Battery Boil & Water

[BlackHeron]

Test all cables for a bad one under load if you can. Check for voltage at each end. You should see zero voltage drop over each sectionnunder load (or near to zero if you have a good meter.) An extra set of hands to wiggle the wires as another is testing may help pinpoint your issue(s) here.

I suspect you have a bad cable. If there is one bad cable there is a chance they are all poorly-made and suspect. It might be time to remanufacture them all with all new ends.