Series or parallel ?

Jaws

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OK... 4 panels all of which have different but similar outputs.. running to a 30a MPPT controller
If in series the out put is 72v give or take
As far as my brain is concerned the max current though will be limited to the max short circuit output of the weakest panel

If in parallel the voltage voltage would proly be about 18v but the max possible current will be that of all the panels added together

Does that stack up or am I having a brain fart ?
 

dabhand

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(y)When solar panels are wired in series, the voltage of the panels adds together, but the amperage remains the same. So, if you connect two solar panels with a rated voltage of 40 volts and a rated amperage of 5 amps in series, the voltage of the series would be 80 volts, while the amperage would remain at 5 amps.

Putting panels in series makes it so the voltage of the array increases. This is important, because a solar power system needs to operate at a certain voltage in order for the inverter to work properly.

So, you connect your solar panels in series to meet the operating voltage window requirements of your inverter.

Just a little bit of Google John
 

DBK

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If they are different wattages put them in parallel for the reason you state. There is also the advantage that in parallel the effect of one panel being shaded is reduced. Victron recommend series connection and this is what I did but that was mainly because I was using the existing wiring which was a bit thin so series connection made more sense because of this.

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Jaws

Jaws

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I did 2 + 2.
2 series, the other 2 series and connected the pair of cables coming off each series pair in parallel.... If that makes sense?

Best of both worlds 👍😎
Thanks for confirming DBK :)

Interesting idea Dazzlin !
dabhand.... Aint got an inverter mate.. Be honest so far never felt the need
I do have a little 300w jobby laying in the spares cupboard but it has never been connected !
 
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You have tree options: 4S, 4P or 2S2P. The combination that works best is dictated by how much apart are the panels in Vmp and Imp, the W is not that important. If the difference is under 5% or equal panels, the voltage on the string you aim is 1,5-2 times the battery voltage, but well under the controller VOC limit. If controller limit is 100Voc, your string should be up to 80Voc to allow for cold voltage rise. The voltage on the panels rises with cold and reduces in heat.

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I follow the logic completely being put forward for the 2S2P approach.

I find it all quite conflicting if using two or maybe three equal output (matched) panels let’s say each is 150W) and also without any existing controller (so let’s assumed that can be specced for voltage or amperage as needed), what is ‘commonly’ deemed to be the best practice approach series or parallel?
 

Gromett

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This show how badly a very slight shadow can have on a series panel array. This is why I will always use parallel on a motorhome.

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I find it all quite conflicting if using two or maybe three equal output (matched) panels let’s say each is 150W) and also without any existing controller (so let’s assumed that can be specced for voltage or amperage as needed), what is ‘commonly’ deemed to be the best practice approach series or parallel?
If you were to compare 2 setups, one series and one parallel, in bright sunshine, they would be giving out the same power, so no advantage to either.

In real life, there are other considerations. For a house roof array, you may be confident there will be no shading of parts of the panels, but for a motorhome constantly moving from site to site, it's a different matter. Parallel is best if there's likely to be shading.

The solar yield over the whole day depends on the time that the MPPT controller input is 5V or more above the battery voltage. Series connection has the edge here, so in theory you will be harvesting solar before a parallel setup starts up, and will continued for longer after the parallel setup has given up. Also if the sun is frequently obscured by cloud, series may yield more than parallel.

So you have to asses the problems you are likely to encounter for your particular lifestyle and locations.

There's nothing to stop you adding a switch to flip between the two setups - parallel for summer, series for winter for example, but most people don't bother.
 
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Jan 19, 2014
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There's nothing to stop you adding a switch to flip between the two setups - parallel for summer, series for winter for example, but most people don't bother.
not bothered with a switch but if you have easy access to the roof it only takes a minute to pop two into one connector Into each line to go to a parallel set up.. ive been running series since I got rid of the kayak carrier off the roof which wasn't ideal for the panels as shade was often an issue..
nothing scientific but the series set up has been as good as the parallel that I ran for years..
Andy

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Jaws

Jaws

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Spent the entire day experimenting ( nailed a flatish battery in ) and experimented with some shade, over all poor light level and briefly when the sun came out full sunshine ( got up to 82v in series ! )

With all the results in I have gone with parallel as in all conditions bar one scenario like for like tests came back the same.. Parallel ultimately delivered slightly higher charging amps

I will just say:
1) Adding the 150w 4th panel was def worth it
2) If I was using the array in a fixed location I might have gone series
3) My calf muscles are gonna explode
4) my knees already have !!!!!!!!!!
 
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