Is 2P 1S panel setup possible? w/o causing issue?

[HOU_Castle]

All,
I'm trying to optimize my Victron MPPT 100/30. Can I set 1S2P panels? w/o causing balancing issue.
Panel spec: 320W, 40.8Voc, Pmax-33.3V, Isc 10.19A, Pmax-9.62A. Fuse rating: 20A.
24V-200Ah Batt.
Thank you in advance.

 

[A.Justice]

I also have a Victron 100/30. I regularly use it with two, 250 watt, 55v panels in 1s2p. I don't see why it would cause any sort of issue.

 

[rickst29]

Panels in parallel will have the Current of all panel added together, while the Voltage appears to the Controller as the Voltage of the lowest panel (i.e., the one in shade, if they are under different amounts of shade).

Panels in Series have the Voltage of all panels added together, but the Current appears to the Controller as the current of the lowest-performing panel (the one in the most shade).

Your configuration is excellent, and has better performance under different amount of shading. In shade, current moves down much more than voltage does - and Series panels behave with the performance of the most shaded panel. Series wiring can have an advantage, however, in allowing for smaller wires. Many configurations with more panels combine the wiring types, e.g., 2x2 or 2x3, but that will require that the number of panels in each parallel string (2 panels, 3 panels), be the same, so that the Controller's received Voltage is the same from each of the Parallel Strings.

With two 'parallel' strings of 'series' panels, you must start from an even number of panels. I personally have an odd number of panels, and must therefore use all parallel (lots of current. big wires) or all Series (lots of Voltage, more sensitivity to shade). My panels are in Series, creating around 85 Volts (which would be a bit too high for your Victron, but it's OK on my controller).

If run in Series, your two panels (40.8 Voc) would be on the high side of your Victron's capability (which I would personally configure at no more than 80% of the rated maximum voltage). So parallel has the best safety margin and the best resistance to uneven shade, you're doing the right thing.

 

[HOU_Castle]

Panels in parallel will have the Current of all panel added together, while the Voltage appears to the Controller as the Voltage of the lowest panel (i.e., the one in shade, if they are under different amounts of shade).

Panels in Series have the Voltage of all panels added together, but the Current appears to the Controller as the current of the lowest-performing panel (the one in the most shade).

Your configuration is excellent, and has better performance under different amount of shading. In shade, current moves down much more than voltage does - and Series panels behave with the performance of the most shaded panel. Series wiring can have an advantage, however, in allowing for smaller wires. Many configurations with more panels combine the wiring types, e.g., 2x2 or 2x3, but that will require that the number of panels in each parallel string (2 panels, 3 panels), be the same, so that the Controller's received Voltage is the same from each of the Parallel Strings.

With two 'parallel' strings of 'series' panels, you must start from an even number of panels. I personally have an odd number of panels, and must therefore use all parallel (lots of current. big wires) or all Series (lots of Voltage, more sensitivity to shade). My panels are in Series, creating around 85 Volts (which would be a bit too high for your Victron, but it's OK on my controller).

If run in Series, your two panels (40.8 Voc) would be on the high side of your Victron's capability (which I would personally configure at no more than 80% of the rated maximum voltage). So parallel has the best safety margin and the best resistance to uneven shade, you're doing the right thing.

Would it be matter if 2P1S or 1S2P configuration? if it does not matter, Victron will see around 80Vs, and 19A? and Victron will push 30A to batt right?
Is 50 ft 12 gauge wire (PV to Victron) ok? I try not to spend more $$ on wire for this.
Thanks!

 

[rickst29]

It DOES matter a lot, because your wire distance is so long - and you're asking to use very small wire.

Both in Parallel, 1S2P, would be 41 Volts and 19.2 Amps, Over such a long distance, 12-AWG wiring would be a very bad idea, it's only rated for 20 Amps maximum and the power loss would be very high. (There are Internet calculators and tables to calculate this power loss). You need at least AWG-10 to wire in parallel, and even that will lose power by heat loss within the wriring.

Panels is Series yields about 82 Volts, but only 9.6 Amps maximum. 82 Volts is as high as I would push the "100 Volt" Victron, but that should be OK, even in cool weather (when Voltage goes up). 10-AWG on the SERIES configuration would be best. But if you've already bought the wire, it's OK to use 12-AWG. You can only use the Series configuration, if you want to stay with 12-AWG wire.

 

[brewmatic]

Over such a long distance, 12-AWG wiring would be a very bad idea, it's only rated for 20 Amps maximum and the power loss would be very high. (There are Internet caculators and tables to calculate this power loss). You need at least AWG-10 to wire in parallel, and even that will lose power by heat loss within the wriring.

