FSGP 2019 Summary

Scrutineerings

• Electrical
• Battery Protection
• Lights/Visions 
• Array
• MOV

Pre-FSGP

• Shorted 12 battery modules (2 strings)
• Lights board shorted 3 controller boards
  • The NCP load switch has some weird behaviours under heavy load (> 4A) when a slew rate capacitor is added
  • Had to cut traces and vias on the rev 1.18 board

July 1: Scrutineering Day 1

• Passed array inspection
  • The array characteristics can be found here. The first section is the three array on the front hood connected in series
  • The inspection equipment is unable to characterize a single solar array due to low voltage
  • Need to create a harness to connect three solar arrays in series
• Tritium Motor Controller 
  • Overheating can be fixed powering the internal fans by an external power
  • The PWM mode (low speed) to sine mode (high speed) transition may cause the motor controller to overcurrent and shutdown. The reason is the PWM mode uses the peak current while the sine mode uses RMS current. Change the sine mode to a lower current limit to prevent shutdown.

July 2: Scrutineering Day 2

• Fixing the AFEs
  • The thermistor measurement of one AFE was around two times of the actual measurement. The isoSPI connection is not reliable as well
    • Fixed by bringing up a new AFE board
  • Another AFE was not able to correctly measure the voltage
    • Fixed by retouching all LTC6804 (AFE IC) pins
• Lights/Visions
  • The break light could not stay on at all time. Blink from time to time

July 3: Scrutineering Day 3

• BPS
  • BMS Carrier cannot communicate with the current sensor and the AFEs
  • Replaced the isoSPI interface ICs multiple times but could not fix the problem
  • Used up all back up isoSPI chips
  • The problem was the poor bonding below the QFN footprint
  • Did not have the right harnesses for scrutineering
    • Testing undervoltage on the most negative cell may cause the second most negative cell overvoltage
    • The proper testing procedure involves connecting the floating power supply to the most positive end of a string, not most negative. Otherwise, the ground reference for other cell readings will be shifted. 
    • The harness has to connect to the subsequent cell as well. Other wise the external voltage source is floating
    • Current sensor reset the zero point on boot, thus the external source must be at the zero point when the car starts up
• Charging
  • Did not bring all the equipments to charge the car in the RV park

July 4: Race Day 1

• Charging
  • Did not have the NEMA 6-20P to NEMA 14-50 adapter for charging
  • The wiring was unclear
    
    • Determined to be black → null line (charger pin A), red → fire line (charger pin B), and ground → ground (charger pin D)
• Solar
  • Two MPPTs were not connected to the array. The maximum output voltage of the MPPTs is below the pack voltage

July 5: Race Day 2

• MOV inspection
  • Fully integrated charging system is required for ASC 2020
    • A relay on the IC side is not necessary
• Solar
  • The MPPTs  did not generate sufficient current to charge the battery
  • Checked the connections in the solar enclosure
    • Lack of any detailed documentation of the old solar enclosure
  • The reason might be the maximum MPPT voltage is too close to the pack voltage
  • Cannot open the solar relays via CAN (closed by default)
• Motor Controller Interface
  • Water was dripped on the MCI board and shorted a MOSFET
  • Brought up a new board and fixed the damaged MCI
• Motor
  • The hall effect sensors were damaged by a mechanical problem (air gap closed during testing)
  • Reharness the hall effect sensors

July 6: Race Day 3

• Horn
  • Using the horn and powering the motor fans at the same time may cause shut down the car
• BPS
  • BPS overcurrent when the car is going up hill at turn 1
• Regen
  • The drivers are not familiar with the regen. The car shuts down due to transition from zero regen to full regen in a short period of time
• MCI Controller Board
  • The controller board on the motor control interface is not flashing, and must be replaced with the controller board from the GPS as several extra controller boards are not working. Reason for controller board failure is unknown.