This is just a fancy "battery holder" ,, BTW that is best search term
I don't think aa batteries have 3-4Ah capacity
IOW, this is just 8.... 1.5V cells in series, no electronics at all
I could find no good information on the actual current use of the rockpro64, so here are measurements i made:
I built a 12V 3A power supply - mains transformer, not swithcing. The no-load output was 17V
power use: ~17V input, with fan installed USB keyboard +usb mouse, no network; cheap digitech DVM
initial early boot pre-X 0.3A fan off
during boot to X 0.65A fan running
static X interface 0.4A "
open firefox 0.8A "
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USING 5V 2A switchmode plugpak = 5.2V : boot fails GPIO pin 2 is 4.5V (instead of 5V), pin 1=3.3V - OK
Use bench power supply (linear regulated) 5.5V - boot fails
Use bench power supply 6.0V: boot succeeds with wired enet , fan running, emmc xfce4, USB key & mouse
GPIO pin 2 is 5.2V ; I did not measure pin 1 - it must be OK
Current measured on Tektronix DVM: during boot has 1.3A peak;
0.5A with peaks to 0.6A with idlle xfce4 display, no apps running
Starting Fifrefox: peaks to 1.7A, static page display 0.6A
Real peak currents will exceed this briefly due to DVM averaging and read intervals
If you are not using add-on devices or the PCI interface it seems you can run on 6VDC.