787 Batteries and Chargers - Part 1

[RR_NDB]

What we know

Hi,

USMCProbe:

"Too many possiblities"

We may think on EMI/EMC (groundind and shielding, etc.). I agree.

So far we know:

1) Both batteries went to thermal runaway WHEN FULLY CHARGED.
2) Cell overvoltage (IIRC > 4.025 V) may trigger the runaway to the cell.
3) A single cell runway promotes the runaway of the others.
4) The battery terminals didn´t exceed 32V
5) Recorded data (if) was not available after BOS case.
6) Batteries (main and APU) are rarely used (delivering power)
7) Bus spikes are not an issue. The batteries are not (most of time) "electricaly isolated from the bus"
8) The main battery DIODE MODULE failure could explain ANA case. We may expect the investigators checked it. Takes few seconds to test it.
9) Both incidents have in common the batteries.
10) The cells are serially charged. Evident from the pictures showing the connections to the cells.
(i would decide for a safer PARALLEL CHARGER)

So, we need more info.