i can really recommend Xiaomi! They are a company from china that produce cheap but high quality products, with their 10Ah Powerbank I am able to charge my phone a minimum of 2-3 times! The even offer a check on their website for entering the serial number of your powerbank to see if it's original! The website i bought my powerbanks is www.banggood.com/. I already bought 3 Powerbanks from them! With these you can go for a few days without charging.