Probably that recently published addition by AvHerald tells a bit more about facts and reasons
On Mar 27th 2013 the JTSB released another
interim report in Japanese summarizing, that a "smoking gun" has still not been identified, the investigation so far has not yet led to "elucidation of the underlying cause". The JTSB reported that the puzzle about the navigation strobe lights has been solved however (see sketch below), with both APU and main batteries showing balanced voltages neither relay would be powered with the related switches off, however, with the main battery's voltage
dropping to 1V a current flow from the APU battery via both relays to ground became possible, both relays activated and the wing tip and strobe lights activated despite being switched off. The wire connecting the battery case to ground was broken and showed evidence of having been blown (editorial note: implicitely suggesting prior to the battery event), however, the aircraft had no history of a lightning strike. There is no evidence, that battery charger, bus power control unit, generator control unit or battery diode module did not perform to specifications. Battery cells 1-8, especially 3 and 6, showed extensive internal damage, there is evidence that a large current flow occurred on the output of the battery towards the hot battery bus.
The bold letters is my addition.
Was quoted repeatedly in the other B787 thread, if a lithium battery is discharged to such a level, no re-charging should occur ! Wether it happened in these cases under investigation is not yet clear. But it should also be clear itīs not only the APU battery that is in jeopardy, the ANA case was the main back up battery.
Regardless what those Boeing
PR people release to the public, as long as the real cause is not found the whole set up is not safe. So no release to normal ops should be allowed.