The saw is battery-powered, so make sure to charge it. It has a voltage of 18 volts and weighs 2.2 kg, so it's not that heavy to carry around.
From OnBuy
Black & Decker BDCCS18N-XJ 140mm Circular Saw 18 Volt Bare Unit
Homebase
BLACK+DECKER 18V Lithium-ion 140mm Cordless Circular Saw with Blade – (battery not included) (BDCCS18N-XJ)