Narrative:

Enroute to jfk at FL380; the first officer mentioned that he smelled some smoke. I also got a whiff of smoke from my seat. We donned our O2 masks as a precaution and the flight engineer ran the appropriate checklist and followed the procedures outlined. At this time; it was just an occasional smell on my side and about the same from the first officer's side. We checked the area to find the source of the occasional odor; which we agreed smelled electrical in nature. [Flight engineer] finally located a stronger odor coming from the main battery area and noticed what appeared to be smoke coming out of louver vents. There was no screwdriver on the plane to remove any panels; but looking through a small opening; he was able to locate what seemed to be the source. [First officer] then checked the same area and reported a good amount of what appeared to be smoke coming from the louvers. The voltage on the battery showed 23 to 24 volts with no amperage. We decided the best option was to head to our coast out etp alternate and closest airport. We were given clearance to make a right turn to return to [the airport]. [Flight engineer] checked the smoke area again and reported the smoke appeared to have stopped. From our crew positions; the smell was still just an occasional whiff; but seemed to be dissipating. Since there did not seem to be any immediate danger or failure; except the battery voltage; we elected not to declare an emergency; since the situation did not warrant it. The rest of the flight was normal. After landing; the mechanic assigned to our aircraft reported that there was a failure of the battery charging system and that it automatically disconnected from the battery.

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Original NASA ASRS Text

Title: A B747 Captain reported electrical smell coming from the battery area on a trans-oceanic flight. The flight diverted to the nearest suitable airport before coasting out where the battery charger was identified as the culprit.

Narrative: Enroute to JFK at FL380; the First Officer mentioned that he smelled some smoke. I also got a whiff of smoke from my seat. We donned our O2 masks as a precaution and the Flight Engineer ran the appropriate checklist and followed the procedures outlined. At this time; it was just an occasional smell on my side and about the same from the First Officer's side. We checked the area to find the source of the occasional odor; which we agreed smelled electrical in nature. [Flight Engineer] finally located a stronger odor coming from the main battery area and noticed what appeared to be smoke coming out of louver vents. There was no screwdriver on the plane to remove any panels; but looking through a small opening; he was able to locate what seemed to be the source. [First Officer] then checked the same area and reported a good amount of what appeared to be smoke coming from the louvers. The voltage on the battery showed 23 to 24 volts with no amperage. We decided the best option was to head to our coast out ETP alternate and closest airport. We were given clearance to make a right turn to return to [the airport]. [Flight Engineer] checked the smoke area again and reported the smoke appeared to have stopped. From our crew positions; the smell was still just an occasional whiff; but seemed to be dissipating. Since there did not seem to be any immediate danger or failure; except the battery voltage; we elected not to declare an emergency; since the situation did not warrant it. The rest of the flight was normal. After landing; the mechanic assigned to our aircraft reported that there was a failure of the battery charging system and that it automatically disconnected from the battery.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.