Looking for a jump starter to keep in your car in case of a winter breakdown? Lucky for you, one of our favorite portable jump starters is available on Amazon for a major discount. That’s why portable jump starters have become a must-have piece of gear for drivers, and right now, our favorite waterproof model is on a major sale. The , which earned high marks in Popular Mechanics’ buying guide to the best portable jump starters, is currently discounted by about 20 percent, bringing its price down to $99.95 at Amazon. That’s especially important for drivers who don’t regularly pop the hood or want a jump starter that’s as foolproof as possible.