Author: @Ravi Shah

Description/Purpose

• Document all decisions regarding high-level integration between boards, systems, and enclosures for the 2025 LHRs car

• This page provides a single source of truth for robust, serviceable, and efficient wire harness design through best practices and common considerations

Preliminary Research

Useful Reading

• Motorsports ECU Wiring Harness Construction

• DESIGN AND INTEGRATION OF AN ELECTRICAL SYSTEM FOR A COMBUSTION FORMULA-SAE RACE CAR

• Formula SAE Wiring Harness Design - Symposium

High-Level Considerations

High Voltage, High Current

• Use case: Battery Box and High Voltage Enclosure HV connections, Motor HV connections

• Connectors

  • Amphenol ePower-Lite

  • Battery Box & HVE: ELRA2A03 Receptacle (Bus Bar Type - 2 Pole, EMI and HVIL), ELPA2A16 Plug (16mm^2 wire, 2 Pole, EMI)

  • Motor: ELRA3A03 Receptacle (Bus Bar Type - 3 Pole, EMI and HVIL), ELPA3A16 Plug (16mm^2 wire, 3 Pole, EMI)

• Wires

  • Internal to enclosures - 6 AWG silicon

  • External - 6 AWG shielded

  • All HVHC wires are orange

• HVIL (High Voltage Interlock Loop)

  • HVIL Explained: A Comprehensive Guide to HVIL in EVs - EV Charging Explained

  • Currently not planning to use these pins on Daybreak

  • Will be integrated into BPS/HV system for 2026

High Voltage, Low Current

• Use case: Array HV connections, MPPT enclosure connections

• Connectors

  • Anderson Powerpole PP15-45

  • Panel Mount: LHRs.PP15-45 Custom 3D-printed Panel Mount Housing Pair Red/Black

  • External: Standard PP15-45 Pair Red/Black

• Wires

  • 14 AWG silicon

  • Positive red, negative black

Low Voltage, High Current

• Use case: Supplemental battery/enclosure connections

• Connectors

  • Amass XT60

  • Panel Mount: XT60E-M Panel Mount High Current DC Connector - Male

  • External: XT60H-F High Current DC Connector - Female

• Wires

  • 14 AWG silicon

  • Positive red, negative black

Low Voltage, Low Current

• Use case: General LV connections (12V, 5V, CAN, AUX signals)

• Connectors

  • Molex MX150

  • Panel Mount: 47725-6010 MX150 Panel Mount Male Connector Assembly, Dual Row, 12 Circuits, Keying Option A, Black Housing, Blue Gasket

  • External: 33472-1206 MX150 Mat-Sealed Female Connector Assembly, Dual Row, 12 Circuits, Keying Option A, with Connector Position Assurance, Black

• Wires

  • 20 AWG - each pair should be twisted

  • Fusebox 12V: Positive red, negative black

  • CAN 5V: Positive red, negative black

  • CAN In: High yellow, low green

  • CAN Out: High purple, low white

  • Aux: Case-by-case basis

• Standardized Pin Definition

  • Top row: +5V, CCANH, CCANL, CGND, AUX, +12V

  • Bottom row: +5V, CCANH, CCANL, CGND, AUX, GNDPWR

  • Any unused pins must be sealed with plugs for waterproofing

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Surface Protections

• Braided cable sleeve for all wires (except HVHC?) - need to determine sizing based on gauge & number of wires in bundle

• Heatshrink at ends

• Cable splices

• Connector backshell

  • For MX150 2x6: Connector Accessories Part 349501210 | Molex

Design Process

For Daybreak - each enclosure is a separate sch/harness project, 000 will just be harnessing enclosures together as black boxes.

Environment Setup

SQL Server

Eplan requires a Microsoft SQL server connection to interface its parts library with schematic and harness projects. We currently don’t have a centralized solution for this, so you’ll have to install Microsoft SQL Server Express locally to use Eplan. Follow the steps in this video and you should be good. Make sure you name the database “LHRs” (without quotes). Now you should be able to see the synchronizer icon in Harness proD Library/Studio turn green, indicating that your parts are being stored in the database.

