Battery Box Meeting Notes [MSXV]

Aux Battery

• Tested 25-ish cells (approx 60 total)

  • Probs finish testing after CAD deadline for 24

• CAD - need mount (will be late by few)

  • will upload to github EOD

• Cells may need balancing, will add balancing taps

Deliverable: Finish the CAD for the 24th

Enclosure

• Design overall → opening mechanism not optimal

• Will recad with bare min.

  • will host a design sprint with first years (sometime week)

  • optimize for air intake

• Box will rest on the floor of aero

• Shem → working on removal tool

• Manufacturing enclosure will have to wait

  • fireproof resin??

• top, bottom, holder will print (module)

• Ports have been found, need to confirm

  • Same as MSXII

• Wire gauge - ? 2-6 AWG?

  • hw → harnessing tell them (jenna)

  • high current speccing

• It was determined the module holders will be epoxied to the base of the enclosure

  • Reviewed w. Micheal the manufacturing process/considerations

Deliverable: Tuesday get a new timeline for the enclosure + Design review

Board Mounts

• Integration meeting happened, got lots of info for mounts

• AFE almost done, carrier and current sense not

• Ideal for current sense and carrier to be on top of each other

• Saturday → sprint for mounts

• Redesign, two brackets instead of two brackets and top plate

• AFE and carrier the same size

• Improve space for wiring, add standoffs for the mount

PVDR

• Use the MSXVII PVDR as much as possible

• Review Sunday 17th 7PM

Module Testing????

• Manufacturing state → as soon as possible

• Kostubh will draft a testing procedure for the pack to validate

  • Cell testing/validation → completed

  • Manufacturing guideline → test + revise as needed

• Will be there Monday to discuss

Coulomb Counting

• Telemetry moved to low-priority task

  • Discussed with integrations and will try to have all state of charge calculations local on the board itself

  • Driver can manually read out the state of charge via radio

• Looking into different integration methods for calculating SoC on STM32, should have some research by the next integrations meeting on Tuesday

  • Will be compared with IC board that Forest found to see which is more accurate

• currently doing research on viable algorithms and will be checking in with integrations on tuesday on our next steps based on the research

This week:

Apply for passes (HTN): shem, nicole, maggie, vaihbav

Nicole → rch session for first years

Summary: Got bodied but tight deadlines before manufacturing can proceed

Module

• add ribs to the L bracket of the module holder

• Make into one part

• Vertical mounts - make sure there is enough space/strong for heat insert

• Test the module to module connections

• Shift the hole to eliminate divet in plate

Cell Holder

• ABS → look into printing services (Micheal, WatIMake)

Busbars

• Only have sigma clad for module to module connections

  • Nickel to nickel for parallel + series connections

  • Due to spot-welding limitations

• Conduct resistivity test of connections

Module to Enclosure Design

• Hex caps MAY interfere with one another

• M3 may be too weak

• Find hardware to fit

Module to AFE

• Highest temp will be in the center

• Change number of thermistors to 24 → change layout

Manufacturing

• Test material resistivity

• No thermal test

• Need a way to measure ambient temperature (post manufacturing)

  • Strat will need this data

Electrical Connections

• Figure out a way, low prio, copper bar works for now

• Chaos

• New members starting to integrate (assigned to projects on Sat)

Production Module Testing (4.5.3)

• keysight: not feasible too long

• two paralle

possible solutions for worst case:

• ask other people? not done yet

• ask profs

• maybe past documentation

• ask teerstra

• ask lab in waterloo

• talk other design teams

• ask prof for battery challenge

Current assessment of module manufacturing & testing

• all modules to be completely manufactured: dec 8th

• will have to check with testing the first module

• do we have prototype module testing goals?

  • draw for 30min and check temperature

  • asc does not outline anything specific

Prototype module testing:

• depends on what we say

  • will say it was first one made (of the production run)

• documentation needed? no but yes (for future etc)

• keep prototype deadline same on pvdr but aim for end of nov

• continue to test for production

Pack & battery systems validation

• different equipment?

  • either use motor or power resistors

  • have a completed plan before jan 2024 (check-in mid-dec)

Actionables:

• module manufacturing timeline done for 06-11 (will check with donna)

• working on on validation plan - check monday 05-11 and review (check with owen)

• jenna will start prototype testing this week, feasibility test (check-in end of week)

  • just draw current 58.2 A and 3.6V with module

why are baffles being redesigned?

• bc safety wire

• too much wire around the box

• not checked

• will not push to git, keep to safety wire

Design change

• one extra cutout need for molex connector

• air duct been designed?

  • cad changed for fan folders to accommodate for air duct (completed)

  • will be stuck with tape

  • once air duct connector cad done will check with jenna

Machining

• only a few extra inches to the order

• jenna will assign to experienced machining people to get it done

3d prints

• fan holders (problem with heat set)

  • two seem viable from prototype, will be used for module

• Hydrophobic mesh for inlet will look into it now -shem will do

• enclosure feet: petg

  • will might need to modify according to weld bead

  • can we print right now? yes can print, but might need to modify to fit bolts to chassis

  • air baffles and diagonal supports can print right now

Electrical integration

• wires who will buy?

