Thank you for your quick (and complete ) answer. I only refer AC adaptor as charger because in normal language it is used to recharge the battery. But you are right. The AC adaptor only “transforms” 230V AC(in my case) in 5V DC and that’s all. From what I saw, it only warm up while the battery is charging. After the battery is charged the unit begins to cool down and stays cool. So, my doubt is gone. Again, thanks for the answer and sorry for changing the name of the AC adapter