Please Could double check this for me Victron RS 450/100

[sarahstaar]

Would be really grateful if I could get somebody to double check this with me and confirm I've got my calculations correct.

Here is the kit I'm using,

1 X Victron SmartSolar MPPT RS 450/100

20 X TRINASOLAR - SOLAR PANEL 425 Watt 24V

The panels will be mounted on a south facing roof with absolutely no shading.

I'm planning on installing two strings of solar panels.

10 panels per string in parallel.

Victron charge controller
450v 100a

Solar panels each
425 watts
42 volts

Solar panels 10 panels in series
4250 watts 11 amps when hot / 4700 watts 10 amps when cold
420 volts

Max amps when cold = 11
Normal amps when hot = 10

The panels will be 45m from charge controller which I don't think will be a problem at 420volts.

I found a good deal on solar cable which is 4 mm² which I think is more than enough.

Do you think this will be okay?

Have I got my calculations correct?

 

[sunshine_eggo]

No. 425V on a 450V controller will exceed 450V at about 10°C/50°F, and I suspect your Voc is actually closer to 500V

Is the 42V Voc or Vmp?

Your other numbers don't support 42V being VoC and 42V is low for 24V panel Voc, so I'm assuming you likely have Voc near 50V.

450V is a NEVER exceed number.

Limit to 8S, one string per tracker provided it never gets below -6°C. If it does, you need to limit to 7S.

Your only option to use all 20 panels is 5S2P on each tracker, and that violates the 20A max Isc per tracker; however, if you don't accidentally hook the pv up backwards, you should be fine.

Each tracker will be limited to 18A, and each tracker is limited to 4000W with a 5760W maximum combined.

Even at 8S on each tracker, you are over-paneled.

When you get your wiring, voltage and current figured out, you can calculate your voltage drop:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Use the Estimated Resistance tab.

 

[sarahstaar]

Thanks for your help, here is the label from the back of the panel..

 

[sarahstaar]

 

[sunshine_eggo]

Yep. 50V panels 8S or 7S maximum depending on your historical low temperatures.

On each tracker: 8S if it never gets below -6°C, 7S if it does.
5S2P on each tracker understanding that you're slightly over the Isc limit of 20A. Should be fine, but if you accidentally reverse polarity, you'll pop the controller, and it can't protect against it.

For the calculator:

8S = 336V/10A
7S = 294V/10A
5S = 210V/18A

Select wire size and ONE WAY distance.

 

[green mountain boys]

I am posting my question here because it closely relates to the above information.

I was watching this video posted on YouTube by Ambition Strikes.

In the video Dexter, from Current Connected, completes the solar installation and connected the 445W bi-facial solar panels in two, 8S strings to the Victron Smart Solar RS 450/100. The 3rd string goes to a second Victron Smart Solar RS 450/100. In the video they said the panels came from SanTan Solar but did not mention the manufacturer. The only panel I found on SanTan's website that was 445W and bi-facial is this Canadian Solar Panel.
https://www.solarflexion.com/v/vspfiles/files/pdfs/canadian-solar/CS3W-445MB-AG_Data_Sheet.pdf
Assuming this is the same panel, I put the information into the Victron MPPT Calculator. The VOC is 48.90V. The calculator indicates the 8 panels in series is only allowable down to -4C or 25F. Since the installation is in Idaho it seems unlikely the lowest annual temperature is 25F.
So my question is: Why did Dexter install these panels in an 8S string as opposed to a 7S string? I do see the advantage of the 8S string since there are 3 rows of 8 panels and this makes for a neat and tidy 3 strings but everything I have seen says do not exceed the maximum voltage of the SCC. If I am wrong and this is not the same panel does anyone know what panel it could be that allows an 8S configuration in cold climate?

Second question: If you were doing this installation is there a different panel and/or SCC you would choose given the same set of conditions?. Cold climate, 8 panels X 3 (24 total) panels, short distance to the SCC and two 10K Quattro inverters.

I really like this installation for it's ability to maximize solar charging in the winter with the 2 axis tilt (so important in an off-grid installation in northern latitude), the use of the shipping container for the mounting point of the solar array and to house the solar components. The Victron components for reliability and durability. Third question: Is there anything in this design you would change to improve it, other than substituting less expensive parts?

