I ran several tests and gave up. If positioned suboptimally the device either got uncomfortably hot, over 45C or even if not was inefficient even though the device signaled it was charging "well". The deal breaker was even when I forcibly cooled the device < 35C and optimized position, at charge termination the battery was not as filled compared to a direct USB connection charge. I monitored charging via in-line hardware volt-ammeter, in-device Android voltmeter and ammeter app, temp sensor apps, physical thermocouple, IR thermometer scan. At best, the ammeters reported the Qi device pulling 1.5A while the phone was receiving charge current at 0.70 A, and that's with the phone powered off.