in that case i wouldnt bother, just connect the 2 batteries. They then both charge and your winch gets plenty of ummph.
Its worked for me for the past 2 years....and guess what it doesnt cast a fortune and cannot go wrong...unlike split charge.
Well my split charge relay is at least 20 years old !!! They're still less than twenty quid.
Don't be fooled into looking at these so called "intellegent" systems. Nothing intelegent about them and nothing that the other relays wont do.
Why fit two batteries for this job.
One big one would do exactly the same.
Really you only need a split charge set-up if you intend using the auxilary battery when the engine is off. ie Camping and running the fridge and lights.
Which alternator do you have fitted? It will help if you have the 100amp one.