Power Bank Buying Guide
Here are a few things that you need to know to ensure you pick the right Power Bank for yourself.

Know your device

1)The battery of your device
Your battery's capacity is specified in mAh (milli-ampere-hour), which is a measurement of amount of charge a battery can store. The larger the mAh, the bigger capacity it has.

2) The Charger of your device
Your battery charger specification is located on the usb adapter bundled with your device. For most Smartphone batteries, the output voltage is 5V and the current is 1A/2A. Higher the current,faster it will charge your battery.
Things to Look For in a Power Bank

1. Capacity (mAh) - Must be higher than the capacity of the battery of your device
The capacity of the power bank you choose must be higher than the capacity of the battery of your device.For e.g. a Samsung Galaxy S6 has a battery capacity of 2550 milli-ampere-hour (mAh). Therefore, we suggest you go for a Power Bank with a capacity higher than 3000 mAh in order to ensure 1 full charge of your device. Also, if you travel a lot or want multiple charge cycles from your power bank, we suggest you go for one with a higher capacity (mAh).
2. Output (A) - Higher Ampere will give a faster charge
A 2A or above charger will charge the device must faster than a 1A. We suggest if you have a device with a battery of 2200 mAh or above, you go for a Power Bank which has an output of atleast 2A (one of the output port should be of 2A).
3. Number of output USB Ports - More is better in case you have multiple devices
4. Type of Battery
Power banks with Polymer (Li-Po) batteries are slimmer, lighter and have a better longevity than the ones with Lithium Ion (Li-Ion) battery.
Note:  Do check the charging instructions given by your devices' manufacturer to ensure safe charging.