Solar panel directions and voltage

[sjordan0228]

I currently have 4 305watt panels wired in series facing south (I plan to modify it a bit to face true south). They are doing a great job until around 5pm or so. That got me thinking, I can add 2-4 more panels on the roof of my shed. I can put 2 on each side which would cover east and west. Being a beginner I struggle understanding how this could impact the overall setup. If I do this is there a chance that the overall voltage could get messed up when the panels are shaded? My inverter only has one PV input. Is this idea not good, or is there a proper way to wire this up to make it work?

 

[rodrick]

Best way to add the panels is use a separate mppt controller, that will have no effect on your present setup and help with some redundancy and give you some afternoon charging

 

[sjordan0228]

Best way to add the panels is use a separate mppt controller, that will have no effect on your present setup and help with some redundancy and give you some afternoon charging

Unfortunately that's not in the budget. I am really just wondering if doing the above will have a benefit or not....unless I am confusing mppt controller with something else.

 

[fat_old_sun]

use a timer driven switch to switch the input of MPPT from the panels in the east, south & west sequentially.

 

[GXMnow]

With just one MPPT, you could run parallel arrays that are at different angles. But each array needs to have the same number of panels in series. IF you have 4 panels in series facing south, you would then also want 4 panels facing east. And/or then 4 panels facing west. What is your minimum MPPT voltage? Could you change the south facing array to be 2S2P? Then you would have 4 2S arrays that could run in parallel. But then you also have 4 times the peak current capability. Make sure that does not exceed the maximum ISC current of the MPPT input.

The idea behind this is that the east array will provide morning power and the MPPT will track that as the highest voltage in the early morning. As the sun rises and more light hits the south array, that will be the voltage source for the maximum power as it takes over from the east array. Since the VMP of the arrays are the same, they will be able to add their currents together. But if the second array is half east and half west to get the 4S panel group, you will only get the current of the weaker lit pair. Any panels wired in series should be at the same angle.

The better solution is the second MPPT controller. What is your battery voltage? I bought a BougeRV MPPT that can do 40 amps and works on 12 to 48 volt systems. It was $140 on Amazon. Not super cheap, but it works well and has a decent blue tooth setup and monitoring app. If you don't care about monitoring and/or you are 12 or 24 volt, there are cheaper options.

 

[Dinobot248]

I have a similar problem with trying to collect more solar energy.

I would say you have to consider your system (usage, battery capacity).

If you have a large battery bank, then put your panels facing south. Any energy collected will be stored and south facing collects the most energy in total.

If you have a smaller battery that cannot store the solar energy, then you can put some panels more east or west facing. This allows you to collect solar throughout the day. Realize you will collect less solar in total, but you can benefit more since the incoming solar energy can support your house load and charge the smaller batteries at the same time. A fully charged battery means you are not collecting solar energy since it has no place to go.


It can get complicated when you account for the seasons. It takes some time (at least 1 year ) to tune and tweak your system to fit your own use case.

Hope that makes sense.

 

[TomC4306]

You want to do what I'm doing with two controllers. One south facing array and one broken array.
I'm sacrificing peak with the rear 18, but it wakes up much earlier in the morning, especially in winter.

Edit - 3s6p to a combiner to one mppt. 150° and 210°
3s 2p to another mppt. 180°

 

[sjordan0228]

Ok I see.

I only have one battery.....but I use Solar assistant. Guess I need to find a cheap MPPT that is compatible with Solar-assistant. Any ideas? I am thinking under $150

 

[#40Fan]

How big is your battery? What state of charge swings are you getting thoughout the day?

 

[sjordan0228]

How big is your battery? What state of charge swings are you getting thoughout the day?

My battery is 5KW hours. Right now with my load its going a bit to low for my liking once the sun is down. Right now I need to get a better baseline since I have only been running this for a few days now.

 

[sjordan0228]

use a timer driven switch to switch the input of MPPT from the panels in the east, south & west sequentially.

I like this idea. Would you mind pointing me to the direction of where a switch like this can be purchased. I am assuming the PV inputs will need to be connected to a bus bar and then feed into the controller?

 

[GXMnow]

My battery is 5KW hours. Right now with my load its going a bit to low for my liking once the sun is down. Right now I need to get a better baseline since I have only been running this for a few days now.

