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Get this PQI Power Bank i-Power 7800 for $19.99 plus free shipping at Newegg. This was the lowest price we found by $7. It can charge USB-charged devices such as smart phones and tablets (including Apple products) and can charge a phone, for example, up to six times before needing to be recharged, itself. It also has a battery light indicator to show you how much power is left. There is no sales tax (except in CA, NJ, TN).