Need to Reduce solar voltage!!

[zanydroid]

Physics police means fire department and insurance company, right?

That, and zombie Isaac Newton or your favorite 19th century electrical scientist/engineer.

 

[Westcliffe01]

I just bit the bullet and got the Sungoldpower 3kW charge controller / inverter. It was $509 + taxes right from the source. I dont need the inverter or AC charger functionality, but in this deal I get them for free, and were my bigger low frequency inverter to take a dump, now I would have a backup. I guess in an off grid situation redundency is a good thing, right ?

This unit accepts up to 450V from the solar array.

 

[timselectric]

I'd say it's time to get the right charge controller. You have pushed your luck far enough. Might as well get one capable of 6s. That's as efficient as you can get.

 

[zanydroid]

This is unhelpful, but when I went back and saw 535W panels were being used, I thought, "This is really a Great power / Great responsibility situation; if you want to use things that big you should also do big investment in planning & researching up front." Vs the safety of numbers of using standard normal residential sizes (and by extension voltage/currents) like 400W +/- 50W.

#10 was also the wrong choice if starting with the cell size with 13A I_mpp and a non-trivial probability of going to parallel strings.

 

[vashkoproimage]

Solar Panel Maximum Voltage Calculator - Footprint Hero

Calculate the maximum open circuit voltage of your solar array. Find your max solar panel voltage to correctly size your solar charge controller.

footprinthero.com

Need to know the lowest temps possible, and the temperature voc coefficient

Missouri -20

 

[vashkoproimage]

This is unhelpful, but when I went back and saw 535W panels were being used, I thought, "This is really a Great power / Great responsibility situation; if you want to use things that big you should also do big investment in planning & researching up front." Vs the safety of numbers of using standard normal residential sizes (and by extension voltage/currents) like 400W +/- 50W.

#10 was also the wrong choice if starting with the cell size with 13A I_mpp and a non-trivial probability of going to parallel strings.

I have close to 20kw of these panels for future setup when house is built. I’m just trying to use this 6kw hybrid inverter with 145v max because it’s been collecting dust for about a year now. The 6kw output works for me for a temporary setup. Just trying to get the solar input to the max I can safely.

 

[Jet]

I can’t do 3s2p. The distance is too far and the voltage will be too low for my 10 gauge wire. I need the voltage to be on the higher side to keep amps down to get away from running long distance. That’s why I went with 2s3p. If I was to running 3s2p then I will have to run 8-6 gauge wire to be under the 3 percent voltage drop.

The difference in voltage drop between 94V and 142V is insignificant. The main determining factor in voltage drop is amperage. If you add another PV circuit (2s3p/3 circuits) you will have the same average per circuit as 3s2p. It might be cheaper to buy a higher voltage mppt then the wire depending on the run length assuming you sell the other one. Unless you have an all in one inverter/mppt (unless it's a modular one ex: Outback Solar).

 

[zanydroid]

I have close to 20kw of these panels for future setup when house is built. I’m just trying to use this 6kw hybrid inverter with 145v max because it’s been collecting dust for about a year now. The 6kw output works for me for a temporary setup. Just trying to get the solar input to the max I can safely.

To summarize my contributions to the thread

2s1p to comply with NEC Isc limits on #10

2s2p if you don't care about that and just care about not smoking the MPPT

 

[Zwy]

Hello everyone. Need to reduce solar voltage on my temporary system. Running 2 sets of (3) 535 watt panels. Controller voltage is 145 max. I hitting that mark. On warmer days I get around 139-140v. This week was colder so I hit the 145-150v mark. I need to drop voltage by 5-10v before going into controller. Any ideas? For now I unplugged 1 panel off each array. Running 3 sets of 2 panels is out of question because of the distance between controller and arrays. View attachment 179235View attachment 179236

Purchase the EG4 48V charge controller. I run a pair and they work very well after updating the firmware. I did review this unit on Youtube both before and after the firmware update. Have worked flawless since the firmware update. It will take 5.5Kw at up to 450V operating voltage.

