Posted by a reviewer on Amazon

We thought initially that one of those portable solar panels would work but then realized those panels have no builtin backup power storage so would only be able to charge the phone whena the phone is attached to itb when the sun is shining brightlyc the panel is aimed toward the sungiven their trip is southbound we realized the panel would not be facing the sun during the day when shes hiking unless she wears it on her chest instead of the pack not good

Posted by a reviewer on Amazon

And the phone could not be charged in camp at night without a backup power source

Posted by a reviewer on Amazon

As pointed out the solar panel on this unit is very low power and takes about 40 hours of direct sun exposure to recharge the battery

Posted by a reviewer on Amazon

But the battery recharges our phones very quickly and if she charges it up fully from a wall plug at the motel prior to the trip should last the week keeping the phone fully charged

Posted by a reviewer on Amazon

This one is great ive not had many others only one but this one charges in the overcast as long as it is daylight it will actually give some power out to charge up the gps and a cell phone

Posted by a reviewer on Amazon

It did take over 10 hours to charge it off my laptops usb port when i bought it

Posted by a reviewer on Amazon

Keeping it topped off or over half charged shouldnt be an issue

Posted by a reviewer on Amazon

Anyways cant say for sure how long it takes as i just leave it on my cars dash but at the same time i charge at home if its below one light as i know it wont last me