Can a third panel be added?

hillside
hillside Registered Users Posts: 149 ✭✭
in Solar Beginners Corner #1
I recently finished a stand alone setup consisting of 2 450 Watt panels in series connected to 4 L16 370 AH batts. with a 40 Amp. Renogy controller. It's for running the house refrigerator and has worked well for about 3 weeks.
 
Now that it's been cloudy every day for the past week it looks like it'd be nice to add a bit more power.
So, the question is, since there is only room on the deck canopy for 1 more 450 Watt panel, could I add one and use a separate controller, which I already have, and feed that into the battery bank?
 It obviously would be a different voltage going in....currently the two panels give readings of 70-80 volts so one panel would be half that.....but would it work?
8- 235Watt panels, 2 strings in series/parallel, 4L16 Deka 6Volt, 370AH FLA. batteries, 3000W Cotek pure sine inverter, SRNE ML2440 40Amp Controller &  40 Amp Renogy controller, 24 Volt system.
5 stand alone PV arrays; 12V gate opener, 24V Dankoff rain water pumping system, 12V Shurflo rain water garden pumping, 12V bathroom LED lighting and fan.
4- 450 Watt panels with 4 L16 6 volt batts./ 2-Renogy Tracer 40 Amp controllers/ Xantrex 1800W PSW Inverter.
Honda EU3000W generator for backup.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,095 ✭✭✭✭✭
    edited April 2022 #2
    Your battery doesn't care what voltage is going into the controllers, just what is coming out and into them. What is your system voltage and battery amp hour capacity and  type? Flooded batteries like 10 to 13% of their amp hour capacity charging rate, AGM up to 20 %

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • hillside
    hillside Registered Users Posts: 149 ✭✭
    #3
    24 volt system, batts. are Deka L16 (4) @370AH. FLA's.
    So one panel will work in adding to the battery bank? 
    8- 235Watt panels, 2 strings in series/parallel, 4L16 Deka 6Volt, 370AH FLA. batteries, 3000W Cotek pure sine inverter, SRNE ML2440 40Amp Controller &  40 Amp Renogy controller, 24 Volt system.
    5 stand alone PV arrays; 12V gate opener, 24V Dankoff rain water pumping system, 12V Shurflo rain water garden pumping, 12V bathroom LED lighting and fan.
    4- 450 Watt panels with 4 L16 6 volt batts./ 2-Renogy Tracer 40 Amp controllers/ Xantrex 1800W PSW Inverter.
    Honda EU3000W generator for backup.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,601 admin
    #4
    Is your 450 Watt panel this one or similar?

    https://www.solar-electric.com/longi-lng-450-lr4-72hph-35-bifacial-450w-module.html

    Specifications:

    • Nominal Power: 450 Watts
    • Watt Class Sorting: -0/+5
    • Vmp: 41.5 Volts
    • Imp: 10.85 Amps
    • Voc: 49.3 Volts
    • Isc: 11.60 Amps
    • Panel Efficiency: 20.7%
    • Dimensions: 82.44" x 40.8" x 1.37" (35mm)
    • Weight: 51.82 lbs.
    Specifically looking for Vmp of 35 volts or higher (for charging a 24 volt battery bank).

    And you have some 12 volt devices? Are you using a 24 to 12 VDC down converter (just fine), or tapping 12 volts from the 24 VDC battery bank (not good)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • hillside
    hillside Registered Users Posts: 149 ✭✭
    #5
    The two are similar (or are) these..Phonosolar.
    .https://www.solarreviews.com/manufacturers/phono-solar-technology/solar-panels/phsot52226twinplusseriesps450m424th

    No 12 volt devices and I'm using a Renogy Tracer 40A MPPT controller with a 3000W Samlex  pure sine inverter.
    I was concerned about the difference in voltage going to the batteries but harbor above says it should be fine.
    So I'll plan on adding a third panel to it's own controller in order to keep these batteries happy (happier) since the controller has shut the system down once in the middle of the night (voltage got low)
    8- 235Watt panels, 2 strings in series/parallel, 4L16 Deka 6Volt, 370AH FLA. batteries, 3000W Cotek pure sine inverter, SRNE ML2440 40Amp Controller &  40 Amp Renogy controller, 24 Volt system.
    5 stand alone PV arrays; 12V gate opener, 24V Dankoff rain water pumping system, 12V Shurflo rain water garden pumping, 12V bathroom LED lighting and fan.
    4- 450 Watt panels with 4 L16 6 volt batts./ 2-Renogy Tracer 40 Amp controllers/ Xantrex 1800W PSW Inverter.
    Honda EU3000W generator for backup.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,601 admin
    #6
    Yes, you can put multiple charge controllers on a single battery bank... If they "do not sync"--The two controllers will not always be in exactly the same modes (one may be in Absorb, the second in Float for a while). This is fine. The controller with the highest voltage set-point will "win".

    I suggest that you "Star" wire the charge controllers to the battery bus... Each controller has its own wiring and fuse/circuit breaker to the single battery bus connection.

    Daisy Chaining the controllers (Controller A to Controller B to Battery Bus) could confuse each other (electrical noise from each controller in MPPT/PWM mode) and reduce the charging current of one or both controllers.

    http://www.solardesigntool.com/components/module-panel-solar/Phono-Solar/6406/PS450M4-24-TH/specification-data-sheet.html
    • Imp 10.87A
    • Vmp 41.4V
    • Isc 11.38A
    • Voc 49.24V
    • NOCT 43°C
    • Temp. Coefficient of Isc 0.05%/K
    • Temp. Coefficient of Power -0.38%/K
    • Temp. Coefficient of Voltage -0.148V/K
    • Series Fuse Rating 20A
    • Maximum System Voltage 1000V
    I guess you are around Miami Florida--So not generally a cold climate... But it can get in the 40's or 30's in winter... I would worry that the Array Voc-cold with two panels in series will exceed the (guess?) 100 VDC max input voltage of your charge controller...
    • (0C ambient - 25C standard temperature) * -0.148V per K = + 3.7 Volts @ zero C per panel
    • +3.7 volts (cold) + 49.24 Voc = 52.94 Voc-zeroC per panel
    • 2 * 52.94 volts Voc = 105.9 volts Voc-array-ZeroC two panels in series
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • hillside
    hillside Registered Users Posts: 149 ✭✭
    #7
    thanks, Bill. You've given me some things to study.
    I'm a little south of Miami. 900 miles or thereabouts.
    Overnight lows in the mid 60', (mid winter)
    You know that broke island that had the big hurricane in 2017?  The one that's "in the middle of the ocean"?
    8- 235Watt panels, 2 strings in series/parallel, 4L16 Deka 6Volt, 370AH FLA. batteries, 3000W Cotek pure sine inverter, SRNE ML2440 40Amp Controller &  40 Amp Renogy controller, 24 Volt system.
    5 stand alone PV arrays; 12V gate opener, 24V Dankoff rain water pumping system, 12V Shurflo rain water garden pumping, 12V bathroom LED lighting and fan.
    4- 450 Watt panels with 4 L16 6 volt batts./ 2-Renogy Tracer 40 Amp controllers/ Xantrex 1800W PSW Inverter.
    Honda EU3000W generator for backup.
    · Share on Twitter

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