Max System Wattage?

serge74
serge74 Registered Users Posts: 7 ✭
in Off Grid Solar & Battery Systems #1
Got a simple question that has been bugging me for a while. I have an Apollo T80 80A charge controller. Currently I have 858Watts of panel, (4) 64W Solrex, (4) 48W Siemens and (2) Sun 205W panels in a 24v configuration. I also have ( 8 ) 6V batteries in a 12V configuration, 880 Ah. Wire permitting and any other small details what is the theoretical max wattage allowed on my system. If I am correct the maximum wattage that I can handle with the single Apollo T80 charge controller is 80A*13.8V= 1104 watts. What I am not sure of if I have the correct nominal voltage, 13.8V or do I take it to the maximum voltage the batteries will ever see, 15V. Any thoughts or ideas? Thanks for your help!
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Comments

  • TnAndy
    TnAndy Solar Expert Posts: 249 ✭✭
    #2
    Re: Max System Wattage?

    The spec sheet for it ( Here ) says: 5200 Watts (maximum when equalizing a 48v battery to 64v at 80 Amps)

    I assume that is at 48v nominal setting, but it doesn't give specs on other nominal battery setups.

    Outback controllers, for example on the MX-60, ( 60amp ) specifically lists 12v at 800watt, 24 volt as 1600, and 48v as 3200 in the manual.

    My "guess" is that your controller on a 12v system would probably be about 1/4 of the 5200w rating, or 1300watts input.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #3
    Re: Max System Wattage?

    Its simply rated maximum amps times the actual battery voltage ... wattage is not how charge controllers are typically rated, its the amperage.


    So for the T80 , its 80 amps * the working voltage
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  • serge74
    serge74 Registered Users Posts: 7 ✭
    #4
    Re: Max System Wattage?

    Thanks for the quick reply TnAndy. That is what I was thinking too and I wanted to make sure before I added another two 205W panels. I'm trying to get my charging rate percentage up to 8% or better in lieu of the 5.57% that I am right now. Ideally the higher the better but I am limited by the roof space that I have.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,634 admin
    #5
    Re: Max System Wattage?

    Your maximum charging voltage should probably be closer to 14.2 or a bit more (around 15 volts for equalization)... 13.8v on a 77F degree battery is a bit low (see battery faq #1 or #2).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • serge74
    serge74 Registered Users Posts: 7 ✭
    #6
    Re: Max System Wattage?

    Bill, thank you for answering that. I was wondering which voltage to use. The nominal 13.3V or equalization voltage of 15.2V. The difference between the two equal out to about 152 watts in difference. Thanks again
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #7
    Re: Max System Wattage?

    Sounds like your trying to not have more PV wattage than battery wattage ... you don't have to be that close. You could go probably 1.5X the battery wattage and only give up 2-5% for an hour or two a day as the PV doesn't put out rated wattage except at solar noon in very cool conditions when the panels are at the right angle with the Sun.

    You can put 10X the solar on the input side ... the controller will just run at its maximum amperage ..
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