As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT AND CREW SMELLED FUMES / ELECTRICAL SMELL IN CABIN DURING ENGINE START. BEFORE PRE TAKE OFF CHECKS, THE BATTERY DISCONNECT AND BUS TIE LIGHTS ILLUMINATED ON THE DASH. ASSESSED THE BATTERY VOLTAGE AND GENERATOR AMPERAGE. EVERYTHING LOOKED FINE BUT THE LIGHTS WOULD NOT EXTINGUISH. MED CREW BEGAN TO SMELL A BURNING SIMILAR TO A HOT BATTERY OR SOMETHING ELECTRICAL.