• so far know:

  • can use hardware money (can check confluence page)

  • all connectors for wiring in and out of box

• deliverable: have a list of everything in battery box in electrical that is not module in enclosure (for saturday working session 11-11) will confirm with jonathan/forest

  • fans, connectors, etc

jigs

• crossbar is good

• chassis is good

mdf

• jenna will let nicole know when done to check

welding

• what happens if it sucks?

  • if too small use 1/8 inch board

  • if too big: need to redo or grind down bars

summary of deliverables:
shem:

• list of electrical components/stuff in enclosure (everything but the modules) for 11-11-2023

• assign 3d printing to new members on sat 11-11 (enclosure feet, air baffles & diagonal supports)

• send update about asc email 05-11

• Hydrophobic mesh for inlet 11-11

nicole:

• jigging as soon as everything is done

• machining to be done?

jenna:

• will cut mdf (will be checked by nicole for wed)

• modify aux bat for securing m4 for 10-11

• air duct will confirm with micheal there is 2

• assign machining as soon as gotten

update: email from asc securing method can be done with pack itself

• sealing required for impounding

• can secure another method post-assembly for during race (ie. fishing wire through modules)

Meeting Notes for December 13, 2023 MeetingMeeting Topics
Things we to talk about Wednesday:

• Elec Integration plan for battery next term

• What has to be done?

• Who will be involved?

• When will we be able to get it done?

• Assembly plan

• General overview

• New check-in & project tracking structure

• Trello & Confluence

• Individual project updates

• Avoiding past mistakes

Meeting Notes:Elec Integration plan for battery W2024:What has to be done?

• Competition in July, we dont know where Owen’s gonna be

• Battery pack with everything assembled by end of next term

• Figure out where all electrical components are going to be placed (confirm positioning with Hardware)

• Figure out wire lengths

• LV can be over-speced, HV can’t because insulation is so thick (can’t bend easily)

• Need custom busbars for main battery pack

• ex. end busbar for pack terminals need to be bent backwards, L shaped

• need to build up all the busbars

• Rear busbars can be built now, others can’t because positioning not confirmed.

• Need plates to place PCBs & solar relay & everything else

• Make sure all the modules fit properly, might need changes if things go wrong. Including baffles, fans and all.

• Terminals and solar relays are the same (from MSXII)

Who will be involved for elec integration?

• Hardware: Jonathon, Forest

• Battery: After enclosure is finished do modules, manufacturing spare modules, electrical integration.

• Doesn’t hurt to talk to other teams in the SDC. Sit-down meeting with questions prepared would be useful.

Endgoal of W2024 for elec integration

• Full pack complete with all boards & components connected

• Assuming BMS is complete, check Hardware’s timeline

Module Testing Side Tangent

• One has been tested, Forest says its good

• Placed a thermistor in the middle of module: 10C change (20-30mins run time @ 10Amps)

• Testing plan is there, work with Forest on it next term

• Goal is to make all modules, then test W2024

• Modules with weak busbar potting. Tried reapplying potting onto top cell plate, didn’t turn out well. Didn’t seem to stick.

• Is potting necessary? Just to hold sigmaclad in place. Tight spacing between modules, moving around w/ vehicle moving, good to have potting. Potting will be done after testing.

• Potting cells after testing (potting material poured over welded connections), potting busbars is necessary. We have to figure out how to redo, if top cell plates can’t be reused, might have to rip them out for new ones.

• Potting process is fine, procedure just weren’t followed correctly.

• Owen says we should do internal resistance test on all finished modules (won’t take long, just multimeter to read resistance)

• Will do both individual module test and full pack test for thermals w/ BMS hooked.

Enclosure Assembly Plan

• Nicole has a plan (rough outline)

• Goal is to print baffles and everything using leftover ABS

• Nicole will print

• Owen’s friend can print some things

• Nicole will put together a sheet of who’s printing what

• Vaibhav will update the Enclosure BOM, put everything small and ez to lose in Enclosure Plastic Bag

• Hydrophobic mesh is pricy ($30), hose clamp ($4). Push things we don't need immediately for next term to buy with WEEF/ENGSOC money.

• Finish assembly before start of W2024

• Need to 3d print validation device to ensure boards sit where they’re supposed to sit. Will look like modified version of the baffles. Design in the works. Nicole is working on it.

• Validation for feet onto chassis

New check-in & project tracking structure

• Bring back trello, with projects updated by only core members (and roping new members in if the consistently are coming in).

• Updates should be made as soon as something is done, not just during check-ins.

• Fall term check-ins (Jericho’s perspective)

• Not so bad, because of going directly to ppl working on projects

• Confluence gets convoluted & outdated, Trello is more readable

• Clearer structure of parameters would’ve been helpful. What materials to use, how many parts to use. Stricter idea of what it should’ve been.

