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John Frame avatar image
John Frame asked

Over paneling a Victron Charge controller and the Data Sheet

Over paneling a Victron Charge controller and the Data Sheet


My question is about over paneling the Victron MPPT charge controllers.

I know you can over panel Victron charge controllers by 30% and that the charge controller will clip the current. I know that the voltage limit is a HARD limit and it cannot be exceeded.

My question is about the data sheet for a given charge controller.

For instance using the SmartSolar 100/50 as an example it has a max PV limit of 700 watts at 12 volts. Is that stated base PV limit or can you go over that 700 watt numbest by 30% to put 910 watts of solar on the 100/50 or is the stated 700 the actual over panel limit.

I believe the 910 watt is the over panel number but I want to be VERY sure of this when designing a system.

MPPT Controllers
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mvas avatar image mvas commented ·

First, in the MPPT 100 / 50 manual that I downloaded it does not say, "Max PV Watts of 700 watts". It actually says, "Nominal 700 PV Watts". "Nominal" does not mean "Maximum".

Secondly, it states the Max PV Voltage = 100V and Max PV Amps = 60A. Therefore, the definitive Max PV watts is 6,000 Watts under any/all conditions. It is that simple.

  • Do not exceed 100 VOC PV
  • Do not exceed 60 Amps SCC PV
  • Do not exceed 6,000 Watts PV

That defines your SAO, Safe Area of Operation for the Solar Array.

Nothing suggests that 910 watts is the max over-panel watts limit.

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kevgermany avatar image
kevgermany answered ·

Rule of thumb... Your example is ok, what they're talking about is cost effectiveness of oversizing the array.

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Nev avatar image
Nev answered ·

I have a 100/50 with an array rated at 810W fed into a 4 cell 300Ah LiFePO4 battery and it self regulates at exactly 50A or any lower current limit I select. In my case the maximum observed is 711W.

Surely although extremely wasteful even a 5000W @ <100V array would not create any issues with the controller self regulating at 50A.

A working 50A current limiting circuit can't pass 60A.

7 years of fulltime travelling and no smoke yet.

Directly from the user manual:

"1a) If more PV power is connected, the controller will limit input power. "




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John Frame avatar image John Frame commented ·

Ok, so you are over paneling by 15.8%.
I know that it will clip the power.

What I was looking at is a definitive answer to my questions but based on some of these answer so far that I am getting from you all it is confirming my original notion that the stated 700 watts PV limit on the data sheet is the base limit and that you can go 30% over that stated specs.

Thanks

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JohnC avatar image JohnC ♦ John Frame commented ·

@John Frame

The 700W is just a nominal output capacity, and to get that they've not used 12V, but 14V in this case as it's closer to actual charge V (and rounded).

The max panels are limited only by the Voc and Isc of the panel array. In theory that could be 60A x 100V =6000W, but in practice will be lower due to the panels chosen and how they're strung.

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kevgermany avatar image kevgermany ♦♦ JohnC ♦ commented ·
My understanding is that Isc is only relevant when wired with wrong polarity.
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JohnC avatar image JohnC ♦ kevgermany ♦♦ commented ·

@kevgermany And other stuff like internal faults, water intrusion, even critters. All makers have this Isc limit, we're talking V's on panel output that can kill. Rather it fail passively than blow itself off the wall and burn the house down.

But @John Frame wants 'definitive', so here it is.. https://www.victronenergy.com/blog/2014/03/28/matching-victron-energy-solar-modules-to-the-new-mppt-charge-regulators/

An exerpt..

"How to determine by how much you can oversize a PV array? This can be done with help from the spreadsheet tool. Here though is the manual explanation of how it is done.

There are two limits, when determining the maximum array size that can be connected to an MPPT:

  1. The Maximum PV open circuit voltage (Voc at STC)

  2. The Maximum PV short circuit current (Isc at STC)

Both values are specified in the datasheets of all our MPPT Solar Charge Controllers. Those two ratings of the PV array must not exceed these MPPT limits.

Note that these two maximum ratings must not be multiplied to determine the maximum installable peak power. Instead, each of them needs to checked by itself:"

Dated 2014, but these things don't change.
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kevgermany avatar image kevgermany ♦♦ JohnC ♦ commented ·
Thanks. I never thought about internal faults and unwanted viditors.
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JohnC avatar image
JohnC answered ·

Hi @Off Gridin It

Forget that "30%", I don't know where you got that from.

And don't confuse the mppt output figures with those of the panels. The 100/50 has a specced input Short Circuit Current (Isc) limit of 60A, so if you have (eg) 80 Voc on the panel strings, potentially that means 4800W of panel allowable. And it matters not if you're charging either 12 or 24V batts.

Given identical panels, the total Isc is calculated from the number of parallel strings, the Voc from the number of panels in a series string. Have a play with this.. https://mppt.victronenergy.com/#

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John Frame avatar image John Frame commented ·

I got the 30% figure directly from my Victron training.
Victron states that you can over panel there charge controllers by 30%.
In fact they recommend it.