What is the system voltage? At 5 KWHs, I would expect this to be a "48 volt" 100 amp hour system, but it could also be 200 AH at 24 volt, or 400 amp hour at 12 volt. Is it reaching full charge when the sun is up? Again, this will take a few weeks at least to get a good trend.

My system has no issues topping up my 36 KWHs of battery when it is sunny and cool. But on hot overcast days, when I also run the central A/C, it can run out of power and not fully charge the next day. But it could get very expensive to provide enough solar panel to cover my worst case days. I export enough power on good days to use grid power on bad days, and still ended up with a net credit on my electric bill. So adding panels would be a waste at this point.

But if you have good average days, and you are still running out of power, then more panel might help. But if you are getting the battery full and it is still running out over night, then you may also need more battery capacity. It is all a balancing act.

From the original posts, you currently just have the 4 x 305 watt panels facing roughly south. In idea conditions, that could produce 1,220 watts at solar noon. Most likely it will be more like 80% of that. Let's round it to 1,200 watts for easy math. Depending on where you are and the time of year, you can get from 2 to 7 sun hours a day. You have DFW listed as your location, so I assume that means Dallas/Fort Worth, Texas. Am I right? In Dallas, with panels just laying flat, you could get just under 5 Sun Hours a day in Sept. A bit more if they are tilted towards south.

Here in So Cal, I typically use 5 sun hours as a rough guestimate. 1,200 watts x 5 sun hours is 6,000 watt hours. That is a bit more than the full 5 KWHs of your battery. With the typical losses and such, it is probably still enough to fully charge your battery if you don't have large daytime loads. In the dead of winter or with cloud cover, you will make less of course, and more solar panel is not a bad thing, but if the charge controller is just sitting on float all day, it's not helping much. The power needs somewhere to go, or the charge controller just throws it away. So unless you are using a fair bit of power while the sun is up, I think more battery is going to be needed as well. Do you have a decent idea of your loads? How many watt hours are you using in a day?

 

[sjordan0228]

What is the system voltage? At 5 KWHs, I would expect this to be a "48 volt" 100 amp hour system, but it could also be 200 AH at 24 volt, or 400 amp hour at 12 volt. Is it reaching full charge when the sun is up? Again, this will take a few weeks at least to get a good trend.

My system has no issues topping up my 36 KWHs of battery when it is sunny and cool. But on hot overcast days, when I also run the central A/C, it can run out of power and not fully charge the next day. But it could get very expensive to provide enough solar panel to cover my worst case days. I export enough power on good days to use grid power on bad days, and still ended up with a net credit on my electric bill. So adding panels would be a waste at this point.

But if you have good average days, and you are still running out of power, then more panel might help. But if you are getting the battery full and it is still running out over night, then you may also need more battery capacity. It is all a balancing act.

From the original posts, you currently just have the 4 x 305 watt panels facing roughly south. In idea conditions, that could produce 1,220 watts at solar noon. Most likely it will be more like 80% of that. Let's round it to 1,200 watts for easy math. Depending on where you are and the time of year, you can get from 2 to 7 sun hours a day. You have DFW listed as your location, so I assume that means Dallas/Fort Worth, Texas. Am I right? In Dallas, with panels just laying flat, you could get just under 5 Sun Hours a day in Sept. A bit more if they are tilted towards south.

Here in So Cal, I typically use 5 sun hours as a rough guestimate. 1,200 watts x 5 sun hours is 6,000 watt hours. That is a bit more than the full 5 KWHs of your battery. With the typical losses and such, it is probably still enough to fully charge your battery if you don't have large daytime loads. In the dead of winter or with cloud cover, you will make less of course, and more solar panel is not a bad thing, but if the charge controller is just sitting on float all day, it's not helping much. The power needs somewhere to go, or the charge controller just throws it away. So unless you are using a fair bit of power while the sun is up, I think more battery is going to be needed as well. Do you have a decent idea of your loads? How many watt hours are you using in a day?

Lots of good info.

Yes it’s a 48v system. And yes I am in the Dallas/Fort Woth area.

I do have a small load on it now and a mini split that is currently set very high so it has only ran a little.

This weekend I am going to start on the permanent install of the solar panels and get them at the optimal and and direction. I think I should get more from them. Right now I don’t think it’s going to be a problem but next year in the summer that mini split will kick in and will likely take up the majority of the pv throughout the day leaving little for charging. I think I may just eventually add 4 more panels than another battery if needed.