BST or battery safety terminal. There is a kit to replace it. Sometimes people will replace the whole bat cable up to the firewall. The entire car operates from the smaller wire. The main cable only goes to the Alternator and starter.

You can jump start the car to drive it. It will need a jump every time. You can actually use a jumper cable from the battery in the trunk to the B+ under the hood and jump yourself.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)