Adding panels to system

woodrose
woodrose Registered Users Posts: 7 ✭
in General Solar Power Topics #1
I have a 48v system with a 16 -12v panels mounted on a Zomeworks tracker, feeding 4-48v circuits through a trace junction box, and then through a RV controller to a 48v battery bank.
I want to add a one more 48v set of stationary panels to the system and run it through the junction box and am concerned about the set not being equal in capacity to the other circuits due to the panels being stationary.
Do I need to safeguard the stationary panels against getting a flow from the ones on the tracker?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: Adding panels to system

    What kind of controller are you using,, and how? MPPT?

    Tony
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Adding panels to system

    In general, the Vmp of the panels is more or less related to its operating temperature... For MPPT (and PWM) controllers, you can parallel strings that face different directions (east/west/tracking/etc.) and you will probably only loose a percent or two of power vs using a dedicated controller.

    However, if the new panel string would exceed the max current/power rating of your existing controller--then you would need another anyway.

    I found a report from one of the MPPT Grid Tie inverter manufacturers that wrote a white paper about east/west panels sharing one controller and posted the link here a couple times--can't find it right now.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • woodrose
    woodrose Registered Users Posts: 7 ✭
    #4
    Re: Adding panels to system

    Tony
    The controller is a RV Solar Boost MPPT. 30A so it has the capacity for the addition.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #5
    Re: Adding panels to system
    woodrose wrote: »
    Tony
    The controller is a RV Solar Boost MPPT. 30A so it has the capacity for the addition.

    Are you sure?

    30 amps @ 48V is ~1500-1600 watts

    You have 16 solar panels now, if they are 100 watt panels you would be at the controllers limit. You didn't mention the panels type/wattage
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  • woodrose
    woodrose Registered Users Posts: 7 ✭
    #6
    Re: Adding panels to system
    Solar Guppy wrote: »
    Are you sure?

    30 amps @ 48V is ~1500-1600 watts

    You have 16 solar panels now, if they are 100 watt panels you would be at the controllers limit. You didn't mention the panels type/wattage

    I have 85 watt BP (6 year old } panels.
    I was using the BP spec of 4.7 A at load in my computations which would equal 18.8 A for 4 strings. The peak amps on the controller reads 22 A so I figured I a 25% increase would be OK. Am I missing something?
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #7
    Re: Adding panels to system

    My Solar Boost MPPT CC has a "name plate rating" of 25 A BUT that is at Isc ...not Imp..In reality I have a 20 amp CC not 25... SB has done a good sales job here...

    you might want to check your panel(s) Isc rating(s) and double check them against the manual for your CC's max amperage... or you may be well over the max.

    EJ
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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