Chris Scott:
As I understand it, the likes of RR_NDB are currently trying to work out how, in
principle, the charging might be done in parallel ?.
It's debatable if there would be any advantage, since better methods exist to
ensure that groups of cells in series are charged and balanced correctly. The
disadvantage is that to do it, you would need high current multipole relays
to switch all the cells from series to parallel configuration. As far as I know,
it's never done that way, either in industry, aviation or anywhere else. The cost
and weight penalty would be prohibitive. It would also mean that the battery
would be offline when charging, since the voltage would then be 4v, not the 32v
required.
For the 787 battery, all the cells are hardwired in series, charged and discharged
in series. What we know thus far is:
1) Cells are organised in series, with cell to cell connections via flat metal straps
bolted to the cell terminals. This is standard practice.
2) Cells are charged in series and there's no evidence of a separate charge circuit
per cell. For 8 cells, it would require 9 high current cables from the charger
and there are only two on this battery.
3) It's almost certain that each cell voltage is monitored.
4) It's not clear if there is a temperature sensor per cell, or one sensor for the
complete enclosure.
5) It's also not clear if electronic cell balancing is being done, though there are
probably enough wires to and from the cells to the pcb's, to do this.
Perhaps someone else can add to the above list if there's anything missing ?...
Regards,
Chris