. Early on, the engineering team envisioned the

high-performance vehicle as a two-speed,despite the fact that an EV's torque curveenables it to work in a single-speed con-figuration. Over time, the engineeringteam ran in ro difficulties, the biggest onebeing that the vehicle was tar less efficientthan they had expected. Engineers arguedwhether rhe exrra gears, clutches andweight were really a benefit to ihe vehicle.

"We sat around a table and said, 'Look,we'd be better off with a single speedvehicle where we put more focus on in-creased torque and power oui of the mo-tor, rather than relying on this old-worldsolution of complicated gearboxes andmoving mechanical parrs,"" Straubel re-calls. "Tn hindsight, it was absolutely theright thing to do."

The engineering team also squeezxdout a tiny bit more range by employing aso-called a "roll-back seal caliper" in

rhe brakes. The device, which pulls the cal i per aw ay from thedisc when the brakes are released, eliniinates residual dragforces between rhe caliper and disc when rhe brakes aren'tbeing acruared.

Straubel says that the caliper and other small fixes enabledTesla to boost its range toward the 250 mark. EPA tests on adynamometer by a third-part}' vendor verified thai the Road-srer achieved a total range of 244 miles.

"At some level, youVe always hoping to do better, ' Srraubelsays of the fact that their effort fell short of 250. "liur we werehappy to get to 244."

Man on a MissionColleagues say Tesla couldn't have done it without Straubel'squiet leadership. Straubel stayed rhe course on rheirgoal of250 miles and was flexible when the team needed him tobe,they say.

"When a strategy doesn't appear to be working, JB is able tostop on a dime and change rhe company direction," says KurtKelry, director ofenergy storage sysrems for Tesla. "Not only ishe able to change his own direction, he's able ro rally everyonearound him to support the new direction."

Most important of all, Straubels dedication to the EV cause

46 DESIGN NEWS SEPTEMBER 2009 [www.designnews.com]

COVER STORY

seems to be the result of a strongly held set of beliefs. Keitysays he has witnessed StraubePs sense of cause, even outsidethe confines of Tesla. "I've caught him on business tripschanging light bulbs in hotels to CFLs (compact fluorescentlamps)," he says. "He has even bought a box of light bulbs andprovided the box to the hotel manager and shown him howeasy it is to make the change."

"JB is atTesIa because he believes it's the best place to puthis efforts in order to make electric vehicles happen," addsDrew Baglino, senior electrical engineer at Tesla. " He reallydoes think that this is where he can make the most impact on aproblem that the U.S. and the industrialized world have."

Straubcl's efTorts to change perception of EVs are evidentlyworking. After Tesla earned some measure of public successwith its stellar EPA rating, former GM executive Bob Lutzadmitted to changing his mind about electrics. "They have areal shot at success," Lutz told Newsweek magazine in Decem-ber, 2007. "Their Roadster, if and when fully reliable, is anextremely attractive proposition."

To be sure, the road hasn't always been smooth forTesIa,and multiple stumbling blocks still lie in its path. In Novem-ber 2008, Newsweek poiiucá om that Tesla was traversing arocky road after its first 40 Roadsters went out of the factorywith drivetrains that needed to be replaced. The company hasalso been beset by messy firings and legal entanglements, anda few reviewers have complained that the vehicle isn't reach-

ing its 244-mile range. (A WallStreetjournalTeviewsnid thevehicle achieved ranges of approximately 144 and 168 miles.)Moreover, price tags for early Roadsters have passed theS100.000 mark, making it a more logical choice for wealthycelebrities like George Clooney and Matt Datnon than formiddle-class Americans.

Still, reviewers have been generally positive. Car and Driver,IAIMIUIKÍ^A'IMII, •ànàAutomobileMagazwCyAmow^otheTS^

have been enamored with the vehicle, especially its 3.9-secondO-to-60 mph acceleration. It has "smooth with amazingaccel-eration, comfortable seats, and plent)'ofhcadand leg room,"says Design News y c^àcï SiiiTin Koford ofC.incinnati, OH,who owns a Roadster. "No problems so fiir."

Straubel, however, won't be satisfied until he can changemore ofthose public perceptions about EVs. Recently, Teslaannounced it will produce a seven-seat sedan called the ModelS, which wi 11 offer a variety of ranges up to 300 miles, startingat $49,900 in 2011. By going to larger production volumes,Straubel believes he can drive the battery price down toS300/kW-hr, ultimately placing pack cost "in the ballpark" ofS 18,000. That, hesays, would help cut the overall cost of thecar. For now, however, Straubel plans keep pusbing the mile-age envelope. Challenges like those are what keep him going,say those who know him best.

"To find a place to do what he loves is amazing," says CarolStraubel. "And to have it matter to so many is that much better."

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