Small system

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  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    #32
    Re: Small system

    Jim said: 
       As you have determined, the controller is not delivering all available PV power when it’s operating in PWM mode (absorb or float). This is a good time to power an "opportunity load" from the “extra” power. For example, once my controller has been in absorb mode for ~1/2 hour, there’s enough "extra" power available from my PV array to power a 200 W attic fan without affecting the controller's ability to deliver enough charge current to maintain target battery voltage. 

    Is there a way to automatically turn on such a load when that extra power is available?

    John
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #33
    Re: Small system

    As far as I know, not as I described above. The OutBack MX60 has a user-programmable AUX output (12 V x 200 mA) that can activate a relay to control a large load. Check the user manual for more details. The Apollo T80 controller has two outputs for "control of external devices".

    HTH,
    Jim / crewzer
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  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    #34
    Re: Small system

    Update:

    I said: 
      Update (340-watts of PV - 420ah battery bank - 800 watt/hour per day load):

    The cloudy/rainy weather is still with us here in Southern Illinois, and I finally had to remove the load due to low battery voltage.  The freezer (load) ran for 24 days up to that point.

    I noted that the charge controller stops applying charge current when the batteries are fully charged, and Jim said:  
         As you have determined, the controller is not delivering all available PV power when it’s operating in PWM mode (absorb or float). This is a good time to power an "opportunity load" from the “extra” power. For example, once my controller has been in absorb mode for ~1/2 hour, there’s enough "extra" power available from my PV array to power a 200 W attic fan without affecting the controller's ability to deliver enough charge current to maintain target battery voltage. 

    Is there a way to automatically turn on such a load when that extra power is available? 

    As far as I know, not as I described above.

    Jim, that sounds like a good project for someone with an electronics background.  Can you briefly outline the specifications of a circuit or intelligent controller that might perform that function?  Thanks!

    John


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