I have been powering my WeMos D1 R1 and D1 R2 Arduinos (with ESP8266) using a simple USB cable connected to a standard charger whose rating is 3.1 amps. Is this sufficient to charge two such Arduino boards (it has two USB slots) simultaneously?
Also, should I be using the other Power Input which I understand is 9V?
All the specs I have seen specify the voltage but not the current usage.
Either way, what is the maximum amperage that the board might need/is rated for? Is it different for the R1 vs. R2? Is it possible to measure how much it is using from any of the pins?