300ER

Does anybody know why there is no checklist for a hot battery ( over temperature) on the B777??

Carnage Matey!

Dunno but they don't have one on the 747-400 either so one could presume its not considered a flight safety issue or it comes under the scope of another checklist.

DAL2728

I dunno.. when I have a hot battery I just submerge it in water and does that trick RIGHT quick!

maui

Maybe cos you have no way of monitoring battery temp in the cockpit. (at least none that I have been aware of in the last 6 years).

Maui

spannersatcx

B744 MEL
Message - BATT CHARGER MAIN Level - Status Condition - Main Battery charger failed or input power to charger failed, or interlock open or main battery overheat
No you can't monitor it as such but you will get a Status MSG.

B777 MEL Message MAIN BATTERY OVHT Level Status Basic Main battery over temperature.

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.

False Capture

In the B777, the main battery is monitored and controlled by the Electrical Load Management System (ELMS). If an over-temp is detected ELMS automatiacally disconnects the battery.

From looking at the overhead panel, you can see that there are no controls (apart from turning the battery on/off) for the DC system. Control of the DC system on the B777 is fully automatic.

MrBernoulli

"Control of the DC system on the B777 is fully automatic"

....... and it makes my life SOOOO much simpler. Wonderful.

spannersatcx

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!

cwatters

Best not spray water on a lithium battery fire though.

DAL2728

You don't say?