I've used some self-fusing silicone tape on my heavy battery cable connections. Its a bit expensive, but seems to work very well. It is a soft, stretchy tape, kind of a semi-cured silicone material. You stretch it as you wrap it around the wires and within a day or so, it shrinks tight and fuses to the wires. Kind of like heat shrink tape, but no heat is needed and it is quite temperature reistant.

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