What sort of systems are used to cool batteries in the air? Liquid cooled? Air cooled?
I am interested in lithium chemistry batteries in the form of either pouch cells or 18650 batteries inside of boxes placed in the fuselage or wing.
As far as I can tell, current aviation lithium batteries do not use active cooling.
I haven't seen any easily accessible info on the Saft batteries for the A350.
From this presentation for the A320 family:
Achieved by ambient air being drawn around the batteries and then vented directly outboard via a venturi.
So the ventilation air provides cooling as well, especially when at cruise altitude. Batteries in the avionics bay are further cooled by a separate aircon system. From the same presentation: