Air carrier Captain reported a passenger boarded with a carry on bag with a 'batteries' label attached. After further review and consultation with ground personnel the batteries were unloaded prior to gate departure.

Narrative

Just prior to boarding complete; one of our flight attendants assisting in economy noticed two carry-on bags in the overhead bin with 'batteries' labels on the bags. She showed me a picture of the bags and expressed concern as to their contents. I had her inquire with the customer as to the contents of the bag and was informed they were Lithium Ion spare batteries. The customer in Seat XX volunteered to have the flight attendant bring one of the bags to the flight deck for us to review the batteries; which she did. Upon opening the bag; we found four Lithium Ion loose batteries rated for 211Wh each. The first officer and I both reviewed FOM and determined that the batteries exceeded the 100Wh limit and 160Wh limit for PEMD outlined in the FOM. I contacted the Chief Pilot to confirm the limit was applicable and make sure there was not an alternative way to carry the batteries. The Chief Pilot consulted with company Dangerous Goods team and confirmed the batteries were not allowed. I requested a CS (customer service) supervisor at the aircraft via operations radio call and a request in the app (I incorrectly stated in the app that it was a checked bag) to find a resolution for the customer. My radio and request for CS supervisor were at XA18. At XA28 I walked up the jetbridge to check on status of supervisor arriving and found the gate agent with a CS lead present at the gate counter. I tried explaining the situation with the lead but kept getting strange follow up questions and no indication the lead wanted to go down to the aircraft to assist the customer with a resolution. After several minutes of discussion; another lead walked up. The original lead explained that it was XA30 and he was scheduled to be off and was happy the new lead had arrived so he could leave.I explained the situation to the new CS lead and reviewed the FOM battery limit reference with him. He immediately went down to the aircraft and was able to resolve the issue. The customer elected to continue on the flight and the CS lead took possession of both bags for the customer to have someone pick up at baggage services. Our flight attendant later told me that the customer attempted to hide the second bag of batteries when the CS lead walked to the back of the aircraft to address the issue. The customer also claimed they had traveled with the batteries as carry-on baggage before with no issues.Upon closing the main cabin door; we had to wait an additional ten minutes for a wing walker to arrive for pushback adding even more delay to our flight. A ramp supervisor approached the aircraft twice with a golf cart and conversed with our crew; but did not assist with wing walking for the pushback.We were given a wheels up time which delayed us an additional 20 minutes. However; we did not receive the wheels up time until we were turning onto taxiway for XXR with no aircraft ahead of us and the delayed engine start already accomplished.