Our BWSC 2019 Story
2019 was a year of unexpected twists and stacking challenges for the University of Minnesota Solar Vehicle Project. It was our first time racing the same solar car twice in the Bridgestone World Solar Challenge, which allowed us to put more time into refinement than had we started from scratch, since the base car was a complete and known quantity. Little did we know, however, that no matter what car we used, the challenges of solar racing would always put us to the test.
Six months before BWSC 2019, our executive team chose eighteen students to represent Minnesota in the most prestigious solar car race in the world. This included five electrical team members, three mechanical team members, three strategy members, two array team members, three aerodynamic team members, and two operations members. Many of the students had attended the 2018 American Solar Challenge, two members had attended BWSC previously, several had never raced, and all were ready to face the challenges and successes that waited in the Outback.
It was all hands on deck for the 6 months before BWSC—working on Eos II (E2), test driving, coordinating our fleet of rental cars, planning team logistics for our time in Australia, and through it all, continuing work on Freya I, our next solar car. The BWSC 2019 upgrade schedule for E2 was extensive and demanding, including
● A secondary 19 kWh battery pack located in the trunk, necessary to complete BWSC 2019 in the face of higher average cruiser speed and major limitations on grid charging locations.
● New side impact bars for E2’s doors, dropping their weight while increasing strength to account for the weight of the new battery
● A new vinyl wrap to replace the scarred and scuffed 2-race-old wrap
● An interior update that replaced all fabrics, revamped the color scheme, and added several user interface improvements
● A new charger, per BWSC regs
● Construction and repair of two motors, so we could run two and have a spare
● Inspection of all mechanical and structural systems to ensure total soundness of the car, given its age and distance driven
● Replacement of all loaded fasteners for safety
By the time we rolled E2 into her shipping crate, we had finished the safety checks and fastener replacements, the door bars, interior, vinyl wrap, and were mostly done with the battery, motors, and the charger. There was still plenty to do when we arrived in Australia.
In mid-September, the first group flew themselves to Adelaide and were immediately faced with the first challenge upon landing. Our shipment, containing both the solar car and all of our tools and supplies, was a week late. The team had to adjust plans on the fly; instead of working on the solar car, we bought a few drills and saws to outfit our cargo van with custom shelving and a cooking workbench and our trailer with ramps for the race, while our logistics team worked ahead in their list of tasks. In the end, the work available was no match for the first group, and we spent the last few days before the second group arrived having fun in the city of Adelaide. The shipment narrowly arrived before the weekend and was delivered to our work area in the last seconds of working hours on Friday. Thrilled to see our car and excited to finish our race preparations, the team unloaded both crates in record time. There was still much to do in the week until we hit the road towards Darwin.
The electrical team had the lion’s share of priority tasks, working tirelessly to get the battery finished. We had to install its protection system, which is the system that measures its temperatures and voltage levels and protects the battery cells from damage. It was nearly complete by the end of the week, but we found we were not able to close the lid of the battery box because some of the new connectors were in the way. We ordered special angled connectors that would solve the problem, but they wouldn’t be received until we were in Darwin, so we made the choice to complete the practice driving exclusively on the front battery pack.
We also had to manage shipping issues with our motor controllers, which are a critical device that inverts the direct current voltage from the battery into alternating current for the motor—two brand-new Tritiums, worth more than $10,000, were flown over in a checked bag and lost in transit. Our team was very worried about the loss, which would cripple our stock of spares, but after a few days and many phone calls, the airport was able to track it down and send it to Darwin for us. Close call.
At this point, we had two working motors, one untested spare motor, and all five motor controllers accounted for. We had also finished outfitting our five support vehicles with equipment needed for the race: an air compressor, generator, tools, food, radios, spare parts, and even our lucky countersink. Our lead escort, which also served as strategy vehicle, was outfitted with a roof-mounted weather station, radios, and satellite phone antenna.
The long drive to Darwin began with trailering E2 up to Glendambo to start the testing at a safer location beyond the busy southern section of the Stuart Highway. We stayed the night under the clear starry sky as members got their first taste of what the Outback is like…hot, dry, and dusty.