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Every time we make a change to our standardized parts library, the database is backed up and updated on Bild (LHRS ePLAN Library\Projects\ePlan Database Backups\ePlan SQL Database.bak). Please DO NOT edit this file if you haven’t checked with a lead beforehand, this is our standard database so we want to make sure it’s fully accurate. To import the current version of the library into your local database, close all instances of Eplan and open Microsoft SQL Server Management Studio. Right-click on the LHRs database, and navigate to Tasks > Restore > Database. Now select device and choose the location of the backup in Bild. Click OK and your local SQL server will be updated with the Bild backup.

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Parts Library (EPLAN Harness proD Library)

Naming Convention

A 3D model (step) of every part we use is stored in the Parts Library folder in the Eplan project on Bild. You MUST follow this naming convention or your part will be deleted :(

Convention: PartNumber_Manufacturer (Extended Description).stp

Good Examples:

• ELRA2A03_Amphenol (Amphenol ePower-Lite 5.7mm 1x2 Key A Bus Bar Receptacle).stp

• 334721206_Molex (Molex MX150 2x6 Connector Key A Receptacle Housing).stp

• CG4020H12_CoolerGuys (CoolerGuys 4020 (40x40x20) Fan).stp

Any custom components (PCBs, in-house connectors, etc.) should be assigned the manufacturer “LHRs”

Adding Parts to Eplan

common functions/workflow for adding parts (PCBs, connectors, etc)

*all the below stuff is AI cause i didn’t wanna write it - will update when i have time*

Schematics (EPLAN Electric P8)

2D Electrical Design: Creates schematics, circuit diagrams, and control cabinet layouts using standardized symbols and automated connections.

Automated Documentation: Generates bills of materials (BOMs), terminal diagrams, and wire lists directly from schematics.

Cable Integration: Defines cables with precise routing paths and dependencies, transferring data to connection lists to minimize manual errors.

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Workspaces (EPLAN Harness proD Studio)

Functionality:

• 3D Wire Harness Design: Routes cables and bundles in 3D using imported mechanical models (MCAD) and electrical data (ECAD).

• Error Checking: Task lists flag issues like bending-radius violations or missing parts during routing.

• Multi-Variant Support: Manages multiple harness configurations and revisions within a single project.

Usage:

• Import wire lists and 3D geometry from external systems.

• Place components (connectors, clips) and route connections using point-and-click or semi-automatic tools.

• Automatically generate cable units for downstream documentation.

Integration:

• Links to EPLAN Electric P8 for synchronized electrical and mechanical data

Nailboards (EPLAN Harness proD Studio)

Functionality:

• 2D Manufacturing Layouts: Converts 3D harness designs into 2D nailboard diagrams for production, showing wire paths, lengths, and fastener positions.

• Cable Drawings: Details cable assemblies with automatic dimensioning.

Usage:

• Drag-and-drop editing in the nailboard environment adjusts wire routing and labels.

• Layers and properties panels customize views for specific manufacturing stages.

Automation:

• Dimensions and bundle diameters derive from 3D models, ensuring accuracy.

• Revisions track design changes across project cycles.

Stuff you MUST have on a nailboard:

• Ends (component A/B)

• Pins on component A & corresponding pins on component B

• Wire gauge

• Wire color

• Wire function (name)

• Overall wire length (takes twisting into account)

• BOM - part numbers for all connectors, wires, and surface protections used

• Notes

Below is a reference I designed for internal harnessing (e.g. inside an enclosure between boards). It’s in the templates folder on Bild so it can be easily imported and modified for a specific use case.

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Tips & Tricks

Eplan Quirks

• Eplan is kinda finicky when it comes to renaming/moving project files. It’s best to export/backup the project from within Eplan and then import it into a fully new project file with the new name/directory.