Is it worth buying a portable iPhone charger?

Hi, I want to buy a portable charger, and I want to know the functions of one. How long do portable chargers charge a phone before going dead? How do you charge a portable charger? How well do these chargers work? Which is better: a portable iphone charger or a wall charger?

Added (1). Also, can you still charge it if there's no electricity?

1. Depends on how much battery life it can hold. My portable charger can hold up to two iphone charges.
2. On a portable charger there's a port that has a usb adapter at the end, then you charge it similarly to am iphone.
3. Mine works amazing. I use it for my fitness, camping and travel.
3. I prefer my portable charger for on the go or if i want to be on the couch, but no where near the charger. But i prefer wall charger to charge my phone overnight.

Depends on the charger you get. If you need that extra battery then yes

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