Answered

Series or parrellel panels

I am installing 3-300wt 24v Tenogy panels on top of my house boat. I am using a Renogy Rover Li 40 Amp MPPT. The distance between the panels and controller is approx 50' feet. Is it better to install the panels in series or parrellel? I would not have any shadowing issues as it is on a boat. I'm assuming series is the way to go to help with voltage drop. Is their anything else I should be aware of?
  • Dspackman,

    For that distance, a series connection would be best, as long as the charge controller can handle the incoming Voltage. Keep in mind the Rover can handle 100VDC solar input, if you cannot achieve that with a straight series connection than a series/parallel connection would be acceptable.



  • What Renogy panel connectors would I use for series connections?
  • For a series connection no extra components are necessary, you would just connect the male(+) and female(-) from two panels together to establish the series connection.

  • That is not correct. If you just connect the male (+) and the female (-) from one panel to the same on the next panel that is a parrellel connection. Series is when you connect the negative from the first panel to the positive of the second panel and the positive from the first panel to the negative of the second panel and so on.
  • dspackman that is correct but parallel requires extra stuff to make the connections!!!! 

    actuall series is a string so the first panel + connects to the controller as well as the last panels neg!!!


    I'm sure 3 x 300 w would exceed the 100v input limit, it is generally based on Voc, so thre times the open circuit voltage of panels is ?? 120v??

  • Thanks Bupkis that is what I was wondering. So you base the voltage input on the voltage open circuit Voc 38.8V and not on the Optimum operating voltage Vmp of 32.2V of the panel?
  • its is unclear with that controller, others mention say 150v based on spec  Voc and a lower rating based on  spec Vmp.


    I'd rather see ya over watt the controller using 4 panels, 2 strings of 2. Now that this is marked answered will admin revisit?

  • I don't think they will look back once it is answered. The customer service on the phone is pretty much useless. I went on Victron site and they have posted. There are two limits, when determining the maximum array size that can be connected to an MPPT: The Maximum PV open circuit voltage (Voc at STC) The Maximum PV short circuit current (Isc at STC) Both values are specified in the datasheets of all our MPPT Solar Charge Controllers. Those two ratings of the PV array must not exceed these MPPT limits. Note that these two maximum ratings must not be multiplied to determine the maximum installable peak power. Instead, each of them needs to checked by itself: Determining the maximum PV open circuit voltage First look at the datasheets of the solar panels to see what their maximum open circuit voltage is. Then multiply that by the number of panels that are in series in the array. The result of the multiplication must not be higher than the Maximum PV open circuit voltage as listed on the MPPT Datasheet. Make sure to take into account the coldest expected temperature. The colder it is, the higher the open circuit voltage on a PV array will be. Determining the maximum PV short circuit current Get the maximum PV short circuit current from the PV Panel datasheet. Multiply by the number of panels in parallel in the array. Having more panels in series does not change the number. The result of the calculation may not exceed the Max PV short circuit current as specified in the MPPT Datasheet. It looks like you use the Voc for calculating the max voltage. I want to try and keep the voltage as high as possible because of voltage drop in the distance I have to run. Looks like the best is to run 2 in series and put them in parrellel with the 3rd. I can't use 4 panels as I don't have the room for 4 panels. That's why I went with 3 300 watt panels. Thanks for your help Bupkis
  • I don't buy any of those as hard limits, just like overpower a controller.


    remember @ Isc and Voc there is ZERO power, Isc is associated with a short / zero volts or no watts and at the other end is Voc associated with sero amps or no watts.


    When the controller 'regulates' it forces the panel to operate @ last know mppt and Voc, or as I say on/off. Voc is panel off when the controller is disconnected!! how can that be an input limit as it is not an input! but that is how they do it and I guess it gives em a safety factor!


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