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    Three 100 watt solar panels into three PWM converters, output merged. Max total output pointed in direct sunlight (Southern California) 8 amps ~100 watts. Is this within the expected range of performance?

  • #2
    Originally posted by Peter Evans View Post
    Three 100 watt solar panels into three PWM converters, output merged. Max total output pointed in direct sunlight (Southern California) 8 amps ~100 watts. Is this within the expected range of performance?
    It seems a little low in the amp department. Maybe because you are using multiple PWM CC's.

    Also remember a PWM is less efficient (amps in = amps out) then a MPPT (watts in = watts out) because the wattage out of a PWM is usually the Amps in times the battery Voltage while for a MPPT the watts in is usually the watts out.

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    • #3
      Thanks for the reply. My pre-purchase estimate for end wattage was 300 watt marketing claimed output times the CPLF (Chinese Product Lie Factor - 75% delivery of marketed capability - ) times the ENRWEF (Engineer Non-Real World Exaggeration Factor (90% of engineer-claimed performance because engineers never test under actual real world conditions) times the efficiency of the controller (of course times the CPLF and ENRWEF) of ~60%. So 300 watts * .75 *.9 * (.90 * .75 * .9) = 123 watts and I am 25% below that rating. Each panel/charger is measured producing almost identical 2.65 amps out. Seems like something is wrong somewhere.

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      • #4
        Originally posted by Peter Evans View Post
        Thanks for the reply. My pre-purchase estimate for end wattage was 300 watt marketing claimed output times the CPLF (Chinese Product Lie Factor - 75% delivery of marketed capability - ) times the ENRWEF (Engineer Non-Real World Exaggeration Factor (90% of engineer-claimed performance because engineers never test under actual real world conditions) times the efficiency of the controller (of course times the CPLF and ENRWEF) of ~60%. So 300 watts * .75 *.9 * (.90 * .75 * .9) = 123 watts and I am 25% below that rating. Each panel/charger is measured producing almost identical 2.65 amps out. Seems like something is wrong somewhere.
        Yep. Each 100w panel should provide about 5 amps (100w / 18V = 5.5A) so with 3 you should be getting close to 15 amps total. But as you claim the products are Chinese and can produce just about anything other then name plate data.

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        • #5
          Something to consider is what you were offering the solar output to during your test. The charge controller limits the current in order to maintain a battery voltage setpoint when not in bulk charging phase. So if you're trying to test maximum output, you need to have batteries that are low enough in SOC to allow for the potential maximum output of the panels. What was the voltage of your controller output when you did your test? If it was equal to the absorption setpoint, then your controller was limiting the current from the panels to the batteries and not allowing the panels to provide their maximum potential.
          I'm an RV camper with 470 watts of solar

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          • #6
            Originally posted by ewarnerusa View Post
            Something to consider is what you were offering the solar output to during your test. The charge controller limits the current in order to maintain a battery voltage setpoint when not in bulk charging phase. So if you're trying to test maximum output, you need to have batteries that are low enough in SOC to allow for the potential maximum output of the panels. What was the voltage of your controller output when you did your test? If it was equal to the absorption setpoint, then your controller was limiting the current from the panels to the batteries and not allowing the panels to provide their maximum potential.
            Good point. I guess I presumed the OP understood what limits a CC output or where they are measuring the current.

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            • #7

              Thanks for the replies!


              Originally posted by ewarnerusa View Post
              Something to consider is what you were offering the solar output to during your test. The charge controller limits the current in order to maintain a battery voltage setpoint when not in bulk charging phase. So if you're trying to test maximum output, you need to have batteries that are low enough in SOC to allow for the potential maximum output of the panels. What was the voltage of your controller output when you did your test? If it was equal to the absorption setpoint, then your controller was limiting the current from the panels to the batteries and not allowing the panels to provide their maximum potential.
              and

              Good point. I guess I presumed the OP understood what limits a CC output or where they are measuring the current.

              I created a 145 amp load (inverter) during the test but with full batteries to start. I also let it drain down the battery for 10 minutes and retested loaded and unloaded, in both cases total amps out was the same at 8.0 amps. I am now thinking that perhaps the test wire (14 gauge 120v lamp cord x 5 feet on the output) is creating a voltage drop, lowering the amperage out. I do not know the relationship between ampere capacity for wire using AC versus DC. As 15 amps is closer to what I expected under ideal conditions I will keep posting with updates.

              Also, I realized that I did not fully take into account that the ambient temperature is ~100 degrees F. Anyone know the approximate percentage of negative impact 30 extra degrees F produces?

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