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Discussion Starter · #1 ·
I'm wondering how OEM VCUs communicate with their motor controllers and switch electronics during start-up of an EV.

Besides the electrical start-up procedure with contactors and pre-charging, VCUs send a bunch of signals to the controller during the starting sequence (via CAN bus). Some of these signals are OEM-specific, but usually they follow a common logic. I figured out some signals that might be relevant:
  • Key position (off/acc/on/crank)
  • Motor mode (standby/torque/regen)
  • Gear lever position
  • BMS message about precharge activity
The question is how these messages interact with electrical operations and in which order. These are common hardware controls:
  • KL15 +12V starts the controller and CAN bus communication
  • HV interlock
  • Main contactor
  • Precharge circuit (if not included in the controller)

The goal is an open VCU for OEM parts control. I have an example OEM CAN matrix, but don't have any expertise in this field.

I would greatly appreciate any hint with OEM insights. I know that this knowledge is proprietary, but it might improve my/our understanding of OEM parts and increase the number of usable parts from salvage vehicles.
 
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