Gooloo via Amazon offers Prime members its Gooloo Quank2 8,000mAh Portable Battery Pack for $39.99. Coupon code "CNVVRCU8" drops it to $19.99. Plus, Prime members bag free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $5.99.) That's $40 off list and the lowest total price we could find. It features an LED flashlight and can purportedly be fully charged within 25 minutes via the included 14-volt car charger.