Wire size battery solar panel

[Katies-travels]

Hi I’m trying to find what cable size and type do I need for my motorhome solar charger to battery if anyone could help I would really appreciate my panel is 140watt and going into a land star dual solar controller also what inline fuses do I need as it states fusing on negative should I do positive as well ?
many thanks

 

[mitzimad]

6mm is plenty

 

[pappajohn]

I don't understand why the Neg should be fused.
The fuse is to protect the wire and if the live wire should touch earth at any point the fuse should blow.
The Neg wire IS the earth so touching earth anywhere along is length is irrelevant.
A 10a fuse in the POSITIVE wire should suffice as I can't see a 140w panel producing much more than 10a