WP 8.1 warns that my car charger charges my 1520 slowly. What are the wiring criteria for fast charge on a 1520? Assuming charger can deliver voltage and current, of course.
If your charger can provide 1A at 5V, try changing your cable.. If the cable is low quality the voltage will drop within the cable and phone will not get the full 5V 1A.
To enable fast charging, the phone must detect USB D+ and D- are wired to each other. If not with what you have, you could cut and modify a USB cable, or modify the charger.
Thanks this is helpful.
Do you know of Samsung's android devices have the same requirement? I think my old N900 does.