Scenario facts: a piece of stranded copper battery cable about 3.5" long with two soldered connectors at each end, used for ground connection on a motorcycle battery. The cable broke in the middle with what looks like a stress fracture. Cable was flexed many times, every time battery had to be taken out or when battery had to be disconnected for electrical tests or electrical modifications to motorcycle wiring.
Son contends it is the fault of soldering connectors onto cable, which heat stressed the cable. I think it is copper work hardening when flexing cable, thinking that heat if anything (maybe to low) would help anneal copper.
Your opinion welcome. cheers T.Alan