The generator/battery and panel manufacturer(s) - or the local distributors of such components in your area - should have connector options available to go from the exterior to the interior...

Generally speaking, it is a BAD idea to use a hole for temporary cable runs between the exterior & the interior. Most likely, too, it's going to violate at least a code or two...

To answer your original question, though: Yes, absolutely, you can drill a hole through that door in that area...

Bear in mind that you'll most likely be penetrating a very thin steel skin, passing through a foam core, and then encountering another very thin steel skin. Use a sharp bit, NOT elbow grease, or else you'll also be smoothing some sheet metal as well. AND make sure that you drill the correct hole size for the proper CONNECTOR that you'll be using, instead!