MS16 Battery Goals & Roadmap

Owned by Shem Kim
Last updated: Dec 10, 2024
4 min read

MS15 Brief Review

What went right?

  • Passed all regulations

  • Didn’t break down or anything

  • It worked

What could have been better?

  • DFA

    • Pack assembly into enclosure was difficult due to interference

    • Baffles being mounted into the enclosure was difficult due to interference

    • Module holders being epoxied into the enclosure floor introduced misalignment

  • Serviceability/Quality-of-Life

    • Module series-to-series connection was difficult to do and undo

    • Modules were difficult to install and remove

    • Hardware mounting on top of batteries made the boards difficult to access for troubleshooting

  • Quality Control

    • We had an issue with a lot of modules having up to 0.5V imbalances between parallel groups. In the end, we did not have enough modules for a pack free of quality issues, which lowered our total pack energy and costed us a lot of time and headache in trying to make replacement modules (which we did not end up having enough time to do).

  • More rigorous testing & analysis + Reliability

    • Due to falling behind on timeline and also some general cluelessness from inexperience, we rushed into manufacturing without having a lot of useful test data. Examples: didn’t have any data or calculations on how cooling will go, didn’t do sims on enclosure mounting into chassis, didn’t have data on actual battery pack capacity going into race, didn’t have any data on if vibrations will be an issue given lack of potting or any significant design considerations there (other than battery box sitting on pool noodles). Fortunately things went okay, but this shouldn’t happen again.

    • Falling behind on timeline also resulted in us not having enough time to properly test our BMS system for reliability.

MS16 Battery Design Constraints & Requirements Overview

For MS16, we will continue with the typical requirements relating to battery design with the most emphasis being placed on safety, serviceability and reliability (meeting timeline so the entire team has time to test). All the other things are important as well and must be met, but those three should be the main focus.

Goal

Constraints & Requirements

Goal

Constraints & Requirements

Safety

Thermal Safety

  • Batteries should remain within safe operating limits (No overtemp, over/under voltage, overcurrent)

  • Ensure all conducting material (current collectors, busbars) will operate within a safe temperature range

  • Mitigate likelihood of thermal run-away and thermal runaway propagation

  • Ensure driver safety in thermal runaway scenario

  • Battery system should be safe from water ingress for raining & wet conditions

  • Accidental shorts should not happen within the system

Mechanical Safety

  • Battery system should not be damaged or lead to driver harm in a crash scenario

  • Battery system should not be damaged from expected NVH (car vibration, sudden bumps)

Electrical Safety

  • Insulate and mark high voltage components to ensure operator safety during assembly and servicing

Efficiency

Weight Reduction

  • Battery system weight should be minimized where possible through good material selection and mechanical design

  • MS16 target goal is 300kg (MS15 was 440kg), battery system should comply to help the car hit the target weight

Minimize Power Loss & Redundant Power Consumption

  • Minimize power needed for cooling

  • Minimize cell internal resistance, connections' contact resistance, and resistance from current collectors & busbars

Performance

  • Battery system should be meet necessary motor voltage and power requirements for cruising, overtaking, uphill driving

Vehicle Reliability

  • Battery manufacturing and assembly should be complete by early Winter 2026 so that testing can be complete by EOT. Spring 2026 is hands-off for mechanical, reserved for drive testing.

  • Entire system should be designed with DFM & DFA to minimize extra work added from hiccups and to meet timeline

Minimize Cost/Stay Within Budget

  • Keep costs down wherever we can (we got 1/2 the budget from WEEF for cells this year compared to MS15, and there are more design teams now than before)

Serviceability/Quality-of-Life

  • Reduce required serviceability time for module replacement and integration with mechanical & electrical systems.

  • Reduce possible instances where catastrophic servicing mistakes can happen. (i.e. situations where you might drop something that can damage aero, situations where you might drop something that can damage hardware boards)

  • Improve hardware accessibility for quick trouble-shooting. Aim for accessibility while operator is outside of the car.

  • Improve ergonomics related with servicing pack & battery hardware (somewhat of a nice-to-have, but keep in mind for design wherever we can)

Constraints & Requirements Relating to Other Sub-Teams

Electrical

  • Hardware constraint

    • Existing ICs may limit certain configurations

    • Certain designs will create a disproportionate amount of work for HW/FW

    • PCB Budget

Mechanical

  • Space claim constraint

  • Centre of gravity constraint

ASC Regulations

  • Will influence some of the above constraints & requirements

  • ASC regulations that don’t have much to do with what’s above:

    • Impounding regs

    • Battery security regs

MS16 Battery Roadmap Overview

Fall 2024

  • Pack configuration, overall layout decided

  • Cell candidates (top 3) chosen

  • Thermal testing & cell testing process outline

  • New member onboarding & getting people established into long term projects

  • Components early ideating

Winter 2025

  • Cell candidate testing

    • Cell testing (IR, capacity, temperature profile)

    • Prototype module testing (temperature profile) IF we happen to end up testing different P counts

    • Finish cell selection and make mass cell purchase

    • Begin mass cell testing if possible

  • Enclosure official design sprint start, finish 90% of design by EOT

  • Module official design sprint start, finish 90% of design by EOT

Summer 2025

  • Finish mass cell testing (early on in the term)

  • Prototyping, finalize enclosure design, begin material purchasing and manufacturing

  • Prototyping, thermal testing, finalize module design, begin material purchasing and mass manufacturing

Fall 2025

  • Finish module mass manufacturing

  • Finish enclosure manufacturing

  • Begin module testing & integration

Winter 2026

  • Finish battery-elec integration

  • Begin and finish characterization of pack

Summer 2026

  • Drive testing finished car