[Andy Brockway]

Originally Posted by Pat Fairbank

We usually pull the wires out of the Anderson connector, use pliers to remove the tab things, and re-crimp, solder, and heat-shrink tube them onto longer and more flexible 4 AWG wire. We never have problems with them after this.

This, and the one above, is the best method. However there are crimping blocks that can be used, just make sure you buy one that can handle two #6 cables. Split bolt connectors such as McMaster Carr #6921K57 is an example. Wrap it well with insulating tape!