Pwm or Mppt controller for this setup

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706jim
706jim Solar Expert Posts: 515 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
I have an old set of panels facing south (about 400 watts) and three 320 watt panels facing west. These are regulated by an old Trace C40 Pwm controller. I'd like to replace the older panels with another three 320 watt panels and if possible keep the same charge controller. Is there any benefit of going with a newer Mppt controller if the panel orientation stays the same, with the southern panels losing sun as the western panels start gaining it? With all of the existing panels facing in the same direction I would see about 42 amps of current. With the two sets separated as described, the old set generates about 8 amps and the newer (western facing) group generates about 30 amps. The reason I ask is that the two groups of panels will never be facing the same direction due to available space to mount them. The C40 is limited to at most 40 amps at the 24 volts I'm running.
Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
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    Depending on the panel specs (esp. Vmp) and local climate, you might get a bit better harvest with MPPT(s).  IMHO the existing controller would probably work ok 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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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #3
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    Another factor might be wiring, if the existing 400w wiring is marginal or too light for the new panels.
    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
    · Share on Twitter

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