FSGP/ASC2014: Pre-Departure, Day 0

Min Ju Lee // // No Comments

What a rough week it’s been. The team had planned on departing to Austin, TX on Thursday morning. But as luck would have it, we blew out our braking system on Zephyr while testing on Wednesday evening.

There were several fatal faults in both the design and implementation of the original brakes. ASC regulation states so that we must have a balanced, co-reactive, dual-braking system, in addition to a parking brake. The braking failure was simple– none of the brakes supplied enough braking power, and eventually blew out our master cylinders. However, the problems were complex– not only did we have to find a way to increase the braking power, we had to redesign and manufacture a system that fit in our incredibly cramped space at the foot of the driver. We faced severe time and design limitations. Since a faulty braking system was capable of causing serious damage to the car and the driver, our only option was to postpone our departure and fix the brakes if we wanted a shot at safely racing Zephyr.

Our members Jake, Sam, Tristan, Chris, and Kyle worked day and night, to design and implement a working braking system by Friday afternoon. It was incredibly stressful and tiring for everyone, especially the aforementioned designer / manufacturers of the new braking system. We bought out relevant components off of every nearby auto parts store we could find; worked in two machine shops for 48 consecutive hours; flew out a member to LA on a very short notice to optimize our modified journey from Berkeley to Texas; cancelled all reservations and made new ones; and many of us even left our full-time industry jobs early and commuted to Berkeley to help.

But as teamwork and resilience would have it, we successfully tested a braking test, stopping 65kmph-Zephyr with 5.1 m/s^2 deceleration. With the new brakes, Zephyr is projected to pass scrutineering, but members will continue to make adjustments to improve the braking performance for safety reasons.

Sam literally lived in the Richmond Field Station from Wednesday to Friday, to help design and manufacture the new brakes.

Sam literally lived in the Richmond Field Station from Wednesday to Friday, to help design and manufacture the new brakes.

Jake and his blackened hands!

Jake and his blackened hands!

As stressful as this week was, in retrospect it was good that we identified the problem prior to the race. This is why there is so much emphasis on testing— often times, it is the well-traveled solar car that will win the SunRayce instead of the flashiest solar car loaded with features. Had we encountered this problem during the race, we would have lost a lot of time to troubleshoot this on the road.

The crew is now on the road to Texas. Wish them safe travels!

Pre-departure photo!

Pre-departure photo!

Independence Day and Celebrating the American Solar Challenge!

Viswanath Chatterjee // // No Comments

With only days until the race, CalSol has been working in overdrive, and the results are showing in the impressive performance of Zephyr. The team is working all hours of the day and night testing the various systems such as the power distribution box contactors, implementing final touches like the dashboard,  and checking off end-stage features such as the regulations-compliant DMV license (Zephyr will be sharing the highways with everyone else during the cross-country race).

On July 4th, teammates gathered at the Richmond Field Station to honor the American tradition of charcoal barbecues and fireworks (heard over the San Francisco Bay), as well as the CalSol tradition of working past midnight wiring bypass diodes, modifying wheel fairing doors, and fixing remaining bugs and issues with the vehicle. In the past few weeks, tremendous progress has been made as the vehicle materialized from its myriad components. New members have made names for themselves through the long hours, experienced members have kept the team on track, and alumni have taken time out of their already busy schedules to help out with their expertise.

The team working on all three of mechanical components, electrical boards and connectors, and controller board code! The bottom shell and chassis is on the left, and the top shell and solar array is on the right.

The team working on all three of mechanical components, electrical boards and connectors, and controller code! The bottom shell and chassis is on the left, and the top shell and solar array is on the right.

It’s likely that this will be the last update before the race, as just the logistics and finishing touches are being figured out now. The team is very happy with Zephyr, and we look forward to meeting our competitors soon!

Electrical Team Making Progress and Giving Thanks!

Viswanath Chatterjee // // No Comments
The Hackerspace has been kept heavily utilized by CalSol lately!

The Hackerspace has been kept heavily utilized by CalSol lately!

The electrical team has been making good headway lately, with new, experienced, and alumni members all working to finish the assembly, testing, and troubleshooting of Zephyr’s electrical system.

The HCI (Human Control Interface) sub-systems are able to communicate among themselves over the CAN bus, which stands for Controller Area Network and allows for communication without a central computer. These sub-systems include the dashboard, accelerator and brake, steering wheel and side panel, and the two motor controller controller (which controls the motor controller, and is dubbed the MC^2). The controllers are working, and the motors are able to spin.

Regarding the solar cells, the solar array is coming together, with the team ready to finish placing the cells. The MPPT’s (Maximum Power Point Trackers, which keep the solar array at an optimal power output by manipulating on the I-V curve) are able to communicate over CAN as well.

Additionally, the two power hubs (which distribute power to the various electrical systems, which need to be kept on lines of separate voltages) are ready, and the BMS (Battery Management System) seems to be operational. All the electrical boards have been soldered, populated with components, and tested. The battery box has been built, and the fuses, connectors, and peripherals are being mounted.

