I want to ask Peter, if there a video, PDF, etc I will pay for... It is about how to switch the charging batteries automatically, one feeding the load and the other one charging, and when the charging is done, switch them and the one that was charging will supply the load now, and the one that was supplying the load will be charging now. 
I am sure someone knows about this.

I am sure someone knows about this.
Though it doesn't cover battery swapping, in all seriousness, having purchased it, I heartily and enthusiastically recommend Peter and Aaron's SSG Beginners Handbook. Peter has a real talent for making the complex understandable.
Comment