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Hedges

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I do a lot worse when I get liquored up and post here.

I get to have more fun when I see a good Freudian slip. Or when someone cluelessly says something they have no idea the colloquial meaning of.
But I couldn't do much with Steppenwolf's typo.
 

Stepandwolf

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If you can "place the rails high enough so the panels aren't blocked by sun lights or exhaust vents" it might be that you really have more options for larger panels. Yes Max Fans raise and you need some clearance, but if they are covered with a panel, you don't need that additional shroud over them.
The biggest obstacle with the width is the AC. Certainly not going to put something higher than that....how will I get through the McDonalds drive-through? I wouldn't even want to try and run a panel over a Max fan. The AC and fans restrain me to the 34" dimension. I wouldn't mind blocking a sun roof as they are lower.
Based on the response from HQST I would purposefully never "be on the same page with them". Just my 2 cents.

Depending on which Victron pieces you buy, you don't need the Smart Shunt.
Hmm.....first I heard that. I don't think I have seen a wiring diagram without the shunt. Already bought the BMV712 shunt meter combo.
"So, it seems partial shading isn't as degrading as I thought, but it still seems to charge controllers makes things even better?" The difference between "to" and "two" is a single keystroke, it doesn't mean you don't know the difference or are illiterate. I do a lot worse when I get liquored up and post here.
Found my error....that is even the stupider of the two ways to use the wrong two.
As mentioned with two SCC you have some redundancy and optimization. You should do it, stuff happens. If you go with all Victron products the equipment pieces will talk amongst themselves and you'll have a better end to end system than with disparate parts. This will probably be more expensive. When I looked at warranties, service in case of RMA and reliability etc, I was sold on using a Victron AIO system. I couldn't come to that conclusion with any other brand. Again just my 2 cents.
If I went with two charge controllers they would probably be like models, i.e. 100/30 version.
It seems $6k for parts doesn't go as far as it used to.
Yikes....I hope to end up at half that!
Thanks
 

Stepandwolf

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I would want the double quantity of panels. That will produce more, make up for bad days or heavier usage.
more is almost always better, but a V8 on a bicycle might be excessive.
We generally recommend larger panels, used or overstock, because the price point is better. What matters for mobile is how many watts you can fit. Are those panels around 20% efficient (200W/m^2)? My older ones are close to 13%, so higher efficiency panels make 50% more in the same space.
I have looked at sites like SanTan. For instance, they have some 305W panels for $125, but they are 65X39". I don't even know where I could put one of them, nevertheless 4 of them to equal the 1200w from the 12 smaller panels I can install.

The ones I am looking at are 18%.

If someone knows of alternative panels that can fit in that space, please let me know. Seems a common size is 27X60" I could put only two on each side and they are 190W for 760W, bar short of 1200W.

Thanks for everyone's advice and suggestions....would like to order panels shortly or at least know the dimensions so I can start on the rack system.
 

Hedges

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Victron shunt communication - I don't find the diagrams now. What I saw had a separate box that measured shunt and communicated to SCC. I don't know if the Smart Shunt also does that; you'll have to read up on them. Look for a data cable going to SCC.


I think Victron Cerbo is the controller that can measure battery current with a shunt and command SCC.

Can't find the details with a quick keyword search. Maybe if you RTFM, or somebody familiar with the feature can chime in.
 

Stepandwolf

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I think Victron Cerbo is the controller that can measure battery current with a shunt and command SCC.

Can't find the details with a quick keyword search. Maybe if you RTFM, or somebody familiar with the feature can chime in.
Thanks for the info....read the info on it. Since I don't know better, I don't know what that $300 does for me. Don't think I have ever seen one in someone's diagram?
 
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Stepandwolf

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I heard back from HQST and they suggest if I want to go with 12 panels, that I use a 3P4S configuration and a 3P2S for 6 panels. Do you guys agree? To run them all on one SCC, I am guessing I would need a 100/50. Still debating if two six panel strings on their own SCCs would be better, if for no other reason than shading issues?
 

MisterSandals

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that I use a 3P4S configuration and a 3P2S for 6 panels. Do you guys agree?
3P4S is mighty strange. Are you sure it wasn't 4S3P and 2S3P?

