After investigating the remains i determine that it was an accident on the new guy's part !
Impossible to tell via the tips of the andersons, they are gonners, but the box ends of the powerpoles are still there and i can tell that with male sides facing up on both ends, it would be impossible to make a proper connection, so they were plugged in reverse polarity !!!
I cut the cables back and re-crimped fresh andersons, checked pack voltage at 50.2 volts, good... Then hooked it up to the controller and it powered on as expected, no fireworks this time !!.. and all is still working correctly !
I would have expected the controller to smoke but it did not !!! Phew !