diy solar

diy solar

Brown bear destroyed our yurt powered by Yeti 3000, so I'm designing solar for a cabin & a bit lost

Are there ways you can incorporate panels into the deck?
Possibly. Our property is heavily forested with trees as high as 80 feet. The sloping down toward the east of the hill the deck is on means we only had to cut down a few trees directly to our east in order to see the mountain range and the sun that pokes above them during sunrise. But if we build on the deck rather than on the two story cabin (two story because of a loft) we *might* have issues with the more distant trees blocking the sun. Then again, maybe not. I'd have to take a better look from that vantage point. I would put those panels below the railing on the deck so it doesn't block the view but I'll have to see if that will work in winter. It very well might, at least enough to get some light anyway.
 
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I'm looking at Victron MPPT charge controllers. I still am not sure if multiple SCCs will need to "talk to" each other in order to most efficiently charge the same battery bank though.
 
When you are calculating max voltage for a SCC you use Voc not Vmp.
Your Renogy 100w panels are probably about 22Voc if 18.9Vmp

Also add on the voltage for cold temperatures which you have in Alaska.
 
When you are calculating max voltage for a SCC you use Voc not Vmp.
Your Renogy 100w panels are probably about 22Voc if 18.9Vmp

Also add on the voltage for cold temperatures which you have in Alaska.
That's great to know. You're correct, the VOC is 21.6 volts. So in series I should be multiplying 21.6 by the number of panels in a series? So doing it correctly would be:

Series of 1A, 1B, 1C wired in parallel with Series of 1D, 1E, 1F = 65 volts/11 amps and therefore tied into a Victron SmartSolar 75/15

It sometimes gets down to -10F where I'm at although the lowest on record is -24F for the area. Based on the temperature correction chat from NEC 690.7 that means the VOC is actually 1.23 more than the 21.6 volts. I'll update the math and greatly appreciate the help!
 
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So doing it more correctly, that should mean that:

Series of 1A, 1B, 1C wired in parallel with Series of 1D, 1E, 1F = 80 volts (65*1.23 correction)/11 amps and therefore tied into a Victron SmartSolar 100/15
I missed that your SCC amps are too low.
Amps on a SCC is output.

6 100watt panels is 600w.
600w into a 12V battery is 50A
600w at 14V charging is 42.8A
 
I missed that your SCC amps are too low.
Amps on a SCC is output.

6 100watt panels is 600w.
600w into a 12V battery is 50A
600w at 14V charging is 42.8A
I got that 5.29 number from Renogy's discussion of this particular panel being wired in parallel. According to them they say:

"When your panels are connected in parallel, you add the amperage together, but the voltage stays the same. For example, if you have two RNG-100D 100 Watt panels, each panel will produce about 5.29 amps. Connecting these panels in parallel will produce 200 Watts (18.9V and 10.58 amps under optimum conditions)."


18.9V * 5.29 amps = 99.981 watts

Do you think that isn't correct? Or is it correct but something additional ups the amperage sent to the charge controller?

I'm wiring panels in series which keeps the amps the same at 5.29 and then only taking two groups of panels in series and wiring them together in parallel. So it seems it should be 5.29amps * 2 rounded up to 11 amps?

Perhaps my confusion is the math when wiring panels in series together in parallel? Hard enough to talk about, so I wouldn't be shocked if I did the math wrong.

Edit: it seems perhaps you are saying that I got the amp limit of the SCC wrong? I assumed the Victron SmartSolar 100/15 SCC can accept volts no more than 100 volts and amps no more than 15 amps. Perhaps that is what I am getting wrong?
 
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I got that 5.29 number from Renogy's discussion of this particular panel being wired in parallel. According to them they say:

"When your panels are connected in parallel, you add the amperage together, but the voltage stays the same. For example, if you have two RNG-100D 100 Watt panels, each panel will produce about 5.29 amps. Connecting these panels in parallel will produce 200 Watts (18.9V and 10.58 amps under optimum conditions)."


18.9V * 5.29 amps = 99.981 watts

Do you think that isn't correct? Or is it correct but something additional ups the amperage sent to the charge controller?
With a 15A SCC you will never get more than about 200w out of those 600w of panels.

You need a 45A to 50A SCC to ever get the full 600 watts at 12V.

MPPT SCC has 2 sides.
Input and output.
57Vmp x 10.5A is about 600 watts

12V x 50A is 600 watts

To size a SCC take the total wattage then divide by battery voltage.
A 24V battery would halve your SCC amperage saving money and allowing smaller gauge cheaper wires.
 
