We picked up our 2016 Model S 90D on March 31, 2016. In April we took a trip from Pittsburgh, PA to Atlanta, Ga and back using the Tesla superchargers. The trip and car were great. Around late summer we started to notice charging was taking longer and the the charging rate was significantly less than we had been experiencing. This got worse as the weather got colder. We got lots of "advice" on cold weather charging but having a degrees in Physics and Engineering I had serious doubts about the "advice" so I started logging remaining range mileage at the start of charging, start time and date, voltage, amps (old display data) temperature, charging station, # cars charging etc. Nothing seemed to supported the "advice" I was getting about charging strategies. After several emails and phone calls with Tesla support over the winter (Nov 2016 - Feb 2017) Tesla engineering finally said I had a bad battery coolant pump. After the replacement pump was installed the charging rate and times improved somewhat but were still significantly less than our initial experience. So I continued with my data collection and discussions until Tesla engineering finally figured out I had a bad fuse block. After the fuse block was replaced the charge rates and times improved dramatically!!! So here is my advice if you are experiencing reduced charging rates and longer charging times. Start a log like I did and bug the hell out of Tesla support until their engineers actually look at your car's data. My guess is you have one or more of the issues I had and it seems you do need to be a rocket scientist or at least an engineer to get Tesla to really look at the issue and not just feed you the company standard line.