I love this charger! I took it on a 9 day backpacking trip in southern Oregon. It kept my Note 4 and my dad's S5 charged for the whole trip. In full sun, it charges at the rate of about 1% per minute. With both phones charging at the same time with mine only having 10% juice and my dad's having 25% they were fully charged in under 2 hours. We did have 2 days of snow and rain and while it was cloudy, you are not going to get much power out of it. So, if you want to be sure that you have power no matter what, you could bring a portable power bank as well as this does not have a battery in it, meaning it cannot store power for use later. I did not bring a power bank and was able to keep my gear charged but if you are expecting a lot of clouds, I would bring a power bank as well.