[jyl]

500 sq ft is no problem for a battery mower.

I use my neighbor's battery mower, it appears to be out of production, pretty old and beat, and yet does the job easily. I'd say just read the reviews on Amazon and pick one. Keep the blade sharp.

The manual reel (push) mowers work well if your lawn is smooth and you mow regularly. They make a nice snick-snick sound.

Have you considered a robo-mower? I'd sure be tempted if I didn't also have the sidewalk strip to deal with. If it does half as good a job as the iRobot robo-vacuum we have, it'd be great.