Configuring 5 100w mono panel system

[DixieMtCR]

I recently purchased a 500w, 5 100w mono panel kit with an MPPT 40a charge controller.

Panels are currently wired, 5 parallel, yielding the highest current under ideal conditions but low voltage in cloudy skys

I am noticing, after 3 weeks of testing before making a permanent installation, the dark days of winter in Oregon takes it toll on solar charging.

Someone on this forum mentioned that it is "too bad" I have and odd number of panels (5). If it were even, then i could have either 2 paralleled sets of 2 wired in series (using only 4 panels), or I could get one more panel and have 3 paralleled sets of 2 wired in series for a bit more current (using 6 panels).

On the clouded days, the charge controller doesn't see enough voltage from the panels to start charging. So, it just sits there.

Who here has the experience to speak to this tech issue with understanding and experience?

 

[Rocketman]

To give a proper answer we need the specs from your solar panels (Voc, etc) and the specs from your solar charge controller(SCC).

In general if the SCC can handle it you Can use the following configurations. (The advantages are a higher voltage = starting (and keeping) the SCC running sooner.


To make any of these work your SCC needs to be a mppt.
5s - five series. the Voc’s all add up (plus get higher in cold weather). If your voltage goes higher than the SCC can handle it will get fried.
2s2p - 2series 2 parallel. Using 4 panels you make 2 large panels by hooking 2 panels in series +’s to -‘s - then those two large panels get hooked in parallel.
Now what to do with the 5th panel- either buy a small SCC just for it, or buy an additional panel and hook up in 3s2p (if the SCC’s voltage can handle it, or add some fuses and go with 2s3p.

Good Luck

 

[DixieMtCR]

You will see attached are the specs for the panels and the SCC. My SCC is MPPT MY40.

 

[Rocketman]

Ok DON’T do 5s - it will fry your SCC - when the sun hits it.
The Voc is 22.5v - 4s will be out too - fried one cold morning.
3s will be just fine or 2s.
I would get one more panel and hook up 3s2p. Until then 2s2p and one unconnected.
With the six panels in 3s2p you will be limited to 520watts (by the SCC). But you will have more power when conditions are not perfect.

Good Luck

 

[DixieMtCR]

You're saying two sets of three in series?

 

[Rocketman]

Yes.
The way they are referenced are to set up the string first 3s then how many strings are tied together 2p - so 3s2p.

So your current arrangement is 1s5p. (In this case most people drop the 1s and just say 5p).

 

[DixieMtCR]

So that configuration will have an optimum voltage of 53.7v and optimum current of 11.16amps, for 599.3watts with 6 panels. Looks like the SCC can handle 780watts on the input. So that looks like the max configuration.

You say that this will cause the SCC to turn on sooner and stay on longer? Sounds good.

Thanks!

 

[DixieMtCR]

Not knowing the full electronic operation or algorithm of the MPPT solar charge controller I really don't know what it does with the voltage and current or the watts that are coming out. in either case whether the panels are all paralleled or in a configuration like this with two parallel strings of three in series, the wattage is the same but the output current is less. So does the charge controller modify the voltage and amps that are on its input to the best usable current and voltage on the output to charge the battery bank?. I know watts or watts and the output is going to match the input minus the inefficiency of the unit.

 

[OffGridEnclave]

i would see to get a 6th module with +- same stats.
run 3 in series. and parallel those 2x3Modules

 

[DixieMtCR]

i would see to get a 6th module with +- same stats.
run 3 in series. and parallel those 2x3Modules

Yes I thought that best. I did order a sixth panel and it came yesterday. So now I have enough to make series three twice and parallel those two series loops. Not sure if you saw the other questions that I had but I was wondering if the charge controller is smart enough to take the 57 volts plus or minus that it gets on a good day from the three series the two parallel setup and put it down to 12 volts and up the current. Like I was saying in the other post the input and output wattage of the six panels 100 watts each is always going to be a maximum of 600 watts. So in in one configuration it might have the 57 volts and the 20 amps or whatever it was and then in the other one where they're all parallel together you only have maybe a maximum of 22 volts and 25 amps but on a non sunny day it never gets enough voltage to start pumping current.