 

[400bird]

Panels come and go. They probably used panels that Santan doesn't stock any longer.
I'm sure Dexter did the math, but let's find out!

@HighTechLab

 

[400bird]

I really like this installation for it's ability to maximize solar charging in the winter with the 2 axis tilt (so important in an off-grid installation in northern latitude),

It really isn't. Even at the winter angle, you'll produce significantly more power than you can consume in the summer. Put them up at an appropriate winter angle (both for sun and snow shedding) and it will be fine.
That is unless you get clouds or need lots of AC in the summer, but your talking about northern latitudes, so I assume not.

 

[green mountain boys]

It really isn't. Even at the winter angle, you'll produce significantly more power than you can consume in the summer. Put them up at an appropriate winter angle (both for sun and snow shedding) and it will be fine.
That is unless you get clouds or need lots of AC in the summer, but your talking about northern latitudes, so I assume not.

Just to clarify, I used the word "maximize" in reference to capturing as much available solar potential energy as possible in the winter months by matching the angle of the panels to the angle of the sun. I do realize winter production is much less than summer production, but winter production is significantly improved by optimizing the angle of the panels. Using PVwatts calculator I changed to angle of the panels and observed the change in production in December for my northern location. Changing the angle of the panels in winter makes it possible for me to consider a fully off grid system in my location. A fixed panel array just was not going to work for me.

 

[400bird]

Just to clarify, I used the word "maximize" in reference to capturing as much available solar potential energy as possible in the winter months by matching the angle of the panels to the angle of the sun. I do realize winter production is much less than summer production, but winter production is significantly improved by optimizing the angle of the panels. Using PVwatts calculator I changed to angle of the panels and observed the change in production in December for my northern location. Changing the angle of the panels in winter makes it possible for me to consider a fully off grid system in my location. A fixed panel array just was not going to work for me.

Right, my point was to permanently mount them at the winter position.

If your in a cold and snowy region, winter is the hard season. Summer is a freebie for most in the northern latitudes.

In the ambition strikes videos they were looking for ways to use the excess solar production in the summer. They had a dehumidifier/water generator that could have run 24/7 using multiple kw continuous. However, the thing didn't make enough water, so they're back to plenty of excess power all summer.

 

[green mountain boys]

Right, my point was to permanently mount them at the winter position.

If your in a cold and snowy region, winter is the hard season. Summer is a freebie for most in the northern latitudes.

In the ambition strikes videos they were looking for ways to use the excess solar production in the summer. They had a dehumidifier/water generator that could have run 24/7 using multiple kw continuous. However, the thing didn't make enough water, so they're back to plenty of excess power all summer.

I have considered fixing the panels in the winter position as you suggest. However, the PVwatts calculator indicates that my June production would fall to a level less than I would have expected at my location. June becomes lower than May and July and nearly as low as December. So my choices would be to put up more panels or try to maximize the production from the 11KW plan I have bouncing around in my head.

 

[HighTechLab]

I can’t find the pic of the panel label but I’ll gladly pull the operating voltages from VRM. We have never had a high voltage alarm triggered on that system.

We also swapped them out to the 450/200 controller at one point because the two strings were a bit over the max wattage of one controller, but 3 strings weren’t over the limit of the 200a.

As crazy as it makes me sound, I’ve designed a lot of systems since then so I can’t recall every detail. They say memory is the second thing to go…but I can’t remember the first.

 

[Hedges]

They say memory is the second thing to go…but I can’t remember the first.

Good, then you don't even realize what you're missing ...

 

[green mountain boys]

I can’t find the pic of the panel label but I’ll gladly pull the operating voltages from VRM. We have never had a high voltage alarm triggered on that system.

We also swapped them out to the 450/200 controller at one point because the two strings were a bit over the max wattage of one controller, but 3 strings weren’t over the limit of the 200a.

As crazy as it makes me sound, I’ve designed a lot of systems since then so I can’t recall every detail. They say memory is the second thing to go…but I can’t remember the first.

When I asked this question it never occurred to me that the person who installed this system might be the one to answer.

