Hi @Rodney Olson , one important specification in choosing a portable charger is compatibility. Buying an OEM (Original Equipment Manufacturer )is the best decision. Although i have no problem with non OEM products, basically they are copy of the same product in terms of components. OEM is the best choice, just because they are verified and tested by the same manufacturer.
In choosing power banks, one key specification is capacity. You should choose a power bank with 2x or higher of your smartphone battery capacity. Example if your smartphone has 2000mAH of battery capacity, you should choose at least 4000mah of power bank capacity. This will guarantee you a full recharge from 0% ...and another 2000mAH as back up power for other devices.
In terms of durability an IP65 certified product should give the charger or power bank a longer use in terms of product protection.
There are lots of portable chargers in the market, comparing them will give you enough information in choosing one.
There are also power banks available in the market today that has larger power capacity as much as 50000mAh that can charge both laptop, table and mobile phones at the same time. So I suggest you should buy a multi purpose power bank that can charge any of your devices and it is important that it has a power indicator so that it's easy for you to monitor if your power bank is arealdy low in power.
There are lots of portable charger but the one which I like the most is the Anker PowerCore 20,100 power bank. It comes with a huge 20,100mAH battery inside, meaning this will be able to charge up your phone or tablet multiple times before it needs a charger. It also comes with high-speed charging for your devices if they use POwerIQ or voltageboost.
What you need, my friend is the portable power bank. They usually have a gigantic 10 - 50,000mAh batteries so your phone can basically last forever with them
Also the prices are ridiculously low for such a useful device. They range from $20 - $50 and they come in all sorts of shapes and colors, so you can match them with your phone and also use them as an accessory aesthetic improvement device
Anker PowerCore Speed 20000
Anker PowerCore II 10,000 Slim
RavPower PowerStation Series 20100mAh
DXPower Armor DX0001
All of these listed are top notch and some of the highest quality and lowest price, look them up and choose for yourself, you can't go wrong with these 4.