Inquiring about updating my solar system.

[Damehits]

Hello everyone. I am new to this forum and would like to ask a question or two about updating my solar system.

My current system is a 400watt solar setup, with a renology 3000 watt inverter and 412ah Sok batteries. 40Amp renology charge controller. My system works well for my needs but I would like to upgrade to a 800 watts of solar. I think the current system is in series. I paid someone to install this system 2yrs ago. Over time I tinkered with it, added a battery monitor, shortened some connections etc, and familiarized myself with it.

My question is:
A) Should I get a second 40Amp charge controller to add to my system, this would save me a little bit of money but not necessarily a concern to me. Is this method easier to do? Is it more efficient? Two 40Amp controller could support up to 1040watts on 12V system. I don't see much of this setup but Ive read that it can be done on a few sites including renology's website.

B) Should I get a 60Amp charge controler which can support up to 800 watts on a 12v system according to renology website. Is this the better option?
I also already have 2 extra 200watt solar panels I will install, and plan on buying another sok 206Ah battery.

Im currently in research phase but figured I would ask for opinions. Any opinion is greatly appreciated and welcomed. Thanks.

 

[sunshine_eggo]

Hello everyone. I am new to this forum and would like to ask a question or two about updating my solar system.

My current system is a 400watt solar setup, with a renology 3000 watt inverter and 412ah Sok batteries. 40Amp renology charge controller. My system works well for my needs but I would like to upgrade to a 800 watts of solar. I think the current system is in series. I paid someone to install this system 2yrs ago. Over time I tinkered with it, added a battery monitor, shortened some connections etc, and familiarized myself with it.

My question is:
A) Should I get a second 40Amp charge controller to add to my system, this would save me a little bit of money but not necessarily a concern to me. Is this method easier to do? Is it more efficient? Two 40Amp controller could support up to 1040watts on 12V system. I don't see much of this setup but Ive read that it can be done on a few sites including renology's website.

B) Should I get a 60Amp charge controler which can support up to 800 watts on a 12v system according to renology website. Is this the better option?
I also already have 2 extra 200watt solar panels I will install, and plan on buying another sok 206Ah battery.

Im currently in research phase but figured I would ask for opinions. Any opinion is greatly appreciated and welcomed. Thanks.

Are the two extra 200W panels the same as your existing 400W array?

 

[Damehits]

Are the two extra 200W panels the same as your existing 400W array?

Are the two extra 200W panels the same as your existing 400W array?

Yes they are very similar. From Newpowa. The new ones are a bit small than the older so they might be different.

 

[sunshine_eggo]

Yes they are very similar. From Newpowa. The new ones are a bit small than the older so they might be different.

If their Vmp and Imp ratings are nearly identical, then you could possibly go with all panels on a single MPPT. If they are significantly different, you'll want to put them on different MPPT.

 

[Damehits]

If their Vmp and Imp ratings are nearly identical, then you could possibly go with all panels on a single MPPT. If they are significantly different, you'll want to put them on different MPPT.

So basically if they are similar I could use the 40amp Scc with 800 watts of solar is that correct? And if not then I would have to go with the 60amp Scc right?

 

[Rednecktek]

So basically if they are similar I could use the 40amp Scc with 800 watts of solar is that correct? And if not then I would have to go with the 60amp Scc right?

No, you'll still need a controller that can handle the higher wattage of more panels. What sunshine_eggo was trying to say is that if the Vmp and Isc ratings on the new 200w of panel are about the same as the panels you already have then you can connect all 6 panels together into a single array. If the specs were wildly different then adding them in would drop all your panels to the lowest common denominator and you'd end up nerfing your performance, hence better to use a second controller.

You'll still need enough controller to handle 600w of panel though, hence a 60a SCC.

As a napkin math example:

Lets say you have 4 of OldPowah's 100w solar panels, they put out 25v Vmp and 4 amps Isc. In a series string you connect them up and get 100v @ 4a = 400w. Now say you got a pair of NewPowah!'s 100w panels putting out 24.9v Vmp and 4.01a amps of Isc then you're so close to the specs of the other panels that it's not going to matter. You can throw them all in series for 150v @ 4a = 600w, or split them up into a 3s(eries)2p(arallel) setup for 75v @ 8a = 600w. You'll still want a 60a SCC in there to make use of all that power, but you only need 1 controller to do it.

