I'm hesitant to put all the blame on your crimping or reattachment of the red wire to ammeter.
If that was the case, then the terminal through the bulkhead shouldn't have failed.
Other than charging, normally there's not a lot of current in that line. But if there are other problems, then that changes. That's why I asked if you noticed what the ammeter was showing before and/or during this meltdown.
