Accumulator: a custom-built HV battery for use in an electric racecar to compete in the annual FSAE EV competition
For the last two years, I have been a member of Formula Electric at Berkeley's Accumulator team and helped to successfully design, test, and run our team's first-ever fully rule-compliant battery pack.
This past year I was in charge of designing the accumulator's segments, the seven individual batteries that comprise our overall battery pack. Coming into design, I had three main goals: safety, electrical performance, and ease of assembly.
This past year I was in charge of designing the accumulator's segments, the seven individual batteries that comprise our overall battery pack. Coming into design, I had three main goals: safety, electrical performance, and ease of assembly.
Cell Choice
For our cell choice, we decided to use premade modules, specifically the Enepaq VTC6 1S4P Modules using Sony Murata 18650 cells. Being a 2 year old team, we faced budget and engineering restrictions in designing a full custom pack, and had no experience in spot welding and designing flex PCBs for temp sensing.
Initial Design
CAD Designs
First Version
FEA of Load Bearing Parts
Final Renders
Segment Removal and Inter-Segment Connections
Different iterations and justifications for design throughout a four-month design process
Assembling Segments
First Test Segment
With the design finalized, I manufactured all the necessary parts to assemble our first test segment. While assembling this segment we ran into challenges, specifically establishing a smooth and fast procedure to assemble the segments, and assembling segments with the bulky high-voltage safety gloves and equipment. To help others to safely assemble all seven segments, I made a segment manufacturing guide, that had drawings of every individual component, and the streamlined steps to safely and quickly assemble segments.
Final Pack
Looking Forward
Looking to next year, we have begun development on our first fully custom battery pack, using Molicel 21700s, which will allow us to have much higher peak current draws. I am excited to tackle the new challenges a custom pack will bring, while further refining my existing design for our next iteration.
