I may have missed the right part from data sheet, but what is maximum current one can drive from 5V A20-OLinuXino-MICRO-4GB?
In USB ports it is listed max. 523 mA, but like for SATA power (that would be nice, as it has fet ready to use on/off https://www.olimex.com/forum/index.php?topic=1696.msg8167#msg8167) I could not find the information. I would be running it most time from 12V battery with LiPo for backup.
If I checked correctly, voltage converter is MP1482DS that provides maximum 2 A. If the board draws itself 350 mA, there is more than 1.5 A available total over all USB ports and SATA port. The FET4 IRLML6402 should not limit this further.