20W USB-C adapter won't charge iPhone via USB-C cable

Question

AKY_Turkiye Author

Level 1

4 points

20W USB-C adapter won't charge iPhone via USB-C cable

I have a unique problem with my Type-C adapter which is 20

Watts and original. I have 2 original Apple cables, type-c to lightning and type-c

to type-c. When I tried to charge Iphone 13 with type-c to lightning cable, it

works. However, when I tried to charge Iphone 17 with type-c to type-c cable,

it does not work. Interestingly, when I tried type-c to type-c cable with another

20W type-c adapter, it works. As a result, I know that both cables are working

because I tried cables with several adapters and phones. And I know adapter is

also working, because it charges with lightning cable. However, when I tried another

type-c to type-c cable with the specific adapter its not working, it seems that

this adapter is not working with type-c to type-c cables. Question is why this

is happening and how to solve this problem.

Posted on Apr 16, 2026 2:35 AM

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Answer 1

Tesserax

Level 10

159,032 points

Apr 16, 2026 7:59 AM in response to AKY_Turkiye

Short answer

There’s no indication that your cables or phones are faulty. The issue is most likely due to how this specific adapter handles USB-C power negotiation, which affects USB-C to USB-C charging but not USB-C to Lightning.

A bit longer answer

The behavior you’re seeing is typically related to how USB-C power negotiation works:

Charging an iPhone via USB-C to Lightning uses a different signaling method than USB-C to USB-C.
USB-C to USB-C charging relies on a protocol called USB Power Delivery (PD), where the charger and device “negotiate” voltage and current.
Your adapter appears to work correctly in Lightning mode but may not be properly negotiating USB-C PD when paired with USB-C to USB-C cables.

This can happen if:

The adapter has a partial or inconsistent USB-C PD implementation
There is a firmware or controller issue in the adapter
The adapter is designed primarily for Lightning-based fast charging rather than full USB-C compatibility

The fact that your USB-C to USB-C cable works with a different 20W adapter confirms that your phone and cables are functioning correctly. That adapter is likely handling USB-C PD negotiation properly.

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