Walmart offers the Stanley 300-amp Peak Jump Starter, model no. J309, for $39.98. (Amazon has it for the same with free shipping for Prime members.) Opt for in-store pickup to dodge the $5.97 shipping charge. That's the lowest total price we could find by $12. It features 300-amp instant-starting power (600-amp peak), built-in 120-volt AC charger, and 270° pivoting LED emergency light.