[QUOTE][We who inhabit this small, damp island have to re-read it several times to confirm that it doesn't mention politicians' misdemeanours, football or breasts in the narrative./QUOTE]
If you said "she's got a magnificent pair of batteries"..you couldn't volt her.
.....sorry, couldn't resist, I blame Slasher's influence.
BACK TO BATTERIES!
@syseng...The diagram you post is very enlightening.What really jumps out at me, is the fact that this battery-pack would appear to be connected straight onto a "dirty" bus via a contactor....No filtering,no diode-protection, so the charging/monitoring circuits are in parallel woth the battery......no series protection whatsoever to protect the cells against transients ,or ,indeed, exccessive voltage on the bus....Unless i'm really thick and missing something blindingly obvious, that there's the elephant in the room.
@ Turin, yes, I understand that the electronics battery cannot be used to start the APU...but unless the RAT is defective as well (in which case "we're all doomed Captain" ) it should deploy and be producing well before the "safe " discharge level is reached on either battery.
I would think that, if the emergency was that dire that ALL power supplies were gone except a glorified car-battery (OK, a
very expensive 75Ah bespoke battery) draining that extra tiny bit of power isn't going to materially alter things....in that situation, a big red switch/button to hook the APU battery to the Avionics bus may be a better last-ditch measure...(with diode/electronic protection to prevent back-feeding if the APU battery is already frazzled.)...so, what happens if the "main" battery self-destructs before/when/during , its call to duty in this "Gimli Glider"that has 4 discrete inop generating systems simultaneously?
Agreed the monitoring wires look tight and I don't buy the Vibration theory. they appear to be standard eyelet crimps and I'd have expected a decent piece of shrink-sleeve over the end support -crimp,extending a cm.or so out along the wire insulation...can't make out if the actual core is crimped or solderedbut i'd really like to see a soldered/spot-welded connection to the busbars,instead of a scabby little self-tapper.
still not impressed after reading all these posts by real engineers who really appear to understand this subject far better than me.
Thank you all, it's a fascinating subject.