# Multiple induction coils in series (phone charging)

I'm doing a DIY project of sorts, and I'm trying to create an array of about sixteen coils in series in a sort of square. The goal of this is to make a larger charging surface than just a small pad, and to charge multiple devices. I have bought a wireless charger to use the guts of as part of the project but I am unsure of a few things: (Bear in mind I have little experience in electrical)

• Does there need to be more energy flowing through the circuit as the number of coils increases? (i.e. from 1 to 16)
• If multiple devices are being charged at once, does there also need to be more electricity flowing through the circuit?
• Will the coils in the array interfere with each other?

Does there need to be more energy flowing through the circuit as the number of coils increases? (i.e. from 1 to 16)

Yes, a coil or inductor simply transfers current to magnetic energy, because of conservation of energy, you'll need more energy in the source coil if you have several load coils.

If multiple devices are being charged at once, does there also need to be more electricity flowing through the circuit?

You'll need more current, yes.

Will the coils in the array interfere with each other? Depends on how they are arranged, the 'source' coil will source a magnetic field, if a receiver coil attenuates the field of a coil adjacent to it then you will have a reduction. Look at magnetic circuits, calculate the magnetic field from your source coil.

This (question) needs to be defined in engineering terms.

What is the impedance of the coil unloaded? Z(f) = Rs + j (2πf)L
What is the impedance of the coil loaded? R in = V²/P (rms out) in parallel with above Z(f). ( using ideal transformed impedance)

If you put 16 high impedance coils in series the applied voltage must be 16 x as much and the current is shared so 16x the input power with no load.

This will not work in series due the high impedance of an unloaded coil.

There is no sharing of power in series or in parallel. Each load requires additional input power and requires that the impedance is matched for maximal power transfer where efficiency is only 50%.

## Impression

This topology will NOT be an effective gang charger.