Walmart offers the Stanley FatMax 8-amp Battery Charger, model no. BC8S, bundled with an Extension Cord for $22.98. Opt for in-store pickup to dodge the $5.97 shipping fee. That's tied with our August mention and the lowest price we could find for the charger alone by $10. It connects with battery clamps, battery ring terminals, or a 12-volt DC plug and features reverse polarity lights that warn against an improper connection.