Originally Posted by 300ER
What I am getting at, is that there is no checklist or procedure to reduce the overtemperature, a thermal runaway could become a serious problem.
There is obviously some built in safe guard, so I would like to know what it is.
To the best of my knowledge (limited!) most modern batteries have a thermal cutout device built in to protect itself from thermal runaway, so theoretically it shouldn't happen with modern day a/c batteries. So that should be the built in safe guard.
Thermal runaway occurs when there is a high charge rate, heat rises internal resistance goes down, which causes the charge current to go up which causes heat to rise which causes the IR to go down etc etc. The protection from this would be sensed by the battery charger, hence the message BATT Charger on the 744. So the charger will sense the increase charge rate and should cut it off, on the 777 (not sure about the 744) the battery temp is also monitored and should cut out on it's own.
I stand to be corrected but that's how I understand it, sort of!