Thanks....I ruled out the "car battery" option for busking eons ago (some buskers use them for their amplifiers). In fact, I tailor my set-up to how much moving about I have to do. Phone + lightweight battery charger + 6 pound amp + backpack for busking supplies + soprano sax is the lightest weight. It goes up from there! tenor sax + large amp + busking bucket + piano (I have two for this, one lightweight and one heavier) + mixer = heaviest.
Everything runs on AA batteries (except, of course, me and the saxophone).
In NYC, I'll not only be setting up and tearing down more than once per day, I'll be taking public transportation and walking. That means lightweight piano (which demands a computer), whichever horn I feel like playing, and the lightweight amp.
As to Ford, I checked out inverters, and they are $400. The van store charges even more for them, and crazy prices for the isolator. I will also need a battery box, etc. I need to figure out where to get this stuff cheaply.