The idea is that you put panels in series first to achieve proper SCC input voltage and then combine in parallel. Technically, the array output, once all strings combined, would be the same to the SCC but you would create higher amps earlier (bigger wire and fuses) and would eliminate any partial shading advantages of parallel strings.
 

Stepandwolf

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3P4S is mighty strange. Are you sure it wasn't 4S3P and 2S3P?

The idea is that you put panels in series first to achieve proper SCC input voltage and then combine in parallel. Technically, the array output, once all strings combined, would be the same to the SCC but you would create higher amps earlier (bigger wire and fuses) and would eliminate any partial shading advantages of parallel strings.
I might have misspoken. They first sent me a six panel diagram that was 3S2P.
hqst 6 panel diagram.jpg

Dacian had suggested 2S3P.

2s3p_dacian.png
and when I asked HQST for a 12 panel solution I got this:

hqst 12 panel diagram.jpg

We are still back to whether I use two controllers and two sets of six, or if I go with all 12 on one controller. I still want 24V out and that was when Dacian suggested the 2S3P and having something to do with the cell count, i.e. two 32 cell (they claim 64) panels in series gets you to 60+ cells for optimum output.

HQST says they stress running their panels in parallel so they go that way.
 

MisterSandals

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I still want 24V out and that was when Dacian suggested
Well Dacian was probably implying for the Electrodacus you would want that voltage (guessing).
Because with something like a Victron 100/30 as you asked about in your original post, then you'd likely want a voltage in the 50-75% range of the max input voltage (which is 100V for the 100/30).

How you wire your panels as you can tell is greatly determined by the requirements and limitations of your SCC and your battery voltage. So arranging the panels depends on your choice of SCC. And when you do choose an SCC, we should make sure that your panels can be arranged to satisfy its input requirements (before you buy).
 

Hedges

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Thanks for the info....read the info on it. Since I don't know better, I don't know what that $300 does for me. Don't think I have ever seen one in someone's diagram?

What I think it would do for you is allow a PV array capable of delivering more current than the batteries should be subject to.
It would monitor battery current and command SCC to regulate exactly the target (for FLA) or maximum (for LiFePO4) current into battery. It would allow more current from SCC if inverter was drawing current.

In my case I have 405 Ah AGM and I programmed for 85A charge current. My PV could deliver 200+ amps to the battery. Instead, its excess capability directly runs AC loads, or is curtailed. (my system uses AC coupling.)

What I think LiFePO4 systems should have is a temperature/charge current contour. If you're lucky they have a low temperature charge cutout. But if your system can charge at 0.5C, that ought to be tapered off at lower temperatures. I don't now if any system from Victron or anyone else (outside of automobile battery systems) manage it that well.
 

Stepandwolf

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Well Dacian was probably implying for the Electrodacus you would want that voltage (guessing).
Because with something like a Victron 100/30 as you asked about in your original post, then you'd likely want a voltage in the 50-75% range of the max input voltage (which is 100V for the 100/30).

How you wire your panels as you can tell is greatly determined by the requirements and limitations of your SCC and your battery voltage. So arranging the panels depends on your choice of SCC. And when you do choose an SCC, we should make sure that your panels can be arranged to satisfy its input requirements (before you buy).
Yes, Dacian might have been giving an answer specific to the Electrodacus. I still think there is something else to do with the cell count, but haven't ever seen that used as a parameter for configuring or choosing panels.

When you say, "want a voltage in the 50-75% range of the max input voltage (which is 100V for the 100/30)." Which voltage are you using to add with? Nominal 12V panel, or the 18V optimum operating voltage, or the OCV? 3X18V would give you 54% of the 100V for the SCC. With that formula, I could go with a 4th panel, but I am not wanting a eight panel string. I am leaning towards the Victron to stay in the "system" given I already bought the Multiplus II and dongle and the BMV712 monitor/shunt.

Thanks!
 

