How much can i put on the roof. (1 Viewer)

[Emmit]

The question is in the title.
I'm fed up of running out of Lecky in the winter.
Assuming we have a 20 amp MPPT controller ( which we have) and assuming the cable coming down from the present feeble system is man enough (sorry all the PC brigade) how much in wattage can I put on the roof allowing the fact that we would not be taking the van to the equater.
I would also like to be given guidance as to how many amps of battery would a perfect fit.
Thank you in advance

 

[DBK]

The more the merrier. But in round numbers your 20A controller is good for 200W.

But if you want extra power in winter you need more (300 or 400W?) and will need to upgrade the controller.

 

[Jev88]

Forgive the simple answer - The more solar you have (with suitable controller(s) ) and the more batteries you have to store collected energy the better?
Saw a picture of FB or someone with 9 panels on their roof!
Alternatively, having some panels mounted on swinging brackets (so you can point more perpendicular to the sun in winter) would help?

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[Emmit]

The more the merrier. But in round numbers your 20A controller is good for 200W.

But if you want extra power in winter you need more (300 or 400W?) and will need to upgrade the controller.

Thanks for answer John, but if I needed the extra solar in winter, wouldn't he lack of usable light as a result of low Sun and shortage of hours balance the need for extra amp coverage in the controller.
That's why I alluded to not going somewhere where the Sun was high above in Winter. Not arguing, just offering my thoughts,(which may be stupidly wrong)

 

[EssexBoy]

I must admit, I was wondering what would happen to the controller if the panels produced more amps than the controller can handle?

Would the controller just max out?would it blow up? Would it blow a fuse? Would it just stop until the panels provided less input?

Anyone know?

 

[Lenny HB]

Even quite a long way south you won't get a lot this time of year.
We are in SW France at the moment near the Spanish boarder, the last few days we have had wall to wall sunshine but only getting 4 amps out of our 300 Watts with a Votronic MPPT regulator. Warmer today 25° solar peaked at 6.5 amps.
Even in southern Spain I would only expect an amp more, also you only get the max for 3 or 4 hours a day.

If you don't want to change your regulator you could add more panels with a switch in line then switch them out of circuit in the summer.

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[DBK]

Thanks for answer John, but if I needed the extra solar in winter, wouldn't he lack of usable light as a result of low Sun and shortage of hours balance the need for extra amp coverage in the controller.
That's why I alluded to not going somewhere where the Sun was high above in Winter. Not arguing, just offering my thoughts,(which may be stupidly wrong)

I think some controllers will limit the output to their rated figure, no matter what you put into them. Other might just produce black smoke. Take your pick I guess. But if you are going to put a few hundred pounds worth of panels on the roof buying a matching controller makes sense to me.

 

[Emmit]

Even quite a long way south you won't get a lot this time of year.
We are in SW France at the moment near the Spanish boarder, the last few days we have had wall to wall sunshine but only getting 4 amps out of our 300 Watts with a Votronic MPPT regulator. Warmer today 25° solar peaked at 6.5 amps.
Even in southern Spain I would only expect an amp more, also you only get the max for 3 or 4 hours a day.

If you don't want to change your regulator you could add more panels with a switch in line then switch them out of circuit in the summer.

That makes two of us(in South West France)
Thanks for the input.

 

[Lenny HB]

I must admit, I was wondering what would happen to the controller if the panels produced more amps than the controller can handle?

Would the controller just max out?would it blow up? Would it blow a fuse? Would it just stop until the panels provided less input?

Anyone know?

The Votronic & Victron ones have over current protection and will limit the output limit the output, not sure what would happen with a cheap one might shut down, might go bang.

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[Raul]

You can overpanel a controler up to a point:
-do not exceed the voc input,voltage open circuit;
-do not exceed short circuit input.
Stay within these limits the controler will modulate it’s output.
As a rule of thumb, you can overpanel at least 1,5 times its output power, specially if they flat on the roof. Not all controllers list short circuit input, so it depends on make.
Victron does on most.

 

[Emmit]

Mine is neither but there again, it got a decent report (as opposed to a Bang!) from a bloke on youtube who took it to bits.
Once again thanks.

 

[dunnah01]

20Amp PWM Controllers are only a few quid so just have one for each panel. You can fit as many panels as your roof space will allow and just put the wiring through the existing cabling hole. I've put in two controllers for 2x180w panels and not blown anything up yet, although I've only seen three storms and darkness since I installed them! (wish I'd put a wind turbine up there instead)

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[Reallyretired]

I have 400w of panels and in the summer can have a bit more than 20A(30A controller) so you should be OK with 300w and a 20A controller.