[LetsrollM550]

Is the 12 volt power in the trunk always on, or does it turn off like accessory mode when the car sleeps? How long does it take to actually go sleep? 2018 M550i, this is my first BMW still trying to get up to speed, car stereo shop today started to add a audio control lc2i and a alpine amp to drive new SWS subs to replace the pathetic HK subs, but they couldn't get the amp and lc2i to power up with speaker level inputs, when he ran a trigger wire to the rear 12 volt power everything worked, but amp would not power down as the key was in the car and it wouldn't go into sleep mode. Thanks, and yes I need a new stereo shop!

[TreyWaters]

The trunk power outlet will power down once the car powers down (ie., when you lock the car), and then powers up when the car powers up (or, when you unlock the car).

[DBO]

If you want constant power from the trunk it couldn't be easier - just take a line from the main battery (fused of course). If you need switched ACC power then that's also available in the fuse panel in the trunk.