The G11 generation of BMW 7-Series poses a number of challenges for installing a hardwired dash cam. Like any late-model BMW, a battery pack is highly recommended if parking mode recording is needed. This is to prevent battery discharge warning messages on the dashboard/iDrive. Even if no messages come up on the screen, the dealership will know that there are battery discharge issues when they scan your vehicle upon bringing it in for service. With a battery pack like the Blackvue B-124 Power Magic Ultra, the idea is that it's only charged while the engine is running and there's no drain on the car's battery while parked. This keeps your car battery happy and increases the longevity since it does not suffer from deep cycling/discharge when parked overnight. It'll also extend parking recording times; with the Thinkware F800 Pro 2-channel for example, the camera can run for just over 20 hours on a full charge of the battery pack.
Another challenge with the G11 is that the back seat typically does not fold down so you'll need to disassemble part of the rear bench to run wire into the trunk compartment. We also removed the trunk lining to better access the fuse box and to tuck the wires better. There's plenty of room under the trunk floor to store the battery pack and even an expansion battery if needed. It's also important to note the rear sunshade if you're installing a 2-channel system. We typically install the rear camera off center which gives it just enough room to not come into contact with the rear sunshade in its up position.