Why bother? its a 20amp PWM controller that costs $125ish. for the same amount of money
you can buy a reall MPPT
controller and not waste the output of your panels
. PWM controllers force the panel voltage down to 12v charging
levels, wasting a lot of energy in the process.
you can get a real MPPT
with the ability to program custom charge voltages for less money
there is a lengthy review of them on youtube. for the money they are much better than PWM controllers