Exceeding 145 Voc

I have been acquiring pieces for my solar array as I come across deals. I have the panels, the batteries and as of last weekend the unistrut to start on my array.

I have two sets of panels rated at 37.2 and 36.8 Voc and 8.85 and 8.54 A Isc respectively and am trying to purchase an MPPT charge controller next but seems to be running into an issue where the max Voc on a lot of things is 145V. With trying to keep costs down and maximizing on wire runs I would like to run a 4S panel setup but that puts me at 148.8V (37.2Voc) or 147.2V (36.8Voc) so I can run 8 AWG and be under current ratings.

I know I would be exceeding the Vmax recommended by some of the online calculators I have used but how critical is exceeding that Voc by a few percent? I figure I can't be the first to encounter this and have heard of over paneling but that's usually in the case of a grid tied setup and I'm shooting for grid tied with no back feeding.

The maximum Voc / Voltage rating is a don't exceed limit with solar equipment, which can lead to damage of your charge controller. Also the Voc of solar panels goes up as temperature goes down, so if your panels are colder then 25c/77f then Voc will be higher then rated,

try for a MPPT charge controller with 200VOC or 250 VOC. I don't think anyone will advise you to run 148.8voc on a 150v controller.

VOC increases as temperatures drop.

ice69man2005 said:

and am trying to purchase an MPPT charge controller next but seems to be running into an issue where the max Voc on a lot of things is 145V

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Which SCCs are you considering?

ice69man2005 said:

so I can run 8 AWG and be under current ratings.

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Is there an exceptionally long distance from array to SCC?

Sounds like you have 8 panels. With 9 panels, running 3S3P is an option but amps will be approaching 30A MC4 connector limits.

ice69man2005 said:

trying to keep costs down and maximizing on wire runs

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Getting a big SCC that would accept all your panels in series would simplify and reduce wiring needs. Without more info, hard to say where money is best spent (usually a better SCC is the better choice as its the heart and brains of your whole system).

I have lucked into a few deals here and there with search monitors so I'm sitting on about 24 kW of solar panels, about 100 kWh of 48V LiFePo4 batteries I got from a solar installer at a huge loss when state laws changed and came across an Outback Radian GS4048A for a heck of a price on eBay and it's still under warranty.

I have a plug in hybrid and live in NY, in the good part upstate lol. I am looking into offsetting my wood pellet heating with a heat pump setup, which I have yet to purchase but am hoping to get next year and get rid of the window shaker AC.

I was checking out a lot of Outback's stuff as to keep to the same brand of stuff but with scale and pricing I was open to other brands. I was looking into the Outback Flexmax, Midnite solar and the one which lead me to post this thread was an EG4 inverter with the 145 Voc max at a great price that could also increase my inverter output and cover my on demand water heater I want in install over the current electric tank unit.

I do know we do get some cold winters but wasn't sure how bad exceeding the Voc by 2.6% or 1.5% was. I'm not trying to get everything all set up right now but looking to expand down the road as overtime allows haha.

I'm also trying to do a ground mount array that's about 120' from the main load center in my house. I'm probably going to wind up putting the batteries into a trailer outside the house for insurance purposes. I'd like to just the solar panels to make the roof of a barn of sorts for outdoor storage and not needing to brush the snow off my car.

ice69man2005 said:

Outback Radian GS4048A for a heck of a price on eBay

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Here's a bigger one in your neck of the woods for pickup only. Would be a steal for $2k.

ice69man2005 said:

ground mount array that's about 120' from the main load center

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Having your voltage as high as possible (all in series?) will greatly reduce the required wire size.

ice69man2005 said:

I do know we do get some cold winters but wasn't sure how bad exceeding the Voc by 2.6% or 1.5% was. I'm not trying to get everything all set up right now but looking to expand down the road as overtime allows haha.

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I don't know how cold it gets there and you didn't post the panel specs for temperature compensation, but count on voltage increasing about 10% when it's cold out.

Here's a calculator that will tell you how far above 145 vdc you're going and by how far that SCC will blow up.

If your array is 120 feet away, the less strings and higher voltage you run will lower wire costs. I'd recommend a 400-600 volt charge controller.

