Panels wattage

trumpets3u
trumpets3u Solar Expert Posts: 35 ✭✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
Lets say I have a 24 volt battery pack and a mppt controller, and I install some high voltage panels let say the Schott ASE 300 watt 50.6 VMP. By bringing the voltage down to 24 volts am I also getting more wattage out of this panels? A bigger bang for the buck?
Thanks Brian
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #2
    Re: Panels wattage

    You are getting the panel wattage because the MPPT charge controller "down converts" the energy from high voltage/low current to lower voltage/higher current using:

    Vmp*Imp - 5% controller loss = Vbatt*Ibatt

    If you where to use a PWM controller, the panels would be capable of outputting 50 volts, but the batteries would only be charging at 25 volts:

    Power = Volts * Current

    So, in that case, the setup would lose 1/2 of the available power because Voltage is 1/2 at the battery.

    You can read more about PWM and MPPT controllers here:

    All About Charge Controllers
    Read this page about power tracking controllers

    By the way, there are panel/battery voltage combinations that do not work well together... Basically high voltage solar panels (roughly over 48 volts Vmp) and 48 volt battery banks... The Vmp of the panel is too low to recharge the battery bank, and two panels in series is too high of voltage for the MPPT charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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