Electronic – Is the efficiency of (Qi) wireless charging affected by a metal surface

chargercharginginductivewireless

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?

Thanks!

  • Dave

Best Answer

Your phone and the charging device form a 'magnetic circuit' across which power is transferred. It is possible to 'short out' the magnetic circuit, particularly with steel. In the comments, alex.forencich suggests the easiest solution:

put the phone and charger on top of a stack of magazines, books, etc. and compare the performance

I can guarantee that the same steel plate between the phone and charger will create a magnetic short circuit and very little energy will get through to the phone, but it is difficult to determine if a piece of steel under the charger would have the same effect without knowledge of distances, thicknesses, materials, etc. that would be difficult to determine without some teardowns.

Let us know how the experiment goes!