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Solar Voltage
- Thread starter Project_Mayhem
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The question is.. Lets say we have panel that has a open circuit voltage of 100 volts (or a maximum power point voltage of 100V) and in full sun produces 5 amps and also has a short circuit spec of 5 amps.
How much power is produced by the panel if its connected directly to a battery rather than through an MPPT controller. Or, if the controller is damaged and looks like a wire, what happens.
The panel is capable of 500 watts. However with nothing connected to the panel, current is zero so the panel is producing zero watts (I is zero so P is zero). The panel is also producing zero watts if shorted even though the current is 5 amps (V is zero so P is zero)
The panel looks "mostly" like a constant current source (link at the bottom).
Put the panel on a MPPT controller with a load capable of taking all the power produced. The controller adjusts the "internal" load to operate the panel at its maximum power points of V = 100V and I=5 amp so power produced by the panel is 500 watts. And of course, current to the battery could be significantly higher than the solar panel current.
Put the same solar panel directly on a 24 volt battery. The panel looks like a constant current source so the current is still 5 amps. This is only enough current to raise the battery voltage slightly. The panel now operates at 24 volts and 5 amps so the panel is now producing 24V*5A = 120 watts.
Put the same panel directly on a 12 volt battery. Still constant current at 5 amps, still only enough current to barely raise the battery voltage. The panel is once again at the battery voltage so the power produced is 12V*5A = 60 watts.
This somewhat illustrates why an MPPT controller gets more power out of a panel than a PWM controller. The solar panel current for either type of controller is the same. PWM operates the panel at the battery voltage but the MPPT controller can operate the panel at a higher voltage and will actually search for that optimum voltage. Same current but higher panel voltage is higher power produced.
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How much power is produced by the panel if its connected directly to a battery rather than through an MPPT controller. Or, if the controller is damaged and looks like a wire, what happens.
The panel is capable of 500 watts. However with nothing connected to the panel, current is zero so the panel is producing zero watts (I is zero so P is zero). The panel is also producing zero watts if shorted even though the current is 5 amps (V is zero so P is zero)
The panel looks "mostly" like a constant current source (link at the bottom).
Put the panel on a MPPT controller with a load capable of taking all the power produced. The controller adjusts the "internal" load to operate the panel at its maximum power points of V = 100V and I=5 amp so power produced by the panel is 500 watts. And of course, current to the battery could be significantly higher than the solar panel current.
Put the same solar panel directly on a 24 volt battery. The panel looks like a constant current source so the current is still 5 amps. This is only enough current to raise the battery voltage slightly. The panel now operates at 24 volts and 5 amps so the panel is now producing 24V*5A = 120 watts.
Put the same panel directly on a 12 volt battery. Still constant current at 5 amps, still only enough current to barely raise the battery voltage. The panel is once again at the battery voltage so the power produced is 12V*5A = 60 watts.
This somewhat illustrates why an MPPT controller gets more power out of a panel than a PWM controller. The solar panel current for either type of controller is the same. PWM operates the panel at the battery voltage but the MPPT controller can operate the panel at a higher voltage and will actually search for that optimum voltage. Same current but higher panel voltage is higher power produced.
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