Question:
Why can I not get 2A charging from the USB charger, even though I have it set for 2A?
Answer:
1) Check USB cable. Ensure that the USB cable attached to the device is designed for 2A charging. Some USB cables use light gauge wire that is not adequate for delivering 2A to the end-connected device without significant loss.
2) Check the state of charge of the battery in the device being charged. If the battery in the device is near 100% full charge state, then the current drawn from the charger will be less. A well designed Li-ion battery charger should automatically transition from current mode to voltage mode when the battery is nearing full charge. In this case the battery voltage is tightly regulated and the charge current is allowed to taper down to 10's or 100's of milliamps. Only when the Li-ion battery is sufficiently discharged (below 80% for example) will the full charge current be applied to the battery.