Hello Friends There are thousand of model of different capacities power bank in market and online stores, these are available from 100-5000 approx.
But the below 1000 are no use full, they can charge 10-50% normal 1500mah-3000 smat phones battery reason behind the truth they have poor quality chinees 18650 battery which have 500-1000 mah capacity , I search 18650 battery over intenet , the minimum cost of 2100 mah genuine battery is Rs 299. Now can judge which power banks works perfectly cheap or costly.