Depends on where you connect stuff. Directly to some wiring loom that is already there? Bad idea, not all connected equipment will take the aditional loads well

Depends on where you connect stuff. Directly to some wiring loom that is already there? Bad idea, not all connected equipment will take the aditional loads well. Going directly to the car battery with dedicated wiring? Doable, but since start-stop is a thing, battery management and other stuff migjt not like that very well neither. Second batery? A bitch since start-stopp. Hence, one needs some good knowledge around that, what to connect where. In the old days, well, just go directly to the main battery with your aftermarket wiring and Bob's your uncle. And none of that, battery management, which equipment can be connected where, has anything to do with the voltage but rather with all the other stuff modern cars have (bus management, battery management, ECus,...) all of which might or might not accept voltage and amp fluctuations very well.