Voltage Regulation from Panels to Mppt device

spacebassspacebass Registered Users Posts: 82 ✭✭
edited February 14 in Solar Beginners Corner #1
I am buying from China an mppt device that has an 80 volt maximum inout , I am according to my existing  Epever mppt units getting a little bit more up to 88 volts from my panels at times that I take it will fry the transisrtors in the new mppt unit, can I limit the output of the panels with a dc motor regulator such as this : | DC 6V-90V 15A DC Motor Speed Controller Stepless Speed Regulation Pulse Width PWM DC 12V 24V 36V 48V 1000W
https://a.aliexpress.com/_msU7hJV ??
plug the panels into in and the new mppt device to motor turn the knob and. measure the volts to motor when above 80 volts??
Or how is it done ??
Thanks


Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,425 admin
    There is no off the shelf component that is used to downconverter/manage Voc/Vmp of a solar array to a lower voltage.

    Could you use a DC to DC down converter (buck type)--Maybe (converter takes a wide range of DC input voltages, and gives a regulated output voltage--Pick 70 volts or whatever)... But there are a lot of variables and would be difficult to justify the work/costs.

    An MPPT charge controller is just a Buck Mode (down convertering) switching power supply. Your typical options would be to 1) rewire the array (need to know the Vmp/Voc of the panels, min/max ambient temperature for your region, and battery bank voltage)--May or may not be possible based on the answers to the questions. Or b) get the right charge controller or solar panels to fix the "mismatch".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,244 ✭✭✭✭✭
    There is no "fix" unless you want to engineer a Current Source DC-DC down converter.    It would be less expensive to just get the right charge controller or drop a panel off the array.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • spacebassspacebass Registered Users Posts: 82 ✭✭
    edited February 16 #4
    BB. said:
    There is no off the shelf component that is used to downconverter/manage Voc/Vmp of a solar array to a lower voltage.

    Could you use a DC to DC down converter (buck type)--Maybe (converter takes a wide range of DC input voltages, and gives a regulated output voltage--Pick 70 volts or whatever)... But there are a lot of variables and would be difficult to justify the work/costs.

    An MPPT charge controller is just a Buck Mode (down convertering) switching power supply. Your typical options would be to 1) rewire the array (need to know the Vmp/Voc of the panels, min/max ambient temperature for your region, and battery bank voltage)--May or may not be possible based on the answers to the questions. Or b) get the right charge controller or solar panels to fix the "mismatch".

    -Bill


    Thanks Bill , I am getting this 88 volts from two 390 watt mono panels in series I have one string that is one of these panels so I think I will buy a 340 watt panel same make but poly v mono and put in series and hope it brings the voltage of the two under 80 volts. 
    88 volts seems high vmp of the mono panels is under 40 volts , I will also  measure the pv voltage myself.
  • BB.BB. Super Moderators, Administrators Posts: 31,425 admin
    What is the Voc of the "old" panels vs the Voc of the "new" panels? Just changing from Mono to Poly may not make enough of a difference....

    What is the battery bank voltage?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Raj174Raj174 Solar Expert Posts: 786 ✭✭✭✭
    edited February 16 #6
    Really, you don't want to be even close to the max VOC input for your controller. IMO, it's just asking for trouble down the road.  

    Rick
    3600W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH LiFePO4, Kohler Pro 5.2E.
  • MichaelKMichaelK Registered Users Posts: 192 ✭✭✭
    It seems like the easiest solution would just be to re-wire the two panels you already have to be in parallel instead of series; that is 1S2P.  Assuming the Voc is going to be ~44V, I'd guestimate that the new 1S2P Vmp would be ~35-36V.  For sure that would be enough headroom for a 12V battery, and maybe enough headroom for a 24V battery?  Again, what is your battery system voltage?  What is it's Ah rating?  Two 390W panels in parallel should give you about (390W X 2 panels)/13V charging X 0.85 lossfactor = 50-51A charging.  That is enough for a LARGE 12V bank, or OK for a medium sized 24V bank.

    What is so attractive about this new controller that makes you want to switch out your Epever?  If it's low price, I would be very, very suspicous that this is actually a fake MPPT?  Can you provide a link to this brand?  What is the shipping weight?  As cheesy as that sounds, weight is a fairly good indicator of the quality of some of these foreign products.  That is, I'd more trust a brand with a shipping weight of 10lb rather than a shipping weight of 10oz.
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
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