Stepandwolf

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What I think it would do for you is allow a PV array capable of delivering more current than the batteries should be subject to.
like in overcharging?
It would monitor battery current and command SCC to regulate exactly the target (for FLA) or maximum (for LiFePO4) current into battery. It would allow more current from SCC if inverter was drawing current.
It doesn't do that anyway? In my ignorance, I assumed the SCC produced whatever current it could and the batteries absorbed what they could while the inverter is tapping what it needs. I can see something is needed to throttle charging, but thought the SCC was smart?
In my case I have 405 Ah AGM and I programmed for 85A charge current. My PV could deliver 200+ amps to the battery. Instead, its excess capability directly runs AC loads, or is curtailed. (my system uses AC coupling.)
In the case of TT use, there is mainly one big draw, the AC. Limited high draws from microwave, or an induction top if I had one. I even bought a slow cooker for the TT in hopes I could use it as well. Not having "lived" in a TT for 30 years I don't know what my real electrical usage will be. Afterall, my last trailer had no AC and it even had an icebox.
What I think LiFePO4 systems should have is a temperature/charge current contour. If you're lucky they have a low temperature charge cutout. But if your system can charge at 0.5C, that ought to be tapered off at lower temperatures. I don't now if any system from Victron or anyone else (outside of automobile battery systems) manage it that well.
Yes, I will have a low temperature cutoff. If I read the datasheet properly, the battery bank is rated at 1C continuous and 2C for 60 seconds. Someone else said these panels configured as 3X2P would be 66V and 13amps. That isn't really so much power.

Thanks sir!
 

Stepandwolf

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Nominal 12V panel is a marketing term. What specific panels and numbers are you considering and asking about?
The first message in this topic has the label from the panel. Per the rooftop diagram I provided, I can only install 12 panels but might start with six.
 

MisterSandals

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I cannot find Victron's MPPT range so its fairly fuzzy recommending a specific optimal setup. Lets do some math with these little panels and see how they work out.

Using 6x of the HQST panels: Voc 21.6, Vmp 18, Isc 6.5, Imp 5.56

3S2P stands out as a first choice with Voc 64.8 well below 100V max input.
Vmp would be 54 and some have thought lower and nearer battery voltage slightly more optimal.

Using 12x HQST
4S ups Voc to 86.4V
If you are in an area where it gets cold, perhaps near freezing, this would probably go over 100Voc.

3S4P probably only choice. This would give you 4 parallel zones which would compartmentalize shading if that is a potential issue.

Just for grins if you got the Victron 150/35

3S2P for 6 panels
4S2P for 8 panels
4S3P for 12 panels

Not a lot of difference choosing a bigger SCC. The panel to SCC matchup is a little unfortunate but not bad.
 

Stepandwolf

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I cannot find Victron's MPPT range so its fairly fuzzy recommending a specific optimal setup. Lets do some math with these little panels and see how they work out.
Do you mean range of models?

models
Using 6x of the HQST panels: Voc 21.6, Vmp 18, Isc 6.5, Imp 5.56

3S2P stands out as a first choice with Voc 64.8 well below 100V max input.
Vmp would be 54 and some have thought lower and nearer battery voltage slightly more optimal.

Using 12x HQST
4S ups Voc to 86.4V
If you are in an area where it gets cold, perhaps near freezing, this would probably go over 100Voc.

I am in NM outside of ABQ. We have moderate weather and although the trailer is 4-season, I don't expect much in the way of winter conditions which is why I left MN.

3S4P probably only choice. This would give you 4 parallel zones which would compartmentalize shading if that is a potential issue.

You just taught me something. I didn't think you had a way to deal with shading other than at a SCC level. What criteria is there to determine what a zone is for shading?
Just for grins if you got the Victron 150/35
150/35 They are $324 and the 100/30 is $226 before my 5% discount. So one would be cheaper than two, but without redundancy. Aside from saving $120, does the 150/35 offer more features?
3S2P for 6 panels
4S2P for 8 panels
4S3P for 12 panels

Not a lot of difference choosing a bigger SCC. The panel to SCC matchup is a little unfortunate but not bad.
All of those configurations are supported by the 150/35? the 4S3P config would work with that controller? They say 1000W/24V for the 35a model and 1300/24V for the 45a model.

Thanks
 

MisterSandals

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Do you mean range of models?
Sometimes they specify the working range or optimal voltage for their particular SCC's. I think it normally around 50-75% of max input voltage.
I am in NM outside of ABQ.
I've been in TorC when it was about 10 degrees about 10 years ago. It was forecast to drop below 0F so we hightailed it out of their on the southern route thru Phoenix with the new RV. So you'd want to keep 15% below max input voltage (roughly, we can do the math if you want to be more precise).

