Combining different size panels

[baker329]

Hello, I am installing a solar power system on my camper. Due to the size of my roof and location of vents, I am needing to use different sized panels. I have 4 Rich Solar panels rated at 335watts, 24v, and 10 amps and then I have 4 Rich Solar panels rated at 200watts, 24v, and 6 amps. I was planning on doing 4 different series connected in parallel. 1st series: 2 335w panels, 2nd series: 2 200w panels, 3rd series: 2 200w panels, & 4th series: 2 335w panels.

These are the panel links:
335 Watt Panels
200 Watt Panels

My questions are:

1. Can I use 1 to 4 y connectors to connect all 4 series in parallel or should I use a combiner box?
2. If I can use the connectors, do I need to use fuses at the connectors?
3. Also if I can use the connectors, any suggestions on the best 1 to 4 y connectors?

Thanks in advance!

 

[rmaddy]

What is your system voltage? 12V, 24V, or 48V? Depending on the voltage you will need 2, 3, or 4 MPPT charge controllers.

You might be able to put the 4 335W panels in 2S2P on one controller and the 4 200W panels in 2S2P on another controller. Or you might put each series pair on their own controllers (4 total).

I don't think you want to try to do this with one charge controller.

 

[baker329]

It’s a 24V system with a Victron 100v/50a charge controller

 

[rmaddy]

With a 50A controller at 24V you are basically limited to 1200W (a little more with some over paneling). There's no way to use all 8 panels on that one controller. That would be 2140W. 75% over paneling is too much. Plus the mismatched panels sizes will really reduce the performance.

Since the panels will be flat mounted and you will likely have some shading at times, you can probably get away with putting the 4 335W panels in 2S2P on the 100/50. The Voc of those panels is 41.6V. With 2 in series that's 83.2V. You are limited to 100V. You should be OK if you never get in temperatures below about -30ºC/-23ºF.

You will need a second charge controller for the 4 200W panels. Given the very high Voc of 45.4V for those 200W panels you would need to use a 150/35 to put them in 2S2P. I find it odd that those 200W panels have a higher Voc than the 335W panels.

Using those two charge controllers lets you take full advantage of all 8 panels.

 

[baker329]

Awesome thank you for your help! I’m completely new to solar, so maybe dumb question… I was planning on having the charge controller go through a small breaker box before it gets to the distribution box and then batteries… So if I have 2 controllers, how should I connect the 2 charge controllers or would they run separately all the way to the batteries?

 

[rmaddy]

I would run them separately. Give each controller its own disconnect breaker and its own run to the batteries (bus bars).

Please note I was making edits as you replied so please reread my previous post.

 

[baker329]

I do see your edits. I think I will go ahead and work on that second controller then. I did think that was kind of weird when I saw the 200w panels being a higher VOC but I didn’t know if that was normal or not since I don’t really know too much yet. I definitely appreciate all of your input!

 

[rmaddy]

How much battery are you planning with all of that solar?

 

[baker329]

2 24v 200ah batteries ran in parallel. So 24v with 400ah

 

[rmaddy]

That should work. I have 990W with a 24V 206Ah setup. Though it really depends on how much of the battery you expect to use each day and how much shade you get on your panels. Given the game of Tetris you played to fit the 8 panels, you may have to deal with shading at any given time so that reduces your wattage.

 

[baker329]

If one panel is shaded, would it effect the other series? For example, if the 4 335 watt panels were divided up into 2 series of 2 and then ran parallel, would 1 panel being shaded effect the other series?

 

[rmaddy]

When wired in parallel a shaded panel has no effect on other panels.
When wired in series a shaded panel will affect other panels it is in series with.

When wired in 2S2P, one shaded panel will only affect the other panel it is in series with. The other pair (in parallel with the affected pair) will not be affected.

Many panels have bypass diodes that effectively split the panel into sections. If any one cell in a section is shaded, that whole section acts as if it is shaded. But that's better than the whole panel being shaded. So you might lose 1/3 of a panel. But it also effectively reduces its series partners by 1/3 as well. The real problem is when the shade is only covering a row or 2 of cells of the panel but across every section. Then you have effectively lost the whole panel. If you have any wiggle room in where you can mount your panels, try to keep that in mind to minimize partial shading effects.

 

[baker329]

Ok I will definitely keep that in mind. I should be getting everything delivered soon. Can’t wait to start installing everything

 

[rmaddy]

Feel free to post a complete schematic of your planned system including wire sizes and lengths, fuses and breakers, and other components. Can't hurt to have some other eyes double check things.

 

[baker329]

Feel free to post a complete schematic of your planned system including wire sizes and lengths, fuses and breakers, and other components. Can't hurt to have some other eyes double check things.

I'll update my schematic and then put it on here. Should I post it on this thread or create a new one somewhere else?

 

[rmaddy]

I'd post it separately in the appropriate forum.