With a 15A SCC you will never get more than about 200w out of those 600w of panels.

You need a 45A to 50A SCC to ever get the full 600 watts at 12V.

MPPT SCC has 2 sides.
Input and output.
57Vmp x 10.5A is about 600 watts

12V x 50A is 600 watts
I think I understand. When I see a Victron SmartSolar 100/15 that does NOT mean the SCC can accept only 100 volts and only 15 amps from the panels.

So I think the issue is that while the SCC can accept higher voltages (and thus less amps) it can only charge the batteries at around 12V which means it has to have a larger amp output to get all the juice into the battery?

So trying this again, the more correct calculation would be:

Series of 1A, 1B, 1C wired in parallel with Series of 1D, 1E, 1F = 80 volts (65*1.23 correction)/11 amps = 880 watts = (880/12 = 74 amps) and therefore tied into a Victron SmartSolar 150/70 (close enough to the 74 amps)

Does that seem like good solar charge controller selection for that string of panels?
 
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I think I understand. When I see a Victron SmartSolar 100/15 that does NOT mean the SCC can accept only 100 volts and only 15 amps from the panels.

I'm not sure how to choose an SCC for each string then to maximize the charge into the battery based on the string I tie into it....
Yes the 15A is max battery charging output.

It's simple. I updated my last post.

To size a SCC take the total wattage then divide by battery voltage.
600w ÷ 12V is 50A
600w ÷ 24V is 25A

A 24V battery would halve your SCC amperage saving money and allowing smaller gauge cheaper wires.
 
Yes the 15A is max battery charging output.

It's simple. I updated my last post.

To size a SCC take the total wattage then divide by battery voltage.
600w ÷ 12V is 50A
600w ÷ 24V is 25A

A 24V battery would halve your SCC amperage saving money and allowing smaller gauge cheaper wires.
Thanks so much for taking the time to cure my ignorance. Very much appreciated.

My error was thinking a SmartSolar 100/15 required no more than 100 volts and no more than 15 amps from the solar panels. It seems, rather, those numbers mean it requires no more than 100 volts from the panels, and can provide no more than 15 amps to the battery when charging.

Unfortunately using the Relion Low Temperature batteries means I have to stick with a 12V system since they cannot be wired in series.

Thanks again for all the help!
 
Those small 100 watt panels and 12V battery is going to cost you.

Wire size from panels to SCC.
Enter
Vmp total of array
Amps total of array
One way distance.
Under 3% is good.
I doubt if your distance is that much.
 
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Series of 1A, 1B, 1C wired in parallel with Series of 1D, 1E, 1F = 80 volts (65*1.23 correction)/11 amps = 880 watts = (880/12 = 74 amps) and therefore tied into a Victron SmartSolar 150/70 (close enough to the 74 amps)

Does that seem like good solar charge controller selection for that string of panels?
Your 6 panels are 100 watts right?
That is 600 watts total not 880.

Your mistake is that you used Voc and temp correction Voltage to calculate watts.
Vmp x Imp = watts.
600 watts panels is 600 watts.
 
Your 6 panels are 100 watts right?
That is 600 watts total not 880.

Your mistake is that you used Voc and temp correction Voltage to calculate watts.
Vmp x Imp = watts.
600 watts panels is 600 watts.

It's 3 panels wired in series (which multiplies the voltage, 21.6*3=65 volts) then multiplied by the temp correction of 1.23 = 80 volts...

which are then wired in parallel with another 3 panels wired in series.

So if my understanding of the effects of wiring in series and wiring in parallel is correct, that equates to 80 volts going to the charge controller for those six panels.

I did this because earlier in the thread you told me:

"When you are calculating max voltage for a SCC you use Voc not Vmp.
Your Renogy 100w panels are probably about 22Voc if 18.9Vmp

Also add on the voltage for cold temperatures which you have in Alaska."

Is my misunderstanding that on a cold perfect day the panels could send 80 volts to the charge controller but that if it did so, it wouldn't send the full amps, and thus the wattage would remain only 600 watts?
 
It's 3 panels wired in series (which multiplies the voltage, 21.6*3=65 volts) then multiplied by the temp correction of 1.23 = 80 volts...

which are then wired in parallel with another 3 panels wired in series.

So if my understanding of the effects of wiring in series and wiring in parallel is correct, that equates to 80 volts going to the charge controller for those six panels.

