MarcBC - great points there.
I did some research and found this page of Renogy's website about their 100 watt panels.
http://renogy.com/wp-content/uploads/2014/11/RNG-100DB-2-page-1-REVISED11252014.jpg
The optimum operating voltage for this panel is 17.7 volts.
So our amps = 100 watts/17.7 Volts
This comes out to 5.7 amps which is what their website states as well.
With 2 panels = 11.4 amps
With 3 panels = 17.1 amps
This assumes idea conditions with full sunlight and no shading.
In real life, it would be unlikely to see that much amperage but I guess it's possible.
This is showing a higher voltage than I originally thought on my prior post so the amps are less by that same equation.
My advice is this: check your charge controller. If it's rated for 20 amps there is no problem. If it's rated for 15 amps, you can probably run it with 3 panels but the risk of burning out your charge controller is high. If it's for 10 amps, I wouldn't even try it with all panels.
Hope that answers your question.