A decent power bank is a very good thing to have handy, be that in an event of a power outage (we had one recently that lasted a day and a half).
Typical iPad batteries range from around 6,600 to 11,500 mAh. Some higher-end smartphones have 3,500+ mAh batteries, but the general trend for the common ones is within 2,500-3,000. Accounting for that, this power bank at the beginning of its' life cycle should supply enough power to charge your phone 3-4 times.
There is an overwhelming amount of power banks of various shapes and sizes available on AliExpress.
This power bank is on the thinner side – the dimensions are 76 x 153 x 10 mm (3 x 6 x 0.4 in.).
On this power bank you will find two outputs: for 1A and 2A – this means that one (2A) will be charging twice as fast as the other one (1A). There also are LED indication lights, and a flashlight, that can be activated by holding the power button for a few seconds. The flashlight is actually pretty decent, and can be used in emergencies.
The power bank had some juice in it when it arrived, just enough to charge my phone once. Note, that before you use it, you need to turn it on first. To me, the On/Off button seemed like it could fall inside the power bank, but I will give it the benefit of the doubt.
It took about 3 hours to recharge from the wall. I noticed that the notification LED's were blinking as it was running out of stored power, and as it was being charged. Once it was full, the light changed from blinking to steady.
Check it out here: http://ali.ski/kOYhyu