 

[740GLE]

The difference in voltage drop between 94V and 142V is insignificant. The main determining factor in voltage drop is amperage. If you add another PV circuit (2s3p/3 circuits) you will have the same average per circuit as 3s2p. It might be cheaper to buy a higher voltage mppt then the wire depending on the run length assuming you sell the other one. Unless you have an all in one inverter/mppt (unless it's a modular one ex: Outback Solar).

He never said how had the panels wired up from say a combined box or mc4 splice to the SCC.

I think assumption was 10awg for his home run from splice/combiner box to the SCC.

 

[vashkoproimage]

To summarize my contributions to the thread

2s1p to comply with NEC Isc limits on #10

2s2p if you don't care about that and just care about not smoking the MPPT

I’m not running the entire system on only (1) set of 10 gauge wire bro. I’m running 2 sets of wires (3 panels) 160ft and second set of wire 100ft distance. And that’s total lengths including positive and negative runs. More than sufficient for 2s3p.

 

[Hedges]

2s2p or 3s2p.
Orient strings differently so the don't all make max current at the same time.

10 awg 90 degree C wire actually has ampacity 40A; it is only the code police who say 30A.

Code says Isc x 1.56, but that's related to nuisance tripping of thermal breakers.
Magnetic-hydraulic breakers don't need the second 1.25x for nuisance trip. That leaves just 1.25x for cloud edge effects (not 1.56x).
Anything beyond that is code writers, not physics or engineering.

Or buy a higher voltage charge controller, as suggested, and let that charge the battery feeding your inverter.

 

[740GLE]

So

I’m not running the entire system on only (1) set of 10 gauge wire bro. I’m running 2 sets of wires (3 panels) 160ft and second set of wire 100ft distance. And that’s total lengths including positive and negative runs. More than sufficient

How do the two strings of 10awg connect to the SCC?

 

[Jet]

2s2p or 3s2p.
Orient strings differently so the don't all make max current at the same time.

10 awg 90 degree C wire actually has ampacity 40A; it is only the code police who say 30A.

Code says Isc x 1.56, but that's related to nuisance tripping of thermal breakers.
Magnetic-hydraulic breakers don't need the second 1.25x for nuisance trip. That leaves just 1.25x for cloud edge effects (not 1.56x).
Anything beyond that is code writers, not physics or engineering.

Or buy a higher voltage charge controller, as suggested, and let that charge the battery feeding your inverter.

2s2p is 4 panels and 3s2p is 6.

 

[Jet]

So



How do the two strings of 10awg connect to the SCC?

2 sets of wire is two strings not three.

 

[vashkoproimage]

So



How do the two strings of 10awg connect to the SCC?

2 Y Branch Connectors before controller. Then single wires through pv breaker then to controller. From Y connectors to controller it’s about 6 feet of total wire. That’s 26 amps running at 126v at normal operating conditions through 6 feet of wire.

 

[740GLE]

So string #1 had 3 panels, string #2 had 3 panels.

Is there any way you could convert string #2 to a 2s2p with a y junction at the panels, same 10awg back to your SCC, then where string 1 and 2 combine up that 6 foot run to #8 or something larger?

2s2p is perfectly fine for 10awg.

 

[kendive]

I can’t do 3s2p. The distance is too far and the voltage will be too low for my 10 gauge wire. I need the voltage to be on the higher side to keep amps down to get away from running long distance. That’s why I went with 2s3p. If I was to running 3s2p then I will have to run 8-6 gauge wire to be under the 3 percent voltage drop.

You need bigger wire... Go 6ga or go home.

 

[vashkoproimage]

To summarize my contributions to the thread

2s1p to comply with NEC Isc limits on #10

2s2p if you don't care about that and just care about not smoking the MPPT

I think it’s a misconception that a ssc will start smoking if supplied over-voltage. My controller personally will not supply any charge with overvoltage. It just cuts pv input off when over 145v. Can’t say this about all scc are this way.

 

[vashkoproimage]

You need bigger wire... Go 6ga or go home.

Sarcasm? Lol Explain why I need thicker wire with running 2s3p setup I have?