Everyone was in their vehicles and ready to go early the next morning, with the solar car driver suited up, the scout vehicle already some distance down the highway, and our checklists completed flawlessly. Everything was ready to go. But as our crew captain told the solar car to pull out, we found the car wouldn’t spin its wheels. This led to an unexpected morning spent under a wooden shelter trying to troubleshoot what was wrong with our drivetrain. After many painstaking hours, we finally figured it out: symptoms we thought were configuration errors with the motor controller profiles turned out to be an electrical error that had developed in the motor windings, likely due to a manufacturing flaw. In the end, the electrical team was able to solve the issue and get Eos II driving on her own power by the afternoon.
Since we had lost more than half a day on motor repairs, we decided to trailer up to the next town, the dramatic and fascinating Coober Pedy. We camped that night at an underground camp site and our photographer took beautiful time lapses of the galaxy passing overhead as we worked late into the night on Eos II, making finishing touches and testing the motors. UNSW Sunswift, an Australian cruiser team, camped there alongside us, fostering some pre-race camaraderie as they also worked tirelessly on race preparation. It was great to see we weren’t the only ones with a solar-electric vehicle in the middle of the Outback that week.
Both motors were working by the next morning, and we drove out with the solar car on her own power. We had to make a brief stop to deal with a loose electrical connection, but after a few minutes of trouble-shooting, Eos II rolled out for the first few hours of testing on the Stuart Highway. The driver immediately found that Eos II had become very difficult to handle at speed with the additional weight from the new battery and charger assembly in the trunk. In order to experiment with different solutions, we found a one-kilometer stretch of paved road next to the Coober Pedy airport and drove laps with E2 in various weight and suspension configurations. In the end, we adjusted the suspension preload and moved our charging supplies to the front of the car to rebalance the weight distribution.
After the work in Coober Pedy, we had a day and a half of uneventful testing as we made our way to the border. We then loaded the car into the trailer, adhering to the Northern Territory’s ban of solar car testing on the Stuart, and began the remaining 2 full days of nonstop driving to get us to Darwin. We made it just in time to secure a garage space at the Hidden Valley Race Track instead of one of the overflow tents, finding ourselves neighbors with the Stanford Solar Car Project and the IVE Solar Car team from Hong Kong. Many members took advantage of this unique opportunity to see literally dozens of other solar cars, and made the rounds to chat with other teams, learning quite a bit about how they design and operate.
The electrical team immediately resumed work on the secondary battery pack and car charger. Their hard work started to pay off early—our team was one of the first ones to get our charger tested and working because ours was custom built rather than commercial. When testing it with BWSC’s charging stations, we initially encountered functionality issues, but in part due to ours being custom built, we were able to adjust it on the fly and get it working. Our battery also hit a major stumbling block when the order of special connectors didn’t make it in time, so we were forced to cut indents into the lid of our battery box to allow space for the original connectors.
Static scrutineering began immediately following our electrical successes and we were one of the first teams on the schedule. Many stations went relatively easily since E2 passed scrutineering in BWSC 2017 only two years ago. We finished the first day with greens on all but mechanical and support vehicles. For mechanical, the officials did not like the orientation of a critical bolt and our determined our steering system had too much slop in it. To fix this, we marked the bolt with nail polish so we could see if it had loosened at all and added it to our morning checklist. For the steering, we added shim stock to a joint in the steering column to take out some slop and added secondary protection to avoid dirt getting into the joint. We also needed larger signage on our support vehicles, which we sourced from a local vinyl cutter. Other significant parts of our static scrutineering were:
● E2 weighed 502.7 kg, which is about 1108 lbs
● E2 had a 24 kWh battery pack
● We had one of the quickest egress time (4 seconds)
● Our safety officer, battery officer, and team manager aced the safety quiz
The battery officials sealed our battery packs so that we could not tamper with them after static scrutineering. However, given the lack of testing time with the new battery pack, we knew there was a high chance we would need to open the rear pack again before race. That night, as the mechanical issues were being resolved, we indeed were forced to cut our rear pack seals to troubleshoot some problems. The officials weren’t thrilled, but we had the pack reinspected and resealed soon after.
After the excitement of passing static scrutineering, we immediately started the figure-eight test for dynamic scrutineering, with an interesting twist. As we were about to test, a famous youtuber from the channel “Veritasium”, working on a documentary about BWSC 2019, came over to our team and asked us about the car. One thing led to another and we gave him a ride in E2 as it performed its figure-eight test, which we easily passed after a few trial runs.