The HCI system, including the LCD readout for the driver

The HCI system, including the LCD readout for the driver

The little nickel strip on the bottom of the module with the hole punched out is used to help measure voltage across the battery banks

The little nickel strip on the bottom of the module with the hole punched out is used to help measure voltage across the battery banks

Careful alignment of the solar array is required, since the indentations on the carbon fiber shell allow for little tolerance

Careful alignment of the solar array is required, since the indentations on the carbon fiber shell allow for little tolerance

We couldn’t have done this without the financial and technical support of our sponsors:

Advanced Circuits, for producing many of Zephyr’s PCB’s!

Bay Area Circuits, also for producing many of Zephyr’s PCB’s!

LEMO, for donating connectors!

Phoenix Contact, also for donating connectors!

Linear Technology, for giving LT boards and chips, providing monetary donations, as well as technical support and guidance!




Thanks for catching up with us, and see you soon!

CalSol PCBs – Thank You, Bay Area Circuits!

Derek Chou // // No Comments

Even as CalSol is working hard for the upcoming American Solar Challenge, we continue to get sponsors for our projects. Bay Area Circuits graciously donated to us the service of fabricating our in-house designed circuit boards, which will make up our dashboard, pedals, motor interface, lights, and battery monitoring systems. Thank you for the boards, Bay Area Circuits! We’ll make good use of them.



Bay Area Circuits


Fairing Success!

Aly Scheske // // No Comments

CalSol has upgraded Zephyr; a feature that no past solar vehicle produced by CalSol since 2005 has had will be debuted at the 2014 FSGP and ASC races. So what is this groundbreaking new feature? Front fairing doors. Masterminded by members of the Chassis and Suspension subteam, the whole team has worked tirelessly to integrate the fairing doors. A lot of thought has gone into the operation, manufacturing, and implementation of the doors. We especially give a shout out to the Shell subteam for being ready to make the incorporation possible. As a team, we all hope to increase the aerodynamic efficiency of Zephyr with the addition of the inner and outer front fairing doors.

So here is the catch- the fairing doors must open up enough so that the solar vehicle can complete a U-turn with a six meter inner turn radius. Thus, the hinge and the fairing door cuts had to be placed carefully to minimize drag and still meet requirements. This takes concerted effort to achieve. Here is a clip of the first turn radius trial-

Since then, we have accomplished our goal of having under a six meter inner turn radius. In fact, the car clears the turn with three feet to spare on both sides! We look forward to putting these doors to good use for the upcoming 2014 American Solar Challenge.

Thanks for your interest in CalSol and keep posted for more updates on Zephyr!

Thank You SunPower!

Min Ju Lee // // No Comments

With the Formula Sun Grand Prix / American Solar Challenge 2014 approaching in just a month, CalSol is in the process of organizing a list of generous friends and company sponsors who made it possible for us to engineer Zephyr and to enter in the SunRayce. In particular, the team decided to give a shout-out to our top three sponsors for this race. This shout-out to SunPower is dear to me because it’s what got me so hooked onto the team and also what led me to become the engineer that I am today.

Team members preparing for solar cell caulking.

Team members preparing for solar cell caulking.


SunPower Corporation is based in San Jose, Calif, and is America’s premier high-efficiency silicon solar cell designer & manufacturer. Almost all competitive teams participating in the American Solar Challenge use SunPower cells because not only are they efficient, they are also incredibly reliable. CalSol has been using SunPower cells dating as early as the late 90s, but we had never established a connection with the company until 2013.

With CalSol encapsulating our own solar cells for the first time this build season, we needed a lot of help. We talked to awesome local and corporate companies such as D2 Solar and Dunmore— the kind engineers from D2 solar and Dunmore gave us many samples to test and generously donated their time to troubleshoot our problems. We learned a lot, but we were far from being able to produce perfectly encapsulated panels.

By half-luck and half-coincidence, I got in contact with SunPower’s senior manager in business development. She is also a Cal grad and was intrigued by our project– and from there, the solar team’s progress took off quickly. We received bare SunPower solar cells, as well as invaluable engineering support from SunPower engineers. It’s been more than a year since SunPower and CalSol has been working closely together– and for over a year, the CalSol members have had the privilege of learning about the solar industry first-hand with the leading solar company in the world. And more importantly, we’ve had so much fun doing engineering.


Chatting up with SunPower's CEO Tom Werner at 2013 All-Hands meeting

Chatting up with SunPower’s CEO Tom Werner at 2013 All-Hands meeting

Impulse, the team, and SunPower's executive officers at the Richmond, Calif. facility.

Impulse, the team, and SunPower’s executive officers at the Richmond, Calif. facility.


Solar cell encapsulation @ the San Jose HQ

Solar cell encapsulation @ the San Jose HQ

The team is recognizing SunPower as one of our top three sponsors for Zephyr / ASC 2014. SunPower has not only provided CalSol with generous in-kind donation, but perhaps more importantly, invaluable engineering and moral support to the team. We know that the people at SunPower are busy individuals, and we cannot thank you enough for taking your time to help us with everything solar-related for Zephyr!


DC/DC Converter – Thanks, Vicor!

