I just sent off a note asking 1 manufacturer, about to send a couple more out to see who can get me the specifics. The one I gave was my guess while getting from the horses mouth. All of the manuals refer to a NEC safety margin of 1.25 when sizing the charge controller, not just the wiring, but no one is giving a reference number. Grid Tied systems running several hundred volts are another story.Derek, you've got me obsessed on this today. For the wiring between panels in controllers on a battery system unless the run is very short do not really apply in the design because of voltage drop is taken into accout which will almost always be larger then the minimum NEC requirement. The maximum current shall be the sum of parallel module rated short-circuit currents multiplied by 125 percent. *690.8(A)(1) Photovoltaic Source Circuit Currents. Regardless, if you use any of the manufacturers' string sizers, you will find that the max Isc output is always 80% of their rating. Therefore, if wired in parallel, Isc x 4 strings x 1.25, or if wired in series, the charge controller drops the voltage by 4 so it increases the current x4, so same math. None of them actually mention a reference, so I assume it is either for 690.8(A)(1)* or for over-irradiance. The manuals for all of the ones I am familiar with say to multiply the Isc by 1.25 for NEC. So what is the 1.25 Correction Factor for the Controller used for? I understand the wiring part, but not the controller as its output is Panel Wattage / Battery Voltage.The charge controller output is the same for either wiring, so the amp rating required is the same, since charge controllers are rated in their output, not input. The input current can be either 5.75 amps or 23 amps, but at 12 volt battery the output is 33 amps. Does not matter how they are configured with MPPT. But that is not required for the charge controller. Huh? If you are talking about the wiring then OK. I viewed their website, and the specs for the 45Amp model, it appeared that it did have "data" logging capablity which I assumed meant it allows you to use an ethernet cord to see the information.īut anyway, my main question here is, what makes Morningstar's controller better than Midnight's charge controller that is around the same specs? I definitely want to expand my system in the future, but both controller manufacturers seem to allow that, so I'm a bit lost as to which one to go with. You can connect the smaller ones to a USB port using their new USB Adapter if you have a laptop locally. I'm not sure if you wanted to monitor the data remotely, only Morninstar's 60A version has internet, their 30A and 45A do not. Your panels have 5.75A ISC x 4 of them x 1.25 NEC = 28.75A, so at least a 30A charge controller is needed. I'm assuming it is a 12V battery system? With an MPPT charge controller, you could change the panels to be wired in series and have 1/4 the current and 4x the voltage on your wire, greatly reducing voltage drop.
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