I am a certified Victron tech, I went though all the certifications and training.
Plus I have been doing this for quite a while.

So I am not confusing the output current of the charge controller with the input current from the panels. The input voltage limit of the charge controller is a Hard limit and can't be exceeded.

So going back to the specs of the 100/50 with a 12 volt battery bank. the data sheet shows 700 watts PV limit.
(The PV limit will change for the different battery bank voltages but I just picked 12 volt for this example.)


So, to reiterate my question about the data sheet for a given charge controller.

The SmartSolar 100/50 as an example it has a max PV limit of 700 watts at 12 volts. Is that stated base PV limit or can you go over that 700 watt numbest by 30% to put 910 watts of solar on the 100/50 or is the stated 700 the actual over panel limit.
30over-01.png30over-02.png

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thanar avatar image thanar John Frame commented ·
Overpaneling by 30% is purely a logistics and waste of resources limit; you can easily overpower by 1000% for all I know, as long as you don’t go over the Voc hard limit.
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Paul B avatar image
Paul B answered ·

Hi John in my opinion the below is the cut and dried answer

on a 100/50 MPPT the MAX output is 50amps at whatever the set output absorption voltage is set at the current voltage output level 12, 13 or 13.5 or 14 or 14.8 max ouput amps is 50amps

so 14 volts its 50 amps or 700watts

at 28 volts its 50 amps or 1400 watts

etc etc

output will NOT exceed 50 Amps

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kevgermany avatar image kevgermany ♦♦ commented ·
Yes, but your question was how much can be overpannelled.
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Paul B avatar image Paul B kevgermany ♦♦ commented ·
I agree with JohnC there really is no overpanel limit and there was no mention of this in my Victron training and I have not seen any buliton saying otherwise, as long as you DONT go over the max O/C voltage, Now if Guy has said 30% I would think he means why would you want to go over by more than 30% anyway

I stand to be corrected here by Victron - but thats my thoughts


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kevgermany avatar image kevgermany ♦♦ Paul B commented ·
Fully agree
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Philip Barclay avatar image
Philip Barclay answered ·

Another way to look at this might be to think about what happens when the battery is fully charged. In this case the SSC will reduce its output to zero, now there is a massive 'over-panelling' effect going on. The beauty of solar panels is they are a controllable power source, the amount of power they generate is purely dictated by the way the load (within the SSC) is applied. If you open-circuit them, or short-circuit them -> zero power output. Somewhere in the middle is the MPPT point and of course any power level between these.

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william-foreman avatar image
william-foreman answered ·

I’m writing an answer in the form of a question I have a 100/50 smart Victron charge controller I have seven 100 W Renorgy (three of the older five busbar panels and four of the new nine busbar panels I don’t know if this makes a difference? )panels,,, my battery bank is 12 V,,,people are saying you can over panel one of these charge controllers but you can’t go over the 100 V OC??? I don’t know how in the world you could over paneling and not go over the recommended OC??? I have to run my wire from my solar panels 100 feet. I have 12 gauge wire I want to wire in series I figure the higher voltage will flow easier over a long distance with 12 gauge wire.So what I want to know is can I Wire six or seven of those panels in series or will that fry my 100/50 charge controller??? if I go series series parallel I’m afraid my voltage won’t be high enough to travel the 100 foot distance in 12 gauge wire not to mention I’ll need to buy more connectors and probably in-line fuses for every positive on the panel??? series would save me some $$$money I don’t know how well it will work as I have only had one system before this one I’m now building some years back and it was 600 W in parallel on an old tracer mppt 4210 charge controller over paneled but worked like a champ. I am building a new small system kind of an emergency back up and mabe help offset the high cost of electricity. I will be using LIFEPO4 batteries and Victron energy 100/50 smart charge controller and a Victron smart battery sense and a Victron smart shunt and I have also purchased a Victron phoenix 1200 W 120 V 60 Hz inverter. i’m also wondering if I can use the inverter without the smart dongle for right now to save money?

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klim8skeptic avatar image klim8skeptic ♦ commented ·

@William Foreman First off, you have 7 panels. This gives you 2 options to wire the array.


7 series. This will result in string voltages of up to 200v. Enough to destroy a 100-50 mppt. You could use a 250-60 mppt, they do cost a bit though. And all panels should have the same Imp / Isc.

7 parallel. Array voltage of 20v. Array current of 34a. Not really an option given the voltage drop, cable cost, and fusing requirement / cost. All panels need the same Voc and Vmp.

A 3 series x 2 parallel array makes more sense. Voc under 100v. No need for string fusing (unless regulations require it), check the series fuse ratings though.

You could wire 2 new and 1 old panel per string, to give the same Voc / Vmp. Any difference in Imp / Isc will result in the output being throttled to the lower value.

Check out the Victron mppt calculator.


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