No, I don't think they could. They severely underestimated the efficiency of induction charging. 450 mAH in the band does not linearly transfer to 450 mAH in the watch.
That's why I added more, to account for the inefficiency. However, after reading up on Qi and inductive charging, I think I should've been using Watt hours, not Amp hours. (I'm a digital guy, not usually analog)
So, more like this (the watch battery size is just a good guess):
- Apple watch battery = 3.8V @ 360mAh = 1.4 Watt hours
- To replace 125% of that charge wirelessly, at 80% efficiency, they need ~ 2.2 Watt hours of energy available in the band.
In addition I think they underestimated the thickness of the needed band. To be reasonably pliable, the battery would need many elements that are joined by connectors or direct wires and controlling circuitry to manage the charging. I don't see any possibility that they can put that in the currently shown band.
A common coin battery (CR2032) holds 0.6 Watt hours. Just four of these (2.4 Watt hours) should be enough to do the deed.
But of course, they're probably too flat and straight. So we look for a more curved solution:
This battery supplier sells all sorts of wearable power sources, including flexible LiPo rechargeables like this:
They have 20mm wide ones that would fit the bill, I think, for a wrist band.
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Of course, as you pointed out, you still need some circuitry.
More importantly, perhaps, is that it would have to speak the same data transfer language as Apple in order to control charging. Monitoring the Apple charger might be enough to obtain the necessary protocol, or might not.
