diy solar

diy solar

PV array voltage significantly higher than expected

So what is really want then is to use Voc multiplied by the temp differential at -40C/-40F multiplied by the number of panels and keep that value below 450vdc not 500vdc to be safe.
I think it's safe to target 500VDC for Voc

After that, you can see whether Vmpp is below 450VDC, probably if you go outside that range the MPPT will derate. You can also apply the temp adjustment too. I'm not sure if it is a hard cutoff like the low range, curious like you what people think. I believe Vmpp is usually far enough below Voc that this won't make a big difference.
This is the best advice, you have plenty of voltage range, and current limit is 18A.
2 in parallel Isc is 10.42A.

Plus, you could add 9 more panels in parallel later for future expansion (use fuses if you do).
I have 10 more panels not installed. I also have a second charge controller. Sadly that circuit has a 10amp DC rated breaker on it already as I was only anticipating 5.2amp max through that circuit in its current configuration.

I have some options though.

I wanted to keep the voltage high as the distance the wiring needs to go is long. I'm trying to minimize line losses. Plus I want to punish any red squirrels who dare eat through my wires. Or moose. Or Bears.
Ok, the EG4 manaul says

Max PV array open circuit: 500vdc
PV array: 120vdc-450dvc

It's not clear why the voc and array max voltages are different then.
SCC is a boost only converter. Output of SCC must not exceed 500vdc. If array exceeds 500vdc it will just pass through boost diode of boost converter and overvoltage 500 vdc internal bus of inverter.

Vmp is typically 0.81 to 0.85 of Voc for silicon panels with good illumination level. If max Vdc in 500vdc, that sets max Voc at 500vdc and max Vmp will be 0.85 x 500vdc = 425 vdc. It is not that the 425vdc means anything in limiting SCC but an array that has an Vmp of 425vdc will have a Voc approaching 500 vdc which does matter.
It's only a red alert when we approach -40F!
I have seen my panels briefly jump about 25% up in voltage and watts than the normal rated output during very cold weather and funky reflective clouds and snow on the ground at the same time…and whatever else is going on up there…be carefull ..

Leave some headroom …nature does weird stuff… even if briefly it can get ya.

I will admit ,perhaps all the “blue stuff “ I have was giving me total erroneous readings when this happened , it was lying to me… it was wrong…(remember it is cheap euro- trash…) 😁

It never has deviated once on anything… ….. I say it was giving accurate readouts …I never expected it to be near what occurred …
I was using a CC much larger than needed temporarily or it would have fried the other smaller one I was remounting…

Head room is always your friend in life.
I think it was Backwards Day for you 😂

Buck-only and Input

Iant the internal bus of a high PV voltage AIO usually in the 300V?
EG4 uses a standard PV boost SCC taken from a 230vac AIO HF inverter that uses a 500vdc internal HV DC bus for 230 vac PWM sinewave switching.

For 120vac EG4 which has a 250vdc HV DC bus, it follows the 500 vdc boosted SCC output with a push-pull down converter DC to DC converter that has a fixed DC voltage down conversion from about 500vdc SCC output to 250vdc HV DC bus for PWM sinewave H-bridge.

The extra DC to DC converter allows 500 vdc max PV input on a 120vac all-in-one HF inverter. It costs an extra couple percent of PV power conversion loss for the additional DC-DC downconverter.

The important part for this discussion is PV input cannot be allowed to exceed 500vdc interim HV DC bus.
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This ^^. Remove 2 of your 18 panels from the string and all is good.
Run single string with 16 only OR do 8+8 2p.
The output of my 8 panel array went up 20% when temps dropped to 0F during the day with wall to wall sunshine and snow on the ground.

Magic smoke appeared from the BougeRV SCC which they replaced free of charge.