MPPT = Maximum-Power-Point-Tracking Charging Method (up to 98% efficiency)
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 MPPT controller the absolute max allowed voltage is defined in the datasheet.
- In case of MPPT controllers do not exceed the allowed generator power in accordance to the system voltage. Eg for the CIS-MPPT If 250W for 12V system (=20A) allowed, do not connect 500W to an 12V system, which may result in occuring of 40A and destruction of the controller. This is specific case for MPPT controller with 98% charging efficiency.
- 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.