As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TOP OF CLIMB, CREW NOTICED AIRCRAFT BATTERIES NR 1 & 2 INDICATING LOW VOLTS. THEY WERE INSTRUCTED BY MAINTENANCE CONTROL TO RETURN SINCE THEY WERE 45 MINUTES OUT. ACFT RETURNED WITHOUT FURTHER INCIDENT. MAINTENANCE REMOVED AND REPLACED BOTH NR 1 & 2 AIRCRAFT BATTERIES AND BATTERY CHARGER PER MD11 AMM 24-34-02 AND 24-34-03. PERFORMED RTS AND OP CHECK, CHECKED GOOD.