Please help with VOC on a 255w panel

[Raul]

Hello guys , I want to re configure my system of 150vdc CC with 18 panels 6 strings of 3's to same 18 panels but 3 strings of 6's. The new controller will have a voc limit of 250vdc . The panels I have are Renesola 255w and by my calcs at -15degC will be 42v , and at stc are 37.5v.
Could you please check this calculation for me please before I commit to the new controller?

These are the panels data http://www.renesola.com/file/Global/...HHD8QVU4VI.pdf

And this is the controller 100A https://www.victronenergy.com/upload...250-100-EN.pdf
Thank you gents.

[Mike90250]

First, you should the charge controllers site for a Sizing Calculator. I don't know the Tc of your panels. But I worry about your math, 6x42= 252V FRIED !!

Second, Taking 200VDC through a CC to a 48V battery, is pushing the limits of the controller That large of differential from PV to battery takes the controller outside the nice 95% efficiency range and it will dissipate a lot of heat. If there is a GOOD reason to move to the higher voltage, then do so, but it seems unneeded to me.

[Raul]

Thank you Mike , the 42v I came up with, from -voc at stc is 30.4v, temp coefficient is 0.30%/ degC and need to know for sure I got it right for -15degC. Charge controller will allow max 250vdc and 245vdc working with a efficiency of 99% at max power. It will not fry it up but will take it off line till the voc decreases, same goes for the power , will de rate or I can limit amps in the settings. The reason I want to re configure is I got 3 controllers on 3 elevations and hoping to shrink to just 1 as they conflict on absorb or when running loads. Some will respond quick but sometimes not. Another option will be to keep strings of 3's and just upgrade the CC with a 100A -150voc CC or so.

[Mike90250]

Things like this, I don't trust my math, I go to any of the charge controller pages, and look for their calculator, and put the panel info & weather info, and see what comes out Use at least 2 different pages, as sometimes, they may have an error.
http://www.midnitesolar.com/sizingTo...playSizing.php

http://www.morningstarcorp.com/en/strings/calc.php

https://www.victronenergy.com/upload/software/VE-MPPT-Calc-2_2.xlsx

From the manual:
Peak efficiency 99% That is NOT efficiency at 245V 98A. It's most likely only at Vbatt +25% @ 30A That's just how the electronics work.
Sadly, they do not show any charts or graphs in the manual, so they actually have nothing to base that on, for the user/buyer to compare to,
Midnight and Morningstar do show eff charts and curves,

And you can't "take the panels off line till the Voc drops". What happens is on a cold morning, the panels get lit, and the Voc is high, Controller frys before it makes a single watt, After the sun heats up the panels, the Voc drops. Doing it manually, it only takes one mistake = fried controller.

[Raul]

In the past I had connected 4 x 37.5 voc on a 150voc victron Controler . In the morning gave a high voltage fault and shut of , then later turned on , and worked. I figured out once I read the stored code and removed the 4 th panel out the string with no ill effect. That's why I was under impression that has some protection against high voc .
Anyways , I'm going to stay with the 150 voc Controler if that's best for eficiency and just upgrade with a bigger amperege CC.

[Brian53713]

I was told by victron solar representative that it will fry if it goes over voltage .

[Raul]

Well it didn't , maybe I was lucky . I am not going to try that again but just wonder ; if this controllers with 250voc and even 600voc are on the market they must have a purpose.

[Brian53713]

I have seen the high voltage warning error also, way before it got cold out and I got close to that. I think it is just the connecting reconnecting once in awhile of panels that can cause that. I did get some Branch connectors to take that scary 97.64 volts down to half of that with my 100/30.