The improved wall adapter, available in a few weeks, has a thermal fuse to prevent current from flowing to the device if an electrical socket heats up. The NSHTA could not be reached immediately for comment. Tesla did not return a request for more information on incidents related to the adapter. Tesla is also under increased scrutiny for safety following several battery-related fires last year. No one was hurt in the fires, which began in the batteries and happened along freeways near Seattle and Nashville, Tenn. In the Seattle case, the Model S hit a curved truck part. The car hit a trailer hitch in the Tennessee crash. Another fire happened in Mexico after the driver ran through a concrete wall at more than 100 miles per hour. The company and its owner, Elon Musk, have stood by the safety of the vehicles.