Outback has a 300volt charge controller, MidNite solar has some new 600 volt charge controllers, as well as some of there classics support up to 250volts, Schindler has a 600 volt charge controller as well. But using higher voltage strings will simplify wiring and reduce voltage drop.

Damn that's a good deal on that Outback inverter right there. Added it to my watch list but it's outside my budget right now even though it would be perfect over anything else inverter wise.

I had to go and check my notes on the two panel types. I have some LG and some AVIM brand

LG 255W
37.2Voc
30.0Vmpp
8.50 Impp
8.85 Isc
Temp Coefficients
Voc -0.306%
Impp -0.420%
Isc +0.042%

AVIM 235W
36.8 Voc
29.3 Vmpp
8.01 Impp
8.54 Isc
Temp Coefficients
Voc -0.340%
Impp -0.460%
Isc +0.040%

I did try researching the coldest days around here and from my recollection it never went in the negative Fahrenheit range. I just didn't know if there was a halfway decent Chinese or Taiwanese MPPT charge controller that was also UL1741 listed (I think that's the one) for the price.

Don't know the quality:

24kw of panels is a lot. If you need that much power, you should have a big system with a sol-ark 15k or eg4 18kpv.

There are inexpensive charge controller only options.
I understand you want outback, but for your long run, higher VOC is better.
It is not known to me if outback has high VOC charge controllers.
I use Schnieder and love thier performance as compared to a few chinese ones i have tried. the Schneider seems to claim about 200 watts more than the chinese ones.

Midnite classic 150 can be bought new for about $500. With hyper voc it allows up to 198v.

And will support 4300 watts of pv

The classic 200 might work even better but supports less wattage. About same price on eBay

1201 said:

Midnite classic 150 can be bought new for about $500. With hyper voc it allows up to 198v.

And will support 4300 watts of pv

The classic 200 might work even better but supports less wattage. About same price on eBay

MidNite Solar - Classic Sizing Tool.

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

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would love to find me a brand new 500$ midnite classic. where are you finding them for 500$?

yodamota said:

would love to find me a brand new 500$ midnite classic. where are you finding them for 500$?

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eBay

I think the MidNite Classics on the solar trailers had some features removed. I don’t recall what these features were, but I suspect these pop up on Ebay. So if I would research that a bit before buying used ones from there.

SilverbackMP said:

I think the MidNite Classics on the solar trailers had some features removed. I don’t recall what these features were, but I suspect these pop up on Ebay. So if I would research that a bit before buying used ones from there.

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The ones I listed are brand new

1201 said:

The ones I listed are brand new

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Yeah I know. Just a general PSA. Someone might see the used ones on Ebay. I don’t remember what features were removed or if they are critical. I just remember reading it.

ice69man2005 said:

I'm sitting on about 24 kW of solar panels, about 100 kWh of 48V LiFePo4 batteries

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24kW of PV would likely run a complete house, and charge the EV - or at least 3-season EV charging.
100kWh of batteries is a very large system.

ice69man2005 said:

I have a plug in hybrid and live in NY, in the good part upstate lol.

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plug in Hybrid would be ideal for winter use. If you don't have sufficient solar, you don't have to charge it.

So you have PV and ESS covered, but the inverter you have (4048) is tiny compared to the scale of the other components.

You don't say what you want to do - what do you want the solar to be able to do for you?
What is the goal?
If you want to take your home off grid then what is the monthly energy use now? (utility bill will tell you this) and what are the peak loads? Do you use Nat Gas for: hot water tank, stove, dryer?
Often the peak load, biggest item to start is A/C units for summer cooling - do you have central air, what is the equipment, what does it take to start it?
Do you have a well pump?

Edit: Albany NY 1971 low temp record -28F (-33C)

You don't need to use 145v PV inputs - that is old tech (that I am using) and you have many great options at much higher PV voltages. The higher the voltage, the lower the amperage, smaller wire sizes, smaller components, easier to install. Look at the EG4 18Kpv - which is a 12kW inverter as an example of the type of modern equipment available. If you can frame the uses for the power, the members on the forum can help you to pick suitable equipment. Budget can be a great help also, since tier-one equipment costs more (once) but is also typically more efficient and come with more features.