to agree that there isn't a problem where you connect the proper sized wires but the greater question is why are you using an isolator and not a combiner? Isolators a cause voltage drops which can lead to under charged batteries, they generate resistance which equates to heat and they have a predisposition for failure. Combiners don't. Just wondering. There easy to install and you can tell when they fail as well. A proper sized combiner will last for years and you can tie all your batteries together with a push of a button.