Either completely coincidence having nothing to do with the battery terminal and most likely the problem is in the steering column: ews antenna or ignition switch (or faulty key) else something could be wrong with the BST at the battery.

Next time It fails see if you have voltage at the jump point in the engine bay. If no voltage most likely failure at the BST contact that is somehow opening and closing. If you have voltage at the B+ under the hood the problem almost certainly is key related: switch/ews/key.

Try the other key. If the problem goes away likely bad solder joint on the ews in the key there is a guy will fix for $60

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