What size MPPT?

[kenmo]

I just picked up 3 of these 370w panels. Photo attached of specs. They will be used in parallel on a 12V system. Am I correct in calculating that I would need a 120A charge controller, or 40A controller per panel?

If so I don't think anyone makes a 120A controller so what would be the best option. 3 40A MPPT's or 1 80A MPPT and 1 40A MPPT? Other ideas?

 

[TCgreg]

Each panel makes about 40v and about 10 amps

If they are in parallel you will have about 40v at about 30 amps total for all 3. In parallel voltage stays the same as one panel and amperage accumulates.

In series you would have about 120v at about 10 amps.

If you are going to wire them in parallel you shouldn't have a problem finding a SCC. A Victron 100/30 would work fine. (max 100v or 30amps)

If you wire them in series (voltage accumulates and amperage stays the same) a Victron 150/35 would be fine.

This would also work fine no matter how you wire the panels.

https://www.amazon.com/SolarEpic-Ch...ocphy=9053123&hvtargid=pla-319377149450&psc=1

 

[svetz]

You might also like Figuring out how many panels in series and parallel based on your MPPT

 

[b.james]

Victron might cost you $300 . I'd look at one of those MPP inverters for $1100 which puts you miles ahead in charging ability and current draw and slowly add more solar and batteries if you are going to.

 

[kenmo]

Each panel makes about 40v and about 10 amps

If they are in parallel you will have about 40v at about 30 amps total for all 3. In parallel voltage stays the same as one panel and amperage accumulates.

In series you would have about 120v at about 10 amps.

If you are going to wire them in parallel you shouldn't have a problem finding a SCC. A Victron 100/30 would work fine. (max 100v or 30amps)

If you wire them in series (voltage accumulates and amperage stays the same) a Victron 150/35 would be fine.

This would also work fine no matter how you wire the panels.

https://www.amazon.com/SolarEpic-Ch...ocphy=9053123&hvtargid=pla-319377149450&psc=1

I just want to get an understanding on all this. What you are saying makes sense to me as the specs state the voltage and amp, but why do I see calculations for charge controller size also calculated by dividing the total watts of the solar array by the battery voltage?

My array of 3 370W panels being 1110W /12V = 92.5A
That is how I came up with the 100A MPPT being needed.

Thanks

 

[woodshed1]

Referenced by what I use, if you buy ONE more panel and go to 24v this will work... https://www.amazon.com/gp/product/B07JP6GSVR/ and it is less than 180.00 US.

 

[atatistcheff]

I just want to get an understanding on all this. What you are saying makes sense to me as the specs state the voltage and amp, but why do I see calculations for charge controller size also calculated by dividing the total watts of the solar array by the battery voltage?

My array of 3 370W panels being 1110W /12V = 92.5A
That is how I came up with the 100A MPPT being needed.

Your math is right but there are other considerations which might save you some $$$ on a charge controller.

Yes, if its sunny and you get full output on all your panels and want to utilize 100% of that power then you will need a rather large capacity controller. This is one reason you see folks starting to up their battery voltage when you start using a lot of solar wattage. If you were using a 24V system then your amp requirements for your MPPT get cut in half. This starts sounding a lot more reasonable.

Also, you probably won't get 100% of the wattage out of your panels so you can cut some there, maybe 10-20% but some testing might be helpful. Or maybe you are willing to lose some of the wattage on a mid-summer day and you bought larger panels to be able to get more power on cloudy or winter days. There's no law that says your MPPT has to convert 100% of the power your panels are putting out. Maybe you decide that 60A is all you really need and on those stellar, sunny days you just don't reap all the power you could.

If I were you I would definitely consider 24V on the battery side. That way, even if you only use a 30A MPPT you are still looking at 720-840W depending on the battery voltage at the time. If your panels operate at 80% efficiency you are using just about all the power they are putting out.

Here are some numbers based on a 30A MPPT.

Output:
1110W x 80% = 888W

12V system usable:
30A x 12V = 360W
30A x 14V = 420W
Yes, you need a bigger charge controller!

24V system usable:
30A x 24V = 720W
30A x 28V = 840W
Hmm, this might be more reasonable.

Based on these estimates you're leaving anywhere from 48-168W on the table (or on the roof) on a sunny day for a 24V system. A 35 or 40W MPPT puts you in an even better place with a 24V battery setup. As you can see, the 12V system would require a much higher amperage and higher cost controller.

I'm sure there are other considerations and even holes in my logic here but I hope it makes a little sense!

 

[Supervstech]

I just picked up 3 of these 370w panels. Photo attached of specs. They will be used in parallel on a 12V system. Am I correct in calculating that I would need a 120A charge controller, or 40A controller per panel?

If so I don't think anyone makes a 120A controller so what would be the best option. 3 40A MPPT's or 1 80A MPPT and 1 40A MPPT? Other ideas?

I agree with the others.
Trying to feed 1100 watts at 12v is going to be difficult. You would need three 40amp controllers. And the batteries will need some expensive wires to feed everything.
better to move up to 24 or 48v and keep the amperages low.
Why are you planning with 12v?