I am trying to power my Pi (3B) from 6 AA batteries, via an UBEC (rated 5V/3A). By itself, the UBEC is outputting some 4.94V.
But plugging the UBEC output into "GPIO" pins 4 and 6, m yPi does not seem to start correctly: the power does not stay consistently on, and I start hearing worrying "hissing" noises from the Pi.
Am I doing something incorrect ? Or what can I do to get more informations about a potential problem ?