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probably battery bank is more best bet imo. I feel like the MagSafe battery pack from Anker just adds bulk to the phone and it feels like your holding a brick instead. Would feel awkward in my pocket with that on.
 
should i buy that or a battery bank ?
This serves as a battery bank as well.


Directly from their website:

Choose How You Charge

Recharge PowerCore, or charge other devices with USB-C input and output for your headphones, tablets, or your friends’ non-MagSafe smartphones.
 
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