This has had me puzzled because I really like this set up and I also live in a cold climate (actually colder I think). I am designing my future system for -30F. I have not found a panel that I could put in 8S at -30F of similar capacity withthe Victron Smart Solar RS 450/100 or 450/200. I know I could go to a smaller panel or 7S but I knew that Dexter did it so I should be able to do it too. Right?

 

[Rocketman]

My guess… over the last few years it seems the Voc has been steadily climbing. So if Ambition Strikes panels were on the older side - 2 years ago - the Voc was probably lower than what you find with new panels today.

But your answer is 7s.

If you have 24 panels 8x3.
Then put 7s into three strings, and get one more mppt 150/35 for the last 3p (can’t do 3s into 150v).

 

[400bird]

I have considered fixing the panels in the winter position as you suggest. However, the PVwatts calculator indicates that my June production would fall to a level less than I would have expected at my location. June becomes lower than May and July and nearly as low as December. So my choices would be to put up more panels or try to maximize the production from the 11KW plan I have bouncing around in my head.

But how does June production compare to June consumption?
Build a tilt if you need or want. Many here prefer the reliability and simplicity of no moving parts.

 

[green mountain boys]

My guess… over the last few years it seems the Voc has been steadily climbing. So if Ambition Strikes panels were on the older side - 2 years ago - the Voc was probably lower than what you find with new panels today.

But your answer is 7s.

If you have 24 panels 8x3.
Then put 7s into three strings, and get one more mppt 150/35 for the last 3p (can’t do 3s into 150v).

I agree, the VOC would have to be lower.

 

[green mountain boys]

But how does June production compare to June consumption?
Build a tilt if you need or want. Many here prefer the reliability and simplicity of no moving parts.

I am all for simplicity and reliability!

PROS
I can weld (SMAW) good enough to make something like this and the materials are easy to source.
The container performs dual uses as supporting structure for panels and shelter for equipment (somewhat climate controlled with insulation installed)
The pipe welded to the top of the container acts as pivot points and would require nearly zero maintenance and last longer than a lifetime.
Adjust the angle of the array with minimal time and effort.
The cost seems to be quite inexpensive compared to other options for ground mounting an array because the container serves dual use.
The wire runs are relatively short going from the panels to the SCC.

CONS
I would anchor the container to the ground a little bit better just to be safe in the event of extreme wind.
A traditional ground mounted array might be more stable in extreme wind event.
A traditional ground mounted array might be considered more aesthetically appealing.
Probably not worth the effort if located in a sunny lower latitude location.

Feel free to add to this list.

 

[green mountain boys]

June production vs consumption?

I plan to pump water for irrigation in the summer.

 

[Zwy]

Reading responses and wondering what the heck everyone is referring to.

I ran my JA Solar 530W mono (not bifacial) thru the Midnite calculator.




I didn't look up the OP's specs but I sure am confused by recommendations for 7S and under unless the Blue Box can't handle it.

Edit: Looked at specs for the Blue Box, yes, it appears it is rated max of 450V, other SCC's are rated for 500V. I'd purchase a 500VOC rated SCC before the Blue Box Eurotrash.

 

[HighTechLab]

This is from Yesterday - now, obviously these are operating voltages (vmp) not open circuit...but aren't even seeing a spike in the morning before the controllers start. Hope this helps.

EDIT: yesterday they were in the low 30F's and it's rare for this location to drop below 8F

 

[green mountain boys]

View attachment 180552

This is from Yesterday - now, obviously these are operating voltages (vmp) not open circuit...but aren't even seeing a spike in the morning before the controllers start. Hope this helps.

EDIT: yesterday they were in the low 30F's and it's rare for this location to drop below 8F

Thanks Dexter,
I think I have this figured out now. I think the panel specifications I used had a slightly higher VOC than the panel you used. I am glad you pointed out that you replaced the 450/100 with the 450/200 due to being slightly over the max wattage of the controller. There is a lot to consider when designing a large system like you did for Courtney and Riley.
The Solar charge controller alone,
Over Voltage,
Over Wattage,
Over amps (not so critical I understand),
All of the above for each tracker,
All these parameters for the SCC as a whole.

Thanks for your input. Much appreciated.

 

[Alarchist]

You know there's a Victron calculator right?

https://www.victronenergy.com/mppt-calculator