I have an AC500 with a B300 connected to it. I just purchased a B300K to get extra storage. I connected a T500 to the AC500 to charge all batteries up to 100%. They were only in the 80% range, so I thought I would hook up AC charging, which was around 1650 watts from the Grid. It charged up pretty fast, and about two hours later I went to unplug the plug from the 110-volt outlet in my office, and the cord was really hot. I touched the metal on one of the plugs and it was so hot I had to let it go immediately; too hot to touch. Point is, the T500 coming down a standard 14-gauge wire to a 15Amp plug in most bedroom or office walls in America is way too much and can start a fire or melt the rubber on the wiring in the walls. I would advise all persons using a T500 transformer to make sure they are using a 20Amp plug, because the wiring is bigger on a 20AMP plug (12 gauge versus 15 gauge; the 12 is larger than the 15 in the electrical world). The larger wire is like a larger straw and lets more electricity flow without getting stressed/hot. The longer the charge, the better chance of a fire from over heating. Beware.
I would suspect that you have a worn outlet that you are plugging your charging cable into possibly causing arcing. 1650 watts is around 13.75 amps at 120 volts, close the the limit but a 15 amp circuit should be able to handle this just fine.