As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
2 HOURS AFTER TAKEOFF ELECTRICAL ODOR IN COCKPIT. OBSERVED MAIN BATTERY VOLTAGE DROPPING THROUGH 22 VOLTS. WITHIN 10 MINUTES VOLTAGE HAD DROPPED TO 13 VOLTS AND ODOR WAS STRONGER. PULLED MAIN BATTERY CHARGER CIRCUIT BREAKER, VOLTAGE (BATTERY) STOPPED DROPPING AND ODOR DISSIPATED.