... since a have a 4pin connector could I run a heavy gage cable from an isolater to the battery?
I believe that adding battery charging to a system with only a 4-pin lighting
connection calls for two
new wires: the +12V charging wire, and an upgraded or replaced negative (or "ground") wire... the existing wiring contains a "ground" (usually white) wire and connection which is heavy enough for the lights
, but not the battery charging current as well.
Does any one know of a heavy connector for one wire?
There are a number of connection options for two
(see above) conductors, but I think a better plan is to go to a common 7-pin RV-style connection. The connectors and cable are readily available and reasonably priced.
See [b]82' 16ft Scamp battery wiring, three wire plug for onboard battery
for a current discussion of essentially the same issue.