The 2016 Mercedes C300 Auxiliary battery location is under the cabin air housing. It can take a bit of work to access, but you can do so from inside your vehicle on the front passenger side.
Getting to your 2016 Mercedes C300 auxiliary battery location involves removing the plastic panel beneath your glove compartment, as well as some of the plastic side paneling along the floor near the door, being mindful of the clips holding them in place and the wires plugged into them. You’ll also have to lift back the floor carpet.
You’ll then need to unscrew a second plastic panel—behind which you should find your Mercedes C300 auxiliary battery location.
It only takes about 45 seconds to get started, and the average driver saves over $800 per year on their insurance after making a switch!