Speaking of on-the-go charging.

Here's a simple question. I have not sat down to figure this out. Suppose you want to carry enough solar panels to charge your cellphone in a convenient time. How much area do you need for the solar panels? I am talking about a charging time of say ... 45-60 minutes. For a modern cell phone, like an iPhone 6 or an Android.

I am trying to see how practical this is. There are small "portable" solar cell units that are sold in wilderness stores. They actually roll up into a convenient carrying package. But I am not clear if they will really charge a cell phone in an hour. If it takes all day - that is far too long.

cheers,
Pete