Pfft. I think you are all wrong. THIS is clearly the way to join wires. Note the extra reinforcing structural wire twists for added durability.
Attachment 146007Attachment 146008
I overhauled a dual battery system in someone else's vehicle as a favour a while ago. The main feed to the second battery (in the tray) involved three individual pieces of random, miss-matched (small gauge) wire series-joined together and this little beauty hidden under a few wraps of electrical tape in the engine bay... Owner was really resistant to "wasting" a length of 16mm2 double-insulated wire I had on hand and using "new-fangled" crimp connections and glue-lined heat-shrink for end-connections. Wanted to solder it properly, like he did last time... And reuse the old wire. To this day he reckons I "overkilled" it and what was there was fine and not contributing to his fridge-running issues at all..