• Trello:

• Active updating, journal entry updates

• Confluence:

• Wiki, ctrl c + ctrl v stuff on trello

• Project specific meetings:

• Have specific meetings for each project (elec integration w/ Hardware & module manufacturing)

• Make sure ppl online aren’t in the dark

• Check-Ins

• General overview of what’s going on in the subteam

• Owen runs

• Have something similar to Summer, not just done after work term. We won’t have as much time to dedicate to onboarding. Check-ins were good way to know whats going on and what projects are available. If it’s right after working session, ppl just left cus they were tired after the work session.

• Check-ins ideally done day after a working session

Meeting times:

• Confirm with #mech-battery-box and core

• Not including Monday, Wednesday evening

Winter Onboarding Side Tangent:

• Maybe 5-10 new members peak in the beginning

• Not spend a lot of time on it

• If not a lot of ppl leads/lead in training can assign project to new member

• No module spec’ing or make your own module

Meeting Notes:

• What is the current state of modules?

  • 9 modules manufactured

    • QA: doing series spotwelds first decreases resistance

      • modules were redone to do parallel spotwelds first

  • About thermals

    • Epoxy will increase rigidity of module and won’t have effect on heat transfer as cells are covered on top and bottom anyways

    • About Thermistors

      • Thermistors should be attached with hot glue instead of kapton tape

      • each module can have 3 thermistors, put them on top of module so it is easier to make?

      • busbars are good conductors, MS14 had thermistors only on busbars. Busbars are better for catching any cell that heats up

      • we should put 1 on each busbar and 1 on center cell on negative end (closer to jelly roll)

  • About Voltage taps

    • NOTE there will be a difference b/w sum of voltage taps and pack voltage (through multimeter) because of Vdrop from busbars Vtap position

    • Donna asked about Vtap positions on bottom of module, Micah says they are ok (placement is closer to some cells, but prob only ~1mv dif

  • 1 tested w/ forest

    • quick test (not following testing plan)

    • future tests to use HV testing room’s Chroma

• What do we need to do W24?

  • 9 modules + 5 spare modules manufactured and tested/validated

  • 3 aux batteries

    • Testing: basic capacity test (full cycle + IR)

• Review Module Testing Plan with Micah

  • About IR Test

    • All modules should be at same SOC when testing IR

    • cannot use multimeter because multimeters measure resistance by sending current through the resistance (doesn’t work for battery)

  • About Balance Test

    • wouldn’t do balance test

  • About Full Discharge Test

    • High current testing is most important

    • Do full discharge for max current test

    • when checking temperature, use temperature rise from ambient rather than absolute temperature

  • Extra test: look at voltage of each individual cell

  • When making tests, what can we do if it doesn’t pass?

  • Pack testing

    • First pack test should be as controlled as possible (chroma e-load)

    • take bench outside with pack and array, discharge and watch array charge the pack

    • OR put the whole system together, see vehicle move, watch array charge

Meeting Notes:

2 new members joined - Shem gave them run-down of team and what we do. One is interested in CAD, and one is interested in Module Testing tasks. I am thinking of giving the enclosure feet validation task to the member who wants to do CAD and have the other member shadow over a module-testing task (if that’s not too troublesome), what do you think?

Enclosure assembly:

• Enclosure still awaiting from powder coating

Module Update:

• Vaibhav gave general updates on thermal testing

• Two modules – 1 (37 degrees celcius) and 2 (32 degrees celcius)

• Accounting for ambient temperature, it should not be a concern at all

Integration:

• Jericho finished drawings on .io file

• Labelling connections between them – Yanshen working with a few people + schematics on how to do that

VDR:

• Completed, waiting for review from Carmelli

• Cell fuses

• Teams who get OTS pack use enepaq and orion BMS

• Fire suppressing material

  • GPO-3

  • Polycarbonate

• Module Enclosure made from G10

• TE Sample program

• Monitoring over-voltage, under-voltage, imbalance. How to separate conditions that are unideal for cells vs conditions that are genuinely dangerous?

  • over-voltage & under-voltage can lead to thermal runaway, better to leave car in this situation (genuinely dangerous situation)

• Currently, BMS will fault if cell goes lower than 2.5V. How much wiggle room is there/can we go a little lower than that or is that a hard limit?

  • We’re currently using LGM50 cells, but there is a newer version LGM50T that exists. The datasheet for LGM50T says 2.5V is the minimum guaranteed/recommended good operating voltage, but lower end for safety is 2.0V. Good cell performance cant be guaranteed (might lose capacity) if you go below 2.5V though. Upper end is 4.25V.

• How large of an imbalance should we allow?

  • Mayy be 0.1V-0.2V (need to confirm)

  • But overall, imbalance itself isn’t an issue. Imbalance is an issue insofar as over-voltage and under-voltage is an issue.

• What's the max current we can draw?

  • 52A

  • Max expected from motors is 30A, so we'll do check at 40A

• Safe temperature?

  • 50C for charging, 60C for operating/discharging

  • Shut regen off and solar input after 50C, firmware will need to update for this

• When should fans kick in?

  • Hard to say, but we’ll ideally want to keep below 50C because of the charging upper limit being 50C