Does the iPhone always chime twice when fast charging?

Does the iPhone always chime twice when fast charging?. 0%-50% in 30 Minutes! Fast Charge iPhone 8/X/XS/XR | Quntis Apple Certified Charger

Does the iPhone always chime twice when fast charging? video duration 1 Minute(s) 56 Second(s), published by Tofu Sushi on 11 08 2019 - 16:30:36.

tl
dr: Not always
When an iPhone is connected to a fast charger (aka USB Power Delivery), it may play the charging notification tone twice
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This is .

tl;dr: Not always.

When an iPhone is connected to a fast charger (aka USB Power Delivery), it may play the charging notification tone twice. The dual chime is often used to distinguish whether an iPhone is fast charging.

Someone asked me for video proof that iPhones does not always play the charging notification twice when connected to a fast charger. So I tested on 3 different USB PD chargers.

Devices used:
iPhone XS Max (iOS 13 public beta 5)
Apple Lightning to Type C (1 metre)
Power-Z KM001C USB multimeter
Verbatim 3 port multi-charger
Anker PowerPort Atom PD 1 (30W)
Apple USB-C 18W power adapter

Both of the 3rd party chargers caused the iPhone to play the charging notification tone twice, but the iPhone only played the tone once when connected to the Apple Type-C charger.

Interestingly, the charging voltage on the Verbatim charger was 15V, but only 9V on the Anker and Apple charger. Both the Anker and Verbatim chargers are capable of operating at 9V and 15V (Apple does not publish the specs of their chargers), so it is not known why the iPhone only requested 15V from the Verbatim charger.