Here's the one I used:
http://www.rvautoparts.com/ZS-RV-ROO...kaAsH4EALw_wcB
Use an inline fuse (30 amp) between the connector and the positive battery distribution connector (circuit breaker) field side. The negative goes to the chassis ground same as the negative from the batteries. That's it.
The portable solar panels should come equipped with a controller that will regulate the amount of power feeding the batteries based on the amount of discharge.
Look at ZAMP or Renogy portable Solar panels. We bought the Zamp and found them to work perfectly!