On Mon, 26 Jun 2017 11:21:58 +1200
nospam.Rick.Christian@f377.n135.z1.binkp.net (Rick Christian) wrote:

> Looked at the Amazon Basics 16.1AH USB battery but it cuts off the
> power ports when you charge. Some one there was looking to do exactly
> what I want, and foudn out its useless.

Add a 120V relay to switch the Pi's power from its regular PSU to the
USB power pack, and a capacitor across the Pi's 5v to sustain it during
switching.  Equally applicable to any other source of backup power such
as a 6V alarm battery on a trickle charger.
Of course you could get the Pi to manage its own sensing/switching,
and indeed charging, but a relay is simple and self-contained.

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