We went out to Gunn Point Road the following day to do some long-distance testing with the secondary pack. There were still some issues with the battery that yet again forced us to break the seal on the rear pack. We called the officials about it right away and they told us we needed to bring the pack to the convention center that same day. This was the worst scenario possible because we needed that time to test drive the car on the secondary pack. To still get valuable driving time, we had to pull the secondary pack out of the solar car and drive it back to the convention center to get it resealed while the solar car continued test driving with the front pack. By now the officials were teasing us about tampering with our battery, like taking cells in and out for strategic reasons, which in reality is almost impossible because of how our battery is constructed. We didn’t want our competition to see how big our rear pack was, so carrying the entire exposed battery in front of everybody at the Convention Center was less than ideal.
We continued testing our motors and controllers during the few days of scrutineering, and determined that one of the two functioning motors, which we had been struggling with since Adelaide, was not functional enough to race on, leaving us with one working motor. Our brand-new motor controllers were also refusing to configure, which stymied us for nearly a week before our neighbors, the Stanford Solar Car Project, were able to help us configure them just a few days before the race started. Thank you, Stanford!
In the end, we got everything squared away—batteries sealed, car working with both packs, at least one functioning motor, and good motor controllers. It was all we needed to race.
Dynamic scrutineering took place the day before the start of the race. We started with the “hot lap,” which is each solar car getting a chance to drive as fast as they can around the Hidden Valley Race Track to get their position on the starting grid. Our hot lap unfortunately came out a little more lukewarm than we were hoping, hurt in parts by the additional weight in the back and the use of fresh, cold tires at high pressure. The tires we use are made to have as little rolling resistance as possible, so with the extra weight of the battery and at a higher pressure, our driver said afterwards she was managing rear tire skid on nearly every major corner. Because of that, we did not get a very high starting position, but still passed dynamic scrutineering easily, despite running the brake test at a higher speed than required.
Finally, the event we had all been working so hard for was upon us. We trailered E2 to the starting line and rolled into our starting position with ease. The race challenges began early when just 15 minutes before start time, the car’s one working motor decided to not respond. However, everyone, especially our race crew captain and electrical team, stayed calm and collected as they inspected the wiring configuration. They spotted the problem when there was about 5 minutes left: a faulty connection to the motor controller. The solution was as simple as swapping a cable and just like that, we were ready to go. Other teams were also feeling the pre-race hardship, one of whom frantically asked to use our cordless soldering iron at the ten-minute mark.
After all the strife that went into her preparation, Eos II pulled smoothly across the starting line and started her journey across 3022 km of the Outback desert.
The excitement of day one was like no other. Right out of the gate, there was a bunch of stop lights and traffic that all teams needed to maneuver through. Teams went extra fast to get ahead of the pack and there were many people lining the streets cheering for all the peculiar-looking solar cars driving down their roads. What some people don’t understand is that the main reason cruiser cars want to be ahead of the pack is because overtaking other solar car teams on a two lane highway takes a lot of excess energy, leading you to be stuck behind a slow team for longer than expected, making it so that your car will need to increase target speed for the duration of the stage. In true competition fashion, this is exactly what we had to deal with for much of the race.
Our team’s first problem arose because some of the black vinyl tape we were using to cover the seams of E2’s array panels for aerodynamic purposes started falling off. We pulled over to add extra tape to keep it down, but doing so caused us to get a flat tire from rolling on the jagged rocks on the side of the road. This led to a quick tire change right at the start.
We were able to make it to Katherine easily and were on track to make it to the first stage stop in Tennant Creek. For those who do not know how the cruiser class is staged, each team had two mandatory stops where they had to stay overnight and were allowed to charge at a controlled metering station. This is so that the officials could know how much energy each team was taking from the grid and could factor that into the end score. A cruiser’s score is also decreased for every minute their solar car is late to a stage stop and teams will be scored in order by the furthest stage stop they can drive to without trailering.
Disaster hit us just 150km away from our first stage stop. We were only running on one motor, but still had the non-functional motor installed on the opposite rear wheel because Eos II is designed with the motor integrated into the suspension of the car. Unbeknownst to us, however, some bolts we purchased and installed in Adelaide weeks before were mislabeled and therefore didn’t quite fit their holes. The bolts failed at speed on the highway, opening up the motor and grinding E2 to a stop on the side of the highway. We worked quickly to install a temporary motor stand-in, which is a part designed to fulfill the motor’s suspension requirement, but isn’t hardy enough to run an entire race on.
