4 100 watt panel system

satmansatman Posts: 4Registered Users
I have 4 100 watt solar panels (HQST) brand,also 30 amp HQST MPPT charge controller.The panels are wired in series (83.5V , 5.6 A.(OC)
Today was rather cool but it was bright and sunny.I may not be understanding this. I was only able to get about 240 watts  from the 400 watt panels.60%. I was running my mini fridge  from a 1200 watt inverter as a load.It draws 91 watts. My confusion is, does the load  determine the actual output of the solar panels?
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  • mike95490mike95490 Posts: 7,654Solar Expert ✭✭✭✭
    edited April 2017 #2
    2 things control the PV output.
    A place to put the power (low battery, heavy loads)
      (a partially or nearly full battery will not accept a lot of power)
    How much sun and angle of Sun vs Panel

    When my batteries are full and loads are light,  5Kw of panels only puts about 20 amps out
    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 ,

  • PhotowhitPhotowhit Posts: 4,544Solar Expert ✭✭✭✭
    satman said:
    Today was rather cool but it was bright and sunny.I may not be understanding this. I was only able to get about 240 watts  from the 400 watt panels.60%.
    This is a bit low, even on cool days the surface of the solar panels will heat up, typically we see about 75% of the panel name plate rating, if the system is in "bulk" (basically taking all the energy the array can produce. You may have been past the "bulk" stage and already in absorb, at which point the charge controller limits the voltage passing to the battery and the battery may have begun to accept less current.
    satman said:
    I was running my mini fridge  from a 1200 watt inverter as a load. It draws 91 watts. My confusion is, does the load  determine the actual output of the solar panels?
    It can at times, There are 3 basic stages in battery charging (for most charge controllers).

    Bulk, where the batteries are accepting pretty much 100% of the current from the charge controller, this continues, depending on battery type and amount of incoming current, until the battery is about 80% full and the voltage reaches maximum safe level. At this point the charge controller will limit the voltage and switch stages. 

    Absorb, Where the charge controller limits the voltage to a safe level, to prevent excessive out gassing and heating of the battery. During this stage the battery begins to accept less current from the charge controller. Once the charge controller has been at this stage for a set amount of time or the controller determines a very minimal amount of current is flowing to the battery. It drops the voltage and begins the next stage.

    Float, In float the charge controller maintains a lower voltage, high enough so that the battery doesn't lose energy, but low enough so that there is very limited charging. During this stage if a load is applied, the charge controller will allow more current from the array to pass, to maintain the set 'float' voltage.

    An applied load will be reflected in more current passing from the charge controller, to maintain the voltage set points during both the Absorb and the Float stages, so in effect it does play a part in the output of the charge controller. If the load is greater than the solar array can handle the voltage will drop below the absorb or float levels as some of the current is supplied by the battery bank.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • mcgivormcgivor Posts: 1,778Registered Users ✭✭✭✭
    edited April 2017 #4
    One additional note, is that the sun doesn't suddenly come with full intensity, so the initial current, along with the voltage, will rise as the sun gets higher, depending on the depth of discharge, the battery may be approaching full charge by the time noon arrives, so the full potential of the array may never be seen. This has been my observation on my system 1, on a typical day by 11 am, the current the battery will accept has tapered down to around 6 amps, if I introduce a load of 1000 watts, the current the array will supply, will rise to 40 amps. Normally at 9 am, the charge current is around 25-30 amps, rarely will I see it higher,  so without a substantial load, would never see the full potential.

    So technically loads do have an influence on the maximum potential, if the maximum potential is masked by factors such as the example in the preceding paragraph, for example.   
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • DConlyGuyDConlyGuy Posts: 80Registered Users ✭✭
    since your like me and only running 400 watts of solar. i would run the panels in 2 sets of 2 at 40 volts and that way you start with the potential of 10 amps instead of the 5 your doing now. that how i run mine on a 24 volt system. it has worked very well for me with my tiny system
    600 watts of solar panels,Epever 30 mppt , 2 PWHR12500W4FR battery's in 24 volt setup
  • satmansatman Posts: 4Registered Users
    I have been testing individual panels for output today.Two tested at 80% and two at about 30%,All the tests were at about hi noon my time. All other factors being the same I can only conclude that the two lower output panels are drawing down my system.Is that a fair assumption ?
  • EstragonEstragon Posts: 2,332Registered Users ✭✭✭✭
    Maybe. You might get better production putting the two better panels in one string, and weaker ones in another.

    Is there any crud on the weaker panels? Dead bugs, bird bombs, etc can cut production a lot.
    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
  • BB.BB. Posts: 27,446Super Moderators admin
    And shading. Any shading, partial shading (twig, antenna, overhead wires, etc.) can kill solar pv panel output (until shading is removed).

    - Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • satmansatman Posts: 4Registered Users
    Estragon said:
    Maybe. You might get better production putting the two better panels in one string, and weaker ones in another.

    Is there any crud on the weaker panels? Dead bugs, bird bombs, etc can cut production a lot.




  • satmansatman Posts: 4Registered Users
    Followup :  I bought another 100 watt panel(poly this time).I wired the 2 mono in series with it and now are getting about 260 watts out of this array, at peak of solar day.Then as another test  I wired the low producing panels in // and could only  get 25-30 watts. I have talked to HQST about this at length . They were really no help. They even questioned the watt meter that had a external shunt . I even tested the diodes and they are normal. Gonna give them a  call again in the AM This is getting frustrating after spending over 200.00 on panels that only put out  about 30% of rated output.
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