Yeah it's weird. You're supposed to keep it plugged in all winter which sounds like lead acid to me. But it says really big on top lithium ion. Truth be told I don't really care: it works. As for 90 pounds, that's hard to believe. There may indeed be other brands that are better in some way, black & decker is the only one I've ever used. Maybe when this one wears out… I just know that I'll always stick with battery power.