There was another, more insidious problem working against us as we rushed to fix the motor. The weather was extremely hot—so hot that it was pushing our battery cell operating temperatures close to their rated thermal limits. Lithium-ion cells function in a way that allows them to withstand higher temperatures when the battery current is negative (discharge) than when current is positive (charging). In addition to the cell’s temperature limitations, the battery cooling provided by airflow when our car is driving is greater than we can provide with the built-in fans when the car is stationary. This meant that battery temperature wasn’t an issue when the car was driving, but became an issue when the car was stationary. We were taking in power from the solar arrays with nowhere but the battery for it to go, so without the increased air flow from the car driving and an ambient temperature in the shade of 108 degrees F, we would quickly exceed a safe operating temperature for our battery cells. When thermal or voltage limits are exceeded on the battery then it automatically shuts the car off and isolates itself to protect the battery from risk of damage. This meant the batteries were killing barely after starting up, keeping the car stationary on the side of the road despite several attempted starts.
We finally got the car rolling enough to generate airflow through the battery, only to encounter one of the weirdest obstacles we have ever seen: a stop light just before Tennant Creek that turned red for 6 mins and then turned green for 40 seconds. Our scout team timed the stop light and attempted to coordinate with our solar car driver so that we would pass the light when it turned green. After a very long slow down, we unfortunately missed the light by a few seconds and were not able to start the car fast enough after a full stop, so we had to wait 6 minutes for it to turn green again. The wait did not treat our battery well, and we had to run to the gas station right next to the stop light and buy 3 big bags of ice to set on top of the rear battery pack until the light turned green. We were eventually forced to unplug our arrays until we got close to the stage stop, at which point we plugged them back in and crawled in on array power, as the front pack was dead and the rear was too hot to even power up. Eos 2 entered Tennant Creek two and a half hours late, decreasing our final score by over 70%.
Once in Tennant Creek, we learned that over half of the cruiser cars did not make it under their own power. We were one of only six cars that actually made it, though weren’t the last, as the Chinese Sun Shuttle team drove in about ten minutes after us. It is times like these that really show the brutality of solar car racing, and how difficult it is to make a reliable and efficient car able to make it across the Outback in the time constraint that BWSC enforces. This was day two, and only six of fourteen teams remained with four days to go.
Tennant Creek was a stage stop, so we were allowed to charge from the grid. The officials lined up the cruiser cars and drove in a single file line to the Tennant Creek Power Station. Our team was frantic before the charging period started because we needed a bucket of sand and a shovel with the car while we charged it just in case anything started on fire. The car that drove our battery officer and electrical team to the charging station had a bucket of sand but misplaced their shovel, leading to a big scramble trying to communicate between the power station and our home base to get them a shovel ASAP because the officials wouldn’t allow us to charge. Once we were able to charge, our custom charger wasn’t responding, but after some quick adjustments from our crew chief, we were able to get it working and were able to get a healthy charge in our battery pack that night.
Our mechanical team spent that night resolving the motor issue so we wouldn't have to use the stand-in. The motor failure earlier in the day left the motor electrically and mechanically compromised so, painfully, we gutted the electrical components and made mechanical repairs, leaving us with a mechanically sound component we could use in the car.
We also had to yet again break the seal on our battery pack to do some troubleshooting the next morning. We informed the unsurprised officials, who told us to get it resealed at the Alice Springs control stop.
The next morning, we set out of Tennant Creek into the second stage of the race. Almost immediately in the morning, a solar module peeled up and flew off the front of the solar car from the high winds. Luckily, our array is designed such that a single module failure doesn’t affect the rest of the modules on the array. Once we stopped for the night, we were able to easily put a replacement solar module on. Lesson learned: do not use only silicone to adhere solar cells to your car.
For much of the time, we were set back by being behind slower challenger solar car caravans. Passing them all took a huge toll on our energy efficiency and unfortunately driving at a slower speed wasn’t an option since we had to make the Coober Pedy stage stop at a certain time (unlike the slower challenger teams). By the time we reached Kulgera, our strategy team told us that we were almost certainly not going to be able to make it to the next stage stop in time. We started driving out of Kulgera with the solar car and shortly made the decision to trailer. Our estimates were that we were going to run out of battery more than 100km before we reached Coober Pedy. This was a very tough decision for the team, as if we were given one more hour, we might have made it. It's in times like these where members start looking for the things that went wrong and what we could have done differently. In reality there were many things: the motors, the charging, the batteries, the array, and every slow caravan we had to pass. It all added up. The challenges kept stacking up and E2 just didn’t have it in her.
