WalMart is usually the cheapest around here, and the warranty is good. Usually they take them back no questions asked if within warranty, but I think I've only had a bad one once. One of the great things is you can get this done just about anywhere in the country. I just paid $67 for their 2-year warranty one. I generally replace the battery at around 3 years anyway, just before the winter so I don't have to deal with a dead one some 20-below-zero morning.