Afaik, the overall power system in the 787 is a UTX responsibility, with Thales managing the auxiliary power aspects. Thales in turn ordered the batteries from Yuasa, but deleguated the battery management to Meggits Arizona based Securaplane subsidiary, which built the chargers. Some reports are circulating that a defective batch of PC boards made in Mexico made their way into the charge controllers.
How Boeing or the FAA for that matter are ever going to get to the bottom of this daisy chain of buck passing and determine both a probable cause as well as a confidence restoring fix remains
TBD.
My guess is a switch to NiMH batteries, to distance the plane from any taint of 'lithium batteries on board'.
That might mean a grounding stretching well into spring, while the new approach is certified.
Does anyone from the regulatory side have any insights to offer?