The safest way to do this is to make up a little loom.
Run one wire from your battery, through a fuse, down to the "always live" on the 12S. That's pin 4.
Use 2.5mm wire (minimum) with a 20A fuse.
Wire up two relays as follows:
Relay 1:
Input (30): Battery
Trigger (85): Ignition
Earth (85)...