Several factors can affect the charging speed of iPhone 17:
Low-wattage charger: Using a charger below the recommended 20–40W range limits charging speed. A 10–15W charger may take twice as long to reach the same battery level compared to a 40W USB-C PD charger.
Non-PD charger: The iPhone 17 requires USB-C Power Delivery (PD) to negotiate the correct voltage and current for fast charging. Using a charger that doesn’t support PD will force the iPhone to charge at a much slower rate.
Poor-quality or damaged cable: Frayed, worn, or uncertified USB-C cables may not handle high current safely. This can reduce charging speed or even cause intermittent charging, preventing your iPhone from reaching full power efficiently.
Heavy phone usage during charging: Streaming videos, gaming, or running multiple apps while charging increases power consumption, which can significantly slow down the charging rate, especially if the charger is already lower wattage.
Overheating: iPhone 17 models automatically reduce charging speed if the battery or device gets too hot to prevent damage. Charging in direct sunlight, on a bed, or under a heavy case can trigger this protective slowdown.