To power every low-voltage system on the car reliably, to give the driver the information they need while driving, and to acquire the data every other subteam uses to validate its designs.
Energy comes from the OEM R6 stator through a Shindengen SH847 regulator/rectifier into an EarthX ETX36C LiFePO4 battery, 8 AWG throughout. A MoTeC PDM15 distributes it: 8 x 20 A and 7 x 8 A outputs with current monitoring and limiting on every output, controlled and monitored over CAN, which replaces conventional relays, fuses and control wiring and expands the digital switch inputs available to the ECU and dash. A CarTek PDM-4C handles auxiliary and test loads (telemetry module, onboard cameras) so those no longer need a dedicated battery. All vehicle parameters, acquired and computed, are logged in one place: the MoTeC M150 ECU. The Bosch DDU11 display handles signal conditioning the M150 cannot, then sends results over CAN to be logged. Frequency-critical parameters go over CAN at 1000 Hz, the M150's maximum logging rate. An Analog-to-CAN device adds 8 more inputs per unit for test-specific or non-critical sensors.
Centralise logging. Moving everything into the M150 forced the CAN network to be optimised and introduced a formal per-subteam datalogging parameter request that specifies rate and signal conditioning, which is how CAN bus load stays at 54% instead of drifting. Buy the sensor that is built for the job. CR22 switched fuel and oil pressure from a Honeywell PX3AN2BS100PAAAX to a RaceGrade M APT G2 DTM 150G specifically because the first was never intended for automotive use. 1. Collect the sensor list from every subteam, agree location and type with the designer who needs the data. 2. Split sensors between ECU and dash based on which parameters are engine-critical. 3. Size the charging system and validate it. A custom current measurement board (50 A bidirectional sensing chip, inline on the rectifier-to-PDM wire) measured what the rectifier actually puts back. 4. Build the datalogging parameter list with rates, then check CAN bus load. 5. Validate on a mock endurance: average battery voltage 13.4 V, minimum 12.1 V excluding cranking on CR26I.
- Improve data acquisition for vehicle tuning and model validation without sacrificing data integrity. - Reduce parasitic draw and make the car charge itself over an endurance. - Reduce connector failures. - Keep electronics inside their thermal limits. CR26I measured 187 C in the exhaust bay and 38.5 C in the underseat at the end of a half endurance; the ECU and PDM ran at 72 C and 75 C against limits of 100 C and 120 C for the LTC and IM-4.
- Connector failures. CR20 and CR21 had repeated failures; moving to Deutsch DT/DTM with closed-barrel terminations and weather-sealing boots addressed it. - Parasitic draw and the car not charging itself. CR22's REC+ wire was originally 16 AWG and could not carry enough current over an endurance; rectifier current dropped off at the end of the Kennesaw endurance as the wire heated. Swapping to 12 AWG fixed it, confirmed on a post-Kennesaw mock endurance. - The MoTeC C185 dash was unreliable; CR26I moved to a Bosch DDU11, which is 6.5 in against roughly 5 in and 239 g heavier, but is shared between the IC and EV cars. - Long lead times. BMRSWired orders have run 2 weeks to 3 months; rectifier/regulator connectors have run over 2 months. From the team's PCB Lessons Learned document, the defects that have cost the most debugging time: - Check every ground. An entire board side used as a ground plane still failed because one via had 3.5 Mohm resistance, which took a long time to find while chasing a rail-to-rail op amp outputting 1.4 V as its low. Ground resistance should normally be under an ohm. - Make sure every trace can carry its current. One trace was nearly too narrow for the required 2 amps; online trace width calculators settle it. - Get mechanical input before choosing connectors. One board's connectors made it very difficult to build a sealed box around it. - Keep hand-soldered pads at least 50 mils from vias, because solder creeps down the vias. Do not place pads right next to vias at all. - Leave via annular rings large; 3 mil made it hard to keep solder inside the ring. - Do not place vias under the plastic of a connector that rests on the board, or the connector will not sit flat. - Ground everything. Running a servo's signal and ground through a board while its power came from elsewhere left the servo power and the board power on separate grounds. - Connect mounting holes to ground through a 0 ohm resistor, so the bolts do not act as an antenna but the link can be removed when chasing unexpected results. - Test surface LEDs with about +2 V before soldering to confirm orientation.
Altium Designer and KiCad for PCB work. RapidHarness for harness design. MoTeC M1 Build and M1 Tune for ECU configuration, MoTeC i2 Pro and Display Creator for data and dash. Bosch software for the DDU11. PodiumConnect 4G LTE telemetry.