On my old iPhone 4, I noticed the back left side got hot while the right side remained cool. The right side is where the battery is located, and I read that LiPo batteries are very efficient at accepting a charge (>97%), so this makes sense. So the heat must be coming from the logic board.
Is this heat purely the energy loss of converting the 5V input to whatever voltage the battery needs to be charged or something else? I remember reading that stepping down DC power is very efficient, so this makes no sense, unless I made that up.
I found this blog entry where the author calculated the overall efficiency of charging the battery of the iPhone 3GS to be 61%. I have no idea how much of that is loss from the wall charger, though. http://kjordahl.net/blog/?p=82
Is this heat purely the energy loss of converting the 5V input to whatever voltage the battery needs to be charged or something else? I remember reading that stepping down DC power is very efficient, so this makes no sense, unless I made that up.
I found this blog entry where the author calculated the overall efficiency of charging the battery of the iPhone 3GS to be 61%. I have no idea how much of that is loss from the wall charger, though. http://kjordahl.net/blog/?p=82