If you need to plane a lot of plank you're doing yourself a favour by using an electric planer. There's no cord to restrict you, just make sure you've charged the battery.
From Amazon
Makita DKP180RMJ 18V Li-Ion LXT Planer Complete with 2 x 4.0 Ah Li-Ion Batteries and Charger Supplied in A Makpac Case
Powertool World
Makita DKP180RMJ 18v LXT 82mm Planer inc 2x 4.0Ah Batteries