I haven't found one but have started making shapes that resemble what I have seen in various airplane diagrams. They don't have things like battery contractors but you can definitely combine existing basic Visio shapes to create new masters.
Your welcome to mine. At the bottom of this page is my actual visio drawings, as well as an html render of them I use when I need info on the road. You will find a lot of templates, and of course a lot of objects and stencils. I have the electrical stencils that I use and custom objects as well. Enjoy.