C-60

Q72
Q72 Registered Users Posts: 11 ✭✭
in Solar Beginners Corner #1
Hi
I have 2 solar systems I am moving and upgrading. One will have 1560 watts @ 24 volts and the other will have 870 watts @ 12 volts. Can my C-60 controllers be used for these systems or do I need 80 amp + controllers?
Thanks Q
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    edited July 2017 #2
    Are either of the Arrays (panels) either 17.5-19 volts (VMP)for a 12 volt system or 35-38 volts (VMP)(or run 2 in series) ? If so you are close to the max for either system.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    More information with regards to the panels would be helpful, VMP IMP etcetera found on thr label on the back, as indicated you are very close to the limitations, ambient low temperatures may be the determining factor but without details one can only speculate. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    #4
    The manufacturers website should contain a string configuration tool. Use that to see if you are in the ball park.
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #5
    Thanks
    12 volt system:
     vmp 18.7
    imp. 7.75


    24 volt system:
    vmp 27.9 - 31
    imp  6.85 - 8.55
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #6
    The so called 24 volt panels you show here are NOT 24 volt panels You have 60 cell grid tie panels. 24 volt panels have 72 cells and are more like 36 Vmp. - 45 volt open circuit. With a C-60 controller you will not be able to properly charge a 24 volt battery bank.

    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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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #7
    What do you mean by properly charge? Are you referring to the advantage of a mppt controller vs the C-60 or is there another problem?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #8
    Q72 said:
    12 volt system:
     vmp 18.7
    imp. 7.75
    Your 6 - 145 watt panels in parallel, will produce as much as 6 x 7.75 amps or 46.5 amps on a very cold/cool day. so that should be fine on a Xantrex/Schneider C60 charge controller.
    Q72 said:
    24 volt system:
    vmp 27.9 - 31
    imp  6.85 - 8.55
    As Littleharbor stated, these panels are to low a voltage to use in parallel and would lose much of their charging potential even if you could use them in strings of 2 on a 24 volt system. Some places do call these 24 volt panels, and while they produce more than 24 volts, it's not enough to charge a 24 volt battery. You will want to look at a MPPT type charge controller for this system. If you list the number of panels and at each VMP we might make suggestions as to how to configure these.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #9
    Thanks
    The 24 volt system will have 6 panels.
    according to the back plate the vpm is between 27 -31
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #10
    Q72 said:
    Thanks
    The 24 volt system will have 6 panels.
    according to the back plate the vpm is between 27 -31

    That makes no sense. Panels should have a specific VMP as well as a specific VOC listed on the back. Are you in the US? It sounded like they were a variety of panels, but for them to have a range for VPM is a very new thing for me!

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #11
    Hi  I believe the range is for different temps. I will check again to be sure as soon as the weather clears. Thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #12
    Generally, a 60 cell panel is rated for Vmp~30 volts at STD conditions of 70F cell temperature and a few seconds under a sun lamp. But under full sun on a hot day, panels get very hot and Vmp can fall to 80% of STD. Or around 24 volts.

    A 24 volt lead acid battery needs around 29 volts to fully/quickly charge. Plus some additional drop for wiring and controller voltage do.

    The voltage / current curve is rounded,  not a sharp peak. So there will be some current flow on a hot day, just not optimum.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #13
    Vmp will vary with temperaure. Typically they're spec'd at STC which I think is 25C, and a temperature offset. To spec a range, the manufacturer would have to arbitrarily set a range of temps. To establish if a panel is going to work for you, you need to figure out if cold panels in your climate will be too high voltage, or hot panels will be too low. Battery temp is also important, as cold batteries will need higher voltage and vice versa.

    For example, I have a bit of a weird situation where I will be using a couple of 300w panels in parallel to float a 48v bank in winter with a pwm controller. Normally, this would be a bad idea. In this application though, there will be no need to get EQ voltage to batteries, the batteries will be mostly warm relative to panels, so need fairly low float voltage, and the pwm controller shouldn't need a ton of headroom over float voltage of batteries to work. I'll know more next spring.

    On your original question, the controller should protect itself from putting out too much current. If you have deeply discharged batteries, the panels would theoretically put more current through a 60a controller can handle, but realistically the controller likely just won't draw that much. I wouldn't design a system where a CC is expected to handle 100% of rated load regularly, but I also wouldn't design a system where batteries are expected to drawn down to low levels regularly. Ideally, I'd add controller capacity, but it should work with 60a controllers.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #14
    Oops hit the post button . I have 4 different systems including the one that charges the fence. I have a new outback mppt for the well, was hoping to get by for a bit with the c-60 on the other. 
    Thanks Q
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #15
    Thank you all for the info. I was going to put the 6 - 260 watt panels in parallel, but from the info you folks have provided it seems I should pair them in series then connect the 3 pairs in parallel? The voltage then should be ample to charge a 24 volt system. The only thing I really need is a charge controller mppt with a high voltage rating.
    Did I understand the info correct?

    Now another question. I am looking at getting some new batteries. I want to go with some L-16s.  Would the 780 watts I have in the 24 volt system be enough to keep one 420 amp hour bank charged?
    Thans again Q
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #16
    Is that 780 watts or 870 watts as mentioned earlier?
    A 420 Ah. battery bank would be fine with 42 amps going into it 54 amps is about max for a heavily used system. For a "weekend" system you can go as low as 21 amps.

    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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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #17
    That would be 780 watts. I don't have enough room for the full 8 panels currently.

    Thanks
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #18
    780 x .75 = 585 watts/28 volts =20.89 amps, pretty low and at 5% of your battery, considered as low as you should go. Is this system for intermitant use?

    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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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #19
    No, it runs a fridge and freezer,  will have to extend my rack or add another for the 2 additional panels.
    Thanks Q
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #20
    With the additional 260 watts - 8 panels, I should have near 28 amps. Would that be enough?
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #21
    It's marginal. Do you have a generator you're willing to use?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Q72
    Q72 Registered Users Posts: 11 ✭✭
    #22
    Yes have a gen, but trying to get away from it. Decided to add more panels . Will go with 6 pairs. Should give me near 42 amps  if I figured correctly. Need to get another rack. Will have to get busy.
    Thank You all for the help
    much appreciated
    Q
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