Could the iPhone 4S be drawing too much current from the MintyBoost when it's below 50%, thus causing the heating issue?
adafruit_support wrote:Could the iPhone 4S be drawing too much current from the MintyBoost when it's below 50%, thus causing the heating issue?
That is very possible. If the boost converter overheats it will shut itself down. This could be what causes the 1 minute cycling.
adafruit_support wrote:In theory, the 4s should respect the current USB charging standard. If you short D1 & D2, it should not try to draw more than 500 mA.
adafruit_support wrote:Yes. D1 & D2 are the two center pins. When shorted, the device is supposed to assume it is a wall-charger and not exceed it's max charge rate (typically determined by the level at which the voltage starts to sag). In general the 4 & 4S seem to have been less problematic than earlier versions (especially the 3GS.)