Long ago and far away an experienced auto parts clerk once told me to substitute soldered joints for crimped ones wherever possible, whenever I repaired 12v. connections. Crimped joints were invented because they are faster, and in production lines that goes to the bottom line. But in this case faster isn't better.
I bought a mini-torch many years ago, for portability and on-vehicle repairs, and to this day I replace crimps with solder wherever I can in repairs or installations. Using alligator clips as heat sinks on wires keeps insulation from burning. I got one of those Coleman soldering pens too, but discovered they are only practical for circuit boards or 22 guage wire, and small diameter solder, because their amperage is useless for the heat conduction necessary on larger wires; so I can't advise buying one in lieu of a torch. I carry a supply of various shrink-tubing sizes also, to seal solder-repaired wires afterward -the mini-torch does second duty there as well. And the mini-torch heats joints far faster than my workbench soldering iron/gun. It's just not always practical or safe, such as in tight configurations near flammables or around battery banks.
;)Joel