I am looking for a cordless impact to change my tires at the track. I brought the hitachi 18 volt combo with the drill and impact for $200 but when I tried to get the lugs off, they would not budge. They are only tightened to 80 ft/lbs. I have already returned the kit and I am looking for advice as to which cordless impact will get my tires off with ease, and have enough charge to change 4 tires 2 or 3 times on one charge. I am also not looking to spend an arm and a leg. Thanks guys.