Small folding solar panels marketed for phone charging typically output far less than their advertised peak wattage in real-world conditions — angle, cloud cover, and panel efficiency all cut into the number on the box, so they work best as a slow trickle-charge backup, not a primary charging method.
Bottom line
Solar charging is genuinely useful as a supplement or off-grid backup, but sizing expectations around realistic sun-hours (not peak panel wattage) avoids disappointment.