Viswanath Chatterjee // // No Comments

It’s been a while since our last blog update, but the intrepid CalSol crew has definitely been busy. Both Zephyr’s mechanical and electrical systems are nearing completion, and with all the work being put into making this our greatest vehicle yet, we’ve got plenty to report with new updates!

We would like to thank Vicor Corporation for their generous donation of the DC/DC converter and its appropriate mounting and connection accessories, as well as the assistance of their applications engineers in selecting the components! But first, what does a DC/DC converter do? (more…)

CalSol Bleeds Carbon Fiber

Brian Graf // // No Comments

The last three weeks has seen a whirlwind of activity from CalSol as dozens of us have pushed even harder than before, toiling away mornings and nights to finish all of our carbon fiber layups. Too many nights have the clocks turned to 1am just to be back at 9am that same day, but we love seeing the massive push of progress. We just entered Spring break and those involved are taking a very well deserved rest for a day – just one – then back to work Monday!

CalSol, unidirectional carbon fiber, carbon fiber, unidirectional, solar car

Zephyr top shell, in our oven, mid-layup with the unidirectional carbon fiber adding stiffness to the structure

Zephyr is being built with a brand new manufacturing method for the team called pre-impregnated carbon fiber and Sam – shell lead – has been the champion of this process. He put in the hours to prep work and designs for the entire rest of the team to help implement. Long rolls of carbon fiber fabric impregnated with thermoset resin is laid out onto our smooth, waxed mold surface. Then CalSol members smooth and stick the fabric to the mold using heat and pressure making sure that there are zero wrinkles or air bubbles in the surface. This process is repeated with a smattering of nomex core, foam, and uni-directional carbon fiber in various areas all to increase the stiffness of the final product. Once satisfied, a release fabric is applied to the carbon fiber, then a cottony breather fabric, and lastly a large vacuum bag encases all of the carbon. Vacuum pumps suck the air out of the bag and press the carbon fiber into our smooth mold. Finally, we close the oven door and bake the carbon fiber to set the resin in place.

Quite a long process right? But now we are proud to say that we have finished all of the layups! We would also like to thank Patz Materials and Technologies for their help in making the pre-impregnated carbon fiber for us

Please enjoy the following photos that outline our thousands of man hours spent over the last 3 weeks.

CalSol, top shell, carbon fiber, solar car, layup

CalSol members having fun while working on the top shell of Zephyr

CalSol, solar car, support ribs, carbon fiber

Support ribs on Zephyr’s top shell to give added stiffness to the solar cells

CalSol, oven, top shell, carbon fiber

This photo was taken at about 1:30am as we pushed to finish the final few crucial steps to preparing the layup to be cooked inside of our oven

CalSol, Zephyr, top shell, pre-preg

We decided to throw a small party while unveiling the final top shell layup. This was our largest pre-preg layup to date and everyone was anxious to see what it would look like!

CalSol, Zephyr, pre-preg

The party was a great success and the top shell came out great! The surface finish is impeccable and the quality of the result is incredibly high.

CalSol, Zephyr, carbon fiber

Just last night we released Zephyr’s bottom shell from its mold and we ecstatic to see that it was just as perfect as the top shell!







Our Beautiful Composites

Brian Graf // // No Comments

CalSol has progressed massively since our last shell team update! At our previous check in we had only finished one of our 8 fiberglass molds, completed zero carbon fiber layups, and we had a long way ahead of us. Now every mold has been finished, brought to a perfect shine, and 2 of the 8 parts of our car have been baked into flawless carbon fiber shells!!! You can’t imagine how happy and excited the team is that the body of our car is coming together!

solar car, sanding, fiberglass molds, shine

The sanding was just getting finished here on our top shell mold

fiberglass mold, bottom shell, solar car, composites

Holly, Jason, Pragaash, and Pol finishing bolting on the supports for our bottom shell fiberglass mold


pre-preg, carbon fiber, layup, composite

Aldrich standing by the pre-preg layup of our canopy for Zephyr

pre-preg, carbon fiber, composite

Our canopy as it came out of the mold, isn’t it beautiful??

pre-preg, carbon fiber, fairing, calsol, layup

Mandy and Sam holding up the rear fairing of Zephyr after some long nights of laying out the carbon fiber





Zephyr Chassis Complete!

Derek Chou // // No Comments
Zephyr Chassis

Zephyr Chassis

We have finally completed Zephyr’s chassis, after a number of long months of design, testing, delays, and welding! Thank you to all of the different companies and people who have helped us throughout the design, verification, and fabrication process:

Garner Heat Treat – Test heat treatment for weld samples & actual chassis heat treatment

Dennis Lee & Michael Neufer – Tube bending, engineering advice, welding verification.

Maxal – Engineering advice and donation of 4943 Filler Rod

80/20 Inc – Donation of 80/20 chassis jig materials

Lotos Technology – Lotos TIG200 Welder – discount pricing

Jimmy Manos – Terminal Manufacturing Co. – Welding advice

UC Berkeley Etcheverry Student Machine Shop – Fabrication equipment and testing.

Tube Service Co. – Laser-cut aluminum tubes

Watch for more updates soon! We are getting lots of work done in these recent weeks.

After heat treatment

After heat treatment