Does the panel output amperage stay fixed no matter what the regulated out voltage?

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rafbo
rafbo Registered Users Posts: 1
in Solar Beginners Corner #1
If a 250w 8a 31.25v panel is connected to a 12v regulator, assuming full sun 31.25v, does the amperage still stay at 8? Based on W/V=A it should be able to handle 20.8 amps.

I'm trying to figure out if one 250w 8a panel hooked up to a 12vdc regulator then to a 2000w inverter could provide 110vac and 12amps.
NOTE: the setup above works from a 12v 160ah battery as the supply and can handle a draw of 15.4amps at 110vac for about 10 minutes. Will a solar panel do?

Thanks.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
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    Re: Does the panel output amperage stay fixed no matter what the regulated out voltage?
    rafbo wrote: »
    If a 250w 8a 31.25v panel is connected to a 12v regulator, assuming full sun 31.25v, does the amperage still stay at 8? Based on W/V=A it should be able to handle 20.8 amps.

    I'm trying to figure out if one 250w 8a panel hooked up to a 12vdc regulator then to a 2000w inverter could provide 110vac and 12amps.
    NOTE: the setup above works from a 12v 160ah battery as the supply and can handle a draw of 15.4amps at 110vac for about 10 minutes. Will a solar panel do?

    Thanks.

    There are two types of Charge Controllers (CCs), a more specific term than "regulator" and implying more functions.

    A Pulse Width Modulation (PWM) CC will just make and break the input to output connection to cause the average voltage to be what it wants. The output current cannot be any greater than the maximum output current of the panel.
    A Maximum Power Point Tracking (MPPT) CC will act as a DC to DC converter and will take the maximum power available from the panel and convert it to 12+ volts at the current corresponding to that number of watts and the current the battery will accept. The output current can be greater than the input current.

    A "regulator" could be a series element like the PWM controller or a power converter like the MPPT.

    All CCs will not work without a battery!!

    Same thing with your "regulator". If it has no energy storage capability, it cannot be used directly to your inverter input. The inverter and the CC both require the presence of a battery in between.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Does the panel output amperage stay fixed no matter what the regulated out voltage?
    rafbo wrote: »
    If a 250w 8a 31.25v panel is connected to a 12v regulator, assuming full sun 31.25v, does the amperage still stay at 8? Based on W/V=A it should be able to handle 20.8 amps.

    I'm trying to figure out if one 250w 8a panel hooked up to a 12vdc regulator then to a 2000w inverter could provide 110vac and 12amps.
    NOTE: the setup above works from a 12v 160ah battery as the supply and can handle a draw of 15.4amps at 110vac for about 10 minutes. Will a solar panel do?

    Thanks.

    No.
    First up, the type of inverters that run directly from solar panels are GT inverters and they do not produce constant output as they are meant to add power to an existing AC system.

    Second, the output of a panel varies according to the amount of light falling on it, the amount of load attached to it, and its temperature.

    A 250 Watt panel is bound to be 8 Amps @ 31 Volts maximum power. If connected directly to a 12 Volt battery or through a PWM type controller it will still be capable of full current, but the Voltage will be pulled down to the battery level. The best you would see here would be 8 Amps @ 14.8 Volts or 118 Watts. Under normal "Float" Voltage it would be 110 Watts.

    Panel output has little to do with inverter power, unless you are trying to balance opportunity loads to make use of what is possible after batteries have been charged. In that case you have to include the inverter's self consumption and conversion efficiency loss. From that 110 Watts the inverter (if a small one) may use 6 Watts, leaving 104 which will be about 98 after the conversion loss. And that doesn't include what power would still go to the battery to maintain Voltage level.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
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    Re: Does the panel output amperage stay fixed no matter what the regulated out voltage?
    rafbo wrote: »
    I'm trying to figure out if (can)one 250w 8a panel hooked up to a 12vdc regulator then to a 2000w inverter could provide 110vac and 12amps.

    Oh no. Even if the panels could drive the inverter without a battery, which it cannot, and IF the whole system was 100% efficient with no losses whatever (which is impossible), you'd have a max of 250 watts output from the inverter, which at 110 volts would be 250/110=2.27 amps, a far cry from your hoped for 12 amps.
    In reality, with normal system losses, which would have to include a battery, you might have roughly half that.
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