What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
During climb-out, the pilot detected a smell like something burning and noticed a wisp of smoke in the cabin. ATC reported that the pilot declared an emergency and returned for landing. The aircraft landed without incident. It was discovered that the right muffler had failed causing exhaust gasses to be directed onto the battery box area. The battery contactor relay and other wiring in the area was damaged as well. It was determined that the end cap of the muffler had failed at the weld and had come completely off.
As the FAA filed it
DURING CLIMB-OUT, THE PILOT DETECTED A SMELL LIKE SOMETHING BURNING AND NOTICED A WISP OF SMOKE IN THE CABIN. ATC REPORTED THAT THE PILOT DECLARED AN EMERGENCY AND RETURNED FOR LANDING. THE AIRCRAFT LANDED WITHOUT INCIDENT. IT WAS DISCOVERED THAT THE RIGHT MUFFLER HAD FAILED CAUSING EXHAUST GASSES TO BE DIRECTED ONTO THE BATTERY BOX AREA. THE BATTERY CONTACTOR RELAY AND OTHER WIRING IN THE AREA WAS DAMAGED AS WELL. IT WAS DETERMINED THAT THE END CAP OF THE MUFFLER HAD FAILED AT THE WELD AND HAD COME COMPLETELY OFF.