What criteria is there to determine what a zone is for shading?
A series string will be greatly reduced if any of the panels or even parts of a single panel are shaded. Strings in parallel to a shaded string are unaffected.
Aside from saving $120, does the 150/35 offer more features?
Not that i know of. I like the idea of redundancy if the cost is not significantly higher.

All of those configurations are supported by the 150/35?
Yes in terms of input voltage. 1200W of solar / 25.6V = 47A
You would have some clipping with the 150/35, meaning that at peak solar, you're leaving 12A on the roof.
In such a case, if/when you expand, a 150/50 would be better sized. I do like the idea of starting with a 100/30 and adding a 2nd 100/30 when you go from 6 panels to 12 panels.
 

Stepandwolf

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I've been in TorC when it was about 10 degrees about 10 years ago. It was forecast to drop below 0F so we hightailed it out of their on the southern route thru Phoenix with the new RV. So you'd want to keep 15% below max input voltage (roughly, we can do the math if you want to be more precise).
States like NM have such varying altitude, that weather conditions can vary a lot. My TT is 4-season, i.e. the tanks are suspended in heated air. I removed the FLA batteries on the hitch and the lithium bats are going under the bed, inside. I am considering a heating pad, but wouldn't be used other than when the TT isn't being used.
A series string will be greatly reduced if any of the panels or even parts of a single panel are shaded. Strings in parallel to a shaded string are unaffected.
awesome to hear
In such a case, if/when you expand, a 150/50 would be better sized. I do like the idea of starting with a 100/30 and adding a 2nd 100/30 when you go from 6 panels to 12 panels.
My only feasible chance for expansion is ground mounted panels and that doesn't appear to me.

You have been awesome giving me the options. I now have the confidence to order the panels and controller!
 

Hedges

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like in overcharging?

It doesn't do that anyway? In my ignorance, I assumed the SCC produced whatever current it could and the batteries absorbed what they could while the inverter is tapping what it needs. I can see something is needed to throttle charging, but thought the SCC was smart?

In the case of TT use, there is mainly one big draw, the AC. Limited high draws from microwave, or an induction top if I had one. I even bought a slow cooker for the TT in hopes I could use it as well. Not having "lived" in a TT for 30 years I don't know what my real electrical usage will be. Afterall, my last trailer had no AC and it even had an icebox.

Yes, I will have a low temperature cutoff. If I read the datasheet properly, the battery bank is rated at 1C continuous and 2C for 60 seconds. Someone else said these panels configured as 3X2P would be 66V and 13amps. That isn't really so much power.

Thanks sir!

Batteries are quite capable of taking too much current and getting cooked. SCC might drive constant current up to some voltage, then constant voltage. Near full charge, what battery accepts at that voltage tails off. But at lower SoC, battery can take excessive current and suffer damage, whether lithium of lead-acid.

If wattage of your PV panels divide by battery voltage doesn't exceed maximum rated (or recommended) battery charge current, you should be OK unless you add another source (like shore power to an inverter/charger.)
13A from PV? But what amperage at minimum battery voltage?

If your 100 Ah lithium battery is rated for 0.5C charging, and PV can deliver 50A, you're good. So long as temperature is 25 degrees C. If temperature gets down to 5 degrees C I think charge current ought to be reduced to about 10A. That's the one where I don't now if any available system does what's best, so I suggest people calculate what "C" rate their PV can deliver to battery, then set low-temperature charge disconnect something higher than 0 degrees C, whatever temperature they available current is OK for.

If you have FLA, it probably prefers exactly 0.12C or something like that. When you use AC loads, battery gets less.

Only some lithium vendors quote charge rate vs. temperature, but I assume all their batteries have similar restrictions. Check out Dzl's post with some that give such specs:

 

Stepandwolf

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Batteries are quite capable of taking too much current and getting cooked. SCC might drive constant current up to some voltage, then constant voltage. Near full charge, what battery accepts at that voltage tails off. But at lower SoC, battery can take excessive current and suffer damage, whether lithium of lead-acid.
Isn't it the job of the BMS to work within certain parameters regarding management of the cells? This is a new 544A lithium build with a BMS. There are a lot of parameters that are set regarding voltages, low temp, etc.
 
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