i have a 250/100 with 7.400 watts and i take 13000 kwh at night so to recharge that . shouldn't take 7 1/2 hrs i think there's something going on, i have 2000 watts on sun up side 2000 on sun down side and the rest for the noon time, should i move them around? thanks for your help
Initial thoughts are that you seem to have 3 sub arrays of solar modules pointing in different directions. These should be connected to 3 individual MPPT's.
Solar modules will only give full output when the sun is full on to the module - changing the angle of incidence reduces the output significantly. From your rough description above, 7.5 hours to replace the 13,000kWh sounds about right.
A lot will depend on your location, and exact orientation of the arrays. You may get more output by placing all the modules in the same plane, and orienting it south (or N if you're south of the equator), with the inclination equal to your latitude. This will certainly be the case if you only have one MPPT.
Hi
Having multiple panels pointing in different directions on one string isn't a good idea. The strings will effectively act as if they are permanently partially shaded. It should be noted panels that are more than 45 degrees off their optimal facing angle will also see a significant reduction in power generation.
There are three ways to address this:
question need to have one to capture the morning sun and one the afternoon sun. Each array needs to be on its own string,, buy string do you mean its own charge controller?,, i can draw a pic so you can see what im talking about ,, i have 1 Victron 250/100 controller 12 /305 watt at 120 volts/ and 16 240 watt at 120 watt panels, i know i loose alittle, but that's what i have now
By separate strings I mean a set of parallel or serial panels with its own independent tracker/MPPT. In the case of the standard Smart solar MPPT's that would be a separate MPPT per string. In the case of the Smart Solar RS that would be a two or four string device.
Something like this (Not accurate, just an example, you would need to calculate the exact size MPPTs based on string structure, voltage and amperage)
Example 1: The existing 250/100 MPPT 12x305 (North/South facing) and then 8 x 240 in each direction on two new 150/45 MPPTs (Early/late sun)
or
Example 2: Existing 250/100 MPPT 12x305 (Early sun) and then 16 x 240 with a new 250/100 MPPTs (late sun)
It would mean you would have to buy one or two more MPPT's
Regards
"Something like this (Not accurate, just an example, you would need to calculate the exact size MPPTs based on string structure, voltage and amperage)"
For realistic purposes, the Vmp of the strings should be similar, Or the cell count per string should be the same.
Recommended array string fusing should be adhered to though..
Agreed, and I would add that with multiple orientations the different sets of panels are likely to exhibit different voltages at different times as their orientation will be more optimal at different times. The arrays not getting the sun will act like "shaded" panels and pull the voltage down of the whole array. At any point in time you will have a set/sets of panels that are in this low energy state. Having panels with varying orientations in one array will work but will result in significantly lower yield than having the same panels all orientated the same way or orientated seperately on their own tracker. Having panels of different voltages in parallel will effectively pull each panel in that array's voltage down to the lowest common denominator, effectively also lowering overall yield.
Bypass diodes will help as they will simply bypass any panels that are pulling the array down, but you lose the power contribution of the bypassed panel.
Its really an efficiency argument, not a function argument. The greater the voltage difference between panels and the implementation of different orientations on the same MPPT will result in reduced efficiency.
Hi Mike, I do have 6 arrays, 4 of them pointing south, and 2 pointing west. connected on the same mppt. As long as your panels have Schottky Diodes integrated, they are protected against any loses due to the installation with other panels in parallel.
No need to have 3 mppts, it works really nicely. I did use in the past 2 mppts, which were "synchronizing" during the charge, and it was a major problem when they did enter the absorption phase, as one was mastering the other, and disabling it ! So it was unable to finish properly the absorption stage.
Using 1 mppt will avoid such problem.
PS: I have optimized the angle of my panels for winter time (60 degrees), as in spring, summer and automn I do have enough power even not being optimized for such periods.
Michel
@MichelG What is the Peak Kw your panels are rated at and what is their daily kwh yield?
Whats to total peak power on one MPPT? The reasoning behind my question is efficiency. You can have multiple panels with different orientations, but this generally results in a significantly lower yield compared to them all with the same orientation or on different trackers. I was just trying to guage the difference for myself.
