I'm planning to build a "mobile pi", including a powerbank for power supply. These parts are put into a closed case with no air flow in it (wooden case with cloth around it). I don't think the Pi itself would take damage, but I'm affraid that the heat of the Pi might cause the powerbank to take damage/explode/leak etc.
Question: Is it likely that the heat causes big damage to the powerbank? Or should I include a fan for cooling?