OK so how bigs yours?

[Lenny HB]

I would never wire them in series on a Motorhome, may be more efficient but one panel in shade all output from all panels lost.

 

[hilldweller]

I would never wire them in series on a Motorhome, may be more efficient but one panel in shade all output from all panels lost.

Not only shade, it's common for different parts of the roof to be quite different dirt wise.

 

[Freespirit1]

I was told by Votronic not to series link so ran all mine parallel.

Martin

If your Voltronic is only rated at around 18v input then that is correct - you have to parallel connect - my controller is rated for a max input of 150v - if I put more panels on which would take it above 150v I would need to series connect 2 sets of panels and then parallel connect the 2 sets to remain below 150v.

 

[Freespirit1]

I would never wire them in series on a Motorhome, may be more efficient but one panel in shade all output from all panels lost.

Not true - and I would always wire in series if the controller is capable of high input voltages - all panels have bypass diodes and each panel has a bipass diode on every other alternate cell within each panel - shade not an issue with these panels unless they are all fully shaded of course - that goes for dirt as well!

 

[funflair]

If your Voltronic is only rated at around 18v input then that is correct - you have to parallel connect - my controller is rated for a max input of 150v - if I put more panels on which would take it above 150v I would need to series connect 2 sets of panels and then parallel connect the 2 sets to remain below 150v.

Ours is 60v max I believe but the advice was irrespective of controller and based on partial shading.

Might be different with your Panels.

Martin

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[Freespirit1]

Ours is 60v max I believe but the advice was irrespective of controller and based on partial shading.

Might be different with your Panels.

Martin

Yes - quite likely if you have frame type mono or polycrystalline panels or even semi flexible panels which I believe have bypass diodes at the top of perhaps 4 rows of maybe 8 cells?

 

[hilldweller]

I've have asked some of the finest brains on another forum, so far the results are:

The small panels set a current limit so effectively the 120W one is demoted to being a 55W one.

Parallel is the way for best all round performance.

 

[Freespirit1]

I've have asked some of the finest brains on another forum, so far the results are:

The small panels set a current limit so effectively the 120W one is demoted to being a 55W one.

Parallel is the way for best all round performance.

Not in my view - for me series connecting will give the best performance - regard all the panels as cells of a battery with specific voltage the 55w ones produce something like 18.5v each and the 120w produces something like 38v which would give 112v using those figures - i’m seeing probably at best 107v - then some slight volt drop in my 16mt Solar 6mm cable to the controller looks about right to me!

 

[hilldweller]

55w ones produce something like 18.5v each and the 120w produces something like 38v

Goal posts just moved. So the 120W is wired as two 60W in series. That clearly would not work in a parallel connection but it does mean they all are reasonably matched at around 4A max current. That 4A also minimises cable losses.


I think you've got a one off there.

 

[Freespirit1]

Goal posts just moved. So the 120W is wired as two 60W in series. That clearly would not work in a parallel connection but it does mean they all are reasonably matched at around 4A max current. That 4A also minimises cable losses.


I think you've got a one off there.

No - goal posts still where they were and so are all the panels wired in series - you can probably see that from the photo earlier I posted of them. Yes - I’ve just checked and the red positives are visible. As I said earlier just think of the panels being cells of a battery - all the cells on every panel are identical - you just have longer connections between some cells (being the interconnecting cables between the panels)

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[Rapido924f]

I’ve got a 10year old 120W solar panel supplying up to 7 amps to 2 x Trojan 6v 215ah batteries via a Steca 1010 controller. With Van Bitz battery master I’ve had no problems with lack of power to both leisure batteries and the vehicle battery in 10 years on 2 motorhomes.

 

[Urs4_2008]

800 watt solar, victron mppt 150/70, Bluetooth, 2 x 95 Ah cheap lead acid. Bogart engineering trimetric 2030 rv battery monitor. Works well

 

[Urs4_2008]

Not in my view - for me series connecting will give the best performance - regard all the panels as cells of a battery with specific voltage the 55w ones produce something like 18.5v each and the 120w produces something like 38v which would give 112v using those figures - i’m seeing probably at best 107v - then some slight volt drop in my 16mt Solar 6mm cable to the controller looks about right to me!

Think of solar panels like batteries in a flashlight, when regarding parallell vs serial connectivity.

As long as the voltage output are equal, you can connect any kind of capacity battery (solar panels are essentially batteries) in parallel and get the total capacity added (ie 100 amp hour 12 volt battery paralleled with a 10 amp hour 12 v battery will yield 110 total ah.) (voltage must be equal).

If you use the same example only in series, the 10 amp hour battery will be depleted after having given 10 amp hours, and at the same time 10 amp hours will be provided by the 100 ah battery, which now has 90 ah remaining. When the smaller battery is empty the current will stop. Try it

I solar panel terms, the total power production capacity will be limited to the smallest panel in the serial connected string of panels.

So short and simplified: only use parallel if panels have the same voltage and only use serial if panels have the same capacity (wattage)

 

[pappajohn]

Saw the front page and thought Roadrunner had returned... Then saw the date..2009

 

[pappajohn]

800 watt solar, victron mppt 150/70, Bluetooth, 2 x 95 Ah cheap lead acid. Bogart engineering trimetric 2030 rv battery monitor. Works well

Only two 95ah batteries with that much solar......what a waste of power.
I had 4 X 110ah and 170w of solar....seemed a good match.

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[Urs4_2008]

Only two 95ah batteries with that much solar......what a waste of power.
I had 4 X 110ah and 170w of solar....seemed a good match.

