Could wireless charging keep an iPhone X happy?

23 May 2018

The iPhone X has a 2716 mAh (10.35 Wh) Li-Ion battery. The depletion rate of the battery depends on how one uses the phone: idle, talk, music, browsing, etc.

The official specifications of the phone list capacity as follows:

  • Talk time (wireless): up to 21 hours
  • Internet use: up to 12 hours
  • Video playback (wireless): up to 13 hours
  • Audio playback (wireless): up to 60 hours

Let’s assume that under normal usage, the battery lasts about 20 hours, so the average power draw is 0.5 Wh.

What if an iPhone X had an embedded far-field wireless charging receiver. Could it remain charged using only wireless charging? Only far-field charging: no charging cable, no Qi pad.

The benefits would be huge: the phone would appear to charge by itself. No more battery anxiety. No more forgetting to place it on the Qi pad. No more broken charging cables.

If you had far-field charging 24/7, you’d need to provide 0.5 Watts to keep the battery from draining. But for 24/7 charging you’d need wireless charging everywhere: at home, at the office, in the car, and so forth. Utopian, but unlikely.

If you had far-field charging for 12 hours a day, you’d need to deliver 1W to keep the battery charged. 8 hours? 1.5W. 6 hours? 2W and so forth.

With the right wireless power technology, that’s a real possibility. With the wrong wireless power technology, it’s not. If your wireless power technology maxes out at 10 or 50 or 100mW, you won’t be able to keep the phone charged. The charging rate would be less than the depletion rate and the battery would empty.

In short, choose wisely.

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