Hey guys 
I’ve been considering one of these Instead of buying some USB C to Lightning cables for charging Apple devices.
I have a collection of Powerline USB to Lightning cables kicking about which are still in good condition (obviously) and wanted to make use of them.
My question is about charging, would using these adaptors noticeably reduce the fast charge abilities?
A USB-C to USB adapter would completely nullify an iPhone’s fast charging via USB-C Power Delivery. USB-C PD requires USB-C tech on both ends. USB-A does not have the same comm lines PD uses for power negotiation. Without that negotiation the iPhone sees a standard Lightning connection and does not engage USB-C PD for fast charging.
That said, fast charging occurs on the iPhone below 70% battery charge. If you regularly plug in your iPhone to charge fast charging isn’t as important to you. You can also get a slower fast charge using the old Apple 2.4A tech. It dates back to the original iPad and iPhone 4, but is still supported on the latest iPhones. A USB-A charger which supports Apple 2.4A (any Anker charger with PowerIQ) will fast charge the iPhone at twice the rate of its included charger. But is still 33% slower than USB-C PD. In the end the iPhone charges ~15-20 minutes slower, going from 0-100%.
If you want to use a USB-C charger stick with Apple MFi certified USB-C to Lightning cables to fast charge an iPhone 8/X/XR/XS/11. All of Anker’s USB-C to Lightning cables are MFi certified.