I'm with skl, although I'd lean towards it being used only as a current shunt.
Hard to believe it was destroyed like that! The virtue of this style of current shunt is that it has a very low resistance which dissipates very little power. As a rough estimate, I would think that it would take 100A (or more) to destroy wire that large.
It's not uncommon to install some sort of circuitry to protect against a battery connected with the wrong polarity. Your device either had a poorly designed protection circuit that couldn't protect the shunt, or perhaps it lacked a protection circuit and other parts are damaged too. You might want to check other components in the area too, even if they don't exhibit external signs of damage.