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I've stumbled upon a few articles saying that wireless charging takes more energy to charge something compared to the cable. Like this one.

Like in the test from the article, it takes 47.33 % more energy.

Why is it? Is there something fundamentally wrong with the principle of Inductive charging?

Or is it may be the current technology is just inefficient by itself and there is a room for improvement, so that it becomes just as efficient as cable charging if not more?

If engineers were to be improving the wireless charging technology, what are the directions to be looking at?

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  • $\begingroup$ What happened to the other question? $\endgroup$
    – Solar Mike
    Commented Aug 10, 2023 at 17:41
  • $\begingroup$ Suppose you wanted to compress air into a room as a means of energy storage. What do you think would be more efficient: blowing air into the room with a continuously spinning compressor, or putting a one-way valve and a membrane on it and repeatedly pushing and pulling on the membrane? It all depends! If I were charging a 200VDC battery off 12VAC, that's like the room already having lots of pressure in it compared to what I have to move my membrane or turn the compressor. Switch to charging 5V off the 12VAC and... $\endgroup$
    – Abel
    Commented Aug 11, 2023 at 1:50

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There is something more challenging with inductive charging, yes. It lives a the intersection of the available electromagnetic materials, achievable geometries, and basic physics.

So it's not fundamental, but it is hard.

The electromagnetic materials that limit this are magnetic core materials (i.e., ferrites) and conductors (i.e., copper). The achievable geometries are influenced partially by available materials (i.e., casing materials need to be strong, precise, and not dissipate energy), and partially by marketing concerns (i.e., you may not want to buy a phone whose size has doubled because someone made the electromagnetic coupling 99% efficient).

If you ask me exactly what to change, beyond bigger magnetics and less separation between them in the charging/charged device pair, I couldn't say.

If the market remains interested, expect incremental improvements over time, similar to how switching supplies have gone up in efficiency from the 50% or so in my 1947 Delco radio (search "vibrator plate supply"), to today where a supply with a 90% efficiency can be fairly called "mediocre", and 98% efficiency isn't unheard of.

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The three efficiency loss mechanisms in inductive charging are electrical resistance in the transmitting and receiving coil wires, flux leakage between the coils (this represents magnetic field lines that do not couple the two coils but "leak out" from between them), and magnetization/demagnetization losses in the magnetic material that forms the core of each coil.

good coupling means the coil cores should be touching, which is not always possible in the design. low magnetization losses can be had by using core material like soft iron which magnetizes and demagnetizes readily. but the resistance of the coils is the stinker because to minimize losses, you have to maximize the cross-sectional area of the wire used to wrap the coils which means the coils get unwieldy big.

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