Orion-Tr Smart 12 / 12-30A (360W) DC-D

I want to use it in my motorhome for charging from the car battery to my battery in living area they are at 360A. The charger is 30A, I have 8 meters between carbattery and the battery in living area. 8m plus and8m minus that is 16 meter and it will charge at 30 Amp, I need a cable at 30mm2 and spec for the orion says it can only take up to 16mm2, what will I do? Can I use 16Mm2 cable or do they burn up? Please help me. I have your solarcharger already and I need the bluetooth function.