Here are some great tips for buying power bank.please check them before buying power bank.
1) check the battery capacity of power bank.if you have a smartphone then I suggest you to buy a power bank with at least 10000mah battery power.
2) go for the good power bank companies like ambarane, Lenovo, syska., Samsung, etc. But don’t go for the unbranded power bank.
3) unbranded power banks charge your phone only 4-5% then after these are unable to charge your phone.
4) see the output socket of the power bank.it should be at least 1 Ampere and above.
So friends these are some great tips for buying power bank.hope it will help you
Thanks