OK, so let's look at the other end. You've got your OldPowah 100w panels at 25v and 4a in series for 400w of panel. Now you grab a single Newpowah panel that's rated at 200w but its numbers are 100v and 2a = 200w. Well, if you throw that new panel in with the old panel you'll end up with the lowest common denominators all the way around, which means 150v @ 2a = 300w of power out of that 600w array. Why? Panels will need to find common ground to work, and it can't run higher than any individual component can provide, in this case you can't get more than 2 amps out because that's all that Newpowah panel can do, so it brings down the rest of the panels to its level.

Does that help make sense?

 

[sunshine_eggo]

So basically if they are similar I could use the 40amp Scc with 800 watts of solar is that correct? And if not then I would have to go with the 60amp Scc right?

Sorta. 800W on a 40A would be over-paneled. 60A would allow you to capture the full array's output.

By similar, the Vmp need to be within 10% of each other.

 

[mikefitz]

If the additional panels have different operational factors, example, shading effects, less tha optimal position, then seperate controllers may give a better total yield.

 

[Damehits]

No, you'll still need a controller that can handle the higher wattage of more panels. What sunshine_eggo was trying to say is that if the Vmp and Isc ratings on the new 200w of panel are about the same as the panels you already have then you can connect all 6 panels together into a single array. If the specs were wildly different then adding them in would drop all your panels to the lowest common denominator and you'd end up nerfing your performance, hence better to use a second controller.

You'll still need enough controller to handle 600w of panel though, hence a 60a SCC.

As a napkin math example:

Lets say you have 4 of OldPowah's 100w solar panels, they put out 25v Vmp and 4 amps Isc. In a series string you connect them up and get 100v @ 4a = 400w. Now say you got a pair of NewPowah!'s 100w panels putting out 24.9v Vmp and 4.01a amps of Isc then you're so close to the specs of the other panels that it's not going to matter. You can throw them all in series for 150v @ 4a = 600w, or split them up into a 3s(eries)2p(arallel) setup for 75v @ 8a = 600w. You'll still want a 60a SCC in there to make use of all that power, but you only need 1 controller to do it.

OK, so let's look at the other end. You've got your OldPowah 100w panels at 25v and 4a in series for 400w of panel. Now you grab a single Newpowah panel that's rated at 200w but its numbers are 100v and 2a = 200w. Well, if you throw that new panel in with the old panel you'll end up with the lowest common denominators all the way around, which means 150v @ 2a = 300w of power out of that 600w array. Why? Panels will need to find common ground to work, and it can't run higher than any individual component can provide, in this case you can't get more than 2 amps out because that's all that Newpowah panel can do, so it brings down the rest of the panels to its level.

Does that help make sense?

Yes it does. Thank you. By the way do you know how to wire two different Scc into one system, I can't seem to find any good examples of how to do it anywhere. I saw a few examples on youtube but the theoretical versions i guess.

 

[Damehits]

If the additional panels have different operational factors, example, shading effects, less tha optimal position, then seperate controllers may give a better total yield.

Do you know how to wire two separate charge controller into one system? Im still figuring this all out. Im glad im in no rush.

 

[Damehits]

Sorta. 800W on a 40A would be over-paneled. 60A would allow you to capture the full array's output.

By similar, the Vmp need to be within 10% of each other.

Got it, makes sense now. Thanks.

 

[Rednecktek]

Wiring in multiple SCC's is really easy. Wire up your first set of panels, program the SCC for your needs, then forget it's there and do it again. Unless you're using one of the few SCC's that can communicate with each other (and there are very few) the SCC's will just ignore each other.

 

[ericfx1984]

So assuming that the new panels are identical or at least extremely similar... You could add them to your existing controller but you won't see a massive increase in performance

Basically in terms of actual usability you're probably only going to have about 500 or 550 Watts usable at the 13.6 volts that you'll likely be charging at with a 40 amp charge controller


One simple way to fix this would be to convert over to a 60 amp charge controller or even larger

That way you can keep your 40 amp for a backup charge controller

The other option is that you could go ahead and connect 800 watts of solar panels to the existing 40 amp controller
.. It will likely start charging a little earlier in the day and stop charging it little later in the day... We're at the bare minimum you will see higher overall chart rates throughout the day and significantly better performance on cloudier days

The other option would be to add a second smaller controller... I personally like the idea of having two controllers on hand that way if one goes down the other one can carry some or all of the charge capability that is lost

 

[JWLV]

For peace of mind, you might just want to get a second charge controller. Having two charge controllers gives you some redundancy. If one goes up in smoke, you still have the other one. It'll at least keep the lights on.

 

[Damehits]

Yes that is my plan at this point. Just waiting on the second controller to be delivered.