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MS15 Brief Review

What went right?

  • Passed all regulations *Reliable

  • Didn’t break down or anything

  • It worked

Note: Reliable as in not breaking down after put into the car or being a source of failure. * asterisk is added because the BMS was not very reliable, and we ought to take some responsibility for not completing earlier so Electrical could have done more testing

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

    • 2 modules had We had an issue with a lot of modules having up to 0.5V -1V imbalance imbalances between parallel groupings and ~6 had 0.2V imbalance between parallel groupings, likely because groups. In the end, we did not test for capacity. At the end, we had maybe 1 module that was suitable to be a back-up replacement, which is a lot of money spent on cells that didn’t go anywhere because we didn’t have the time to make new modules in the endhave 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 extra the most emphasis being placed on DFA and serviceability.

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Constraints & Requirements

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Relevant Components

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Description & Examples

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Safety (Thermal, Electrical, Mechanical)

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  • Thermal management

  • Module

  • Enclosure

  • Cell

...

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.

  • Thermal management

  • Module

    • Enclosure other subteams

    Goal

    Constraints & Requirements

    Safety

    Thermal Safety

    • Batteries should remain within safe operating limits (temperature, capacityNo 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 batteries are safe from damage in crash-scenarios

    • Ensure batteries are safe during expected drive conditions (NVH, raining/wet conditions)

    • Ensure driver safety in crash and thermal runaway scenarios

    • Ensure operator and battery safety during servicing

    Minimize weight

    • Module

    • Enclosure

    • Cell

    • Simplify design and do good material selection

    • Overall MS16 weight 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)

    Minimize power loss/redundant power consumption

    • Everything

    • Minimize power requirement , 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 and , connections' contact resistance, and resistance

    Minimize manufacturing & assembly time (DFM/DFA)

    • Module

    • Enclosurefrom 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.

    • Reduce parts, simplify design

    Minimize cost/stay within budget

    • Everything

    • Wasn’t necessarily a problem with MS15, but based on our cell funding being $2500 this year (the lowest option available, we received $5000 for MS15), it’s important to keep budget in mind. Especially since 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 this year than when MS15 started.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

    		Everything

    Electrical

    • Electrical:

      • Design with hardware & firmware’s constraints & requirements. (ex. new boards? available ICs? PCB budget? )

    • Mechanical

      • Design with overall mech & other mech sub-teams' constraints & requirements in mind. (ex. space claim? CoG?)

    ASC Regulations

    • EverythingHardware 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