I recently picked up a Galaxy S7 Edge and love it. I've also gone "all in" on wireless charging, now owning three chargers: a third party standard charger, a third party QC 2.0 (15W) Adaptive Fast Charger, and an OEM Samsung fast charger. The standard wireless charger is slow, and the Samsung quick charger is fast. The third party quick charger, however, measures a healthy 720-950mA, but never fully charges the phone after eight hours overnight.
I have a replacement charger on order, but was wondering if perhaps the surface under the inductive wireless charger would make any difference. The charger that fails to produce a complete charge is sitting on a large, heavy gauge steel box (safe). My question for the EEs is, could the "ground plane" from this big steel surface cause the third party quick charger to somehow be less efficient? Could some of the inductive energy be getting absorbed, perhaps due to eddy current losses, by the large steel surface?