Flexible solar controller cables?

I added a 1500 watt MSW inverter to a previously owned Class C MH. I ordered a single large (black) cable with lugs (don't remember the gauge, but it was at least thumb size). I cut it in half, bared the ends, attached the bare ends to battery clamps, then to one of the batteries. I put red tape on the ends of the + cable.
I believe the same could be done for solar controller to battery.

one of the reasons solar panel cable is stiffer than some other wire is the insulation is rated to be exposed to the sun and not break down it also has better abrasion resistance than some other wire.

you could use a terminal strip next to the solar controller to connect thicker cables from the battery and then a shorter pieces of thinner wire from the terminal strip to the controller that fit its terminals.
doing so will keep the voltage drop to the batteries to a minimum it depends on how far your batteries are from the solar controller.

WindyNation 10 gauge from each of my three panels to the combiner box, 8 gauge from the box to the controller and 6 gauge from the controller to the battery.

This place should be able to help.

You want welding cable, maybe #6. My system is 48v so I'm only 15 amps.

you're welcome

use wire ferrules to go to the right size for your victron.

Use this website to calculate the wire size you need:

https://www.omnicalculator.com/physics/dc-wire-size