PWM controller rating question

S2T_Bama
S2T_Bama Registered Users Posts: 8 ✭✭
in Solar Beginners Corner #1
Hi All,
I hope this is a simple question. I have read and believe I understand that MPPT charge controllers are essentially rated by the battery charging amperage.
But, I was looking at the PWM CC's  in the sponsor's store, e.g. OUTBACK POWER SMARTHARVEST 10 AMPS 12/24 VOLT.

I would have thought that the amp limitation would correspond to the Isc for the panel(s) being attached. An example would be a KYOCERA150 WATT 12 VOLT panel with 
Open Circuit Voltage (Voc)22.5 Volts
Short Circuit Current (Isc)8.87 Amps
Basically, I thought the panel will really never produce more than 8.87A. Is that correct?

But instead the specs for the Outback CC indicate a maximum PV power of 120W = 12V x 10A.

I thought the PWM technology doesn't use transformers and thus couldn't increase the panel's "native" amperage. Is that not right?

Thanks for your help understanding the terminology!
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Comments

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
    It is my understanding also that PWM controller current output won't exceed input current. Pmax could be higher than Pstc if the panel was really cold at very high altitude though.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    As Estragon said possible, but not likely. Even in cold areas panels warm up as the sun hits them. Mine will cut the frost/ice glaze in just a few minutes of direct sun. Mostly it's the voltage that rises, increasing the overall power output.

    Usually you can use the IMP since panels will usually warm before direct good angle sun light. Some can even handle a bit of over current!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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