From this:
Boeing readies short-term battery fix, facing uncertainty | Business & Technology | The Seattle Times
The battery control system will have sensors to monitor the temperature and
voltage of each individual cell rather than the battery as a whole, one source said.
...and this:
FAA Says Boeing Needs to Address Battery Risks Before Dreamliners Will Fly Again | Frequent Business Traveler
Boeing also said it plans to develop a new battery design that will measure
the temperature and any voltage changes in individual cells.
Looks like the original design did in fact only have a single temp sensor,
even if they were managing individual cell voltages. Beats me how such a
design ever got past engineering.
I wonder if the group here will be able to send bills for consultancy fees
to Boeing ?
...