Being a HAM RADIO guy and liking to play with things when OFF-ROAD Camping I found the best solution was to run HD cabling (4AWG in my case) from the battery location to the other end of the trailer storage bay area and mount one of the BLUE SEA 12VDC SUB STATIONS. Mine is properly fused using BLUE SEA fuse block. I also run a good solid 4AWG cable from the 12VDC SUB STATION to frame ground of the trailer close by. All of my primary DC wiring uses ANCOR Brand marine quality cables with proper ring terminals hand crimped in place.
![](http://ecx.images-amazon.com/images/I/31DsG5daFzL._SL500_AA300_.jpg)
This gives six or more ATC fused circuits to use for additional 12VDC items that I need to install. These connections will use #10 ring terminals and you can run 2-conductor 12-14GUAGE "BOAT WIRE" to your 12VDC device you need to power up. Connectors on the device end can be good quality 12VDC Power connectors like you see at Radio Shack or Auto Parts stores
![](http://ecx.images-amazon.com/images/I/31zEQAOqCWL._SX300_.jpg)
Anderson cable connectors makes a great high quality connector for 12VDC items
![](http://images.motorcycle-superstore.com/ProductImages/OG/0000-Ballistic-Quick-Disconnect-Kit---.jpg)
I would think just finding an unknown 12VDC source cable and tapping into is asking for big troubles.
Roy Ken