Using 6 100 watt panels, all exactly the same, can I hook 2 panels in series, then in parallel with 4 panels in series or will that give me less performance than 3+3? I'm familiar with series/parallel, but I always see each side with equal number of panels. Thanks for any insights.
Panels in series/parallel? Does each side need to be balanced?
- Thread starter B.T.
- Start date
Yes they need to be equal.
If they are unequal - my understanding is the smaller side rules for volts and amps.
Assumption for example - panel is voltage 25v 5A
So 2 in series will be 50v 5a paralleled with 4 in series 100v 5a - you will get 50v 10a (you just lost the two panels). So it is not good. You would want to have 3s2p or 2s3p.
If they are unequal - my understanding is the smaller side rules for volts and amps.
Assumption for example - panel is voltage 25v 5A
So 2 in series will be 50v 5a paralleled with 4 in series 100v 5a - you will get 50v 10a (you just lost the two panels). So it is not good. You would want to have 3s2p or 2s3p.
Why would you even need to hook up 6 panels in 4s and 2s ?
Why not a balanced 3S2P or 2S3P?
Usually people ask about unbalanced configurations because they have an odd number of panels like 3 or 5 or 7 panels.
Is this a theoretical question and do you have a SCC for those 6 100 watt panels?
Thanks for the responses. What little I do know so far on this subject told me that would likely be the answer. I was just wondering about it and as I did my research all I could find were examples of odd numbers, so I figured this would be the place for a quick and easy answer, and so it was. Although I did have an inkling, part of me said well why wouldn't ALL the power just flow to the MPPT. Thanks again.
MisterSandals
Participation Medalist
What are you trying to do? Or what symptoms/problems are you experiencing?
No problems, just trying to get an idea of how I can utilize the panels. My idea was to have 2 panels on my vehicle and then to be able to deploy the other 4 wherever the best exposure was. So now I know that I need to divide them 3S (x2P), perhaps you can answer another question I have come up with. If I put 3 in series on my vehicle and deploy 3 in series at optimum exposure, (and the 2 sets in parallel) if the 3 on the vehicle are in the shade will they bring the 3 with good exposure down to their level? Again, with my research I THINK that it should not since running in parallel is suppose to be better in shade. But if you know absolutely what the result would be I will be extremely grateful for your opinion.
MisterSandals
Participation Medalist
No, the parallel strings will not affect each other if one is shaded. Paralleling strings/panels is the solution to shading issues.
Another option, depending on whether you can or want to put 3 panels on your roof would be to make 3 distinct strings: 2 panels in series on roof, 2 panels in series, 2 panels in series. Bring these 3 strings (or carry out only one set of 2 panels if needs are lower) together in parallel at a 3 way Y combiner (or combination of 2 way combiners).
With 3 strings in parallel, the amps of the strings will be combined so the Y connectors, fuses and wiring will need to handle that.
This is all reasonable and workable. You have a few options. If you can imagine your most likely scenario for using the system you can probably make that work.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 21,045
No, the 3 in series with one shaded won't sink enough current to pull the other 3 down. Voc will be about 3x Voc of one panel.
But perhaps Yes in a practical sense, that could be the impact on power harvested.
If this had been two strings of 6 but one panel shaded in one string, then I would expect little degradation, power about 11 panels worth.
As SCC draws down voltage from 3x Voc to 2x Voc, current will rise from zero to about 1x Vmp (because that's how much current the unshaded string of 3 produces.) SCC may find a maxima of power in that range, and may stop there (only some SCC explore below the highest voltage maxima.) If so, you get the power of 3 panels.
If SCC draws down voltage below 2x Voc toward 2x Vmp, current will rise to 2x Imp (and a bit higher, because the string of 3 unshaded will deliver slightly more current. If so, you will get slightly more power than 4 panels.
Exactly where between 4 panels and 5 panels worth of power this ends up, I'm not sure exactly. Would have to model the IV curve of the panels and evaluate it. If what you had was just one of two diode-bypassed portions of one panel shaded, it would deliver pretty close to 5.5x the power of one panel, because Vmp of the two strings would be similar.
If your configuration was 2s3p, then any shading of one string drops its voltage so low it won't contribute, and you'll have power of 4 panels.
Shading from objects on your roof will move slowly, but shading from trees will move much faster; soon multiple panels will be shaded so any optimization of partial shading won't last long.
Okay, thanks for all the great answers! I've decided to go with the 3S2P configuration as that will give me more power as I travel to my destination and also give me a higher voltage which I understand helps me to deploy at a greater distance without using huge cable (plus I won't have to buy another set of parallel connectors). When I only had 4 panels I always ran them in series so I know the MPP can easily handle this. If I am going to be at a camp for several days and I find the panels on the vehicle are being shaded too much I can also remove and deploy them fairly easily. I'd like to try all 6 in series, but I think from the voltage I've seen on the MPP with 4S that likely won't be possible. Thanks again for all the help.
MisterSandals
Participation Medalist
Am i mistaken or did we stumble thru this without knowing what SCC you have or the max input volts?
I have the MPP 2424LV with the MPPT controller. The max PV open circuit voltage is 145Vdc, max PV charge is 80Vdc and the max charge current is 140A. Even with only 6 100 watt panels (Voc=21.6, Vmp=17.9, Imp=5.72A) in series, I believe the 2424LV has safeguards against the "magic smoke". LOL, that's a term I haven't heard since my years in RC car racing. And as I recall the magic smoke never smelled as sweet when it was your car and not your competitors 
. ( 4 SOK 100Ah 2S2P @ 24Vdc)
. ( 4 SOK 100Ah 2S2P @ 24Vdc)