 

[Rocketman]

Yes a mppt controller will take the 57-ish v and 11.8 a and convert it to 14.4v @ 40 amps.

under perfect conditions:
Math: 57v *11.8a = 672 watts - max power ok. Will clip it to 520watts
520watts /14.4v = 36amps of charging.

(Your batteries can handle 36 to 40 amps of charging current- correct?)

Most of the time you will not get anywhere near the perfect conditions. So the advantage of over paneling like you have done is even when conditions are about 80% of perfect, you can still get full charge from the SCC. And all the times conditions are less than 80% of perfect, you will get all your panels can produce.

 

[MichaelK]

It seems like your single biggest limitation is the low Voc limit of your 40A controller. For a bit more money you could get Epever's 50 or 60amp controller that has a Voc of 150V. Here is an idea I gave another poster recently about expanding his system. If you replaced your 40A with the 50A you could then safely wire all 5 of your panels in series to get 89.5V.

EPEVER Solar Panel Battery Regulator Charge Controller MPPT 50A 60A 80A 100A USA | eBay

Find many great new & used options and get the best deals for EPEVER Solar Panel Battery Regulator Charge Controller MPPT 50A 60A 80A 100A USA at the best online prices at eBay! Free shipping for many products!

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That by itself though is not going to solve your low output problem. What you could do though is buy some cheaper 250W grid-tie panels and create parallel strings of those. I'm getting 240-250W 30V grid-tie panels right now for about 55-60$. If you wired three grid-ties in series to get 90V, you could parallel them with the 500W of panels putting out 89.5V. That would make your system 500W + 750W.

Take this even further, and get 6 grid-tie panels. You can then wire your panels in 3S+5S+3S. All together that would give you 2000W. That much power though would be 77A at a charging voltage of 26V. Higher than what the controller might handle. What you could do is place the first 3S string facing SE, the 5S string facing South, and the second 3S string facing SW. At any one time, all three strings would not be at full output, so your controller wouldn't get overloaded. I'd predict though that utilizing the 3 directions SE, S, and SW, you'd likely be putting out 40-45A between 9am and 3pm.

On cloudy winter days when production is only 1/10 of normal, the weak, cloudy light would be more even across the three directions, and you might still be able to make 200W+ at noon in the rain.

BTW, after writing all this, I checked back and saw your system voltage is 12, so I guess skip the third array, that would be too much amperage.

 

[DixieMtCR]

It seems like your single biggest limitation is the low Voc limit of your 40A controller. For a bit more money you could get Epever's 50 or 60amp controller that has a Voc of 150V. Here is an idea I gave another poster recently about expanding his system. If you replaced your 40A with the 50A you could then safely wire all 5 of your panels in series to get 89.5V.

EPEVER Solar Panel Battery Regulator Charge Controller MPPT 50A 60A 80A 100A USA | eBay

Find many great new & used options and get the best deals for EPEVER Solar Panel Battery Regulator Charge Controller MPPT 50A 60A 80A 100A USA at the best online prices at eBay! Free shipping for many products!

www.ebay.com

That by itself though is not going to solve your low output problem. What you could do though is buy some cheaper 250W grid-tie panels and create parallel strings of those. I'm getting 240-250W 30V grid-tie panels right now for about 55-60$. If you wired three grid-ties in series to get 90V, you could parallel them with the 500W of panels putting out 89.5V. That would make your system 500W + 750W.

Take this even further, and get 6 grid-tie panels. You can then wire your panels in 3S+5S+3S. All together that would give you 2000W. That much power though would be 77A at a charging voltage of 26V. Higher than what the controller might handle. What you could do is place the first 3S string facing SE, the 5S string facing South, and the second 3S string facing SW. At any one time, all three strings would not be at full output, so your controller wouldn't get overloaded. I'd predict though that utilizing the 3 directions SE, S, and SW, you'd likely be putting out 40-45A between 9am and 3pm.

