Combining different panels

HumMichael · February 2017

Since this is for beginners, I will ask here.
I have about 10 Renogy 12v 100w panels and 6 of their 260 watts at 24v.
I understand that mixing is no good so I am thinking of two scenarios. Of course I will measure Vmax for my cc and not go over tje maximum voltage.
First
Serial connect all 100w together for one string and the same for all 260w together.
Run both strings to a MNPV6 combiner and then feed to my Midnite200 cc.
Second
Run each string to a separate cc, I have Morningstar MPPT45, but charge the same battery bank. Even though my system will not communicate but the second string will face more West for afternoon sun.

Also how do you calculate circuit breaker size for a long series array?

I am certain there are factors I am forgetting but your knowledge will be appreciated.

BB. · February 2017

What is the Vmp of the two types of panels?

The 12 volt probably are around Vmp~18 volts.

The 24 volt panels can either be Vmp 30 volts or 36 volts.

It makes a difference in what you can do.

And what voltage battery bank?

-Bill

HumMichael · February 2017

18.9v
37.6v
I have used Morningstar calculator for 100w and I see what I can do.
I think my question is whether I can safely charge one 12v battery bank of 1200ah using two separate charge controllers. One will have 24v series setup and the other one at 48v strings.
Thanks

BB. · February 2017

OK--You can set up both panels (1x37.6 volts in parallel with 2x18.9 volts in series) for Vmp-array ~ 37.6/8 volts--And since you are using MPPT controllers, they will nicely step down to your 12 volt bank.

Note--You can run Vmp-array from ~37 volts or upwards of 64 or even (possibly) 103 volts (depends on how cold it gets in your area (cold raises Vmp and Voc of panels--And you do not want to exceed the maximum input/working voltage of the MPPT controllers--Use the string calculators).

Picking the "high voltage" Vmp-array is nice if your cable run from the array to the charge controller+battery bank is long. If the run is not long, then you can run lower array voltage (roughly 2x battery bank voltage is nice) and the MPPT controllers are more efficient.

You can use a voltage drop calculator like this simple one to figure out how large of cable diameter you need to keep losses to an ideal of typically 1% to 3% maximum loss range.

-Bill

Estragon · February 2017

Just to add to Bill's great advice, using 2 controllers to charge a single bank is not only ok, it's better to have differently oriented arrays on separate controllers. That way, each controller can optimize for light condition on each array as the day passes.

littleharbor2 · February 2017

HumMichael said:

18.9v
37.6

The 260 watt panels aren't 24 volt panels. The voltage on the 260 watt panel is 30.4 Vmp and 37.6 Voc. You need to get your answers correct if you expect an accurate answer.
Using two separate CC's is fine but you cannot series wire all 10 100 watt panels unless you use a high voltage controller such as a midnite classic 250 or one of the 600 volt controllers.
With this many panels and the proposed 1200Ah battery bank you really should be going 24 or even 48 volts, not 12 volts. You need very expensive high amp charge controllers to handle all the potential amperage produced by this large of an array.
All your panels should have a series fuse rating on the data label.

HumMichael · February 2017

I came to a conclusion that I need 48v system a while ago. I was not calculating max volt carefully upto this point. I have looked up array calculator this morning and fixed the mistakes.
I am going to arrange the second array due west tomorrow.
I have slowly acquired 48v equipments overtime including Magum4448s with their mounting panels, etc.

What kind of wires from a combiner should I run if it will be exposed to outside? I am thinking its going to be about 200ft run. I have pv 10 gauge but the voltage drop may be reasonable with enough panels in a series.
Thanks
Michael

Combining different panels

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