Currently you have 6A coming to your battery at 12 volts, that gives you about 70Watts, A mppt charge controller will draw power from your panel at its max powerpoint of 30volts. Depending on the amount of sunshine and the temperature and the angle of incidence of the sun onto the panels and atmospheric conditions, you may see upto the 240watts going to the batteries. you might see upto 20 Amps into your batteries. I will try to post a photo of what my mppt charger is currently doing. 70v at 6.3A coming from panels, 29.5v at 14A. that 441watts coming from panels, 413watts going to batteries. thecharge controller uses some power, but you will win big time.
Lots of South African Southern sunshine to you all!