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PWM = Puls-Wide-Modulation Charging Method

Sizing the charge controllers in PV off-grid systems:

Do not exceed the controller allowed max current and voltage A/V defined as Isc/Voc.
In PWM controller max allowed voltage results from battery.min.voltage +30V (eg in 12Vdc systems: ~10Vmin.bat + 30V = 40V max).
In MPPT controller the absolute max allowed voltage is defined in the datasheet.
The real occuring current and voltage of the panel depends on temperature coefficient of the panel. Calculate additional 25% (A/V) which may occur under low temperature, as safety buffer (eg if panel Isc 8A, calculate +25% = 10A which may occur).
To choose the correct battery capacity, multiply the controller nominal current x10 (eg for an 10A controller choose 100Ah battery).
Always check the controller's datasheet and manual for individual parameters.

Diagrams Guide PV Off-Grid Systems