I charged for the first time at a Tesla supercharger. There were 4 bays, with one car using the first bay, so I opted for the 4th bay. At first, I was getting charge rate of 480 miles/hour. Then as I neared the remaining %, it slowed down to around 15 miles/hour! Is this normal? I've heard that if you park next to another car who is charging at the same time the charge rate is split between the two, but there were two empty bays in between myself and the other car. Also, a few minutes after I starting charging, there were a few knocking noises coming from below the car. I'm guessing it was the battery. Is this normal?