The 2amp port is ok to use with android device although I would start off trying the 1 amp port first.

Start with your phone internal battery is fully charge. Plug the charge cable into the 1amp port. Then go to your navigation screen with the gps enable. Press the on button on the external battery and be sure that the charging indicator light on your phone is showing external power or charging. Try it for an hour and see what your battery level is presently shows. If it had drained, then switch to the 2amp port.

These and most other external battery have an auto shutoff built in meaning that when there is very low or no current draw, the external battery will shut off. This feature has it pros and con. Personally i rather just have an on/off switch but that the way they make most of them these days. If you leave your screen and gps on, your external battery should not shut off automatically because there should be sufficient current dtaw to prevent the auto off features of the external pack. Not sure if the auto shutoff is more or less sensitive between the two port, so I would think it is best to use the 1amp port if your phone does not draw more than the one amp with screen on maxium outdoir brightness and gps running, otherwise switch to the higher output port and you should be fine.