Thanks, folding's better for camping, but whatever is available. That linked one is super thin and light, and much smaller area than my old one. Their claimed

Thanks, folding's better for camping, but whatever is available. That linked one is super thin and light, and much smaller area than my old one. Their claimed "20% conversion" is higher, IIRC, part explains it. The exact direction makes a disproportionate difference (beyond dot product), and probably cloudiness too. I hadn't thought of using a car cigarette lighter USB adapter - isn't there an issue with non-smooth voltage regulation, that might harm a smartphone? Actually, I don't know what phones can handle, nor what panels typically put out, nor how the "solar chargers" deal with it. A better long-term solution might be to replace a phone's Li-on battery with (small 12v motorbike) lead-acid battery, for far longer life-time. But heavier for camping etc.