Consider that there are 2 battery packs in an EV.what do you mean by "main pack"?
"main pack" may be a redundant expression, but i use that for the Main Battery Pack under the car, the Main High Voltage Energy Source for all the HV loads. There is a harness from the pack to the PDM; i suspect that there is a HV Interlock circuit at the connector of the pack into the pdm.
The other battery pack i call the Auxiliary or 12V Starter Battery. It is used for all the Low Voltage loads and power supplies for relays, contactors and ECUs, and to "Start" the car to READY mode. This battery is very important for an EV to operate or charge, and an old, weak or worn out aux battery is frequently the cause of numerous issues for an EV.