mppt amps calculator
To work out what size solar charge controller you need, you can calculate it by using the following formula:
(The Maximum Solar Panel Watts) / (Battery Voltage(12/24/48)) = MPPT Amps (for example 240W/12V = 20A)
Use our simple calculator below, if possible allow an extra 10%. This is only for panels in parallels.  

MPPT Amps Calculator

MPPT Amps:

You also need to know the maximum voltage of your string of solar panels.
You will then select an MPPT that fits that based on Maximum Voltage of String of Panels | MPPT AMPS for example 75 | 10.
75 Maximum voltage of solar panels and 10 MPPT Amps.