I did this because earlier in the thread you told me:

"When you are calculating max voltage for a SCC you use Voc not Vmp.
Your Renogy 100w panels are probably about 22Voc if 18.9Vmp

Also add on the voltage for cold temperatures which you have in Alaska."

Is my misunderstanding that on a cold perfect day the panels could send 80 volts to the charge controller but that if it did so, it wouldn't send the full amps, and thus the wattage would remain only 600 watts?
Voc V Open Circuit is the max voltage when your panels are not under load. Open Circuit.

Vmp V Max Production is what is flowing when your panel is producing power.

3 100 watt panels in series is about 54Vmp which you use to size the wire gauge.

On a cold sunny morning the raised voltage but very low amps could fry your SCC so that's why you size using Voc.
You don't see Voc out of a panel when it is producing power.

But to size a SCC use the watts on the label and divide by battery voltage.
600 watts into a 12V battery needs a 50A SCC.
 
Voc V Open Circuit is the max voltage when your panels are not under load. Open Circuit.

Vmp V Max Production is what is flowing when your panel is producing power.

3 100 watt panels in series is about 54Vmp which you use to size the wire gauge.

On a cold sunny morning the raised voltage but very low amps could fry your SCC so that's why you size using Voc.
You don't see Voc out of a panel when it is producing power.

But to size a SCC use the watts on the label and divide by battery voltage.
600 watts into a 12V battery needs a 50A SCC.
Thanks as always! Slowly learning. Soon I'll be ready to start investigating bigger panels once I get a handle on the charge controllers. Cheers!
 
Yes the 15A is max battery charging output.

It's simple. I updated my last post.

To size a SCC take the total wattage then divide by battery voltage.
600w ÷ 12V is 50A
600w ÷ 24V is 25A

A 24V battery would halve your SCC amperage saving money and allowing smaller gauge cheaper wires.

Those small 100 watt panels and 12V battery is going to cost you.

Wire size from panels to SCC.
Enter
Vmp total of array
Amps total of array
One way distance.
Under 3% is good.
I doubt if your distance is that much.

I think I'm now ready to try to understand this better. I'm limited to a 12V battery bank due to the "low temperature" requirements of the Relion batteries I'm using.

I'm under the assumption that I can have regular old MC4 wire from the panels to the SCCs. That's the way I do it with the 1600 watts of panels connected to our two Yeti 3000s. But given that the voltage and amps will be higher with these larger panels, perhaps my assumption is incorrect?

I'm also assuming that with the SCCs mounted just above the 12V battery bank, that while the wires may need to be thicker, it will be a short distance and so not too costly.

I haven't put any thought into the wires obviously, so thanks for any continued education. The longest run from a solar panel to a charge controller will be under 30 feet in our case.
 
Sorry to hear about your yurt. Alaska is so pretty from what I'm told and yet so chilly. You're braver than I for sure!

I'm probably too late to the thread but as an installer I think there might be a cheaper way to do this. Even with my installer/dealer pricing and discounts I'm glad to give forums members, you're looking at a crazy high bill as was mentioned already. Plus a lot of wiring. If you're intending to buy an inverter or inverter(s) to use with your Relion batteries though, we can reduce your cost quite a bit. And even if you're not, we can still probably shave a few hundred or more off if you're interested.

Before I flesh that out though (if you have interest), are you intending to buy an inverter(s) or are you looking to reuse your yetis?
 
We're intending to buy the panels, the nine charge controllers, and a DC-DC charger and an inverter. I think we're going to go with two battery banks. A single 12V Relion LT battery for one battery bank, and two 300AH non-LT Relion batteries for the second bank (wired in series for a 24V system). One of the strings and charge controllers will charge the 12V LT battery bank, all the rest will charge the 24V battery bank. We'll have a DC-DC charger on the LT that will also charge the 24V battery bank when the 12V battery is full.

I think we'd rather go this way so that we can expand our battery bank as needed over time and not be locked into a 12V system. But we want one low temp battery as part of the system for powering security stuff in the winter.

I'm planning on installing it myself unless I come to the conclusion that it's too cosmic. I need to figure out the wire gauge from panels to the charge controllers, and then wire gauge from the charge controllers to the battery banks, shutoff switches for each PV array to the SCCs, and perhaps select a "trough" for the wires running from the SCCs to the batteries and such, but I would think I could do this myself but I'm just learning.
 
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