Amazon offers the Black & Decker 20-volt Battery Pack, model no. LB2X4020-OPE, for $52.18. At the final stage of checkout, it falls to $42.18. With free shipping, that's the lowest total price we could find by $34. It's compatible with Black & Decker's 20V Max platform of lithium-ion cordless tools and outdoor equipment. Deal ends March 30.