Using Cyrex with a victron12 12 30 dcdc to enable parallel battery connection

I have a Victron 12 12 30 dcdc charger installed to my two ODX-AGM34 850 batteries. I wish to parallel connect these batteries when i use my winch on my truck to give maximum amps to winch motors.
I have ordered a cyrex 12/24 400 amp and wish to instal this into my system. If i connect this between the two positive terminals of my batteries and wire a switch remotely using the appropriate connection on the cyrex will this parallel connect the batteries when switched with out affecting the dcdc charger? Any links to appropriate wiring diagrams ? Tia Graham