Walmart offers the Red Fuel Portable 8,000mAh Jump Starter and Portable Battery Pack for $34.98. (Amazon charges the same.) Choose in-store pickup to dodge the $5.99 shipping fee. (You can also pad your order over $35 to be free shipping.) That's $4 under our May mention and the lowest price we could find by $6. It can provide up to 20 jump starts per charge and features two USB ports.