Solar panels and Victron ratings

[rwoodnz]

Hi (from another thread it got lost in)

I have a couple of 100W solar panels that are nominally 6.1A open circuit, 5.5A rated, but when I test them open circuit on my multimeter I get 4.1A each in great sunshine facing the sun.

If I get six of these solar panels can I use them on an Victron 100/30?

What happens if I exceed the 30A rating? Does it just cut out or does it blow a fuse or something that would require shop repair?

[john61ct]

You only need to worry about the **voltage** rating, as far as damage is concerned.

80-85 total Voc to be conservative with that SC's 100V rating.

That 3A ceiling is maximum current **output**

You can **input** much higher current, no problem.

That is called overpaneling, and an excellent way to increase **average** power produced in normal conditions, get better value for money per SC purchased.

You will hardly ever get maximum amps from your panels, so silly to use that as a limiting factor.

So, let's say your max charge voltage is 14.9V, *30A is ~450W.

So 550 total watts would hardly be sacrificing anything, even in brief peak conditions.

600W a bit more, but no chance of damaging the controller.

[FlyingScot]

Originally Posted by rwoodnz

Hi (from another thread it got lost in)

I have a couple of 100W solar panels that are nominally 6.1A open circuit, 5.5A rated, but when I test them open circuit on my multimeter I get 4.1A each in great sunshine facing the sun.

If I get six of these solar panels can I use them on an Victron 100/30?

What happens if I exceed the 30A rating? Does it just cut out or does it blow a fuse or something that would require shop repair?

Is your house bank 12v or 24v?

600 watts / 12.5 volts = 48 amps.

Your controller will peak at 30 amps and thus you will run at max percentage a lot of the day and likely shortening the life of your controller. Victron 100/30 also throttle output at 105F. Running it at max amps will likely cause it to throttle due to heat.

Therefore you will be giving up substantial portions of your harvest.

I would not do this on a 12v house system. If 12v, get two controllers.

[john61ct]

Yes, double the wattage numbers if you have a 24V bank.

Victron has built its controllers to run all day for years at the rated amps - output is capped.

And even overpaneled by 20% you will still **very rarely** be getting anywhere close to that cap.

Sure, fork over another $100 to go to the 50A model if you like, but I guarantee with 600W of panels that won't buy you more than say an extra 10-20Ah potential output per day, and that **only in peak insolation** conditions anyway.

[FlyingScot]

Originally Posted by john61ct

Yes, double the wattage numbers if you have a 24V bank.

Victron has built its controllers to run all day for years at the rated amps - output is capped.

And even overpaneled by 20% you will still **very rarely** be getting anywhere close to that cap.

Sure, fork over another $100 to go to the 50A model if you like, but I guarantee with 600W of panels that won't buy you more than say an extra 10-20Ah potential output per day, and that **only in peak insolation** conditions anyway.

https://www.victronenergy.com/upload...-100-50-EN.pdf

Victron recommends a max of 440wp on 100/30. 600 watts is 36% over paneled.

I would do two controllers. Maybe one port and one stbd.

[john61ct]

Good idea, but I'm guessing not 75/15s 8-)

[Scott Berg]

I'd use 6 panels and 6 75-15's. Cost per watt not that different and much better performance. I've written a lot on this; all tests show significant advantages with individual MPPT controllers in an inherently shady environment.

[smac999]

the panel current is not what you need to be looking at.

the 30a rating is the current into the batteries. which unless you have 12v panels will not be the same as the current from the panels.

IE if the panel is putting out ~4a at 18v the controller will be putting in ~6a into the battery at 13v. it's the toal of output of controller you need to watch. not the input.

[john61ct]

No need to "watch" any current issues, that 30A is the limit the SC will put out.

Just convert to **watts** for different voltages

> So, let's say your max charge voltage is 14.9V, *30A is ~450W.

If the bank was 24V, thus charging at 29.8V, the output of 30A yields double the power at 900W. Thus 1000 or even 1100W worth of panels could be efficiently serviced by this one $200 controller.

Notice the amps rating of the panels is nowhere involved in the calculation.

Other SC makers do things differently.

I do also agree that a 1:1 ratio deals with shading better, but the that single panel should ideally be well matched to the controller. A 75/15 with a 240-280W 40Voc would work well.

More wiring, space and complexity though.

[StuM]

Originally Posted by smac999

the panel current is not what you need to be looking at.

the 30a rating is the current into the batteries. which unless you have 12v panels will not be the same as the current from the panels.

Not quite, it's the max current to service the loads from the batteries accepting charge plus any house loads. If the onboard electrical systems are drawing 10 A, the maximum current into the batteries will be 20 A.

[rwoodnz]

Thanks everyone for this input and explanations.
I should have made it clear I already have a Victron 100/30. I have two panels with two more panels arriving soon that take it for four.
So I will add the two panels to the existing controller in a 2x2 setup so if one side is shaded.
When I go to six panels later I will add a second controller (port vs starboard) - good to have redundancy also.

[noelex 77]

Originally Posted by rwoodnz

Hi (from another thread it got lost in)
I have a couple of 100W solar panels that are nominally 6.1A open circuit, 5.5A rated, but when I test them open circuit on my multimeter I get 4.1A each in great sunshine facing the sun.

If I get six of these solar panels can I use them on an Victron 100/30?

What happens if I exceed the 30A rating? Does it just cut out or does it blow a fuse or something that would require shop repair?

Note: the answer below assumes a 12v battery bank:

No, a fuse will not blow. The Victron regulator will limit the output current to 30A to protect itself. Personally, I don’t think relying on this mechanism is good for the long term health of the regulator, particularly the Victron models that use passive cooling and run reasonably hot even when driven conservatively, but this this only an educated guess. It should also be noted that it exceeds Victron’s recommendation.

Running 600w through a regulator rated at 30A that can therefore can handle a maximum of less than 450W, is going to waste a reasonable amount of power even if it causes no long term problems. It looks like your solar panels are not putting out their rated power, but I still think it is worthwhile looking for a different solution. Two Victron 100/20 controllers would be perhaps be most cost effective given the slightly lower than specified output of the panels. The smaller regulators from Victron are not very expensive so 2x 100/20 will not be a great deal more money than 1x 100/30. The smart solar version comes with Bluetooth built in and is arguably worth the slight extra cost.

Originally Posted by john61ct

And even overpaneled by 20% you will still **very rarely** be getting anywhere close to that cap.

John, “over panelling” is perhaps good advice for a home or possibly even an RV installation where there is plenty of room to add extra panels. This is not true for most boats where there is simply not enough room to add more panels to make up for the loss of a regulator that is too small.

To add more panels to make up for the lost power of a regulator that too small even if this feasible will also often quite expensive on a boat. The mounting system often needs to be constructed. Even adding extra panels to a bimini means good quality flexible panels are needed. It is not the same as domestic system where an extra cheap rigid solar panel added to an array on the roof will often be more cost effective than spending money on a better or large controller.

“Over panelling” may make sense in a domestic installation, but not on a boat.

Originally Posted by john61ct

Sure, fork over another $100 to go to the 50A model if you like, but I guarantee with 600W of panels that won't buy you more than say an extra 10-20Ah potential output per day, and that **only in peak insolation** conditions anyway.

An extra 10-20Ahrs even occasionally is often a significant improvement. Few boat owners can lightly dismiss this amount of power.




Edit: Rwoodnz, I see you already have a 100/30. You can still add a 100/20 as the second controller. The different size will not cause problems. Use the smaller controller on the older panels. I suspect these might have deteriorated slightly with age.