Solar power banks: capacity and the small-panel limitation
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Choose a solar power bank first as a battery for charging devices. Treat a small built-in panel as supplementary. Capacity in mAh does not tell you how quickly the bank recharges from sunlight; panel power and actual illumination are separate limits.
Compare battery and USB specifications
Check the voltage behind the capacity rating, stored energy in Wh where stated, supported outputs and charging protocols. The energy delivered to a phone is lower than nominal battery energy because conversion and operation have losses.
Confirm the required cable, output power and mains-recharge time. A large mAh claim cannot compensate for unsuitable charging output.
Assess how solar energy will be collected
A small panel has limited area and may take a long time to replace the energy used. Do not interpret the battery's capacity as its daily solar yield or rely on sunlight assumptions missing from a marketing claim.
For regular off-grid recharging, compare a separate folding panel with a compatible power bank. Observe the product's temperature and exposure instructions rather than leaving any battery in excessive heat to maximise sunlight.