Solar Combiner

[sandog]

I have 16 zshine, 540w bifacial panels, and will end up going to 4 inverters, 2 pairs running in parallel, and was wondering what is the best methodology, or if feasible, to run all 16 panels to all the inverters. Should they be ran in string of 4 each to hit the 160v DC from them, or microinverters on each of them?

Any additional ideas or feedback would be great.

Thank you

 

[ScrotpusGobbleBottom]

Inverters should never share panels. I would do just as you said. Group panels that are most directionaly the same and utilize however many mppt inputs you need to. All the mppts are on the same battery bank? Then it wouldn't matter. If you are within voltage and amp limits you could put them all on one mppt.

 

[sandog]

Inverters should never share panels. I would do just as you said. Group panels that are most directionaly the same and utilize however many mppt inputs you need to. All the mppts are on the same battery bank? Then it wouldn't matter. If you are within voltage and amp limits you could put them all on one mppt.

Why is that, from what I have researched, it seems ok to share panels.

 

[BentleyJ]

Not sure what research you are referring to. PV inputs on an inverter or charge controller have Maximum Power Point Tracking algorithms built in. Meaning the electronics will adjust the current such that the resulting PV voltage is maximized to produce the highest wattage for prevailing solar conditions.

If 2 separate MPPT controllers are pulling from the same PV array the results may very well be LESS than maximum as they will tend to fight with each other. This topic has come up previously on the forum and the consensus is not to share the PV array. If you have an inverter or charge controller installation manual that says otherwise please link it here, I'd like to see that.

 

[ScrotpusGobbleBottom]

If 2 separate MPPT controllers are pulling from the same PV array the results may very well be LESS than maximum

That is what I was referring to. Sorry if my use of the word inverter threw you off. I should have said AIO mppt inputs.
Just so Im clear. Tell me if this works.

30 panels, 10 strings of 3 into a combiner box with ONE output. Lets call this 12,000 watts. We have 2 AIO's working in tandem. Each mppt input doesnt like more than 10,000 watts.
Would you split the array or hook both mppt inputs of BOTH AIO's to the single output of the combiner box?

 

[BentleyJ]

I should have said AIO mppt inputs.

An MPPT charge controller input is the same. Doesn't matter if you are referring to a stand alone Charge Controller like a Victron or an input on an AIO. The function is the same. To convert the variable PV panel output into a stable, voltage and current controlled battery charger.

30 panels, 10 strings of 3 into a combiner box with ONE output. Lets call this 12,000 watts.

NO, that is way to much unnecessary wiring & hardware. Typically, the panels are combined in series to maximize voltage and thus reduce current (which requires smaller, less expensive wire) and the number of strings that need to be combined. Many of the new AIO products accept up to 500V or even 600V and have at least 2 separate MPPT inputs per inverter. These are very flexible with regard to PV array arrangement.

Would you split the array or hook both mppt inputs of BOTH AIO's to the single output of the combiner box?

With 30 panels and 2 AIO's here a couple of scenarios. In all cases, none of the arrays would be split between 2 inverters.

1) Assuming that each AIO has 2 separate inputs and a Max Voc to support 10 panels in series. 3 strings of 10 panels would be connected in series. One of the AIO's would have 2 strings attached, one to each of the separate MPPT inputs. The other string would be attached to the other AIO on MPPT input 1

2) Assuming the AIO's Max Voc will not support 10 panels in series. Then something like 6 series strings of 5 panels. Take 2 strings and combine them in parallel and connect them to MPPT input 1, and one string of 5 and connect that to the other MPPT input on AIO #1. Do the same for AIO #2.

3) Same as 2 but each AIO only has 1 MPPT input. Combine 3 strings in parallel for each of the 2 AIO's.

There are other combinations. Keep in mind that multiple MPPT inputs on a single AIO are usually separate so the number of panels in the string does not have to be the same on MPPT 1 as on MPPT 2. However, if 2 series strings are combined in parallel each string should have the same number of panels to keep the voltages equal.

 

[BentleyJ]

Forgot to mention how to deal with shading in the above examples. For example lets say there are 4 panels that get shade in the late afternoon. Those 4 would all be used in one of the 5 panel strings that gets connected to its own MPPT input rather than having 1 shaded panel in 4 different strings.
Individual panel optimizers could also be considered.