Rated pv power
The rated pv power on a mppt controler, is based on the voltage of the solar panel, or on the voltage of the battery?.
The parameter of the mppt controler say. .
Rated pv 12v system 260w on 20 amp, 390w on 30 amps, 520w on 40amp. 780w on 60amp.
Which model of charge controller are you looking at?
Generally speaking, the rated max PV input power (W) is governed nominal battery bank voltage.
Also be mindful of the maximum input voltage of the charge controller. A 150 VDC unit has a max PV string length of 2-3 modules (depending on location and module Voc).