Finally got around to wall mounting my Fire HD 8 as an ActionTiles controller; and am leveraging the existing legacy alarm control panel wiring for power alongside the Konnected setup.
I've placed a 12v to 5v 3a power converter in the alarm box in the basement to provide power the tablet, and see a steady 1.8amp and 5.1 volts at the tablet mircro-usb connector when testing with my multimeter.
Despite this, the tablet will not maintain a charge, nor recharge. It shows the charging icon, but the battery quickly loses power (same as unplugged - not "slowed discharging" as if its drawing more than the input).
Looking for a sanity check here with anyone who's wired up their own custom USB cables. Its pretty simple; red to positive, black to negative; check voltages and mA, and should be good to go right?