Actually maximum allowed amps depends on insulation temperature rating. For 12 AWG wire 20Amp limit is for 65C rated insulation. If you have a 90C rated wire insulation you can use 12AWG for up 30Amp https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/

About power loss:
On 50ft distance you'll have 100ft of wire. 12 AWG wire has 1.588 Ohm per 1000ft.
Parallel configuration ~ 20Amp P=20*20*0.1588 ~ 64 Watt
Series configuration ~ 10Amp P=10*10*0.1588 ~ 16 Watt

So you can use parallel configuration if your cable insulation rated above 60°C (140°F). But you will loose up to 48 Watt more in comparison with serial configuration.

 

[HOU_Castle]

It DOES matter a lot, because your wire distance is so long - and you're aksing to use very small wire.

Both in Parallel, 1S2P, would be 41 Volts and 19.2 Amps, Over such a long distance, 12-AWG wiring would be a very bad idea, it's only rated for 20 Amps maximum and the power loss would be very high. (There are Internet caculators and tables to calculate this power loss). You need at least AWG-10 to wire in parallel, and even that will lose power by heat loss within the wriring.

Panels is Series yields about 82 Volts, but only 9.6 Amps maximum. 82 Volts is as high as I would push the "100 Volt" Victron, but that should be OK, even in cool weather (when Voltage goes up). 10-AWG on the SERIES configuration would be best. But if you've already bought the wire, it's OK to use 12-AWG. You can only use the Series configuration, if you want to stay with 12-AWG wire.

Can you elaborate of how you end up with 41V and 19.2A for 1S2P? Does 1S2P mean 2 panels in parallel?

 

[HOU_Castle]

I have 3 PV panels, can I use all 3 panels at the same time with mppt 100/30? 2 panels in parallel, then series with the other one?

 

[chrisski]

When you do that calculator, you can look at different things like connecting them in parallel closer to the battery than farther away. Placement of the combiner box makes an issue.

The 100/30 can take 6 AWG wire, but the MC4 connector off the panel can only take 10 AWG wire. You could splice it in somehow, but there would be some loss At this butt splice or whatever method you use. I know of no way to estimate the loss.

I have panels 3S2P on my RV roof where the combiner box is in the battery compartment. I have a separate array where they are combined on the roof and fed into the battery bay with 6 AWG.

There is a huge loss to running the panels 2S if shading is involved. One panel in my 3S 50% shaded drops my overall output by 75%. Just two of 30+ cells on a single panel shaded I lose 25%-33% of power. Losses could be significantly reduced if you put panels in parallel.

 

[rickst29]

Can you elaborate of how you end up with 41V and 19.2A for 1S2P? Does 1S2P mean 2 panels in parallel?

Yes, 1S2P means that the panel layout has only 1 panel in series, but 2 in parallel. ('2S2P' would be 4 panels, consisting of 2 Series Panels in each of 2 parallel strings.) 41V comes from your first post, 40.8V(oc). That's the voltage which the controller must handle.

 

[rickst29]

I have 3 PV panels, can I use all 3 panels at the same time with mppt 100/30? 2 panels in parallel, then series with the other one?

No. Per my post #3, If you were to put 3 panels in this arrangement then the Voltage would be additive once (About 82 Volts for open-circuit), but the current would match only the weakest panel - the one which is alone, at only 9.6 I(mp). It would behave like only two panels in Series.

When mixing Series and Parallel connections, you need to start with an even number of panels.

 

[HOU_Castle]

No. Per my post #3, If you were to put 3 panels in this arrangement then the Voltage would be additive once (About 82 Volts for open-circuit), but the current would match only the weakest panel - the one which is alone, at only 9.6 I(mp). It would behave like only two panels in Series.

When mixing Series and Parallel connections, you need to start with an even number of panels.

So, the PV setup needs to be even number of panels. Thank you.

 

[chrisski]

So, the PV setup needs to be even number of panels. Thank you.

For parallel set ups, Not a prime number of panels is better. You can have odds.

I am going to be setting up 9 panels as 3s3p. You could set up the three panels you mentioned as 1s3p

 

[MisterSandals]

So, the PV setup needs to be even number of panels.

This is not correct. When connecting strings in parallel, each of the strings need to have the same number of panels. If you have 4 panels, you can connect all panels in parallel 4P (4 strings of 1 panel), or 2P2S (2 strings of 2 panels in series) or 4S (1 string of 4 panels in series).

You can have an odd number of cells, like 9 cells in a 3S3P (3 strings of 3 panels in series).

 

[HOU_Castle]

This is not correct. When connecting strings in parallel, each of the strings need to have the same number of panels. If you have 4 panels, you can connect all panels in parallel 4P (4 strings of 1 panel), or 2P2S (2 strings of 2 panels in series) or 4S (1 string of 4 panels in series).

You can have an odd number of cells, like 9 cells in a 3S3P (3 strings of 3 panels in series).

Aha, got your point. Thanks!