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Discussion in 'Solar Power' started by timber, Mar 5, 2011.

  1. timber

    timber WindyNation Engineer

    Re: SunTura 400 Solar Tracker System

    Question about panels output voltages allowed by tracking unit electronics.

    I'm looking at Blue Sky controllers, initially I'm looking over the SB6024HL or SB6024HDL, 60A, MPPT Controllers to use in conjunction with the SunTura 400.
    I want the capability of adding more solar panels to the system later so I need to be able to handle a minimum of 800W to 1200W max. at a later date.
    I haven't figured out the Amp rating of the controller yet since I'm not sure which input voltages apply to the controller.

    Ideally, I would be able to place the (4ea) 100W tracker panels in series to get the highest voltage for smaller wire size to the controller.
    At least some of the Blue Sky controllers have the ability to take a high input voltage and output to a 12 or 24 volt battery bank since these are MPPT controllers.

    The question is:
    Assuming that I have a separate 5W solar panel, 6A PWM solar controller and 9Ah AGM battery to run the tracker motors, can I configure the output voltage of the (4ea) 100W solar panels in series for a maximum voltage output of 107.36VDC (or whatever the actual maximum in-series voltage really is).
    Are there electronics on-board the tracker that can handle the highest output, series voltage or do I have limitations as to the maximum tracker panel output voltage at the tracker?

    I do, of course, have to stay within the MPPT controller specifications also Re: input voltage there (and I'm not sure what those are yet).

    Just trying to calculate solar system parameters and determine what would be my best MPPT controller.


    timber (aka Dave)
  2. Minnesota

    Minnesota WindyNation Engineer

    Suntura owner's manual says max 30VDC to the tracker electronics, so you could run off your 12 or 24V battery bank. I have a Suntura and SB50 coming myself. :D
  3. timber

    timber WindyNation Engineer

    Hi Minnesota,

    I see, In other words (it's not that complicated) I can look at the (4ea) panels as an independent circuit from all electrical/ electronics on-board the tracker and output whatever voltage, be it parallel, series or series/ parallel that may be appropriate for the controller. Motors AND tracking circuit would operate from my 12V (or 24V) circuit powered from my 5W Mono panel (also placed somewhere on-board the tracker but isolated from panel circuit).

  4. Minnesota

    Minnesota WindyNation Engineer

    It is not yet documented how much the tracker will consume for power each day. That will be needed to help size the separate PV panel and battery to run it. 5w likely is not enough.
    I plan to just run a line back from my core battery bank to the tracker.
  5. bluejay

    bluejay WindyNation Engineer

    I tried the motor inside at the GT power supply and it only drew 15 watts,,Why run seperate power? Sounds like you are making it more complicated then it needs to be :?:
  6. timber

    timber WindyNation Engineer


    Josh had noted in another thread Re: Suntura-400 Tracker that:
    "The two motors only draw about 1.5 amps each at 12 volts. They move very slow but they are very powerful.
    Figure at most the motors will move or will be "on" for a total of 3 minutes per day. Each motor draws 18 Watts while "on" which is roughly 36 Watts or 3 amps at 12 volts. That is only 0.15 amp hrs per day. The electronic control box is always drawing energy but it is in the 25 milliamp range so it is basically nothing."

    If the 5W panel I have isn't enough ( seems like it should be for the above draw), I have a 30W panel as well so can just use that if needed.
    The 5W mono-crystalline panel is compact and would easily go along for the ride (with a bracket off of one of the rails) so I'll use it if possible.

    I'll probably incorporate a mini PMW controller with the drive/ control circuit but this would require another waterproof enclosure so maybe I can get away without it.

  7. timber

    timber WindyNation Engineer

    Ok, so you are going with the SB50, looks like it will be a killer combination, getting every advantage via MPPT and Panel Tracking.
    Sure would be interesting to have the above combo sitting next to equivalent stationary panel wattage using a standard (non-MPPT) controller and see the real world difference.

    In sizing the Blue Sky controller (i.e. model) I'm not sure what I'll go with yet.
    Looks like the SB50 will let you place up to 1.2kW panels at 24V panel input.
    Appears the 3048 will allow a higher voltage panel input which would be good if there is a longer run from panel to controller.
    The 60A I mentioned previously here is likely overkill for any system I will ever have.
    Guess I need to read and size things up a bit more to see which controller I'll go with.

    Not sure why but I have been gravitating toward the Blue Sky brand overall.
    Any information on Blue Sky's track record in comparison to other brands?

  8. timber

    timber WindyNation Engineer

    Hi Bluejay,

    Not sure if you were addressing me or Minnesota regarding running separate power, if me, this may explain.
    Motors and tracking hardware run at 12/ 24VDC, To keep the cost of wire down, I want the panel voltage in series (probably 48+VDC). Don't want to bring grid power or DC from battery bank back out to the tracker, therefore the separate, small solar panel, small controller and on-board battery. Just don't want to be dependent on grid power to run the tracker.

  9. windyguru

    windyguru WindyNation Expert


    You are correct. You can think of the tracker electronics as a separate entity with respect to the solar panels.

    I think a 5 Watt panel should be enough to power the electronics and actuator for the tracker. I think something like a 0.5 amp-1.0 amp trickle charge to a battery might not even need a charge controller. When people leave their boats or RV's parked for long periods of time, it is common to see a 5 or 10 Watt trickle charge solar panel hooked up directly to the battery. This just keeps it topped off. I am pretty sure there is no charge controller involved with this method and you would probably be fine without one.
  10. timber

    timber WindyNation Engineer

    Great, no waterproof enclosure and a few bits less electronics.
    I like it, Thanks for the clarity on this!


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