We also had it in our minds at the time that we would still be scored for the third leg of the race. Because of this, we trailered sooner rather than later so we wouldn't waste any energy that we would have to make up charging and that in return would hurt our efficiency score for stage 3 of the race.
We trailered into Coober Pedy and found out that we were not the only ones; two more of the six remaining teams also trailered, the German team from Bochum and Sun Shuttle. Only 3 teams remained on their own power: Eindhoven, Sophie, and Sunswift. Coober Pedy was yet again a stunning experience. The charging station was right in front of a drive-in movie theater, where our members were able to watch a movie called “Red Dog” and share an Aussie barbecue with other teams and the race officials as Eos II charged to full.
The last leg of the journey went beautifully. The weather was not too hot, the motors worked without any issue, and we didn’t get any flat tires beyond one in the stage stop parking lot. Our media crew even chartered a plane out of Coober Pedy to get aerial footage of the solar car. We drove South to Glendambo, then to Port Augusta, where we camped alongside Bochum and Sun Shuttle. We finished the third leg of the route completely on our own power.
There was some confusion at the finish line as some race officials told our chase car to drive away from the ceremonial finish line, and five of our members weren’t able to cross the finish with the rest of the team. However, the five rushed back just in time to be in the big picture. After jumping in the fountain and celebrating with Bochum, who rolled in ten minutes after us, we rolled Eos II into the “Cruiser Pavilion” and parked next to all the other top cruisers. We had the whole day to spare until the practicality judging, so we took this time to relax and prepare Eos 2 for practicality judging.
Practically judging went smoothly. All the cruisers were put in a grid and told to roll their car on a stage in front of ten judges. The team would give out pamphlets and have three minutes to present their car and five minutes to allow the judges to sit and look closely at all the features of the solar car. We came away with the 5th highest practicality score in the pool, 2nd highest of the six ranked cars. Our car practicality features include:
● A modular battery pack system
● A monocoque shell and metal roll cage for extra safety
● Ease of access to mechanical components (tire changes take less than three minutes)
● An array normalization system that allows the arrays to be flipped up to 90 degrees
● A charger that works with the standardized US electric charging stations
● A center console touchscreen with many different features
○ Fingerprint sensing
○ Bluetooth audio
○ Infotainment center
○ RGB button for hazard lights
● A stereo system
● Cruise control
● Cupholders
Then came the awards ceremony. The BWSC staff did an amazing job creating a video that captured the excitement of the event.
The cruiser rankings were as follows:
Eindhoven, Netherlands
Sunswift, Australia
Sophie, Hong Kong
Bochum, Germany
University of Minnesota, USA
The challenger rankings were:
Agoria, Belgium
Tokai, Japan
University of Michigan, USA
Top Dutch, Netherlands
Kogakuin, Japan
The team spent the night before and night of the awards ceremony taking a well-deserved break, playing games at the campsite and going to bars with the other solar car teams, trading away all our extra race shirts. Spirits were high and we were happy. At this point, we had spent about 40 days in Australia. We spent a few busy days re-packing the shipping crates around celebration time. Many of the students flew straight back to Minnesota after the crates shipped to get back to school work and working on our next car, Freya I. However, others stuck around and gave themselves a well-earned vacation in Australia and New Zealand.
We experienced many challenges over these past weeks—that’s why it is called the World Solar Challenge. Students don’t come into this because it is easy, they come because it is hard. These are some of the brightest engineers the University of Minnesota has to offer. As many successful leaders, entrepreneurs, and engineers have told us: failing early is one of the best things you can do. We might have not gotten the score we hoped for, but we are proud of each other and the work we’ve done. We still proved to the world that we are the number one cruiser class team in America. We will learn from our mistakes and teach them to the next generation of engineers. There will be no stopping our spirit for innovation and dedication to building solar cars. We look forward to making many more stories.
This has been our WSC 2019 story. We hope you enjoyed it. This kind of experience is like no other, and these stories will be told by these 18 students for the rest of their lives. If you’d like to support our team to allow more members to attend BWSC 2021 please consider donating. This journey is possible because of donations that go towards paying for our food, lodging, tools, and materials to build our next solar car. For more information please visit umnsvp.org/donate
Thank you again, now we look towards ASC 2020.