[Richard Crowley]

"Matt" wrote ...
Would an external battery pack/ power supply be acceptable?

I don't see why not. A wall outlet might be a problem, so where would
I get an external battery pack from in the UK?

If so, anything that uses a wallwart supply can be used indefinitely
up to either its memory limit or the size of the external pack.

What's a "wallwart supply"?

It is a power cable with a "wart" or large "plug"
which contains the mains power supply. It is
intended to connect to the mains outlet.

Since you won't reveal the application, are we to
assume that it must be portable and self-powered?

If you want to continue to play a game of 20-questions,
your responses will be limited to those who also wish
to play.