On cloudy winter days when production is only 1/10 of normal, the weak, cloudy light would be more even across the three directions, and you might still be able to make 200W+ at noon in the rain.

BTW, after writing all this, I checked back and saw your system voltage is 12, so I guess skip the third array, that would be too much amperage.

I'm still not catching on to the notation 3S+5S+3S. Are you saying 3 panels in series, and another set of 3 in series, and another set of 5 in series, and then those 3 series strings in parallel? That doesn't make sense to me. The series of 5 panels would have 2/5 more voltage than the series of 3 would have. All parallel branches have to have the same voltage.

Current is additive when equal voltages are paralleled. Voltage is additive in series but current is constant on a series leg.

It seems like your single biggest limitation is the low Voc limit of your 40A controller. For a bit more money you could get Epever's 50 or 60amp controller that has a Voc of 150V. Here is an idea I gave another poster recently about expanding his system. If you replaced your 40A with the 50A you could then safely wire all 5 of your panels in series to get 89.5V.

EPEVER Solar Panel Battery Regulator Charge Controller MPPT 50A 60A 80A 100A USA | eBay

Find many great new & used options and get the best deals for EPEVER Solar Panel Battery Regulator Charge Controller MPPT 50A 60A 80A 100A USA at the best online prices at eBay! Free shipping for many products!

www.ebay.com

That by itself though is not going to solve your low output problem. What you could do though is buy some cheaper 250W grid-tie panels and create parallel strings of those. I'm getting 240-250W 30V grid-tie panels right now for about 55-60$. If you wired three grid-ties in series to get 90V, you could parallel them with the 500W of panels putting out 89.5V. That would make your system 500W + 750W.

Take this even further, and get 6 grid-tie panels. You can then wire your panels in 3S+5S+3S. All together that would give you 2000W. That much power though would be 77A at a charging voltage of 26V. Higher than what the controller might handle. What you could do is place the first 3S string facing SE, the 5S string facing South, and the second 3S string facing SW. At any one time, all three strings would not be at full output, so your controller wouldn't get overloaded. I'd predict though that utilizing the 3 directions SE, S, and SW, you'd likely be putting out 40-45A between 9am and 3pm.

On cloudy winter days when production is only 1/10 of normal, the weak, cloudy light would be more even across the three directions, and you might still be able to make 200W+ at noon in the rain.

BTW, after writing all this, I checked back and saw your system voltage is 12, so I guess skip the third array, that would be too much amperage.

 

[OffGridEnclave]

yes your Mppt will take care of the voltage levels, that is what you have it for ...
as your system is 12V you dont wonna add to much panels and stuff to it anyhow.
cable thickness on 12v goes up a lot if you want a proper wattage.
on bigger systems the cable price alone can make it reasonable to switch to 48V.

your system is +- the max i would recommend people to run on 12v,
anything bigger go 24V or 48V

 

[MichaelK]

I'm still not catching on to the notation 3S+5S+3S. Are you saying 3 panels in series, and another set of 3 in series, and another set of 5 in series, and then those 3 series strings in parallel? That doesn't make sense to me. The series of 5 panels would have 2/5 more voltage than the series of 3 would have. All parallel branches have to have the same voltage.

Current is additive when equal voltages are paralleled. Voltage is additive in series but current is constant on a series leg.

I did the math for you? 3 x 30V = 90V. 5 X 17.9V = 89.5V. The voltages of the two different strings are almost identical. Remember, in series voltage add and amperage stays the same. In parallel amperage adds, while voltage stays the same. So, if you created three strings of panels, two strings with three 8A 30V panels, and one string with five 5.58A 17.9V panels, what you would get is 8A + 5.58A + 8A at (90V + 89.5V + 90V/3) = 21.58A at ~89.83V. In the real world you will never see voltages that precise. Wire them as I stated and be happy! It will work.