MSXV Power-Up Sequence

Owned by Jonathan Xie
Jul 13, 2023
3 min read

PHASE 1 (initial start-up, before HV pack is engaged):

  1. In order for Main Power Switch relay to be engaged, it needs to receive power and signal from the AUX batt

  2. aux batt needs to first flow through the N.C. rear switch in the back of the car (external E-stop), as well as the front switch (N.O), which is located next to the driver. Closing this switch is 'phase 1' of the power-up sequence

  3. AUX power flows through UV cutoff, which currently has active protection to cut off the power if its voltage is too low

  4. AUX flows into Power Select, which through pure hardware, selects the power source used to power the LV system. The priority is JUMP > DCDC > AUX

  5. during phase 1 (initial start-up), only AUX is available, so Power Distribution will output power from AUX (purpled line on diagram)

  6. BPS will be powered off this purple line, and will check the status of the main pack. If the main pack is okay, then BPS will close the 'BPS Switch' (N.O. relay, powered by purple line)

  7. If all the above conditions are met, then purple line will power and enable the Main Power Switch relay, activating the HV system

PHASE 2 (HV pack is engaged, but car is not fully on yet)

  1. Main pack power flows into DCDC, which creates DCDC LV power

  2. Power Select now identifies DCDC is available, and allows PD to distribute DCDC to power the rest of the LV system

    1. Note that the purple line now becomes DCDC, so BPS and BPS Switch are now powered by DCDC. BPS MUST be powered off DCDC after start-up, but BPS Switch doesn't have to, so maybe we can leave it powered by AUX after start-up?)

    2. Fans, horn, telemetry, will always be powered by AUX (unless aux dies, in which... maybe telemetry & horn need to be taken over by DCDC. See Phase 3 #3)

  3. Centre Console is now powered by DCDC, meaning that its buttons and indicators become active.

  4. Pressing the 'POWER' button on

PHASE 3 (car is fully on)

  1. Motor controllers, MCI, and all other HV and LV systems are enabled.

  2. In the event of a BPS emergency:

    1. BPS will open the BPS Switch, thus cutting the power and signal to the Main Power Switch, thus disabling the HV and DCDC systems

    2. Power Select will now select AUX as the LV power source such that the driver can safely steer to a stop, and the driver + onlookers are notified of the emergency (this require BPS lights, CC, steering, pedal, etc to all still be active and powered off AUX)

    3. Once the car is in a safe place, the driver can disconnect the Front Switch, or someone from outside the car can hit the Back Switch, to fully disable the car

  3. In the event of AUX failing: (which is likely to never happen, because aux batt should last an entire racing segment)

    1. BPS Switch (if we choose to power it off AUX in Phase 2/3) will switch to DCDC as its power source

    2. Horn may have to be powered off DCDC (is it critical to still have horn?)

    3. Telemetry may have to be powered off DCDC (or can the driver just walkie-talkie to the trailing vehicle?)

  4. In the event of both failing:

    1. ?????????

To turn off the car:

  1. Press the POWER Button on CC (with brakes pressed?)

  2. Flick the Front Switch to OFF