Additional panel?

[Pusscat]

Hi,
just musing at the moment. We have a factory fitted 100w Sargent 12v solar panel and I was thinking of adding a Panasonic HIT 250 12v to bump it up to 350. Also thinking of an additional leisure battery as well. Thinking was to eventually fit a compressor fridge so we can have really cool drinks etc abroad in summer months!

I’ve heard about not mixing panels but also heard about not mixing different voltage panels…so that they are both 12v panels, would this be ok to mix as long as they were connected in parallel and with a suitably powered controller?

any advice or comments would be welcomed.

 

[I2C]

I've gone for 2 panels the same size (yet to fit as weather is rubbish!), this article gives a good explanation regarding missmatched panels. You can but you may not get as much output as you expect.

 

[Pusscat]

Thanks…interesting article. So looks like having the voltage the same in parallel connection, I should get my full 350w!

 

[Guigsy]

Thanks…interesting article. So looks like having the voltage the same in parallel connection, I should get my full 350w!

My understanding is you're unlikely to get the same voltage from two different panels. So one will drag down the other?

 

[I2C]

From my reading of the article, 2 different sized panels in parallel will give you the best results but unless I have it wrong I think you won't get 350w, though I can't work out what you would get in my head, need to find a pen and paper for that... The actual voltage from the panels is more than 12v, the specifications will give you the values.

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[Pusscat]

I think from the article, in parallel, the voltage would be the limiting factor but since they are reportedly both 12v, then that theoretically, wouldn’t result in a drop. I’ll have to look at the panels spec and work it out as yes, I think the voltage will be greater. not sure what happens if one panel happens to shaded and the other in sunlight though!

 

[Guigsy]

I think from the article, in parallel, the voltage would be the limiting factor but since they are reportedly both 12v, then that theoretically, wouldn’t result in a drop. I’ll have to look at the panels spec and work it out as yes, I think the voltage will be greater. not sure what happens if one panel happens to shaded and the other in sunlight though!

They are for a 12v system, but that just means they output something above 12v at any time there's some useful sunlight to be harvested. Both the voltage and current change depending on the amount of sunlight AND the load on the panel. And different panels will act differently depending on their size, layout, the technology they use, and the age of the panel.

 

[Greame.M]

Since I live in Scotland and sometimes it's not sunny here I thought about putting them in series. That way the batteries wouldn't get such a strong charge as in parallel, but they would have a longer charge with less current with series due to be being more efficient in lower light levels.

 

[funflair]

The safest bet with different spec panels is to put each one onto its own regulator.

 

[Diabalo]

The safest bet with different spec panels is to put each one onto its own regulator.

How would that work, I would have thought one of the regulators would see the other charging and so go into float mode.

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[funflair]

How would that work, I would have thought one of the regulators would see the other charging and so go into float mode.

It only does that when the batteries don't need the power that would come from the second regulator, when the batteries need the amps they suck the voltage down to the point where both regulator output, I have had this for 8 years on two different vans.

 

[wolfie2]

Pusscat.... if your present panel is wired via the controller and then the Sargent unit I believe the max that the Sargent can handle is 120w. Might be worth checking.

 

[Pusscat]

Thanks Wolfie, I’m connected via votronic MPPT, the Sargent unit was rubbish to be honest!

 

[Raul]

The panasonic hit can not be mixed and should not be mixed with 36cell 12v panels. Your 100w panel it’s a 36cell. Panasonic 250w it’s a 72 cell panel outputting in excess of 40v. It needs its own controller in your case. It’s a fantastic panel, hibrid and the best in cloudy weather. A victron 100/20 controller will suit very well.
I have the panasonic 300w with 96 cell and gives over 50v.
You can mix panels where the parameters are close, but will be losses and hot spots will develop on the weaker panel.

 

[Pusscat]

Many thanks for that Raul! Gives me an excuse to take the 100w off completely and use it for the well in the garden! I would imagine 250 W going into 2 leisure batteries will be enough for an off ecu for a 12v compressor fridge…

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[Raul]

You’re welcome. The 250w will be enough for a compressor fridge from March to September. A compressor will average 350wh or 30ah per day. From may to end of august the 250w will be able to harvest 700-1000wh daily. In winter you will need double panel power.