How to choose the right controller?
If you need to make some quick calculations, the following information can help you to manually figure out the amperage of the controller needed:
The wattage of the solar array
The battery-bank voltage (12, 24, or 48). Typical bank voltage because inverters are offered in these voltages.
Now Ohm’s Law comes into play:
Amps x Volts = Watts
Example: 3,000watt array/48volt battery bank = 62.5 amps, so you would need a controller capable of 62.5 amps. Most controllers out there are either 60, 80 or 96 amps so you would pick the controller with the next higher rating. In this case, it would be the 80 amp controller.