30mA @ 6V is less than 0.2W. Perhaps you need a brighter sun.mAh means mA times hours. So with 30mA you're would be getting 30mAh in an hour. But how reliable that 30mA is in real life conditions is anybody's guess.And then how long it will take to charge a battery will depend on what the capacity of the battery is in mAh and how efficient the charger is. But it is likely to be so long that the sun will have gone in (several times). If you're actually relying on the sun then I'd guess between 5 and 10 DAYS from a typical 18650.Steve
Most solar cells are the same efficiency, so there is no such thing as a small panel that will effectively charge a cell phone. I'm presuming you don't want to wait a week for a full charge.There are a lot of junk solar charging power packs out there. The cells inside are probably fine, but the solar panels are so small, they simply cannot do more than a slow trickle charge.