Right now my house batteries are also my starting batteries... and they are deep cycle RV type group 27 from Costco (They don't carry group 31, which are only slightly larger).

I am thinking of isolating starting from house, and I am wondering if I can use a smaller battery for starting... as it will be dedicated to starting and not be deep cycle. As I understand the setup, the CCA from a starting battery is higher than that from a deep cycle battery.

Any words of wisdom there?

Also what about cross connecting the house with the starter... should there be a failure in one system or the other. Is there a good way to do that?