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?


  • Dave
  • 2
    \$\begingroup\$ Simple experiment: put the phone and charger on top of a stack of magazines, books, etc. and compare the performance. \$\endgroup\$ – alex.forencich Apr 1 '16 at 16:34

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!


Yes if the metal can be magnetized and if the metal is placed between the charger and phone. If you place an steel, the magnetic fields will attract the metal causing the some of the magnetic fields to not travel through the receiving end.

  • \$\begingroup\$ Thanks for the quick reply. In my case, the charger is sitting on TOP of a steel box, with the phone resting directly on top of the charger. I've read other StackExchange articles that talk about steel BETWEEN the charger and phone causing eddy current loses, but didn't know if a steel plate below the charger would make any difference. \$\endgroup\$ – ViperGeek Apr 2 '16 at 21:02

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