Waterloo Formula Electric: Integration and Validation

The Problem

The 2024 low voltage system was the limiting factor on the car. It faulted often, and finding the fault was slow.

• PCBs as old as 2019 still in the car, with features we did not understand
• A harness built from many different connector families and tracked in a spreadsheet
• Boards mounted all around the car in their own enclosures, in places you could not reach
• Very few test points, so debugging usually meant pulling a board out of the car

Example: The Old PDU

• Blade fuses: when one blew you measured every fuse to find it, then swapped it by hand
• The backup battery charging circuit never worked
• A low side shunt put the board ground above the connector ground, a grounding setup we did not like

What Changed for 2025

• Every old board was redesigned from first principles: cut what we did not need and redid every circuit, so every design decision was ours
• The BMU was split into the BMU and the PCU, keeping all the HV in its own area of the Ebox and making isolation requirements much easier to meet
• New enclosures give access to any board in under a minute
• Standardised TE AMPSEAL connectors on all boards, cleaning up the harness significantly
• Harness management moved from a spreadsheet into RapidHarness
• Test points on every trace, so any signal can be probed in place

Boards designed for 2025:

Other projects:

Bench Validation

The goal was rev 1 of every board built and brought up before Christmas, when I would be leaving for my Figure co-op.

• The BMU was tested against a 1:1 bench setup of all its external connections before it went near the pack
• The PDU's thermals were validated up to 30A with a 300W e-load

Using the 2024 Car as a Test Bench

Once the boards were brought up on the bench, I built adaptor harnesses that connected them into the 2024 car's harness before the car got stripped. That let firmware run on a real car with real sensors, so full hardware and firmware integration happened before the 2025 car was even built.

• Every board ran in the old car through the car's original harness and an adaptor harness per board
• Firmware got to the point where the full system ran at HV and spun the wheels with no faults

Results

• First time powering on the 2025 car, it ran for 1 hour with 0 faults thanks to the integration on the 2024 car, and only stopped because the HV battery died
• Passed technical inspection at all 4 competitions we attended
• The first and only autocross time under 40 seconds in Formula Hybrid + Electric history
• 1st of 35 teams at Formula Hybrid + Electric 2025