Solar panel system - figuring out the right specifications
If you are going to run external power to your phone, you need to know how much power the external port consumes. 

Your present estimate of 5W based on the internal 3.7v 2600mA battery capacity lasting 3 hours may or may not be good. It's possible for a phone to be quite wasteful in its use of cheap external mains (what it thinks is mains) power.

If we look at your 'half a day' exercise (let's call that 12 hours), then we have a 10W solar panel illuminated for a strong 6 hours, would supply 60 Wh. It's not clear how much energy your battery started the exercise with, but if it didn't last, then at the end it was zero. A 12v 7Ah battery stores 84Wh, and you've used somewhere between 0% and 100% of this. This gives a range of 60 to 144 Wh used by your phone in 12 hours, or a power of 5 to 12 watts. I've neglected power conversion inefficiency through charge controllers and USB supplies, as they're generally quite efficient, and the uncertainty in your 5-12W range dwarfs the odd 90% efficiency figures.

Let's pick a round figure at the top of that range, of 10W consumption. 

As your solar panel supplies power for 6 hours of a 24 hour day, you need a minimum of a 40W panel. Going larger increases the tolerance to misalignment, ageing, dirt.

As your batteries supply power for 18 hours a day, you need a minimum of 180 Wh. With a 12v battery, that's 15Ah. Going larger reduces the depth of discharge, so improves the cycle life. If you ever have a dull day, then you would need to run for 24+18 hours, rather than 18, so you'd need a basic 35Ah. A battery of that size would offer you good cycle life on a daily basis, and have the emergency capacity to take you two days from time to time if you needed it.

The charge controller has to recharge the battery in 6 hours, so would need to be rated at a minimum of 30W (the 30W * 6 hours charge time to supply the 10W * 18 hours use). At 12v, 30W is 2.5A. It doesn't hurt to have it rated a little more, but the panel power capacity would limit it.

Once you've measured the power consumption of your phone properly, you can scale the other power and capacity numbers appropriately.