I have been wanting to add a set of jumper cables that attach to the trailer battery on the theory that if I have them I will not need them. The idea is that is that if weather is bad enough or trees dense enough that the solar panels can not bring the battery up, jumper cables from the TV will do the deed. Harbor Freight has a sale on 16' 6 ga jumper cables for $17.99. These appear to be genuinely 6 ga and are very flexible (fine strand wire).
When I wired the Morning star inverter I used some left over 8 ga wire which was very stiff and used Anderson Power Poles for the connections to the battery.
I cut three foot off of the new jumper cables added Power Pole connectors and copper battery lugs salvaged from the previous iteration and a couple of new ones, soldered it all up and I have a much more flexible assembly. The Anderson SB50 connectors are good to 50A.
So why did I not just use the battery posts and a conventional set of jumper cables (I have a set made of 00 welding cable)? The Lifeline battery has bolt terminals and there are a bunch of wires attached including the shunt for the Victron battery monitor, this inside a battery box with the two solar controllers mounted on top so not easy to get to.