Dual battery setup in van conversion with auto relay isolating battery system

Full manual to cheap DIY installation of auto-isolating dual battery system in my sprinter van conversion setup.

Scheme explanation - https://youtu.be/FWTvoyIrRXo
Items used in this installation:
- 200A relay http://s.click.aliexpress.com/e/mYV7uvb
- Automatic relay http://s.click.aliexpress.com/e/jMJ6u3Z
- 200A fuse/breaker http://s.click.aliexpress.com/e/3faeyfI