Dimensions and capacity
In general, the bigger the battery, the greater the capability and variety of ports. Power banks that fit easily in your pocket are generally good for a full phone charge or two, but anything meant to keep you running all day would necessitate using a bag or a purse.
On the pocket-friendly front, most smaller sized batteries that stress mobility have a capability of 5,000 mAh or less, offering only enough energy to charge most phones when.
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