The 18V 13-inch Ryobi trimmer is $99, while the 20V, 12-inch Black+Decker trimmer is $93.28. As for the 40V models, Amazon sells Ryobi's stand-alone 12-inch trimmer for $99, and it has the Black ...

Black and Decker trimmers use either a 20V battery or a 40V battery. The higher the voltage, the greater the power potential. Additionally, each battery has an amp-hour rating.

The Black and Decker 40V and 20V batteries have completely different sizes, with the 40V being larger by a few inches. It measures 5.9 by 3.4 by 7.2 inches, while the 20V variants are only 4.5 by ...