Today's N.Y. Times carries an obituary for Stefan Kudelski, founder of Kudelski SA and inventor of the Nagra tape recorder, which was the first practical, high-quality battery-powered tape recorder.
Yes, a sad loss. I met him a few times; a great man and a great innovator that will be sadly missed.
Actually, the first Nagra was clockwork powered - the battery only ran the electronics (valves - about a decade before the transistor). Very cleverly he thought why should I take power from the battery to move the tape when swill clockwork can do that and leave all the battery power for the electronics.
Stefan won the very first International Recording Contest with his home-made recorder. While everyone else was stuck inside with large mains machines, Stefan was ou and about with his portable unit. He so impressed Swiss Radio that they immediately ordered 6 from him - and that was the start of Nagra.
Nagra is Polish for "will record"
And the International Recording Contest is still going strong and celebrated it's 60-years the same time as Nagra. See
HERE.