Teryei via Amazon offers its Teryei 15,000mAh Dual-USB Solar-Powered Portable Battery Pack in several colors (Black pictured) for $21.88. Coupon code "TeryeiSC" drops it to $15.32. Plus, Prime members bag free shipping. That's the lowest price we could find by $10. This water-resistant battery pack can be charged via its solar panel or micro-USB port and features two USB charging ports, dual LED flashlights with four lighting modes, a compass, and metal carabiner. Deal ends March 28.