Yeah... a bit of "it depends" goes into the equation.

I don't have a solar array, but I did work on the solar car team back in college.... so I can present the theory... but I am sure someone else out there can speak from experience.

-The theory-

The 30 Amp charger will tell you the maximum amps you are putting into your batteries, but the actual power will be less than that. (The 30 Amp charger should have a larger capacity than your solar array... or you would smoke your charger).

The actual solar power will vary during the day... it may be near 30amps at peak times, but typically much lower than that.

To calculate, you would need to know the average amp output of the solar array during the day, and multiply that times the number of hours to get an idea of the amp hours your are putting back into your batteries.

Also your charger is not 100% efficient, so for a more accurate equation, you would need to multiply the solar array amps times the effiicency of the charger (been a while, but 80% is a good rule of thumb based on automotive alternators) to figure out how much is going to the batteries. That should get you pretty close.

I would think the solar array has an watt or amp indicator on it. (watts are volts times amps) with that you should be able to start estimating the re-charge time.

Good luck!