There was battery operated TVs in 61'. The first genuine portable was mabe by philco in 1959 more info on it can be found here
http://www.earlytelevision.org/philco_safari.html Other companies may have gotten into the batery operated portable game soon after. I know Sony entered that game at least as far back 1964 because I have one from that year, and from reasearching it I learned it was the smallest production TV set in the world up to that time (which blew me away as it was a childhood impulse buy long before I collected TVs).