When cloudy, rainy or early / late season i can assure you it’s not a waste of power

 

[Tanya_and_Mick]

Only x2 150w

 

[pappajohn]

So short and simplified: only use parallel if panels have the same voltage and only use serial if panels have the same capacity (wattage)

In series the largest capacity panel is the maximum amps output but the voltage is multiplied by the number of panels....
Series...4 X 100w and 1 X 150w = 150w output @ 60v.
Parallel..4 X 100w and 1 X 150w = 550w @ 12v.

Parallel multiplies amperage/watts
Series multiplies voltage

 

[Urs4_2008]

In series the largest capacity panel is the maximum amps output but the voltage is multiplied by the number of panels....
Series...4 X 100w and 1 X 150w = 150w output @ 60v.
Parallel..4 X 100w and 1 X 150w = 550w @ 12v.

Parallel multiplies amperage/watts
Series multiplies voltage

Everything depends on the panels number of cells which in turn produces voltage, and how it’s configured internally.

Last three statements I concur, except most “12 volt” panels have vmax at about 17 or 18 volts.

Unfortunately, I have to respectfully disagree on the series statement. Given identical voltage on the different panels you will get 100 watts at about 85 volts, loosing the extra 50 watts you could have gotten if wires in parallel or having a second, separate charger for this bigger panel.

To add to the complexity, if the max current of the 150w panel is equal to the max current of the 100w panels, your statement is correct. But in practice these panels then will have to have different system voltages.

I would still claim that provided vmax is equal, configure different capacity panels in parallel and same capacity (max current) panels in series if you have a MPPT charger that supports the total added panel voltage and want to reduce cable losses. If you have a pwn controller the equal capacity panels can still be connected in parallel, but calculate cable losses due to high current / low voltage and design with a safe and appropriate thick cable to avoid losses and high/dangerous temperature.


http://solarpanelsvenue.com/mixing-solar-panels/

 

[autorouter]

Parallel multiplies amperage/watts
Series multiplies voltage

These rules may be true for resistors, which obey Ohm's Law, but solar cells fart in his general direction, to use a technical description.

Basically in a series string, the amps is limited by the lowest amperage panel. If you try to push more amps through, the panel starts going into reverse mode and blocks any increase in current. The volts add together, just as you'd expect.

So the rule is, only use series if the panels have the same amperage. (if they all have the same voltage, then they will have the same wattage. But technically they could have different voltages, in which case the wattages would be different too. The important thing is that the amperage is the same).

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[Urs4_2008]

These rules may be true for resistors, which obey Ohm's Law, but solar cells fart in his general direction, to use a technical description.

Basically in a series string, the amps is limited by the lowest amperage panel. If you try to push more amps through, the panel starts going into reverse mode and blocks any increase in current. The volts add together, just as you'd expect.

So the rule is, only use series if the panels have the same amperage. (if they all have the same voltage, then they will have the same wattage. But technically they could have different voltages, in which case the wattages would be different too. The important thing is that the amperage is the same).

It seems we agree, only you explained it better. English is not my native language

 

[SuperMike]

Four 100w panels. Two pairs wired in series and then those total two pairs wired in parallel. Best of both worlds.

 

[Urs4_2008]

Four 100w panels. Two pairs wired in series and then those total two pairs wired in parallel. Best of both worlds.

Which is how I’ve connected my 8 panels. Two strings of 4 in series connected in parallel

 

[Urs4_2008]

Only two 95ah batteries with that much solar......what a waste of power.
I had 4 X 110ah and 170w of solar....seemed a good match.

But you know what they say... Big solar system, small.....

 

[Em and Tim]

That's the problem with buying a van when they are already fitted, you should have a rough guess, do you have a battery monitor, rough size of the panels, does it not say on the side what they are if you go up there?

Exactly!
Can anyone tell us what size this one is?
It has 4 by 9 cells, is 50-54cm by 116-120cm. Depending on how you measure it.
It feeds our two 130ah agm batteries through a CMTP03 PWM control unit with what look to me to be perilously thin wires coming to it 2.5mm^2, and 4mm^2 between it and the battery.

There is a mount for a second panel, so we are thinking we may as well fit one, but it would be good to know what we have (recently we have been struggling to get enough from the one panel, October in Scandinavia..... and Em wants the heating on!). Any ideas greatly appreciated. Thanks

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[autorouter]

Can anyone tell us what size this one is?
It has 4 by 9 cells, is 50-54cm by 116-120cm. Depending on how you measure it.

As an estimate, I found that a Photonic universe 36-cell panel, size 1480 x 670mm = 1 square metre area is 160 watts. So your panel, size 1160 x 500mm = 0.58 square metres, should be about 160 x .58 = 93 watts. Probably a 100 watt panel, then.

It has 36 cells, so its open circuit voltage will be about 22 volts.

 

[Ralph-n-Bev]

Blooming heck Roadrunner thats a blast from the past ! Wonder what he’s up to now a days ?

 

[HandyAndy]

About 7 inc.... Oh
Umm 200watts at the moment and both of them are portable ones..
I keep meaning to get up on the roof and measure up for some proper permanent ones but like everything, I've not got round to it yet.

Oh crap. an 8 year old thread..

 

[Janine]

Blooming heck Roadrunner thats a blast from the past ! Wonder what he’s up to now a days ?

Different Roadrunner in your post!

The original Road Runner disappeared from the radar a long time ago.

Much missed Funster.

 

[pappajohn]

Different Roadrunner in your post!

The original Road Runner disappeared from the radar a long time ago.

Much missed Funster.

He did reappear on the forum for a very short while a few year ago.
I believe he contacted Jim a couple of years ago and said he was well.
As I recall he was never in the best of health and kept losing the odd extremity to poorly controlled diabetes.
You never know, it may have caught up with him but he was last seen viewing the forum on Jan 5th this year.

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